dwightlooi

DOHC or SIBC for Corvette C7

244 posts in this topic

Which engine Corvette fans will like to see in the next corvette...

GM's next generation 5.5 liter Small Block push-rod V8 with DI and AFM,

or a 60 degree V8 derived from the high specific output 3.0 liter DOHC V6 engine?

corvettec7engine.gif

0

Share this post


Link to post
Share on other sites

There is no better V8 made than Chevy's smallblock. Best to keep it.

0

Share this post


Link to post
Share on other sites

The OHV motor simple. No OHC motor belongs in a Corvette.

Fail

ZR1enginearea12808.jpg

Edited by Satty
0

Share this post


Link to post
Share on other sites

And it's not offered anymore... replaced with a pushrod.

The fact remains that one of the fastest, most exclusive naturally-aspirated Corvettes in the history of the name was DOHC.

0

Share this post


Link to post
Share on other sites

Well it being 2009 and the C7 is still a few years off. Here is my out look.

The Vette is expected to be smaller and lighter. This is a known. Also known GM will have to go to smaller V8 engines for the trucks. That means the Vette will have to use these said engines or at least be baised on them. Also add in the fact the entire industry is not going OHC and DI.

A smaller displacment engine with VVT, DI and Turbo could deliver punch most engines in the past never could think of. The VVT give the low end torque and keeps it flat all the way up the RPM range.

Turbo's thrive on DI. GM and Fod have proven this already.

IF GM can get 290 HP out of 2.0 liters with 315 ft lbs and 325 HP out of a 2.8 V6 Imagine what they could do with a V8. The Leno Camaro also shows 3.6 DI Turbo can put out the same numbers as a LS engine.

So a small Turbo V8 DOHC I feel would keep the Vette up to date and give it a power plant GM could still use in other heavier vehicles. Cost is everything and the Vette will still be expected to share parts with other cars to live on and still pay the rent.

Also some still have to get over the illusion the present LS engine is a small block Chevy. Other than some odd bore center spacing and a lot of marketing the present engine has as much to do with the old one as the original Dodge Hemi has to do with todays Chrysler Hemi.

The fact is GM and Chrysler both did these engine to contain cost and save money they did not have. If GM has not has money issues they would have been gone long ago. The whole saving grace here is Ford Screwed up on the 4.6 mod engine and never really got it right. The new Eco engines they have are right this time and they will have a V8 to go with it. So GM and Chrysler both need to stop the BS on the 2 valve and move into the best DOHC V8 they can now before it is too late.

The original ZR1 was a over piced chunk of aluminum. They tried to do too much with too little elctonic technology. The computer technolgy just was not there to support what they really wanted to do. Today they can do it in a smaller packackage and make it work.

You can either just have another evolution and get left behind or create a new revolution like the original small block did in 1955. GM has the best powertrain engineers in the world and it is time they are left to do what they can with all the technology available not just what is on hand and affordable.

If you want a V8 in the future you will need to use all things available to keep it on the road unless the CAFE comes down. GM needs to get more from less and DOHC is the way to the future. Everyone else has figured it out.

Not the two companies that still use the 2 valve V8 are the ones that filed chaper 11.

I remember back in WW2 that some pilots fought to keep the piston engine too. At first it looked like the right idea till they did get the jets rigt.

Right or wrong like it or not this is just my 2 cents. Some of the best engines I have ever driven has more than two valves and no GM name on them. It is time the best in the world should again come from GM.

Edited by hyperv6
0

Share this post


Link to post
Share on other sites

The LS engines are still the best performing, most-efficient,most cost-effective V8s in the non-exotic realm today. I'd look for evolution, not revolution here. Not to mention the fact that they are far easier to package and maintain than DOHC V8s.

One point Hyper makes is certain, what goes into the trucks will find its way into the Vette in some form.

0

Share this post


Link to post
Share on other sites

The fact remains that one of the fastest, most exclusive naturally-aspirated Corvettes in the history of the name was DOHC.

"most exclusive" = "hardest to find parts for"

It was fastest for it's generation, but it's not the fastest of the naturally aspirated ones.....

0

Share this post


Link to post
Share on other sites

I thought we already did this thread. There are 2 members on here (smk4565 and hyperv6) that think the Corvette needs a bunch of un-necessary tech, expense, and weight, while everybody else loves the small block architecture.

