465 HP versus 730 HP
#61
Does Chuck think that ALL OHC motors have electric actuated valves???!!!...Mark
#62
Le Mans Master
Those engines demonstrate even within the confines of the rules, what is possible using a DOHC design. Those motors "Even" with rule/s limitation/s are developing 300hp per liter ( 60 cubic inches) that is 5HP per Cubic Inch!!!....ASTONISHING in my opinion!!!...Mark
#63
Pro
The point remains that an F1 engine looks the way it does because more sensible designs are prohibited by the rules. These rules are necessary for competition purposes but do not apply to street cars. On a street car, the F1 engineering trade-offs are terrible - even if lap times were your only concern (which they aren't).
#64
Le Mans Master
#65
Le Mans Master
And 4-valve V-motors will have twice as many of them (or shims), plus twice as many valves, valve springs, and four times as many camshafts, cam gears (or pulleys) and a more complex timing chain (or belt) arrangement.
If you can't recognize that a multi-valve DOHC motor is more complicated than a 2-valve pushrod motor, whatever its other advantages, then it's ridiculous to even go on having this conversation.
Last edited by torquetube; 12-05-2013 at 12:58 AM.
#66
My point is very simple, a DOHC motor out preforms a OHV motor when all other factors are equal. The single most important component of an engine in developing HP is...the cylinder head/s. How is the MOST N.A. air flow created in a cylinder head?!...4+ valves per cylinder...PERIOD!!!...Mark
over simplified.
there are obvious advantages that outweigh DOHC in this application.
yeah
#67
Team Owner
The real question is why can't a 730 hp Ferrari run a faster lap than a 460 hp base Corvette around Laguna Seca. I was there watching some of that test when the Corvette engineers downloaded the latest suspension settings and went out and supposedly matched the F12 time. They did not use that faster time because it was not their normal timing equipment that was used. It was a handheld timer and they had already finished their testing. Regardless, the Corvette had ran an even faster lap than they published. I have no reason to downplay Ferrari as I have owned a few of them. I've always enjoyed the Ferrari experience but I'm also a prior Corvette owner. Loved both cars and I'm now interested in the C7 ZO6 or ZR1. If Ferrari's Fastest can't outrun the base Vette, what's going to happen when the hi-po Vette's get here?
2. The type of track plays a big role in what is faster around it. Compare the two around a high speed circuit and the results may vary.
3. I doubt Ferrari owners will care. You're comparing apples and oranges as far as price goes for most buyers.
#68
Le Mans Master
Member Since: Jul 2009
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1. Street tires will only put so much power to the ground. That is a huge equalizer.
2. The type of track plays a big role in what is faster around it. Compare the two around a high speed circuit and the results may vary.
3. I doubt Ferrari owners will care. You're comparing apples and oranges as far as price goes for most buyers.
2. The type of track plays a big role in what is faster around it. Compare the two around a high speed circuit and the results may vary.
3. I doubt Ferrari owners will care. You're comparing apples and oranges as far as price goes for most buyers.
Funny thing is that his wife didn't seem to like this talk.
#69
That is always the problem with the dohc argument Mark. If we were in a dyno room and were trying to get the most hp per cubic inch from two engines then I agree with you that the 4 valve engine could be made to produce more hp than the 2 valve engine.
Most of the hp advantage in the Ferrari comparison is due to the higher rpm. Not just the 4 valves.
In the real world where packaging, weight, cost, etc are factors it is not so cut and dried.
Getting hung up on hp/liter of displacement is also misleading. GMs method of efficiency with larger displacement engines running a lower rpms almost always lends itself to better fuel mileage and much longer life than the smaller, high rpm engines do. The Ferrari only uses that peak hp for a few seconds each lap where as a corvette uses much more of the available hp (torque). BTW I love the high pitched scream of a formula one engine as much as anyone.
Most of the hp advantage in the Ferrari comparison is due to the higher rpm. Not just the 4 valves.
In the real world where packaging, weight, cost, etc are factors it is not so cut and dried.
Getting hung up on hp/liter of displacement is also misleading. GMs method of efficiency with larger displacement engines running a lower rpms almost always lends itself to better fuel mileage and much longer life than the smaller, high rpm engines do. The Ferrari only uses that peak hp for a few seconds each lap where as a corvette uses much more of the available hp (torque). BTW I love the high pitched scream of a formula one engine as much as anyone.
Last edited by ChucksZ06; 12-08-2013 at 10:10 AM.
#70
Funny thing is that his wife didn't seem to like this talk.
#71
Le Mans Master
Corvette won't have a DOHC because the economics aren't there. Has nothing to do w the best engine configuration. That's why nobody at GM Powertrain gives a crap about the LT-5. They don't even acknowledge it as being a GM motor because they didn't build it. Typical NIH.
