Why GM should NOT build a DOHC V8

[smk4565]

I never experienced a Rolls V12, but that car has loads of sound deadening also. But the BMW inline six is better than their V8 in a lot of ways. The engine is just so smooth, balanced, it revs easily, never sounds harsh. And it is good in a luxury car or good in a sports car.

[Drew Dowdell]

No no... I was questioning your implication that a DOHC V8 was smoother than a Rolls 6.7 liter pushrod.

[David]

All of you that think you don't need a DOHC V8 don't own one. Once you get used to having a DOHC V8 it is hard to go to anything else. The only thing I have driven that is better is the BMW straight six, that is the smoothest engine out there. Fuel economy concerns though will push the DOHC V8 crowd like myself to DOHC V6s, possibly with turbo or supercharger.

Having owned a Northstar caddy, I still prefer a push rod V8. Anyone who needs to pull anything will know this is the only type of V8 to have and those that really want power/performance also knows the Push Rod V8 is superior to the DOHC V8 or anything else.

You can drink the cool aid all you want on how Superior DOHC engines are in the Asian, Italian, euro cars and yet when it comes down to real numbers and long life, I have yet to see DOHC last the years of real use that Push Rods do.

[Robert Hall]

You can drink the cool aid all you want on how Superior DOHC engines are in the Asian, Italian, euro cars and yet when it comes down to real numbers and long life, I have yet to see DOHC last the years of real use that Push Rods do.

Riiiight...

How about all the Crown Vic taxis, etc w/ hundreds of thousands of miles or Ford F-series trucks from the last 15 years? Those are all OHC engines... I'm sure Ford had good reasons for going away from pushrod 20 years ago...

Edited September 27, 2012 by Cubical-aka-Moltar

[Drew Dowdell]

You can drink the cool aid all you want on how Superior DOHC engines are in the Asian, Italian, euro cars and yet when it comes down to real numbers and long life, I have yet to see DOHC last the years of real use that Push Rods do.

Riiiight...

How about all the Crown Vic taxis, etc w/ hundreds of thousands of miles or the Merc Taxis in Europe w/ hundreds of thousands of miles? Or Ford F-series trucks from the last 15 years? Those are all OHC engines...

Mercedes Cabs (when not diesel), Crown Vics and F-150s are SOHC not DOHC..... and there is faaaaaaaaaaaaaaaaaaaaaaaaaaaar less advantage to SOHC almost to the point of "why bother? just make it a pushrod and increase the displacement"

The Crown Vic with its "superior" SOHC V8 never ever ever exceeded the performance of the 1996 LT-1 pushrod.

[Robert Hall]

You can drink the cool aid all you want on how Superior DOHC engines are in the Asian, Italian, euro cars and yet when it comes down to real numbers and long life, I have yet to see DOHC last the years of real use that Push Rods do.

Riiiight...

How about all the Crown Vic taxis, etc w/ hundreds of thousands of miles or the Merc Taxis in Europe w/ hundreds of thousands of miles? Or Ford F-series trucks from the last 15 years? Those are all OHC engines...

Mercedes Cabs (when not diesel), Crown Vics and F-150s are SOHC not DOHC.

So? Still OHC. SOHC or DOHC are equivalent for this discussion which is OHC vs pushrod. And Merc diesels are OHC, aren't they? Bottom line, 99% of the worlds' automakers long ago moved on from pushrod to OHC engines...GM has for everything except V8s. What's holding them back? inertia? stubbornness? myopia? Can't use the truck excuse as Ford has built a hell of a lot of OHC trucks over the last 15 years. It's interesting how people keep defending an obsolete approach when the world clearly has moved on.

It's all a moot point, though, because the future is clearly 1.4L 4 cyls...

Edited September 27, 2012 by Cubical-aka-Moltar

[Drew Dowdell]

SOHC has no tangible benefits over pushrod in a V engine. You get none of the additional breathing available from a DOHC engine yet you get most of the complexity and additional friction, and you lose packaging flexibility and ability to increase displacement. At best, you get slightly more flexibility with variable valve timing, but not enough to make a noticeable difference.

GM and Chrysler still make pushrod V8s, and their pushrod V8s are still among the most respected. You've driven a 300c right? I drove one back to back with an S550.... there is basically no difference in power, delivery, NVH....

[Robert Hall]

GM and Chrysler still make pushrod V8s, and their pushrod V8s are still among the most respected. You've driven a 300c right? I drove one back to back with an S550.... there is basically no difference in power, delivery, NVH....

I've driven a 300 w/ the new V6...it was fine. I haven't driven one w/ a Hemi, definitely want to....but the rentals are V6s. I like pushrod V8s and OHC V8s...have a lot of experience w/ the classic Ford 5.0 engine and more recently the Northstar for an OHC engine.

GM and Chrysler went to DOHC for their V6s, so why not for the V8s? It's just curious because both companies have built OHC V8s, but still build pushrod ones. Chrysler had their 4.7 OHC V8, but seems to have let it fall by the wayside and GM quit evolving the Northstar years ago. Very strange.

Edited September 27, 2012 by Cubical-aka-Moltar

[dwightlooi]

You can drink the cool aid all you want on how Superior DOHC engines are in the Asian, Italian, euro cars and yet when it comes down to real numbers and long life, I have yet to see DOHC last the years of real use that Push Rods do.

Riiiight...

How about all the Crown Vic taxis, etc w/ hundreds of thousands of miles or the Merc Taxis in Europe w/ hundreds of thousands of miles? Or Ford F-series trucks from the last 15 years? Those are all OHC engines...

Mercedes Cabs (when not diesel), Crown Vics and F-150s are SOHC not DOHC.

So? Still OHC. SOHC or DOHC are equivalent for this discussion which is OHC vs pushrod. And Merc diesels are OHC, aren't they? Bottom line, 99% of the worlds' automakers long ago moved on from pushrod to OHC engines...GM has for everything except V8s. What's holding them back? inertia? stubbornness? myopia? Can't use the truck excuse as Ford has built a hell of a lot of OHC trucks over the last 15 years. It's interesting how people keep defending an obsolete approach when the world clearly has moved on.

It's all a moot point, though, because the future is clearly 1.4L 4 cyls...

How about clarity on the technical merits of Pushrods vs OHC designs. The argument that you should do what everyone else does without any factual or technical justification is no better than to say that if everyone believes that the sun orbits the earth you should jump on that bandwagon.

As far as Ford OHC V8s vs GM Pushrod V8s, the GM engines had always beaten and continues to beat Ford's SOHC and DOHC designs in output, fuel economy and weight -- and always in at least two of the three categories simultaneously. This is true both in pickup trucks and in muscle coupes.

Ford F150 4x4 w/ 5.0 DOHC V8 -- 14 (city) / 19 Hwy MPG

Ford F150 4x4 w/ 6.2 SOHC V8 -- 12 (city) / 16 Hwy MPG

Chevy Silverado 4x4 w/ 5.3 Pushrod V8 -- 15 (city) / 21 (Hwy) MPG

Chevy Silverado 4x4 w/ 6.2 Pushrod V8 -- 403 hp / 417 lb-ft -- 12 (city) / 18 (Hwy) MPG

Ford Mustang BOSS w/ 5.0 Hi-Po DOHC V8 -- 444 hp / 380 lb-ft

Chevy Corvette Z06 w/ 7.0 Pushrod V8 -- 505 hp / 470 lb-ft

Where's the OHC advantage?

