What costs more?

[rkmdogs]

O.K. bean-counters & you inside techies..... Let's play a hypothetical game. GM needs a new engine for a new mid-size car. What do we power it with? Decision must be based on engine build cost. Let's assume both engines would have the same displacement, and have to be a 90 degree V-configuration. What should we choose? A high tech V-6, but that has the component costs of a counterbalance shaft, to eliminate vibration, and the bearings for it to run in, and gears or a chain/belt to drive it. Or, A V-8, but that has 2 more pistons, connecting rods, and 4 more valves. But it doesn't need a balance shaft. Which would take more assembly time (labor) which has to figure into this cost equation? O.K., let's have some opinions, based on facts.

[razoredge]

Extra shaft and gear is more machine work than 2 extra rods and pistons, however V8 block - 2 more holes to line bore, heads - larger manifolds-2 more runners, crank - two more journals to machine, more camshaft, larger heads 4 more valves/2 chambers. So you tell me ? Myself with DOD in V8's Id like to see GM produce 2 smaller aluminum 8's say a 4 & 3.5 or less, something compact for the smaller cars. F1 is going to V8 now at very small displacement. Lots of power to be had in small bore short stroke V8 and not take up much more room than a I4 but do it so much better.

[capriceman]

V8 will have Low end torque which is good for acceleration. and the V8 is faster to build.

[Sixty8panther]

Like I keep saying: GM should make a modern day 215. A small aluminum V8 engine that would range from perhaps 2.9 to 3.5 liters. Small, cmopact and lightweight but with all the appeal of a SBC. Imagine an ALL V8 division from GM wiht a full size range of cars! Like Cadillac and Buick. Even a compact Skylark could have a 2.9 liter V8 standard. Add to that the fact that it could me mounted longetudinaly and transversely and you've got a winning combo! :metal:

[PontiacTechNJ]

until the silly catera , cadillac was all V8

[Teh Ricer Civic!]

a 2.0L V8 w/ DoD might be kinda cool... but then again with hp/L off a LS2 its only 133hp... and about 130torque. But then again.... at such a small size it could be built to easially revv, it would make enough torque throughout the powerband to still have reasonable power in the low end... but w/ a redline of 8000 or so it could plausibly make about 150hp. based on the LS7... 142hp. but then again i doubt this engine would get better mileage than an I4, and its only comparable to a current I4... maybe a 2.5L... about 166hp to LS2 standards... 2.8L V8... 186 (only slightly more than the Colorado 2.8 I4) how about a 3.0L V8 option as a very sporty engine... definately not mainstream in any way... give it a redline of 9000rpm... lets assume that at 8500rpm its still churning out meh.... 140 lb/torque.. thats about 225hp... kinda lethargic.... maybe with VVT and 3v and such it could make like 180 torque... 291hp... a 291hp 9000rpm V8 would be a very fun engine to drive. Maybe an RS option on a Camaro?

[rkmdogs]

All interesting wishes guys, but nobody put economics into the equation --- and that is what the bean-counters would do! I too, have very fond memories of the ol' 215cu.in.(3,5L), all-aluminum BOP engine of the early sixties that GM foolishly sold to B-L for the Rover. But you have to recall the reason that they did that. Besides money, it was a "dirty" engine that even Rover was never able to clean up enough to meet pollution standards until they got rid of the carburetor. And then there was the porosity issue of the castings----- but technical advances have solved both of these problems. I would love to see GM produce another all-aluminum 3.5L engine, maybe based on an LS2, but with some cam sophistication, maybe DOHC and VVT and DOD! But I don't think corporate would allow it in any-front drive platform, and we all know what's available NOW in RWD................... in an appropriate sized vehicle---- 0!!!!!!

[razoredge]

Gee, I thought I did a good job putting economics into the equation. There is no doubt the extra 2 holes in the V8 is far more than simply two more holes/4 more valves. Besides that I have 4 V6's here that have no balance shaft, not the best thing at idle but not an issue otherwise. Im not suggesting a new engine with no balance shaft. Only way to know which is best, cheapest, most profitable in the future is to watch what the Japs, Koreans, and Chinese do. All else will be just as you say "interesting wishes". :unsure:

[Teh Ricer Civic!]

Rotaries for all!! 6.0L 6 rotor Rotary truck engine!! 450lb torque @ 6000rpm!!! 685hp @ 9000!! :P that my friend is the engine of the future

[Eric Bryant]

A high tech V-6, but that has the component costs of a counterbalance shaft, to
eliminate vibration, and the bearings for it to run in, and gears or a chain/belt
to drive it.

Is an countershaft even effective at balancing out a 90-degree V6? It has a primary imbalance, not the secondary imbalance of a inline-4, and so I think it's a completely different situation.

Frankly, the cost difference between the two engines is basically a wash compared to the big question that's out there - which one can be run down an existing assembly line? If the V6 shares the same 4.4" bore spacing as the current GM V8s, then it'll be far less expensive to tool-up than a smaller V8 with a reduced bore spacing.

