2009 Corvette ZR1 LS9 Engine

[monaroCountry]

Again, provide comparative data. Show other motors under similar conditions. Also, remember that the LS7 is tuned more for power than anything else. Would the data be the same if we used the LS3 or other versions of the motor that are less powerful? I could be wrong but I believe that many things that are done to make a motor more powerful often hurt its overall efficiency. Things such as short intake runners help high RPM breathing and thus peak HP but hurt volumetric efficiency at lower RPM and can lower peak volumetric efficiency for a given engine. Drawing a generalization from a specific set of data can be very misleading.

compared to many high end European and Japanese exotics of the same power and torque, the LS7 is actually very frugal. Its one of the few >500hp cars that doesnt get slugged with the gas guzzler tax.......not to mention one of the fastest and quickest 500hp supercar.

[kingofthering]

compared to many high end European and Japanese exotics of the same power and torque, the LS7 is actually very frugal. Its one of the few >500hp cars that doesnt get slugged with the gas guzzler tax.......not to mention one of the fastest and quickest 500hp supercar.

If you can afford to buy a Ferrari, gas prices are the least of your worries.

[hightower99]

You were the one stating that the data was bad. It is thus on you to show that the data really is bad by showing other data. I’m not interested in doing that work as I didn’t make the claim.

I posted that info to make the point that the fuel milage that the LS7 can get has nothing to do with the actual thermal efficiency of the engine. It is plainly obvious that it isn't an overly efficient engine at all (averaging roughly 26% thermal efficiency over the whole rev range under optimal conditions). If you wanted to know how far behind it is then I would post some other data, otherwise I expect that you are fully capable of seeing the point (but maybe I give you too much credit?).

Again, provide comparative data. Show other motors under similar conditions. Also, remember that the LS7 is tuned more for power than anything else. Would the data be the same if we used the LS3 or other versions of the motor that are less powerful? I could be wrong but I believe that many things that are done to make a motor more powerful often hurt its overall efficiency. Things such as short intake runners help high RPM breathing and thus peak HP but hurt volumetric efficiency at lower RPM and can lower peak volumetric efficiency for a given engine. Drawing a generalization from a specific set of data can be very misleading.

You are joking right? One of the most used remarks about the LS7 is that GM stopped when they achieved just over 500HP. Do you understand what BSFC is? Do you understand its importance? The LSx engines that are less powerful are smaller displacement then the LS7. Why are you talking about VE? that doesn't have a direct relation with thermal efficiency! The data is perfectly suited for showing the thermal efficiency of the LS7.

Unless you drive around at 100% throttle all the time, part throttle is what we care about when we are looking at fuel economy.

WOT operation will be more efficient than any part throttle setting! I have shown data that shows that the LS7 is not overly efficient even when working at WOT (which is more efficient than part throttle). Part throttle BSFC figures will be worse!

You are arguing about fuel economy yet harping on WOT conditions. You should know that cruise and city driving is typically not done at WOT thus performance at WOT is not necessarily indicative of fuel economy. To assess economy we would really never need data that shows power over say 100hp. Much over 100hp and we are “having fun” which is a whole different game.

Do you know what a "throttle" is? Do you know how it works and how it effects the engine? WOT is more efficient than part throttle. I showed data for the whole rev range so if you only want to talk about 100HP or less then you can choose to only look at the low RPM range.

Either way, if you actually think about the conditions that we care about WOT BSFC are not relevant.

Yes it is because it shows how efficient the engine can be. Part throttle conditions will be worse.

If my car needs 50hp to overcome drag, friction etc on the highway I really can’t used WOT BSFC numbers to estimate mileage or for that mater, efficiency as it maters in cars. If you don’t realize that then you shouldn’t be having this conversation. If you do then you are twisting the facts to fit your premise. Either way, the argument doesn’t hold up because it’s using condition A to make a claim about condition B without showing that A and B are related.

You don't use BSFC numbers to estimate milage... You use it to determine that actual thermal efficiency of the engine when it is running at its best. Again it seems you don't even know what BSFC numbers actually mean...