Edited September 27, 2012 by dwightlooi

[Drew Dowdell]

GM and Chrysler still make pushrod V8s, and their pushrod V8s are still among the most respected. You've driven a 300c right? I drove one back to back with an S550.... there is basically no difference in power, delivery, NVH....

I've driven a 300 w/ the new V6...it was fine. I haven't driven one w/ a Hemi, definitely want to....but the rentals are V6s. I like pushrod V8s and OHC V8s...have a lot of experience w/ the classic Ford 5.0 engine and more recently the Northstar for an OHC engine.

GM and Chrysler went to DOHC for their V6s, so why not for the V8s? It's just curious because both companies have built OHC V8s, but still build pushrod ones.

There are rental 300c out there, I've had them. They are my favorite long distance rental.

GM and Chrysler went to DOHC for their V6s because they needed to consolidate engine lines, it had less to do with the valvetrain layout and more to do with having multiple V6es in the same power range. You might as well ask "Why doesn't GM build 2.8 liter or 3.0 liter V6es anymore?" They've consolidated completely around the 3.6 as the 2.8 is gone and the 3.0 will be gone soon. If/When the 4.3 V6 finally dies, GM will have 1 V6 corporate wide.

The 3900 was a perfectly competent engine that was both efficient and smooth... smother than the 3.6 even. The only thing it didn't do was produce 300+ horsepower... but it was so small externally, GM could have put it in a Cruze if it wanted.

The reasoning is simple. You can fit a 5.3 liter pushrod engine into the same space you have to shoehorn a 3.6 DOHC into. You can put a 7.0 pushrod into the space a 5.0 liter DOHC barely fits.

[dwightlooi]

Without going into the details of 30~40 V8 engines, I can make the following general statements with confidence:-

• At the same displacement, a Pushrod Design is almost always more Fuel Efficient than a DOHC design, although it will make less power
  
• At the same power output, a Pushrod Design needs 15~20% greater displacement and delivers comparable fuel economy
  
• At the same displacement or the same output, a Pushrod Design is almost always smaller, lighter and cheaper than a DOHC engine
  

Without cluttering this post with over a 100 V6 and V8 data points, I can also make the following statements with confidence:-

• A Pushrod V8 design can deliver higher output at a lower weight, size and cost than a DOHC V6 Bi-turbo design
  
• At a comparable output, a Pushrod V8 design can also deliver Fuel Economy comparable to a DOHC V6 Bi-turbo design if it has similar technological content (eg. DI, VVT, etc)
  
• A DOHC V8 does not enjoy the same advantageous because of its increased frictional losses, weight, size and costs.
  

Finally, I will like to say that the common objections to American Pushrod engines in terms of refinement, performance and/or fuel economy is generally true in the 80s and 90s. However, these have nothing to do with the valvetrain configuration but rather the reluctance of American automakers to incorporate the technological content into their Pushrod designs. This is no longer true, but perceptions linger.

[Drew Dowdell]

Finally, I will like to say that the common objections to American Pushrod engines in terms of refinement, performance and/or fuel economy is generally true in the 80s and 90s. However, these have nothing to do with the valvetrain configuration but rather the reluctance of American automakers to incorporate the technological content into their Pushrod designs. This is no longer true, but perceptions linger.

Again, for the other viewers out there, driving the 300c feels like driving an S550 with a budget interior. As far as the engine goes, there is no difference in smoothness or refinement.... and the 300c gets me over 30mpg highway.

[smk4565]

So? Still OHC. SOHC or DOHC are equivalent for this discussion which is OHC vs pushrod. And Merc diesels are OHC, aren't they? Bottom line, 99% of the worlds' automakers long ago moved on from pushrod to OHC engines...GM has for everything except V8s. What's holding them back? inertia? stubbornness? myopia? Can't use the truck excuse as Ford has built a hell of a lot of OHC trucks over the last 15 years. It's interesting how people keep defending an obsolete approach when the world clearly has moved on.

It's all a moot point, though, because the future is clearly 1.4L 4 cyls...

Hit the nail on the head.

[Drew Dowdell]

So? Still OHC. SOHC or DOHC are equivalent for this discussion which is OHC vs pushrod. And Merc diesels are OHC, aren't they? Bottom line, 99% of the worlds' automakers long ago moved on from pushrod to OHC engines...GM has for everything except V8s. What's holding them back? inertia? stubbornness? myopia? Can't use the truck excuse as Ford has built a hell of a lot of OHC trucks over the last 15 years. It's interesting how people keep defending an obsolete approach when the world clearly has moved on.

It's all a moot point, though, because the future is clearly 1.4L 4 cyls...

Hit the nail on the head.

Not really, he hit his thumb. SOHC and DOHC are not​ equivalent and if you bothered to read the rest of the thread, you'd see how.

[smk4565]

Hyundai had no V8 5 years ago and had to build one from scratch. And they built DOHC, they spent a lot of money on that engine, it could have been anything they wanted and they went with DOHC. The only reason GM and Chrysler still use them is lack of funds to design the replacement. I understand the argument of GM should continue to use the pushrod rather than spend the money to make a DOHC V8 from scratch at a time when V8s are dying, maybe it isn't a good investment. But I don't buy that pushrods are better, why doesn't Lamborghini or Ferrari use a pushrod V12 or V8 then? How are Lexus, Audi, Mercedes, Aston Martin, McLaren, Jaguar, etc all wrong, and Chrysler/Dodge and Chevy are using the superior engine?

[balthazar]

Moltar's exact same post could be repeated, substituting in 'inline engine', but nooooo; there; obsolete stubbornness is alllll good.

money is not the issue, perception is not the issue (well, it shouldn't be a guiding factor), results are.

[smk4565]

So? Still OHC. SOHC or DOHC are equivalent for this discussion which is OHC vs pushrod. And Merc diesels are OHC, aren't they? Bottom line, 99% of the worlds' automakers long ago moved on from pushrod to OHC engines...GM has for everything except V8s. What's holding them back? inertia? stubbornness? myopia? Can't use the truck excuse as Ford has built a hell of a lot of OHC trucks over the last 15 years. It's interesting how people keep defending an obsolete approach when the world clearly has moved on.

It's all a moot point, though, because the future is clearly 1.4L 4 cyls...

Hit the nail on the head.

Not really, he hit his thumb. SOHC and DOHC are not​ equivalent and if you bothered to read the rest of the thread, you'd see how.

I did read the rest, SOHC is worse than DOHC but no one really makes them any more either. But either way, OHC is better than pushrod, the example of the Crown Vic is because the engine was left the same basically form the early 90s. Comparing a bad SOHC V8 to the best pushrod on the market isn't really making any sense. That is like comparing the GM 3900 V6 to the Nissan GT-R V6.

[dwightlooi]

I did read the rest, SOHC is worse than DOHC but no one really makes them any more either. But either way, OHC is better than pushrod, the example of the Crown Vic is because the engine was left the same basically form the early 90s. Comparing a bad SOHC V8 to the best pushrod on the market isn't really making any sense. That is like comparing the GM 3900 V6 to the Nissan GT-R V6.