Dwightlooi: Why have you started a new thread about the same topic? http://www.cheersandgears.com/index.php/topic/40869-which-engine-for-the-c7-corvette/

Edited by Chevy Nick
0

Share this post


Link to post
Share on other sites

I thought we already did this thread. There are 2 members on here (smk4565 and hyperv6) that think the Corvette needs a bunch of un-necessary tech, expense, and weight, while everybody else loves the small block architecture.

Dwightlooi: Why have you started a new thread about the same topic? http://www.cheersandgears.com/index.php/topic/40869-which-engine-for-the-c7-corvette/

If you put my post name with that one I may have to change my mind just because of that. LOL!

0

Share this post


Link to post
Share on other sites

The torque numbers answer this question.

That, along with the RPMs at which they're achieved.

Again, the C7 is going on a huge diet. Even if the current LS engines are used, if the Corvette slims down to the weights that Dwight is proposing, the performance gains will be significant. Just go with the SIBC and be done with it.

0

Share this post


Link to post
Share on other sites

"Also some still have to get over the illusion the present LS engine is a small block Chevy. Other than some odd bore center spacing and a lot of marketing the present engine has as much to do with the old one as the original Dodge Hemi has to do with todays Chrysler Hemi."

Excuse me? Let's get one thing straight. With the smallblock, the line of evolution has never stopped since 1955. Chrysler's "Hemi" descriptor, which I respect, has been on many different architectures... even a four cylinder, with many stops and starts since what, the early 50's?

I will take the straightforward, reliable, easy-to-modify pushrod V8 any time over a DOHC.

0

Share this post


Link to post
Share on other sites

The LS engines are still the best performing, most-efficient,most cost-effective V8s in the non-exotic realm today. I'd look for evolution, not revolution here. Not to mention the fact that they are far easier to package and maintain than DOHC V8s.

One point Hyper makes is certain, what goes into the trucks will find its way into the Vette in some form.

The truck key is the big one. the truck engine will have to get more MPG and better emissions. I get the feeling we will see more composites on the truck to cut weight but that is not going to be enough.

Just a gut feeling we will see a DI engine with less displacement in the truck and we will see a Turbo package option of some kind. The other factor is Cadillac will share in this engine too. GM will not do more than one V8 and it have to be adaptable from a Truck to a Vette and even the top line Cadillac. Unless they make some changes to the Alpha I expect a twin turbo V6 for the future Camaro.

As for Exotic DOHC is no longer Exotic. It has become the norm. It is what the buyers want and expect from other brands. If you want to win any over you have to give them what they want. The GM fans will buy it no matter what.

0

Share this post


Link to post
Share on other sites

"Give them what they want" <--- WTF? All other vehicles in the Corvette's class are looking at its four round taillights on the race track... we don't need to prove a THING.

0

Share this post


Link to post
Share on other sites

"Also some still have to get over the illusion the present LS engine is a small block Chevy. Other than some odd bore center spacing and a lot of marketing the present engine has as much to do with the old one as the original Dodge Hemi has to do with todays Chrysler Hemi."

Excuse me? Let's get one thing straight. With the smallblock, the line of evolution has never stopped since 1955. Chrysler's "Hemi" descriptor, which I respect, has been on many different architectures... even a four cylinder, with many stops and starts since what, the early 50's?

I will take the straightforward, reliable, easy-to-modify pushrod V8 any time over a DOHC.

The 1955 Small Block you speak of stopped many years ago. That engine shares nothing with todays engine. I would expect a fan of the present LS engine to give it more credit for being a all new modern 2 valve engine that relied on nothing of the original engine. The last LS engine I was in has nothing shared with anything on my last 1970 350 engines I had. To compare a original SBC and to a LS is selling the LS short.

The 2 valve LS is a great engine but GM kept it because at the time it was much cheaper to build. Less parts less cost more profit for a cash starved company. Also without VVT less low end torque with the 4 vlaves. Today the computers can handle it.

As for the Hemi... You know what I mean. Chrysler has tried to convince many this was the second coming of the 426 HEMI. It was all marketing. The new Hemi in fact shares more similarities with the LS engine than any other.

All I can say is I was able to spend time with John Lingenfelter several a few visits and just sit and talk to him. He by far was one of the best builders of the SBC, LT and LS engines there has been. At the time of his death he was well into the Ecotech and the DOHC V6. He was seeing numbers that as strong or stronger than some of his best LS engines. He was sitting on 2,000 HP with the DOHC V6 Turbo with not many aftermarket parts. None were avaiable and he often had to mod stock parts. In fact it was this car that took his life. If he had lived I could only imagine where this would have gone. He loved these kinds of challanges and was making great head way.

But I do have to admit his Twin Turbo LS Vette and LS Sonoma would even make a ZR1 blush.