[hightower99]

compared to many high end European and Japanese exotics of the same power and torque, the LS7 is actually very frugal. Its one of the few >500hp cars that doesnt get slugged with the gas guzzler tax.......not to mention one of the fastest and quickest 500hp supercar.

That has nothing to do with the engine being better...

and everything to do with the engine only having to propel a lightweight, aerodynamically efficient shape with relatively little frontal area, with a double overdrive transmission.

[monaroCountry]

That has nothing to do with the engine being better...

and everything to do with the engine only having to propel a lightweight, aerodynamically efficient shape with relatively little frontal area, with a double overdrive transmission.

What else is there? Faster low speeds, faster high speed, same weight, both aerodynamic etc. If both engines used the same car (with everything the same) I would bet that the corvette would still win and do it without using as much fuel.











2007 Ferrari F430



Engine: 4.3L V8
Power hp: 490
Torque lb-ft: 343
Weight lbs: 3196
0-62: 4sec
Top speed: 196mph
EPA Fuel Economy mpg: 11/16 – 13 combined





2007 Chevrolet Corvette Z06



Engine: 7L V8
Power hp: 505
Torque lb-ft: 470
Weight lbs: 3132
0-62: 3.7sec
Top speed: 198mph
EPA Fuel Economy mpg: 16/26 – 18 combined

[hightower99]

If you installed the LS7 in the Ferrari and somehow still used the Ferrari transmission (or at the very least the same ratios), you will find that the LS7 would get the same or possibly slightly worse milage.

The gearbox ratios is what allows the corvette to get that milage... not the engine.

Conversly if you installed the Ferrari engine in the 'vette you would see that the Ferrari could match the stated milage, no problem. It will however be noticably slower and won't be able to accelerate very well in 6th gear (because it is a much smaller displacement engine with lower engine torque).

[harddrivin1le]

If you installed the LS7 in the Ferrari and somehow still used the Ferrari transmission (or at the very least the same ratios), you will find that the LS7 would get the same or possibly slightly worse milage.

The gearbox ratios is what allows the corvette to get that milage... not the engine.

Conversly if you installed the Ferrari engine in the 'vette you would see that the Ferrari could match the stated milage, no problem. It will however be noticably slower and won't be able to accelerate very well in 6th gear (because it is a much smaller displacement engine with lower engine torque).

It is the Corvette's COMBINATION of engine and transmission/gearing that are responsible for its fuel economy and its performance.

Both the F430 and the Z06 are APPROPRIATELY geared for their engines and are virtually identical in performance. Yet, the 'Vette's fuel economy is vastly superior.

Swapping those engines and transmissions would be an example of exceedingly poor engineering.


Here's what you can't grasp:

Kinetic Energy = 1/2 mass X VELOCITY SQUARED.

The Ferrari's engine may be "more efficient" and use less use less fuel per revolution, but it must rev much higher in order to produce the same rear wheel torque as the Z06 at any given vehicle speed.

Those high revs result in much higher engine part velocities (e.g. piston speeds).

Since velocity is SQUARED, the amount of energy (in the form of fuel) required by the Ferrari is exponentially higher - even if the engine itself is "more efficient" by certain units of measure.

That is the paradox of small displacement engines that "should" be more fuel efficient at first glance.

Hence, the Ferrari, with its small displacement, high revving engine yields very poor real world fuel economy.

[culver]

I posted that info to make the point that the fuel milage that the LS7 can get has nothing to do with the actual thermal efficiency of the engine. It is plainly obvious that it isn't an overly efficient engine at all (averaging roughly 26% thermal efficiency over the whole rev range under optimal conditions). If you wanted to know how far behind it is then I would post some other data, otherwise I expect that you are fully capable of seeing the point (but maybe I give you too much credit?).