It is perfectly alright for you to have that opinion. However, to sway anyone you'll need to explain how it is better. And, you'll need to articulate it better than "everyone is using it, therefore it must better" or simply declare that it is so -- that won't do anything but make your case sound kinda silly.

You'll notice that I do not simply say that Pushrod engines are more fuel efficient. I explain why are. I don't simply say that they are lighter and smaller, I show you the weights and the photos. I don't simply make a declaration, I support my positions with facts. You are free to challenge my reasonings or facts.

Let's start with one advantage of the DOHC setup -- any one -- and why you feel that it is important. Do that and I am sure everyone can have a meaningful discussion.

Edited September 28, 2012 by dwightlooi

[David]

You can drink the cool aid all you want on how Superior DOHC engines are in the Asian, Italian, euro cars and yet when it comes down to real numbers and long life, I have yet to see DOHC last the years of real use that Push Rods do.

Riiiight...

How about all the Crown Vic taxis, etc w/ hundreds of thousands of miles or the Merc Taxis in Europe w/ hundreds of thousands of miles? Or Ford F-series trucks from the last 15 years? Those are all OHC engines...

Mercedes Cabs (when not diesel), Crown Vics and F-150s are SOHC not DOHC.

So? Still OHC. SOHC or DOHC are equivalent for this discussion which is OHC vs pushrod. And Merc diesels are OHC, aren't they? Bottom line, 99% of the worlds' automakers long ago moved on from pushrod to OHC engines...GM has for everything except V8s. What's holding them back? inertia? stubbornness? myopia? Can't use the truck excuse as Ford has built a hell of a lot of OHC trucks over the last 15 years. It's interesting how people keep defending an obsolete approach when the world clearly has moved on.

It's all a moot point, though, because the future is clearly 1.4L 4 cyls...

Lets look at the average life of a Ford Engine. Especially non V8 OHC/DOHC and Ford has a dismal record. They might have sold the blue color working world that they have a great truck, but so far from the plastic interiors to the lack of quality in how their trucks last that I have seen here in the NW, Ford does not cut it yet. Rusty, noisy plastic bucket of bolts. Not to mention not sure which is worse, the noisy smelly Powerstroke or Cummins. But the Duramax kicks them all cleanly and clearly.

[Drew Dowdell]

So? Still OHC. SOHC or DOHC are equivalent for this discussion which is OHC vs pushrod. And Merc diesels are OHC, aren't they? Bottom line, 99% of the worlds' automakers long ago moved on from pushrod to OHC engines...GM has for everything except V8s. What's holding them back? inertia? stubbornness? myopia? Can't use the truck excuse as Ford has built a hell of a lot of OHC trucks over the last 15 years. It's interesting how people keep defending an obsolete approach when the world clearly has moved on.

It's all a moot point, though, because the future is clearly 1.4L 4 cyls...

Hit the nail on the head.

Not really, he hit his thumb. SOHC and DOHC are not​ equivalent and if you bothered to read the rest of the thread, you'd see how.

I did read the rest, SOHC is worse than DOHC but no one really makes them any more either. But either way, OHC is better than pushrod, the example of the Crown Vic is because the engine was left the same basically form the early 90s. Comparing a bad SOHC V8 to the best pushrod on the market isn't really making any sense. That is like comparing the GM 3900 V6 to the Nissan GT-R V6.

Fine. The Hemi V8 is a better engine than the Nissan VQ-V6 and VK-V8 because it is more efficient, smoother, and offers better power delivery. The Hemi V8 is so compact, it will fit in any engine bay that would hold the VQ and even in it's lowest spec produces far more power and torque than the VQ.

The M56 is maxed out at 5.6 liters and 420hp while the Chrysler 300C SRT-8 can go to 6.4 liters (and likely larger) with 538hp.

There are a lot of potential reasons to buy an M56 over a 300C SRT-8, but powertrain isn't one of them.

[dado]

Without going into the details of 30~40 V8 engines, I can make the following general statements with confidence:-

• At the same displacement, a Pushrod Design is almost always more Fuel Efficient than a DOHC design, although it will make less power
  
• At the same power output, a Pushrod Design needs 15~20% greater displacement and delivers comparable fuel economy
  
• At the same displacement or the same output, a Pushrod Design is almost always smaller, lighter and cheaper than a DOHC engine
  

Without cluttering this post with over a 100 V6 and V8 data points, I can also make the following statements with confidence:-

• A Pushrod V8 design can deliver higher output at a lower weight, size and cost than a DOHC V6 Bi-turbo design
  
• At a comparable output, a Pushrod V8 design can also deliver Fuel Economy comparable to a DOHC V6 Bi-turbo design if it has similar technological content (eg. DI, VVT, etc)
  
• A DOHC V8 does not enjoy the same advantageous because of its increased frictional losses, weight, size and costs.
  

Finally, I will like to say that the common objections to American Pushrod engines in terms of refinement, performance and/or fuel economy is generally true in the 80s and 90s. However, these have nothing to do with the valvetrain configuration but rather the reluctance of American automakers to incorporate the technological content into their Pushrod designs. This is no longer true, but perceptions linger.

Do you maybe have any specific data on V8 twin turbo from Mclaren (M838T)? Or Ferrari engine from Italia 458? Graphs for specific fuel consumption, size (for mclaren turbochargers should be included), Co2 emission, price of the engine, etc.? just curious since i can't found those data .

I think small block is excellent engine...for corvette...or tucks..or some "cheaper" cars. But if GM ever tries to go in price range of 200 000$+ they will have to offer DOHC..or something totally different with ohv .Like it or not small block doesn't have anywhere near the image of the engine like the uberrev,small displacement engines from competition .

Not to mention GM has been experimeting with v8+ size ohc engine in cars (concepts) for couple of decades.

There was v12 sohc from sixties

then

v12 from 1989 concept cadillac solitaire

V12 from cien

Of course there are V8 DOHC too in this mix. (northstar, LT-5, almost finished ultra V8). In this high price range which i just mentioned (200 000+$),advantages likes price of the engine, weight of the engine, fuel consumption...isn't soo much important .O.K weight is...and image...

But you can use expensive but light materials to get weight of the car down (and we are not talking here about big differences..what 10-20 kg in engine weight between LS3 and other more expensive v8).Size ..well i don't have dimensions of Mclaren's or italia's engine but i think GM could make something similar in size with their DOHC v8 if they would want to. Fuel consumption..c'mon we are talking here about 150-200 000+ cars.

But...if GM doesn't develope a car in that high price range i don't think they will ever offer or develope any v8 dohc for their lower priced cars..for them (and not just for them) it isn't worth it. But who knows.

[Drew Dowdell]

I"m not against GM building a DOHC V8... I'm against the unwarranted slander against excellent pushrod V8s.

For Cadillac's flagship, they should fit the new small block with DOHC heads if they want to go the DOHC route.... but I'm willing to wait and see what the new small block is capable of first.

[David]

I did read the rest, SOHC is worse than DOHC but no one really makes them any more either. But either way, OHC is better than pushrod, the example of the Crown Vic is because the engine was left the same basically form the early 90s. Comparing a bad SOHC V8 to the best pushrod on the market isn't really making any sense. That is like comparing the GM 3900 V6 to the Nissan GT-R V6.