Corvette gains it's Best Bang for the Buck moniker because it can spread the cost of engine and technology development (read PCM hardware/software) across the millions of trucks sold. Ferrari can't, doesn't do that. And just as Porsche has wrung the bejesus out of a flat six hung over rear end of a car, so too Chevrolet has maximized what they get out of OHV. Without doubt, they are the masters of it. Regardless of cost, I highly doubt F1 would select OHV over OHC.
Chuck,
The question of higher rpm hp is due to the design of OHC. That's where they want the hp. And it's available there because you aren't transmitting energy through about a foot of valve train while changing direction at least twice doing it.
Overall, this is really a question of application. No ultimate right or wrong.
But what is it about OHV that GM sees that virtually no other performance car manufacturer does? I submit it's the $$$.
Corvette gains it's Best Bang for the Buck moniker because it can spread the cost of engine and technology development (read PCM hardware/software) across the millions of trucks sold. Ferrari can't, doesn't do that. And just as Porsche has wrung the bejesus out of a flat six hung over rear end of a car, so too Chevrolet has maximized what they get out of OHV. Without doubt, they are the masters of it. Regardless of cost, I highly doubt F1 would select OHV over OHC.
Chuck,
The question of higher rpm hp is due to the design of OHC. That's where they want the hp. And it's available there because you aren't transmitting energy through about a foot of valve train while changing direction at least twice doing it.
Overall, this is really a question of application. No ultimate right or wrong.
But what is it about OHV that GM sees that virtually no other performance car manufacturer does? I submit it's the $$$.
#75
The fact that a 60k GM sports car is compared to 400k exotics is testament that GM did something right with the c7. Someone commented it is stupid to compare such cars, but I'm happy to see the c7 compared to these cars and win.
Lots of drawn out opinions in this thread, but if you track often as I do you'll know the answer to the ops question right away. Why does a Cayman S with 300 hp have faster lap times than cars with 2x more hp? It's quick light and balanced. 700 hp Lambo will never keep up with newer cayman with pdk and good driver because you can drive 10/10s into the corners. Try that in a Lambo and you'll fly off the track. Same goes with f12 comparison. You have a heavier car with more hp which you would think would equate to faster track times. It doesn't.
C7 is comparable to cayman on the track in terms of balance. It's a little heavier but very capable. That's why I'm selling my FBO 480 whp 335 for the c7.
Lots of drawn out opinions in this thread, but if you track often as I do you'll know the answer to the ops question right away. Why does a Cayman S with 300 hp have faster lap times than cars with 2x more hp? It's quick light and balanced. 700 hp Lambo will never keep up with newer cayman with pdk and good driver because you can drive 10/10s into the corners. Try that in a Lambo and you'll fly off the track. Same goes with f12 comparison. You have a heavier car with more hp which you would think would equate to faster track times. It doesn't.
C7 is comparable to cayman on the track in terms of balance. It's a little heavier but very capable. That's why I'm selling my FBO 480 whp 335 for the c7.
#76
That is always the problem with the dohc argument Mark. If we were in a dyno room and were trying to get the most hp per cubic inch from two engines then I agree with you that the 4 valve engine could be made to produce more hp than the 2 valve engine.
Most of the hp advantage in the Ferrari comparison is due to the higher rpm. Not just the 4 valves.
In the real world where packaging, weight, cost, etc are factors it is not so cut and dried.
Getting hung up on hp/liter of displacement is also misleading. GMs method of efficiency with larger displacement engines running a lower rpms almost always lends itself to better fuel mileage and much longer life than the smaller, high rpm engines do. The Ferrari only uses that peak hp for a few seconds each lap where as a corvette uses much more of the available hp (torque). BTW I love the high pitched scream of a formula one engine as much as anyone.
Most of the hp advantage in the Ferrari comparison is due to the higher rpm. Not just the 4 valves.
In the real world where packaging, weight, cost, etc are factors it is not so cut and dried.
Getting hung up on hp/liter of displacement is also misleading. GMs method of efficiency with larger displacement engines running a lower rpms almost always lends itself to better fuel mileage and much longer life than the smaller, high rpm engines do. The Ferrari only uses that peak hp for a few seconds each lap where as a corvette uses much more of the available hp (torque). BTW I love the high pitched scream of a formula one engine as much as anyone.
(0) Forced induction
(1) Displacement
(2) RPM
There are different automakers experimenting with all three and with combinations, but those combinations get expensive fast.
If you go down the high rpm path, which Ferrari did, you need to maximize the valve area to enable airflow in and out of the engine cylinders but you also need to minimize valve weight, to allow the rpm. That's why virtually all high rpm engines use 4 valves/cylinder (instead of just two giant valves).
If you go down the large displacement path, which GM mainly did, it gets hard to run the engines at high rpm because the reciprocating assembly is too heavy and so the forces needed to accelerate the rods+pistons are too high.
The best combination of displacement+rpm is the Mercedes M156 (6.2L) which, in the SLS AMG Black series, turns up to 8000 rpm from the factory. Pure awesomeness. And that engine alone probably costs as much as a 2 yr old C6.