You didn’t make the point because you didn’t post comparative data. Off the top of my head I don’t know what the thermal efficiency of say an LS3 motor is. I also don’t know what it is for any Porsche, BMW, Audi, Ford, Toyota etc motor. The numbers sure do look low compared to the last time I looked at that sort of information for a “motor”. However, that was a GE combined cycle gas turbine generator. Oddly enough it doesn’t use an Otto cycle.

My point is you can’t just wave one set of data out their and claim it as proof unless you have other data to say others are better. Further more, as this is a performance version of the motor it is likely that it traded economy for power. Does the LS3 and the Chrysler HEMI also suffer poor efficiency? Heck, can you tell me if the overall poor efficiency is inherent to the pushrods or is it due to say an overly aggressive cooling system resulting in higher parasitic losses?

Again, you waved info out their as if it were the answer but you didn’t provide the rest of the information needed to actually provide the answer.

You are joking right? One of the most used remarks about the LS7 is that GM stopped when they achieved just over 500HP. Do you understand what BSFC is? Do you understand its importance? The LSx engines that are less powerful are smaller displacement then the LS7. Why are you talking about VE? that doesn't have a direct relation with thermal efficiency! The data is perfectly suited for showing the thermal efficiency of the LS7.

Yes, thank you I do know what BSFC is.
I’m talking about VE in context of an example where I might do something that would increase the peak power of a motor (say short runners for high RPM breathing) but would hurt low RPM breathing. So in my example of two otherwise identical motors I now have one that has good peak power but looses low range power and efficiency. IE some things I will do to get better max power are NOT good for efficiency. Thus we can not draw a general conclusion that pushrod designs are inherently inferior to DOHC just because the LS7 has what you have claimed (without proof) is poor efficiency for a 500hp road car motor.

For more information about my specific example please check out Heywood’s Fundamentals of Combustion Engineering.

If it makes you feel better, I will admit that when I worked for Rolls Royce I was doing combustion analysis of gas turbines, not gasoline piston motors. Perhaps I’m just fuzzy after ten years.

Do you agree that given a motor family some of the things I do to increase power can have a negative impact on efficiency?

WOT operation will be more efficient than any part throttle setting! I have shown data that shows that the LS7 is not overly efficient even when working at WOT (which is more efficient than part throttle). Part throttle BSFC figures will be worse!

You are right. Of course thanks to the long gearing the LS7 gets to run closer to WOT at curse. Then again, you have admitted as much. However, when we talk about fuel economy WOT doesn’t mater. The fuel economy tests aren’t conducted at WOT. When I drive to work I almost never use WOT. What we are doing is requesting some level of power less than full. We care about how efficient the motor is at that lower setting.

You can talk about WOT BSFC all you want but really we care about the BSFC at a particular engine RPM and output power needed to maintain say 70mph on the highway. You haven’t shown the motor is more or less efficient than it’s competition under those curse vs full power conditions. Then again you haven’t shown it to be more or less efficient under any conditions because you haven’t presented comparative data.

Do you know what a "throttle" is? Do you know how it works and how it effects the engine? WOT is more efficient than part throttle. I showed data for the whole rev range so if you only want to talk about 100HP or less then you can choose to only look at the low RPM range.

Being condescending isn’t proving your point. I understand what throttling is. I also understand that I don’t drive at WOT all the time. My turbo SAAB may get lousy mileage at WOT but it does nicely on the highway at part throttle.

Yes it is because it shows how efficient the engine can be. Part throttle conditions will be worse.

Yes, I understand that thanks. Part throttle conditions will be worse but how much? Again you can talk all you want about WOT but we don’t measure economy at WOT. We spend VERY little time at WOT. How are pushrods in general (not just the LS7 which is atypical as it is a high power motor) when it comes to part throttle efficiency. Can you show that when asked to produce say the 50hp needed to move a car down the highway that the LS7 or the LS3 or the HEMI or any of GM’s other LS based V8s are less efficient than other motors of similar power? Are they the most efficient (not likely)? Are they the least efficient (again not likely)? Are they middle of the pack? If they are middle of the pack it would suggest that there isn’t really a pro or con just a different way of doing things. I suspect you would find they are middle of the road.