It is perfectly alright for you to have that opinion. However, to sway anyone you'll need to explain how it is better. And, you'll need to articulate it better than "everyone is using it, therefore it must better" or simply declare that it is so -- that won't do anything but make your case sound kinda silly.

You'll notice that I do not simply say that Pushrod engines are more fuel efficient. I explain why are. I don't simply say that they are lighter and smaller, I show you the weights and the photos. I don't simply make a declaration, I support my positions with facts. You are free to challenge my reasonings or facts.

Let's start with one advantage of the DOHC setup -- any one -- and why you feel that it is important. Do that and I am sure everyone can have a meaningful discussion.

Only Advantage I can think of in regards to a DOHC v12 engine is the Italians use them in their 1% crowd auto's to save space and due to over all weight issues. Yet I am not impressed with these High revving High Horsepower and Little bit of Torque Engines.

DOHC reminds me of being the worlds biggest Body Builder with the littlest pecker and not able to really populate the world with Quality people.

[dado]

I did read the rest, SOHC is worse than DOHC but no one really makes them any more either. But either way, OHC is better than pushrod, the example of the Crown Vic is because the engine was left the same basically form the early 90s. Comparing a bad SOHC V8 to the best pushrod on the market isn't really making any sense. That is like comparing the GM 3900 V6 to the Nissan GT-R V6.

Well i can see DOHC V8 having better image...but ..what else?

What is there i can use in real live that DOHC v8 does better than OHV v8?

Is coyote v8 better than LS3?

Yes, best DOHC v8 engine is maybe better than best V8 OHv (but i'm still interested to know which are criterias) but how much does best DOHC v8 cost? Does GM has car in which they could put that engine and price it accordingly?

Also,just to see which criteria do you consider important (i don't mean to be offensive just curious) here is a list of some DOHC engines..which one do you think is(just the engine not the car) better? And why?

5.0 l v8 TT from koenigsegg agera

4.5 l v8 from Ferrari italia 458

M838 TT from Mclaren

6.5 l v12 (L539) from Lamborghini aventador

Synergy V8

AMG M159

AMG M157

Edited September 28, 2012 by dado

[David]

I did read the rest, SOHC is worse than DOHC but no one really makes them any more either. But either way, OHC is better than pushrod, the example of the Crown Vic is because the engine was left the same basically form the early 90s. Comparing a bad SOHC V8 to the best pushrod on the market isn't really making any sense. That is like comparing the GM 3900 V6 to the Nissan GT-R V6.

Well i can see DOHC V8 having better image...but ..what else?

What is there i can use in real live that DOHC v8 does better than OHV v8?

Is coyote v8 better than LS3?

Yes, best DOHC v8 engine is maybe better than best V8 OHv (but i'm still interested to know which are criterias) but how much does best DOHC v8 cost? Does GM has car in which they could put that engine and price it accordingly?

Also,just to see which criteria do you consider important (i don't mean to be offensive just curious) here is a list of some DOHC engines..which one do you think is(just the engine not the car) better? And why?

5.0 l v8 TT from koenigsegg agera

4.5 l v8 from Ferrari italia 458

M838 TT from Mclaren

6.5 l v12 (L539) from Lamborghini aventador

Synergy V8

AMG M159

AMG M157

Did you not want to state why you think these DOHC engines are better than Pushrod? I do not see any of them being better, unless Google is not showing me the right info, I do not see any of them with better HP/Torque ratio or fuel consumption than what is already being attained out of a Pushrod engine. In most cases, the Pushrod beats these engines.

[dado]

Did you not want to state why you think these DOHC engines are better than Pushrod? I do not see any of them being better, unless Google is not showing me the right info, I do not see any of them with better HP/Torque ratio or fuel consumption than what is already being attained out of a Pushrod engine. In most cases, the Pushrod beats these engines.

I want to see criteria which smk4565 use to determine which engine is better? Fuel consumption doesn't depend only on engine but also on car, transmission etc. Specific fuel consumption is one of the criteria which is in relation to engine only. Just like Weight of the engine/ Hp of the engine. Or physical size of the engine. All this (and much more) can be used as criteria (by individual) to determine why is one engine better than the other. I don't have that much (and more) information to determine which engine is "better". i don't considere type of valvetrain to be criteria..but i know some people who does.

Edited September 28, 2012 by dado

[dwightlooi]

Did you not want to state why you think these DOHC engines are better than Pushrod? I do not see any of them being better, unless Google is not showing me the right info, I do not see any of them with better HP/Torque ratio or fuel consumption than what is already being attained out of a Pushrod engine. In most cases, the Pushrod beats these engines.

I want to see criteria which smk4565 use to determine which engine is better? Fuel consumption doesn't depend only on engine but also on car, transmission etc. Specific fuel consumption is one of the criteria which is in relation to engine only. Just like Weight of the engine/ Hp of the engine. Or physical size of the engine. All this (and much more) can be used as criteria (by individual) to determine why is one engine better than the other. I don't have that much (and more) information to determine which engine is "better". i don't considere type of valvetrain to be criteria..but i know some people who does.

What I try to do when making fuel economy comparisons in this regard is to compare two cars of similar horsepower, weight and transmission type. Afterall, we are comparing the merits of engine layouts here not chassis, aerodynamics and/or transmission technology.

I cited the BMW M3, Camaro SS and the C63 AMG, not because I like these cars or because they sell into the same market segment (they don't) but because they are relatively close in weight and engine output. Both the M3 and the SS can also be had with 6-spd Manual Transmissions which helps with comparing apples to apples. That all three engines lack diret injection or VVL also helps equalize the technological field. The C63 actually has the advantage of a 7-speed auto (but it loses the mpg game anyway).

In anycase, the Pushrod LS3 is the clear Fuel Economy winner here and is midpack on power while being the lightest and most compact engine amongst the trio.

BMW M3 -- 4.0 DOHC V8 (445lbs) engine -- 3705 lbs veh wt -- 414 hp / 295 lb-ft -- 14 (city) / 20 (hwy) EPA MPG

Chevy Camaro SS -- 6.2 Pushrod V8 (403 lbs) engine -- 3859 lbs veh wt -- 426 hp / 420 lb-ft -- 16 (city) / 24 (hwy) EPA MPG

C63 AMG -- 6.2 DOHC V8 (438 lbs) engine -- 451 hp / 443 lb-ft -- 12 (city) / 19 (hwy) EPA MPG

You cannot make a case for DOHC being more efficient or providing better performance amongst these three cars.

[Drew Dowdell]

If you give the same amount of engine room to Chevy as Mercedes gets to put their 6.2 in, then Chevy will just fill it with silly things like extra displacement. If you're looking to fill a fixed space with as much power as possible, pushrod is the way to go.

I'd bet the GM 7.0 would fit in the same engine bay as the Benz 6.2 and still equal or beat the Benz fuel economy.

[dwightlooi]

The 7.0 (LS7) fit in exactly the same space as the 6.2 (LS3) or the 5.3 (LS4) if you disregard external factors like the placement of the alternator and AC compressor. The blocks' exterior dimensions are the same. The smaller displacement engines simply have more metal in the cylinder walls.