Note that in this context, 6500 rpm is not considered "high rpm".
Pat
Last edited by catpat8000; 12-08-2013 at 07:37 PM.
#77
Burning Brakes
The real question is why can't a 730 hp Ferrari run a faster lap than a 460 hp base Corvette around Laguna Seca. I was there watching some of that test when the Corvette engineers downloaded the latest suspension settings and went out and supposedly matched the F12 time. They did not use that faster time because it was not their normal timing equipment that was used. It was a handheld timer and they had already finished their testing. Regardless, the Corvette had ran an even faster lap than they published. I have no reason to downplay Ferrari as I have owned a few of them. I've always enjoyed the Ferrari experience but I'm also a prior Corvette owner. Loved both cars and I'm now interested in the C7 ZO6 or ZR1. If Ferrari's Fastest can't outrun the base Vette, what's going to happen when the hi-po Vette's get here?
#78
Mostly agree with Chuck. There are three ways to make power:
(0) Forced induction
(1) Displacement
(2) RPM
There are different automakers experimenting with all three and with combinations, but those combinations get expensive fast.
If you go down the high rpm path, which Ferrari did, you need to maximize the valve area to enable airflow in and out of the engine cylinders but you also need to minimize valve weight, to allow the rpm. That's why virtually all high rpm engines use 4 valves/cylinder (instead of just two giant valves).
If you go down the large displacement path, which GM mainly did, it gets hard to run the engines at high rpm because the reciprocating assembly is too heavy and so the forces needed to accelerate the rods+pistons are too high.
The best combination of displacement+rpm is the Mercedes M156 (6.2L) which, in the SLS AMG Black series, turns up to 8000 rpm from the factory. Pure awesomeness. And that engine alone probably costs as much as a 2 yr old C6.
Note that in this context, 6500 rpm is not considered "high rpm".
Pat
(0) Forced induction
(1) Displacement
(2) RPM
There are different automakers experimenting with all three and with combinations, but those combinations get expensive fast.
If you go down the high rpm path, which Ferrari did, you need to maximize the valve area to enable airflow in and out of the engine cylinders but you also need to minimize valve weight, to allow the rpm. That's why virtually all high rpm engines use 4 valves/cylinder (instead of just two giant valves).
If you go down the large displacement path, which GM mainly did, it gets hard to run the engines at high rpm because the reciprocating assembly is too heavy and so the forces needed to accelerate the rods+pistons are too high.
The best combination of displacement+rpm is the Mercedes M156 (6.2L) which, in the SLS AMG Black series, turns up to 8000 rpm from the factory. Pure awesomeness. And that engine alone probably costs as much as a 2 yr old C6.
Note that in this context, 6500 rpm is not considered "high rpm".
Pat
sorry for the shitty sentence lol
#79
Madison Wisconsin
Valve vs Valve is not the issue. See Vizard the Wisard...
Just a short note on this. The 2 vs 3 vs 4 value debate is not totally valid. It is not a question of the number of values, but the total linear cliff area of the value line. A single value can out perform a double valve and a double value can out perform a single valve. It is much more complex than valve count. It involves the value angles and how many angles, and the seat area and the lead-up curves, but also the exhaust performance and it involves the total line of cliff. If yo want to know more, David Vizard has a great 2 hour lesson on how these all perform and relate. It is worth the time if you are really into this. It is a bit old, but the principles are constant. Click on... and have a beer and be ready to listen to an engine wizard. I wish I know half of what he does.
#80
I invite you to try the above with any LSx engine, even the LS7...it won't happen. Keep in mind the LT5 is 5.7L displacement...many people have taken the engine to 415, 427, and 442 cu in and made 600+ HP with the stock cams which made a silky smooth 500 RPM idle and even more torque at 500 RPM. BTW, the common rev limit is at least 7500 RPM when doing any mods (even just a tune) because the HP curve is almost a flat line from about 5500-7500 RPM.
The LS7 is at the limit for N/A HP at 505 and it really isn't that reliable at that point...there are many threads in the C6 Z06 forum about blown engines with most of them valve related. The LT5 is as reliable as an anvil, you can beat on it all day and it comes back begging for more. I've been beating on mine for 21 years now with zero issues. To get to the 600 HP level with an LSx engine, a supercharger had to be added which now makes it equal to the LT5 in weight, packaging, and complexity. Add DI and VVT to a 7L LT5 and 650 HP N/A is easily attained in a very quiet running reliable package...and yes, it will also run at 500 RPM in 6th gear and it will get way better MPG than any similar HP LSx.
Keep in mind I love all Corvettes and the LSx engines, I bought a '99 coupe and then a '11 GS for my daughter so I'm not a hater. I will say I absolutely love the LT5, it's just a disappointment to see a lot of hate on this DOHC engine based on misperceptions about all DOHC engines. And just a FYI, the bottom end architecture of the LSx engine came from the LT5...so in a way, they are at least brothers.