You don't use BSFC numbers to estimate milage... You use it to determine that actual thermal efficiency of the engine when it is running at its best. Again it seems you don't even know what BSFC numbers actually mean...

I can use it to estimate mileage if I know how much power I need to move the car down a road (say 50hp) and I know at what gearing I want to use. I would actually use a table of BSFC vs output power vs engine RPM to help select the optimum ratios for fuel efficiency.

You need to understand that the engine performance numbers that affect fuel economy are not the peak power numbers. They are part throttle numbers. Many people seem to confuse that. Peak power and WOT conditions don’t mean anything when we are looking at part throttle cruising conditions.


One more thing. If you insult me again I am done with this. We may not agree but insulting me is inappropriate and not going to make your points any more or less right.

[harddrivin1le]

It astounds me how many times I see differently scaled graphs used wrongly.
So many times I've pointed out the error for those "stuck" with the "look how flat mine is" arguemtn.

So to END IT, I've put in the effort to rescale and overlay the two graphs you provided...

And it "astounds me" that you would overlay two plots of two different units of measure in an effort to prove anything. (The Camaro's torque figures were originally plotted in FT-LB, while the Porsche's were plotted in Newton Meters.) You would therefore have to convert one of the two plots in order to obtain a COMMON unit of measure in order to produce a meaningful overlay.

There's no need to do that, however, since percentage variations can be easily calculated and compared. When we do that (see below), we see that the Camaro's torque curve, in terms of percentage deviation from its average, is FAR flatter than the Porsche's.

Camaro: ~ 300 FT-LB +/- ~25 FT LBS = +/- ~ 8.3% DEVIATION

Porsche: ~ 284 Newton-Meters +/- ~54 Newton-Meters = +/- ~ 19% DEVIATION.

In other words, the Camaro wins by a landslide. Furthermore, the Camaro's torque curve is smoother and far more robust.

[monaroCountry]

If you installed the LS7 in the Ferrari and somehow still used the Ferrari transmission (or at the very least the same ratios), you will find that the LS7 would get the same or possibly slightly worse milage.

The gearbox ratios is what allows the corvette to get that milage... not the engine.

Conversly if you installed the Ferrari engine in the 'vette you would see that the Ferrari could match the stated milage, no problem. It will however be noticably slower and won't be able to accelerate very well in 6th gear (because it is a much smaller displacement engine with lower engine torque).

So what pushes the car and what sips fuel?..........the engine.

Both gearing and engine efficiency are the biggest contributors to how fuel efficient a car is (amongst other things). The corvette has taller gearing because it has tons of usable torque. Of course the corvette would have a slightly worse fuel economy using the Ferrari gearbox. However looking at those EPA economy figures I would say that the corvette would still be a far better fuel sipper........so that really leaves the engine!!!!!!!!

Engine wise, the corvette has a better engine (engineering wise).



Ferrari F430
EPA Fuel Economy mpg: 11/16 – 13 combined
Gear Ratio: 3.29:1, 2.16:1, 1.61:1, 1.27:1, 1.03:1, 0.82:1

Corvette ZO6
EPA Fuel Economy mpg: 16/26 – 18 combined
Gear Ratio: 2.97:1, 2.07:1, 1.43:1, 1.00:1, 0.84:1, 0.56:1

[hightower99]

Both the F430 and the Z06 are APPROPRIATELY geared for their engines and are virtually identical in performance. Yet, the 'Vette's fuel economy is vastly superior.

So you don't think that if you changed the ratios in the 'vette it couldn't be made faster?

Kinetic Energy = 1/2 mass X VELOCITY SQUARED.

The Ferrari's engine may be "more efficient" and use less use less fuel per revolution, but it must rev much higher in order to produce the same rear wheel torque as the Z06 at any given vehicle speed.

Those high revs result in much higher engine part velocities (e.g. piston speeds).