The 7.0 is really not bad from a fuel economy stand point. At 505 hp / 470 lb-ft, the LS7 powered Corvette Z06 nonetheless turns in 15 (city) / 24 (hwy) mpg. That's 1~2 points down from the 6.2 powered run-of-the-mill Corvette, but not bad at all in the company of 500+ hp supercars. The 7.0 is also the highest reving production smallblock with a 7000 rpm rev limit and a 6300 rpm power peak. And, that's without variable timing, cylinder deactivation or direct injection -- features we can confirm will be in the Gen V V8s.

The Mercedes M156 DOHC 6.2 V8 in the E63 made 518 hp / 465 lb-ft and turned in 13 (city) / 20 (hwy) EPA MPG. Although the MPG comparison is hardly fair given that the E63 is a 1000 lbs heavier.

Edited September 28, 2012 by dwightlooi

[smk4565]

I did read the rest, SOHC is worse than DOHC but no one really makes them any more either. But either way, OHC is better than pushrod, the example of the Crown Vic is because the engine was left the same basically form the early 90s. Comparing a bad SOHC V8 to the best pushrod on the market isn't really making any sense. That is like comparing the GM 3900 V6 to the Nissan GT-R V6.

Well i can see DOHC V8 having better image...but ..what else?

What is there i can use in real live that DOHC v8 does better than OHV v8?

Is coyote v8 better than LS3?

Yes, best DOHC v8 engine is maybe better than best V8 OHv (but i'm still interested to know which are criterias) but how much does best DOHC v8 cost? Does GM has car in which they could put that engine and price it accordingly?

Also,just to see which criteria do you consider important (i don't mean to be offensive just curious) here is a list of some DOHC engines..which one do you think is(just the engine not the car) better? And why?

5.0 l v8 TT from koenigsegg agera

4.5 l v8 from Ferrari italia 458

M838 TT from Mclaren

6.5 l v12 (L539) from Lamborghini aventador

Synergy V8

AMG M159

AMG M157

Koenigsegg has the best engine, it makes 1,000 hp end of story.

The McLaren V8 is impressive for the amount of power it makes from a small displacement, but the AMG M157 wins there. The AMG engine has almost as much horsepower but way more torque and is more efficient. The Ferrari Italia V8 sounds good, but I'd probably rather have the McLaren or Mercedes V8 instead.

[smk4565]

The Mercedes M156 DOHC 6.2 V8 in the E63 made 518 hp / 465 lb-ft and turned in 13 (city) / 20 (hwy) EPA MPG. Although the MPG comparison is hardly fair given that the E63 is a 1000 lbs heavier.

And that engine is gone, the replacement gets up to 563 hp and 664 lb-ft and 15/23 mpg in the S63, slightly less power but 1 mpg more in the E63. The E63 gets 16/24 mpg now. The CTS-V gets 12/18 mpg with automatic and weighs 174 lbs more than the E63, so not really seeing the weight and fuel economy savings of the pushrod there.

The sad thing is the CTS-V is the only GM sedan available with a V8 anymore and Ford doesn't have any. The V8 sedan is dying, outside of Mercedes where it seems to be alive and well. Even BMW is pushing the straight six all the up to $100k cars.

[Drew Dowdell]

Well then it's probably a good thing GM canceled the UV8, they can be a leader instead of a follower.

[dado]

Koenigsegg has the best engine, it makes 1,000 hp end of story.

The McLaren V8 is impressive for the amount of power it makes from a small displacement, but the AMG M157 wins there. The AMG engine has almost as much horsepower but way more torque and is more efficient. The Ferrari Italia V8 sounds good, but I'd probably rather have the McLaren or Mercedes V8 instead.

So your criteria is power and torque.Am i right? To you by default most powerful engine wins (than the engine from SSC ultimate Aero should be better than all of this engine) ? Or is HP per liter also calculated here?

Now LS9 has 638 hp and 820 Nm of torque.That is 103,5 hp/l

Mclaren 838 has 617 hp( that is 162 hp/l) and 600 Nm of torque

M157 from Mercedes -AMG makes 571 (103,8 hp/l) hp and torque of 900 Nm.

Now according to yours criterias LS9 engine is better than M838TT (2 wins) and on pair with M157(LS9 has higher HP raiting but lower torque and preety much same Hp/l rating)?

Am i getting this right?

[Drew Dowdell]

numbers and facts don't actually matter to SMK, what is best is whatever SMK says is best.

[Guest smk4565]

NVM and sound matter as much as the power numbers. I don't worry too much about fuel economy but the higher the better. I wouldn't buy a car based on the mpg numbers though.

To use a football analogy, the LS9 is like Matthew Stafford. Puts up big numbers and flashy stats, but at the end of the day isn't Tom Brady or Peyton Manning (before the injury). Stafford can throw for more yards than Brady, doesn't mean he is a better QB.

When I bought my car the final 2 was Aurora 4.0 or Grand Prix GTP with the supercharged 3800, and the Grand Prix had more power and acceleration, but the Aurora killed it on NVM and how the engine sounded. Not to mention the interior is better.

[dwightlooi]

And that engine is gone, the replacement gets up to 563 hp and 664 lb-ft and 15/23 mpg in the S63, slightly less power but 1 mpg more in the E63. The E63 gets 16/24 mpg now. The CTS-V gets 12/18 mpg with automatic and weighs 174 lbs more than the E63, so not really seeing the weight and fuel economy savings of the pushrod there.

The sad thing is the CTS-V is the only GM sedan available with a V8 anymore and Ford doesn't have any. The V8 sedan is dying, outside of Mercedes where it seems to be alive and well. Even BMW is pushing the straight six all the up to $100k cars.

Again, you refuse to compare apples to apples. The whole purpose of this thread was the comparison of Pushrod vs DOHC, yet you bring a Bi-turbo, Dual VVT, direct injected, 7-speed Dual Clutch equipped, M157 into comparison with a port injected, Supercharged (which costs additional consumption to drive), LSA engine with a 6-speed torque converter automatic. How is that supposed to "show" that DOHC is more efficient? It doesn't.

The fact is that, in every instance where two engines of comparable power output and features (VVT, Cylinder Deactivation, Direct Injection, materials, etc) are compared. The Pushrod configuration turns out to the the more efficient design -- in terms of fuel economy, weight, size or cost. What will be a valid comparison will the between the Direct Injected 5.5L M152 engine in the SLK55 AMG and the upcoming Gen V pushrod V8 in the C7 Corvette. That however will have to wait till 2013.

The fundamentals do not change though and the advantages of the Pushrod design in terms of size, weight, frictional efficiency and cost shall always remain when compared to DOHC designs.

[smk4565]

Maybe GM should spend some money on a new transmission then. And use bi-turbo VVT, DI, etc. No one is telling GM that they can't, shell out the money and build a new engine with all that stuff on it.

We can compare the Bentley Mulsanne 6.75 liter bi-turbo pushrod V8 with the S63 AMG 5.5 liter bi-turbo DOHC V8.

Bentley makes 505 hp, and 752 lb-ft put through and 8-speed transmission and gets 11/18 mpg.

S63 AMG makes 564 hp and 664 lb-ft sent through a 7-speed transmission and gets 15/23 mpg.

Both are similar in weight and the Bentley has an extra gear which should offset the weight advantage the S63 has.