As to comments from others about the V8 having "more torque", keep in mind that when talking about engines of equal displacement, the one having fewer cylinders will typically have a higher peak torque at a lower RPM. Simply compare the average sportbike 1000cc V-twin to a 1000cc I4 and see what the powerbands look like. V8s are not inherently torquey; they're that way because they carry a lot of displacement.

[rkmdogs]

Is an countershaft even effective at balancing out a 90-degree V6? It has a primary imbalance, not the secondary imbalance of a inline-4, and so I think it's a completely different situation.

Frankly, the cost difference between the two engines is basically a wash compared to the big question that's out there - which one can be run down an existing assembly line? If the V6 shares the same 4.4" bore spacing as the current GM V8s, then it'll be far less expensive to tool-up than a smaller V8 with a reduced bore spacing.

As to comments from others about the V8 having "more torque", keep in mind that when talking about engines of equal displacement, the one having fewer cylinders will typically have a higher peak torque at a lower RPM. Simply compare the average sportbike 1000cc V-twin to a 1000cc I4 and see what the powerbands look like. V8s are not inherently torquey; they're that way because they carry a lot of displacement.

[post="48725"]<{POST_SNAPBACK}>[/post]

Eric,
The big ogre that I initially was thinking about was the friction horsepower.
For those of you who may never have read Internal Combustion Engines, which was a college text written by Prof. Edward F. Obert, he discusses this design
factor in the section called: performance factors.
He says that this is a very difficult to determine even with operating and test
conditions on a working engine.
He defines it as the power that is used to overcome the internal friction in the engine from the number and surface area of the moving parts, the induction of the
fuel-air charge and also the delivery of the exhaust gases.
The math equation he uses says that:
indicated horsepower equals brake or delivered horsepower plus frictional horsepower.
A measure of some of it is accomplished by turning an engine with an external
electric dynamometer(engine not firing), but other factors such as oil temp,
throttle setting, rpm must be fixed and noted. This factor then helps in determining
a given engines' mechanical efficiency.

Maybe I did not fix enough of the variables when I set up this question? Edited December 3, 2005 by rkmdogs

[Member55]

How about this, lets say that HF 3.6 V6 and LS1 V8 cost the same to build(I know the LS1 is not made anymore). IIRC the CTS's base MSRP with the 3.6 and automatic is about $35.8K. So, take the LS1 and put it in the CTS and charge only $1k extra(to cover for better brakes and suspension upgrade). Nobody could complain that the Cadillac is using "old tech" engine because it would be up to the customers to pick a DOHC engine with less power or an LS1 with more power for about the same money. Cadillac would own the market while still making the same profit per sold CTS as they already do. Selling 100K CTS's a year would be a piece of cake.

[razoredge]

You make a good point. Now the LS1 would have been last years CTS-V engine though wouldnt it ? 350hp ? No doubt in my mind they would see better profit on that LS1.

[Member55]

You make a good point. Now the LS1 would have been last years CTS-V engine though wouldnt it ? 350hp ?

No doubt in my mind they would see better profit on that LS1.

[post="52923"]<{POST_SNAPBACK}>[/post]

The LS6 was in the CTS-V.

[Carguy]

please----((PLEASE!!))----NO SMALL 3.5L or 215CI WEAK V8's!! That would be a HORRABLE IDEA to have a V8 thats NO BETTER then competiters V6's!! I agree with Member55 and have said like things before about useing a SB V8 in the REGULAR CTS. With the PROPER GEARING and DOD a OHV SB V8 powered CTS could get BETTER FUEL ECONOMY then a LOWER GEARED HIGHER REVVING LESS TORQUEY 3.6L DOHC V6 does! Why not KILL the competiters over just competing with them? Let CADDY be a ALL V8 brand AGAIN!!

[rkmdogs]

Hey guys, this is a tech section, not a sales and marketing forum! Get back to the basic question, which was about engineering and manufacturing cost!

[razoredge]

please----((PLEASE!!))----NO SMALL 3.5L or 215CI WEAK V8's!! That would be a HORRABLE IDEA to have a V8 thats NO BETTER then competiters V6's!! I agree with Member55 and have said like things before about useing a SB V8 in the REGULAR CTS. With the PROPER GEARING and DOD a OHV SB V8 powered CTS could get BETTER FUEL ECONOMY then a LOWER GEARED HIGHER REVVING LESS TORQUEY 3.6L DOHC V6 does! Why not KILL the competiters over just competing with them? Let CADDY be a ALL V8 brand AGAIN!!

[post="52945"]<{POST_SNAPBACK}>[/post]

We werent talking about Caddy to begin with just as an example in the last few posts. If there is balance complications with the V6 why not make the smaller displacement engines V8's. They only need to compete at that 3-4 litre level but be capable of running smoother and haveing DOD. Having claims of an all V8 brand and ideas of that sort will not sell cars and even has less novelity in these times.

A few of us have covered all the aspects of V6 vs V8, RKM, I guess your just going to have to break the suspence.