On last thing to consider. If GM has had to use displacemnt on demand to improve fuel economy just as Chrysler. That should tell you smaller and more efficent is needed. Ford OHC engine have not needed it.

I guess it comes down not so much to what we want but GM needs to survive the regs for the long term future. The next engine needs to last more than 8 years and were all this is going.

0

Share this post


Link to post
Share on other sites

420 hp from a 4.0 liter is like an M3 engine, it would have to be really high revving. How did you come up with the gas mileage estimates and give the pushrod 2 more mpg than it gets now?

How about an apples to apples comparison. 6.2 liter pushrod with 420 hp like the Vette has now, or 6.2 liter DOHC V8 with 518 hp like the Mercedes E63 has. If you want power, DOHC makes more. If you want economy, use a Nissan GT-R type engine.

0

Share this post


Link to post
Share on other sites

You ignore my "line of evolution" caveat. And simplicity trumps complexity, even with computers.

0

Share this post


Link to post
Share on other sites

420 hp from a 4.0 liter is like an M3 engine, it would have to be really high revving. How did you come up with the gas mileage estimates and give the pushrod 2 more mpg than it gets now?

you don't think adding direct injection, an 8-speed DSG, and VVT would add a bit of fuel economy....

0

Share this post


Link to post
Share on other sites

You ignore my "line of evolution" caveat. And simplicity trumps complexity, even with computers.

Absolutely right, an unbroken lineage.

The original smallblock was such an amazing design that the basic architecture ran all the way from '55 to the nineties.

The LT1 and LT4 were a bridge to the truly all-new LS series, when even 1-8-4-3-6-5-7-2 no longer applied.

Despite the wholesale design differences, application and envelope of the LS series make them a direct descendent of the original

0

Share this post


Link to post
Share on other sites

Q&A

Q: Why did I start this thread instead of continuing a previous thread also on C7 engine options?

A: Because this is about which V8 for the C7 assuming we are set on a V8, that was about whether the Vette should get a V12.

Q: Why did I compare a 4.0 liter DOHC with a 5.5 Pushrod?

A: The idea is to get to ~420hp. Also, a 4.0 liter DOHC will weigh about the same and take up about as much space as a 5.5 Pushrod.

Q: Why a 60 deg DOHC V8?

A: Because the idea is to minimize R&D, as well as share most components and the manufacturing line with the existing 90hp/liter liter LF1 60 deg V6 (3.0 270hp). Besides, a more compact 60 degree V8 is required if the engine is to fit in the same width as a 5.5 liter pushrod V8. A 60 degree engine won't be even fire, but neither is a flat crank V8. In a sports car, that slightly off-beat pulse is perhaps even a plus. 60 deg V8s are not horrible or all that rare... the Taurus SHO 3.4 V8 and the Volvo 4.4 V8 are both 60 degree designs.

Q: Where did the fuel economy estimates come from?

A: The 5.5 pushrod's estimates come from assuming a slight improvement over the current 6.2 liter LS3 engine. This assumption is based on incorporation of an 8-speed dual clutch transmission, taller cruising gear ratio, higher compression, Direct Injection, Cylinder deactivation and a lower displacement. This accompanied by about 10% lower weight and slightly smaller size projected for the C7 led me to estimate a 1 mpg improvement in city driving and a 2 mpg improvement in highway cruising. I don't think they are unreasonable estimates. If anything they are a bit conservative.

Q: Why did I assign lower fuel economy numbers to the DOHC engine?

A: Because DOHC V8s of today have worse economy numbers than pushrod V8s today. The reasons are mainly that they have higher internal friction due to having twice as many valves & guides, four times as many cams and a much longer serpertine cam drive chain. In addition, because DOHC engines make a given horsepower with less displacement, less torque, but at higher revs, they also tend to be geared to keep revolutions higher. This often increases pumping losses more than the reduced displacement saves. For example... The 6.2 liter Camaro SS posts 16/25 with an automatic, the 6.3 liter C63 AMG posts 13/20 mpg, the 4.0 liter M3 posts 13/20mpg. The Camaro weighs 3859 lbs, the C63 logs 3924 lbs whereas the M3 tips scale at 3726 lbs.

Edited by dwightlooi
0

Share this post


Link to post
Share on other sites

Your content will need to be approved by a moderator

Guest
You are commenting as a guest. If you have an account, please sign in.
Reply to this topic...

×   You have pasted content with formatting.   Remove formatting

×   Your link has been automatically embedded.   Display as a link instead

Loading...