Perhaps the closest comparison is the Genesis 5.0 and the 300C because both have VVT. The Genesis is rated at 17/26, the 300C at 16/25 mpg even with cylinder deactivation. But again the Genesis has a better transmission, and the Hyundai 5.0 makes 66 more hp than the Hemi.

[David]

Pushrod Versus OHC/DOHC - Winner Pushrod!

Now why do I state the above? I base this on spending half a day at the store locally that sells this new amazing v4 engine and a technical write up in the October 2012 Car & Driver Page 28 Story titled:

"Pushrods in Perpetuity - Technology in use since 1886 is still kicking."

Since the magazine does not seem to have this great write up on their web site and I do not wish to get Cheers and Gears in trouble, I will only quote sections of this article,

In the second paragraph after talking about all the trash talk blame the pushrod v engines get as the favorite fall guy for OHC/DOHC engine makers to use when those engines fail to out perform the OHC/DOHC engines they ask a very important question.

Quote: "How can pushrods persist when dual overhead cams and multivalve combustion chanbers offer so many compelling advantages - better breathing, higher efficiency, and lower emissions to name three?"

The answer seems to be from Motus Motorcycles and their new MST Sport Touring Bike!

http://www.motusmoto...s.com/kmv4.html

This new American Motocycle Startup built from scratch a New Pushrod V4 Engine that is already being used in a VW based Dune Buggy as well as their own line of hot American Made Motocycles. The company hired Katech to create a Fuel efficient, powerful small foot print light weight engine and Katech drew upon their years of experiance in powering corvettes to six class victories at Le Mans. According to the web site and the Car and Drive story, Katech sat down and reviewed old and new technologies using the most efficient parts from what the world has engineered to create a 1.6 liter Motus Baby Block V4. This intriging water cooled 90 degree aluminum engine with cast iron liners and billet crankshaft yields a 345-90-195-90 degree firing intervals.

Katech tried the following and dumped them due to the added friction and weight gained nothing. sump mounted balance shafts, direct injection with electronic controls and throttle operation and Motus did not see any payoff, do DI was dumped. There were many things tried which failed and in the end Katech and Motus tapped the wealth of small block Chevy v8 knowledge to produce a valvetrain consisting of one block mounted camshaft opening two valves per cylinder through hydraulic lifters, pushrods and rocker arms. Reinventing the combustion chamver and valvtrain seemed a waste of time when a low friction, efficient solution was already in front of them.

The result is a 165HP 100 cubic inch Baby Block 130lb V4 that revs to 8000rpm. This engine has a 11.5 to 1 compression ratio and runs on 87 octane. This engine allows Motus to undercut competitors by 100 to 150lbs. It is more compact and easier to work on and its center of gravity is lower than that of competing OHC/DOHC engines. Motus also has a hotter 185hp version for the MST-R bike. Credit for creating a 2nd motor cycle company that falls between the archaic Harley Davidson and the tech compulsive imports.

The Dune Buggy seems to get even more power and with taking up 1/3 less space than straight 4 bangers it would appear that car companies need to revisit the benefits and efficient nature of a pushrod v engine.

http://www.motusmoto....com/index.html

End result is after spending a day reviewing this information and making a trip down to Hinshaws Motorcycle Store in Auburn washington this bike rocks, is extremely compact and is nothing short of but amazing.

Pushrod Wins again!!!

Your Thoughts????

[dado]

Pushrod Versus OHC/DOHC - Winner Pushrod!

Now why do I state the above? I base this on spending half a day at the store locally that sells this new amazing v4 engine and a technical write up in the October 2012 Car & Driver Page 28 Story titled:

"Pushrods in Perpetuity - Technology in use since 1886 is still kicking."

Since the magazine does not seem to have this great write up on their web site and I do not wish to get Cheers and Gears in trouble, I will only quote sections of this article,

In the second paragraph after talking about all the trash talk blame the pushrod v engines get as the favorite fall guy for OHC/DOHC engine makers to use when those engines fail to out perform the OHC/DOHC engines they ask a very important question.

Quote: "How can pushrods persist when dual overhead cams and multivalve combustion chanbers offer so many compelling advantages - better breathing, higher efficiency, and lower emissions to name three?"

The answer seems to be from Motus Motorcycles and their new MST Sport Touring Bike!

http://www.motusmoto...s.com/kmv4.html

This new American Motocycle Startup built from scratch a New Pushrod V4 Engine that is already being used in a VW based Dune Buggy as well as their own line of hot American Made Motocycles. The company hired Katech to create a Fuel efficient, powerful small foot print light weight engine and Katech drew upon their years of experiance in powering corvettes to six class victories at Le Mans. According to the web site and the Car and Drive story, Katech sat down and reviewed old and new technologies using the most efficient parts from what the world has engineered to create a 1.6 liter Motus Baby Block V4. This intriging water cooled 90 degree aluminum engine with cast iron liners and billet crankshaft yields a 345-90-195-90 degree firing intervals.

Katech tried the following and dumped them due to the added friction and weight gained nothing. sump mounted balance shafts, direct injection with electronic controls and throttle operation and Motus did not see any payoff, do DI was dumped. There were many things tried which failed and in the end Katech and Motus tapped the wealth of small block Chevy v8 knowledge to produce a valvetrain consisting of one block mounted camshaft opening two valves per cylinder through hydraulic lifters, pushrods and rocker arms. Reinventing the combustion chamver and valvtrain seemed a waste of time when a low friction, efficient solution was already in front of them.

The result is a 165HP 100 cubic inch Baby Block 130lb V4 that revs to 8000rpm. This engine has a 11.5 to 1 compression ratio and runs on 87 octane. This engine allows Motus to undercut competitors by 100 to 150lbs. It is more compact and easier to work on and its center of gravity is lower than that of competing OHC/DOHC engines. Motus also has a hotter 185hp version for the MST-R bike. Credit for creating a 2nd motor cycle company that falls between the archaic Harley Davidson and the tech compulsive imports.

The Dune Buggy seems to get even more power and with taking up 1/3 less space than straight 4 bangers it would appear that car companies need to revisit the benefits and efficient nature of a pushrod v engine.

http://www.motusmoto....com/index.html

End result is after spending a day reviewing this information and making a trip down to Hinshaws Motorcycle Store in Auburn washington this bike rocks, is extremely compact and is nothing short of but amazing.

Pushrod Wins again!!!

Your Thoughts????

Pushrod Versus OHC/DOHC - Winner Pushrod!

Now why do I state the above? I base this on spending half a day at the store locally that sells this new amazing v4 engine and a technical write up in the October 2012 Car & Driver Page 28 Story titled:

"Pushrods in Perpetuity - Technology in use since 1886 is still kicking."

Since the magazine does not seem to have this great write up on their web site and I do not wish to get Cheers and Gears in trouble, I will only quote sections of this article,

In the second paragraph after talking about all the trash talk blame the pushrod v engines get as the favorite fall guy for OHC/DOHC engine makers to use when those engines fail to out perform the OHC/DOHC engines they ask a very important question.

Quote: "How can pushrods persist when dual overhead cams and multivalve combustion chanbers offer so many compelling advantages - better breathing, higher efficiency, and lower emissions to name three?"

