I'll say it one more time there is no inherent advantage to an OHC motor over a OHV motor unless you look at intended RPM ranges and/or breathing capabilities needed in a force air application.

 

And you'd be wrong.............

Of course the LS motors put out great numbers using OHV but with huge cubes.

The DOHC N/A motors when tuned to their inherent advantages (like Ford does not do but BMW/Mercedes does) will match or exceed OHV #'s with up to 2 litres less displacement.....compare the mighty 7.0 LS7 to the BMW 5.0 V10.

I will 100000% agree with you concerning a 4500 RPM truck motor, however.

 

Which brings us full circle.........Ford has the arsenal to compete with their current hardware IMHO.

 

Not so quick. For the BMW to make the same power as the LS7 it has to turn 1500+ rpms more. Its peak hp is at 7750 compared to 6100. Turning 7750 rpms by default means OHC for any type of reliability.

 

Right on!!!

But could you imagine the DOHC 4 valve having equal cubes???

The VE would be greater PLUS you have a lot more flexibility with VVT.

At the risk of being redundant, multi OHC/multi valve technology can make up for a lot of cubes............with a few exceptions, Ford doesn't put this architecture to work.


What's kinda ironic was that Ford thought the smaller bore would make the future tighter emmisions easier to manage.......GM followed with their small blocks also having the bore shrunk.........even the old 454 based 8.1 was due for extinction for a smaller bore V10!!!

Then something strange happened.........be it electronics or maybe the emission stranglehold loosened......but the bores started getting larger again; with the 7.0 going over 4"!!!

So all the hoopla of controlling flame travel and more complete burn with smaller bores got lost somewhere and Ford is stuck with a small bore spacing and limited growth.


(geeeez how many times can "bore" be used in 1 post??)

Kinda boring if you ask me.

 

You could have equal cubes in a DOHC 4 vavle set up but what does it buy you. Again you have to look at the intended RPM ranges you want the engine to operate. If you are not going to turn over 6000-6500 rpms it is not justified all things being equal. i.e. no multi runner setups, forced air, variable valve timing. All you did was increase physical size of the engine, increase the wieght and increase the parasitic loss by having more moving parts vs that you can accomplish the same thing with a OHC without penality.

Remember GM did have a overhead engine in the vette at one time, the ZR-1 with the LT-5 engine. By any measure today the LS2 is as good or better and the LS7 blows it away. Will GM come out with a new DOHC engine, you bet and it will find its way into the Vette. But IMO it will be a forced air solution and probably a smaller engine than we see today. But it will only be there if they can put the whole package together.

If you have any Vette friends that get Covette Quaterly take a gander at the Spring edition. Read the article Run Faster, Run Farther. It is a great insight on how I think designers should approach the way to build a car or truck. I mean these Vette designers are amazing. If Dodge and Ford would have guys like this they would be competition.

P.S. I truely think BMW makes some wonderful engines. The only problem I have Efficiency is not at the top of there vocabulary. While the M5 is a nice car 12 city and 18 highway are not very good numbers. And this IMO is a direct result of building an engine that produces it power at such a high rpm level.

 

Again you're correct with "all things being equal".......the fact remains if you utilize the benefits of a multi valve set up it'll show gains....even at lower R's.

Your ZR-1 example works against you IMO.......compared to the OHV pushrod motor it DIRECTLY competed with at the time, the Lotus designed/Mercury Marine built DOHC motor had....if memory serves me correctly....150HP more. (245 vs 385 and then 400??)


The Beemer does have some bad MPG numbers.........but it also tips the scales at or near 2 tons........nearly 1000 pounds heavier than the plastic wonder-car.

I will look for that Vette publication. Heck, someday I hope to have it sent directly to me!!

 

Oddly, there is a corporate directive out there in GM-land that no Corvette will carry a "gas guzzler" surcharge on the window sticker, so efficiency is not an optional part of the engine design.

 

How much does the BMW V10 cost compared to a Z06? Ultimate money pit! We can speculate all we want about what Ford should, might, could, maybe will do, but the truth is that in the United States, they are BEHIND in the HP wars. My right foot doesn't care about DOHC, SOHC, pushrods, flame fronts, bore size, bore spacing, etc. All I know is that both GM and DC have engines in trucks I can buy right now that can out power a Ford. 300 HP in a 1/2 ton truck doesn't cut it anymore as far as HP is concerned.

 

I would agree that you can build a DOHC, utilizing all the tech available and make an engine that has more power RPM for RPM. Dual runner setups, VVT, etc. But you still pay a price in increased weight, size and more power to turn all those parts.

Actually the M5 is 800 lbs heaver than the Vette. That will affect the mpg figure for sure. But IMO the biggest thing that hurts it is the engine itself. I would love to see a dyno chart of an un-modded engine. Peak torque for that engine is at 6300 rpm if I remember right. I would really like to know what RPM the engine turns at 70mph.

The reason the Vette does so well other than being lighter is because of all the torque it has. On the dyno at the rear wheels I have 300ft lbs of torque or more from 2000 rpm through 6000rpm. At 70mph it only turns 1500 rpm and unless the hill gets pretty steep it won't down shift. RPMs in general kill mpg as well as increasing wear and tear.

 

I'll agree with that. 427 cubes will make some torque.

 

Ford still has the highest HP and torque gasser in the 3/4-1 ton market (unless GM uses the 6.2 which would still have less torque.) which is a good example of how less displacement can be made up with multi-valves.....6.8L>8.1.



And while I kinda agree the 1/2 tons could use more HP.........the F-150 still stuffs the higher performance offerings from Dodge, Nissan and Toy where it counts the most.................sales.

 

Don't have the Z06, waiting for Polarbear to say it's time. Then I will know what 427 cubes feel like.

 

Tmyers my complaint was it puts you out of the torque curve at highway speeds. Great fuel mileage but no passing power. Forces you to shift.

 

You said it it is either that or 8mpg. It the case of my Vette at 70mph I'm only turning 1550rpms. While I don't have a torque figure for under 2000rpms I can tell you that for most times I need to pass people I don't really have to down shift.

I read some where that to move the Vette at 70mph only required 30hp. I think with the advancement of we've have seen not only in engine tech but tanny tech, areo and weight there is no reason that a car like this can't see 40 mpg in the very near future and at the same time having as good or better performance than we see today.

I know GM is looking at and I would imagine that Ford and everyone else is looking at newer techs as well. One thing that has been talk about is doing away with cams all together and this is the holy grail IMO. But from what I have heard is that for this to be effective they need to move to a 24volt or 48 volt system. Not a change that is easy to do.

Anyway I think we are in for some very exciting times. The hp wars are in full strength and they keep uping the power and in many cases getting the same or more MPG than before. I hope the Hurricane can push the enevolpe even more. Ford built the GT and proved to the world that you could build a supper car and do it for 100's of thousand less than the comp. GM upped the anti again doing it for half that cost with the Z06. ANd not only do you have a car that can compete it also is docile enough to be used as a daily driver and gets better than twice the MPG over the comp. I can't wait for the next challenger.