[Member55]

Hey guys, this is a tech section, not a sales and marketing forum!

Get back to the basic question, which was about engineering and manufacturing cost!

[post="52976"]<{POST_SNAPBACK}>[/post]

My post was about manufacturing cost.

[Carguy]

We werent talking about Caddy to begin with just as an example in the last few posts. If there is balance complications with the V6 why not make the smaller displacement engines V8's. They only need to compete at that 3-4 litre level but be capable of running smoother and haveing DOD. Having claims of an all V8 brand and ideas of that sort will not sell cars and even has less novelity in these times.

A few of us have covered all the aspects of V6 vs V8, RKM, I guess your just going to have to break the suspence.

[post="53044"]<{POST_SNAPBACK}>[/post]

A weak small V8 to compete with V6's is a ((BAD IDEA!!))---And Member55's point allong with mine are GOOD! How do these points NOT FIT IN THIS FORUM?? <_<

[Teh Ricer Civic!]

you could probably tune a V8 to get better gas mileage than a V6 at roughly the same power cant you?

[razoredge]

A weak small V8 to compete with V6's is a ((BAD IDEA!!))---And Member55's point allong with mine are GOOD! How do these points NOT FIT IN THIS FORUM?? <_<

[post="53079"]<{POST_SNAPBACK}>[/post]

and why ((DO YOU SAY THIS ??)) What is your POINT and MEANING behind USING ((WEAK)) in referenceing small displacement ENGINES for the SMALLER cars ((?????)) It is after all ABOUT ECONOMICS in MANUFACTURING as well as ECONOMICS for the CONSUMER.

And RAZOREDGE made the first GOOD evaluation of all the WORK and MATERIALS involved ALONG TIME AGO, and that apparently DID NOT FIT IN THIS TOPIC EITHER (((!!!!!!!)))

I'M NOT SURPRISED :unsure:

[Newbiewar]

a v8 has to be a larger displacement motor, because... there are more moving parts and generally heavier moving parts... so if a 2.0 v8 or a 2.0 4 I4 were to go head to head... the 4 banger should win due to its weight advantage... it should have less piston mass to move and less rockers lifters, etc to move....

[razoredge]

I dont know about that as far as it being carved in stone. Its all old news now and passed history and not really applicable to common road cars but the Italians have been building small displacement V8's and V12's for decades that matched and sometimes even beat engines half again larger. I feel the main point of interest lies in the fact that a V8 is such a smooth and uncomplicated engine at this time when everyone seems to be most interested in how smooth and quite a engine is. It would cost more to build small displacement V8's but the results may be beneficial.

[rkmdogs]

a v8 has to be a larger displacement motor, because... there are more moving parts and generally heavier moving parts...

so if a 2.0 v8 or a 2.0 4 I4 were to go head to head... the 4 banger should win due to its weight advantage... it should have less piston mass to move and less rockers lifters, etc to move....

[post="53856"]<{POST_SNAPBACK}>[/post]

Total crap! That's like saying what weighs more, a pound of lead or a pound of feathers! If the engines are of the same displacement, the mass of material CAN
be the same!
The question still comes back to internal friction. More pistons, rod, etc of V-8 are
offset by extra balancing components required in the V-6, if both engines are 90 vees. That is, unless you want to live with a "shaker".

Change the Vee angle, and you have an entirely different ball game!

Razor finally made a good point. The Italians have been building small displacement V-8's and more that out-perform other engine configurations. Efficiency, is the key; at that brings in the issue of internal friction again. Anybody listening? <_<

Razor, this was not a trick question. I don't have an answer, because the answer
depends on the flexibility of the engine manufacturing operations; the adaptability of the transfer machines in their set-ups and fast tool change capability. This is something your manufacturing engineers would know.
Technology has come a long way, since I was doing hands-on stuff.
Old-time stumbling blocks don't even cause a hiccup with todays technology and
the advent of computer-controlled machining. Once the programs are written
and proved out, --- some machines could be run by trained apes!..........
Come to think of it, some are! (joke)!!!!!! Edited December 7, 2005 by rkmdogs

[razoredge]

Extra shaft and gear is more machine work than 2 extra rods and pistons, however V8 block - 2 more holes to line bore,  heads - larger manifolds-2 more runners,  crank - two more journals to machine, more camshaft, larger heads 4 more valves/2 chambers.

So you tell me ?

Myself with DOD in V8's Id like to see GM produce 2 smaller aluminum 8's say a 4 & 3.5 or less, something compact for the smaller cars.

F1 is going to V8 now at very small displacement. Lots of power to be had in small bore short stroke V8 and not take up much more room than a I4 but do it so much better.

[post="40114"]<{POST_SNAPBACK}>[/post]

I make alot of good points :lol: everyone doesnt want to listen :rolleyes:

It seems obvious that V6 is cheaper, otherwise we'd be seeing small V8's instead of the V6's. Correct ?

I figure if the 6 is such a hastle go for 3 litre V8. 90* packages better, especially with OHCams those 60*'s are some tall engine.