The answer seems to be from Motus Motorcycles and their new MST Sport Touring Bike!

http://www.motusmoto...s.com/kmv4.html

This new American Motocycle Startup built from scratch a New Pushrod V4 Engine that is already being used in a VW based Dune Buggy as well as their own line of hot American Made Motocycles. The company hired Katech to create a Fuel efficient, powerful small foot print light weight engine and Katech drew upon their years of experiance in powering corvettes to six class victories at Le Mans. According to the web site and the Car and Drive story, Katech sat down and reviewed old and new technologies using the most efficient parts from what the world has engineered to create a 1.6 liter Motus Baby Block V4. This intriging water cooled 90 degree aluminum engine with cast iron liners and billet crankshaft yields a 345-90-195-90 degree firing intervals.

Katech tried the following and dumped them due to the added friction and weight gained nothing. sump mounted balance shafts, direct injection with electronic controls and throttle operation and Motus did not see any payoff, do DI was dumped. There were many things tried which failed and in the end Katech and Motus tapped the wealth of small block Chevy v8 knowledge to produce a valvetrain consisting of one block mounted camshaft opening two valves per cylinder through hydraulic lifters, pushrods and rocker arms. Reinventing the combustion chamver and valvtrain seemed a waste of time when a low friction, efficient solution was already in front of them.

The result is a 165HP 100 cubic inch Baby Block 130lb V4 that revs to 8000rpm. This engine has a 11.5 to 1 compression ratio and runs on 87 octane. This engine allows Motus to undercut competitors by 100 to 150lbs. It is more compact and easier to work on and its center of gravity is lower than that of competing OHC/DOHC engines. Motus also has a hotter 185hp version for the MST-R bike. Credit for creating a 2nd motor cycle company that falls between the archaic Harley Davidson and the tech compulsive imports.

The Dune Buggy seems to get even more power and with taking up 1/3 less space than straight 4 bangers it would appear that car companies need to revisit the benefits and efficient nature of a pushrod v engine.

http://www.motusmoto....com/index.html

End result is after spending a day reviewing this information and making a trip down to Hinshaws Motorcycle Store in Auburn washington this bike rocks, is extremely compact and is nothing short of but amazing.

Pushrod Wins again!!!

Your Thoughts????

Actually Katech sells even more powerful versions of this engine

One with 280 hp and one with 426 hp(this one seems to have direct injection)

Katech V4

[riviera74]

Well then it's probably a good thing GM canceled the UV8, they can be a leader instead of a follower.

GM can have Cadillac get away with v6 engines in the ATS, CTS, and the XTS. But once above that, the Ultra V8 becomes necessary. While the smallblock is the best v8 GM has ever built (and the v6 engines should be derived from that engine, not the European I4 DOHCs), the perception is that DOHC v8 engines are better even if that perception belongs in the 80s and is no longer true. There are still those who want DOHC even if the engines themselves are not better. That is why pushrod I4 and V6 engines are virtually all gone as of 2012.

[dwightlooi]

GM can have Cadillac get away with v6 engines in the ATS, CTS, and the XTS. But once above that, the Ultra V8 becomes necessary. While the smallblock is the best v8 GM has ever built (and the v6 engines should be derived from that engine, not the European I4 DOHCs), the perception is that DOHC v8 engines are better even if that perception belongs in the 80s and is no longer true. There are still those who want DOHC even if the engines themselves are not better. That is why pushrod I4 and V6 engines are virtually all gone as of 2012.

Pushrod I4s never made sense -- there is no packaging or efficiency advantage over an SOHC I4. The reasons for DOHC small displacement engines have been more than adequately covered in the thread.

As far a the Ultra V8, I do not believe it is necessary or a good investment. At the end of the day luxury buyers are not acronym buyers by and large. If you have the right output, the right refinement and right MPG numbers, it won't matter if you have a pushrod engine or 2-stroke engine with no valves. The direct injected Gen V in a 6.2 liter trim delivering between 450~500 hp will be a more than attractive engine for Caddy's V8 needs if it gets MPG numbers in the 15~17/24~28 range in a 4000 lbs car.

If GM wants to build an exclusive, premium engine for Cadillac, the money is better spent on an over-the-top 7.2 liter V12 based doubling the LFX 3.6 V6. Such an engine will deliver about 640hp / 550 lb-ft in normally aspirated trim, rev to 7000 rpm and if turbocharged for special applications yield a 1000hp powerplant. Development cost will be relatively low given that it is not a ground up architecture -- the valves, lash adjusters, pistons, sings, bearings, rods, combustion chamber modelling, injectors, cam phasers and many other parts will come directly from the LFX 3.6's parts bin. Only the block, crank and camshafts will be unique. And, given that the bore size, spacing and bank angle are identical to the 3.6 it can be made on the same assembly line and with the same tooling.

[David]

GM can have Cadillac get away with v6 engines in the ATS, CTS, and the XTS. But once above that, the Ultra V8 becomes necessary. While the smallblock is the best v8 GM has ever built (and the v6 engines should be derived from that engine, not the European I4 DOHCs), the perception is that DOHC v8 engines are better even if that perception belongs in the 80s and is no longer true. There are still those who want DOHC even if the engines themselves are not better. That is why pushrod I4 and V6 engines are virtually all gone as of 2012.

Pushrod I4s never made sense -- there is no packaging or efficiency advantage over an SOHC I4. The reasons for DOHC small displacement engines have been more than adequately covered in the thread.

As far a the Ultra V8, I do not believe it is necessary or a good investment. At the end of the day luxury buyers are not acronym buyers by and large. If you have the right output, the right refinement and right MPG numbers, it won't matter if you have a pushrod engine or 2-stroke engine with no valves. The direct injected Gen V in a 6.2 liter trim delivering between 450~500 hp will be a more than attractive engine for Caddy's V8 needs if it gets MPG numbers in the 15~17/24~28 range in a 4000 lbs car.

If GM wants to build an exclusive, premium engine for Cadillac, the money is better spent on an over-the-top 7.2 liter V12 based doubling the LFX 3.6 V6. Such an engine will deliver about 640hp / 550 lb-ft in normally aspirated trim, rev to 7000 rpm and if turbocharged for special applications yield a 1000hp powerplant. Development cost will be relatively low given that it is not a ground up architecture -- the valves, lash adjusters, pistons, sings, bearings, rods, combustion chamber modelling, injectors, cam phasers and many other parts will come directly from the LFX 3.6's parts bin. Only the block, crank and camshafts will be unique. And, given that the bore size, spacing and bank angle are identical to the 3.6 it can be made on the same assembly line and with the same tooling.

I totally disagree with your first statement that Pushrod I4s never made sense -- there is no packaging or efficiency advantage over an SOHC I4. The reasons for DOHC small displacement engines have been more than adequately covered in the thread. While this thread started off with why GM should not build a DOHC V8, I feel that there is more than enough justification to prove that DOHC is OVER RATED! Katech has proven that you can get very powerful efficient engines without all the extra complexity of the DOHC small displacement and loss of torque.

To me, the research and history has shown that while marketing did a great job to convince people that they needed to move to DOHC small engines it is not due to better efficiency or gas mileage improvements.Change for change sake does not always make things better.

[Intrepidation]

You know what's even less complicated? An electric motor.

[ocnblu]

bleh

[David]

You know what's even less complicated? An electric motor.

No No No, Electric cars are a commuter inner city auto only. They cannot work in the real world of the suburbans or as a travel trip car.

Pushrod V4, 6 & 8 have us well covered with some amazing advances with our computer capability that will allow us to have some amazing engines.

[dwightlooi]

I totally disagree with your first statement that Pushrod I4s never made sense -- there is no packaging or efficiency advantage over an SOHC I4. The reasons for DOHC small displacement engines have been more than adequately covered in the thread. While this thread started off with why GM should not build a DOHC V8, I feel that there is more than enough justification to prove that DOHC is OVER RATED! Katech has proven that you can get very powerful efficient engines without all the extra complexity of the DOHC small displacement and loss of torque.

To me, the research and history has shown that while marketing did a great job to convince people that they needed to move to DOHC small engines it is not due to better efficiency or gas mileage improvements.Change for change sake does not always make things better.

Ok, let me try to explain it a bit better...

(1) A SOHC I4 with 2-valves per cylinder has all the frictional benefits over a Pushrod I4 with 2-valves per cylinders. In fact, it has two additional benefits -- the valves can more easily be made opposed as opposed to side-by-side and the absence of pushrods makes the sprung mass lower allowing slightly higher revs although this is probably not useful.

(2) The SOHC head is taller than the pushrod head. However, it is not any wider unlike a DOHC head. The additional height is traditionally handled by slanting the I4 to one side in RWD applications or reclining it in FWD applications. This allows the engine to be no taller than a Pushrod I4 while the addition in width is also essentially zero because the exhaust manifold would have projected sideways by approximately the same amount had the engine been upright anyway.

To put some numbers into the discussion, if GM ditched the 1.4 litter turbocharged DOHC-16v Inline-4 for a 2.3 liter SOHC-6v line-3 running on an Atkinson intake cam, the Cruze would have have superior MPG numbers while delivering approximately the same output of 140 hp. Specific output should not matter. That 2.3 liter engine would only make 140 hp should not be embarrassing, if one understands that it weighs about the same as the 1.4 turbo (with its forced induction hardware), while delivering better fuel economy and a similar output.

[aldw]

What about using a gasoline fuel cell replacement for IC engines instead?

[David]

I totally disagree with your first statement that Pushrod I4s never made sense -- there is no packaging or efficiency advantage over an SOHC I4. The reasons for DOHC small displacement engines have been more than adequately covered in the thread. While this thread started off with why GM should not build a DOHC V8, I feel that there is more than enough justification to prove that DOHC is OVER RATED! Katech has proven that you can get very powerful efficient engines without all the extra complexity of the DOHC small displacement and loss of torque.

To me, the research and history has shown that while marketing did a great job to convince people that they needed to move to DOHC small engines it is not due to better efficiency or gas mileage improvements.Change for change sake does not always make things better.

Ok, let me try to explain it a bit better...

(1) A SOHC I4 with 2-valves per cylinder has all the frictional benefits over a Pushrod I4 with 2-valves per cylinders. In fact, it has two additional benefits -- the valves can more easily be made opposed as opposed to side-by-side and the absence of pushrods makes the sprung mass lower allowing slightly higher revs although this is probably not useful.

(2) The SOHC head is taller than the pushrod head. However, it is not any wider unlike a DOHC head. The additional height is traditionally handled by slanting the I4 to one side in RWD applications or reclining it in FWD applications. This allows the engine to be no taller than a Pushrod I4 while the addition in width is also essentially zero because the exhaust manifold would have projected sideways by approximately the same amount had the engine been upright anyway.

To put some numbers into the discussion, if GM ditched the 1.4 litter turbocharged DOHC-16v Inline-4 for a 2.3 liter SOHC-6v line-3 running on an Atkinson intake cam, the Cruze would have have superior MPG numbers while delivering approximately the same output of 140 hp. Specific output should not matter. That 2.3 liter engine would only make 140 hp should not be embarrassing, if one understands that it weighs about the same as the 1.4 turbo (with its forced induction hardware), while delivering better fuel economy and a similar output.

Have you checked out the Katech V4? This engine puts the SOHC or DOHC to shame in a very tiny package with awesome power outputs. I think this engine shows that you do not need the complexity of the SOHC or DOHC to get the Mileage or power out of an engine.

[David]

Due to rising demand, Katech designed and manufactured an innovative, highly efficient, high power density, compact and configurable V4 engine to power your auto-sport, aviation, marine, ATV and industrial applications.  The V4 draws on the legendary architecture of the Corvette LS series V8. The engine is very light and because of its’ compact design can be retro-fitted into almost any application.</p>

KV4 Street Specs

• Displacement: 1.6L (100 CID)
  
• Power: 160bhp @6,600 rpm
  
• Torque: 127 lb-ft @5800rpm
  
• Redline: 7,800 rpm
  
• Dry Weight: 140 lbs
  
• Induction: Naturally aspirated
  
• Intake System: Individual runner or plenum
  
• Oiling System: Wet Sump
  
• Fuel System: Port Fuel injection
  

KV4-R Motorsport Spec

• Displacement: 2.0L (122 CID)
  
• Power: 280bhp @9,500rpm
  
• Torque: 180 ft-lbs @7,200rpm
  
• Redline: 9,500rpm
  
• Dry Weight: 138 lbs
  
• Induction: Naturally Aspirated
  
• Intake System: Individual runner or plenum
  
• Oiling System: Wet sump/Dry sump
  
• Fuel System: Port fuel injection
  

KV4-RR Motorsport Spec

• Displacement: 2.4L (147 CID)
  
• Power: 462bhp @7,200rpm
  
• Torque: 360lb-ft @3800rpm
  
• Redline: 8,000
  
• Dry Weight: 162 lbs
  
• Induction: Forced Induction
  
• Intake System: Individual runner or plenum
  
• Oiling System: Dry sump
  
• Fuel System: Port fuel injection/ Direct injection
  

http://www.katecheng...tech-v4/</a><br />

This company rocks, the new KV4-RR is a freakin amazing engine and only 162lbs of weight. I see no reason why GM could not use this style of design for a V8.

[dwightlooi]

This company rocks, the new KV4-RR is a freakin amazing engine and only 162lbs of weight. I see no reason why GM could not use this style of design for a V8.

There is a difference between crate engines or race engines and production engines covered by a 5yr/100,000 mile warranty expected to endure the drudgery and neglect of mundane automobiles. Production also has to have a wide and tractable power band whereas motorsport engines only have to perform within a relatively 2000~3000 rpm range and it is the job of the racer to not allow rpms to fall out of the prescribed range.

The problem with reving any engine that high is that you end up using a lot of valve lift, duration and overlap to get the engine to breath with good volumetric efficiency high up. Cams like that generally don't idle well at 600 rpm, most do not idle at all that low. VVT mitigates that somewhat by allowing you to dial out the overlap but it still results in a rather soft lower rpm response. Besides, the high valve spring rates needed to prevent valve float at such rpms causes increased wear and reduced fuel economy.

With Pushrod engines in the 45~50 cu-in per cylinder bracket, we know that we can get to about 6600 rpm without using exotic materials. Throw in titanium valves and the like and you can push it to about 7000 with no reliability or durability issues. With DOHC 4-valve designs, you can get to about 8200 rpm using the "normal" stuff, about 9000 if you really try. For most production cars though, these are all more than adequate rpm capability.