Since velocity is SQUARED, the amount of energy (in the form of fuel) required by the Ferrari is exponentially higher - even if the engine itself is "more efficient" by certain units of measure.

A few problems:
First, the Ferrari engine is more thermally efficient. That doesn't just mean it burns less fuel per RPM it means it burns less fuel per HP per unit time.
Second, the peak piston speeds of both engines are not that far from each other (Ferrari probably 20m/s while LS7 should get at least 19m/s at redline), thing is that the Ferrari engine is doing 8500RPM and the LS7 is only doing 7000RPM. So that means that at the same RPM the LS7 piston speed will be higher than in the Ferrari. It also means that for the same piston speed the Ferrari will be at a significantly higher RPM. So the overall difference in piston speed for both engines when making the same wheel torque is not going to be that big at all. Next I would like to point out that kinetic energy of the internals is not that high (since we are talking low mass and relatively low velocity). The big killers are inertia and Newton's 3rd law combined with the fact that we are talking about reciprocating engines.

That is the paradox of small displacement engines that "should" be more fuel efficient at first glance.

The Ferrari engine is more fuel efficient it just doesn't get as good mileage because it is running a normal close-ratio, single overdrive transmission instead of a wide range double overdrive like the 'vette.

[hightower99]

Listen culver: People where saying that one of the reasons that the 'vette has such good fuel mileage was because the LS7 is a highly efficient engine. The data I posted speaks for itself, the peak efficiency is not even 30% and the average is significantly lower, therefore the engine is not overly efficient compared to its rivals. The actual values don't really matter.

Do you agree that given a motor family some of the things I do to increase power can have a negative impact on efficiency?

Yes I agree 100% with that statement. However the LS7 is not an overly tuned engine at all. It was designed with fuel mileage (not thermal efficiency) in mind and besides it is the engine we are talking about. I am not trying to make this into a OHV vs. DOHC thread at all and I would appreciate it if you didn't continueously try to turn it in that direction.

You can talk about WOT BSFC all you want but really we care about the BSFC at a particular engine RPM and output power needed to maintain say 70mph on the highway. You haven’t shown the motor is more or less efficient than it’s competition under those curse vs full power conditions. Then again you haven’t shown it to be more or less efficient under any conditions because you haven’t presented comparative data.

So you are speculating that even though its peak thermal efficiency is relatively low (under optimal conditions) that it will be more thermally efficient during part throttle conditions then comparative DOHC engines? Is that what you are saying?

Yes, I understand that thanks. Part throttle conditions will be worse but how much? Again you can talk all you want about WOT but we don’t measure economy at WOT. We spend VERY little time at WOT. How are pushrods in general (not just the LS7 which is atypical as it is a high power motor) when it comes to part throttle efficiency. Can you show that when asked to produce say the 50hp needed to move a car down the highway that the LS7 or the LS3 or the HEMI or any of GM’s other LS based V8s are less efficient than other motors of similar power? Are they the most efficient (not likely)? Are they the least efficient (again not likely)? Are they middle of the pack? If they are middle of the pack it would suggest that there isn’t really a pro or con just a different way of doing things. I suspect you would find they are middle of the road.

The LS7 is not atypical, Yes alot of high grade material science went into it but it is still an OHV 7L V8. You agree that part throttle conditions will be less efficient than WOT yet you continue to question the simple reasoning behind my point (which is: Lower WOT efficiency = lower part-trottle efficiency). Sorry to burst your bubble but the actual thermal efficiency of the LSx series of engines is in the low end of the spectrum. Look that up on your own. OHV engines can only be optimised over a small amount of the rev range, and the majority of manufacturers choose to place that optimised zone in the upper rev range so that the engine performs well. That means that they cannot be as efficient as a DOHC engine with VVT systems that can be optimised over almost the entire rev range. Facts of life.

I can use it to estimate mileage if I know how much power I need to move the car down a road (say 50hp) and I know at what gearing I want to use.

ummm then as stated you need to alot more than just the BSFC figures...

I would actually use a table of BSFC vs output power vs engine RPM to help select the optimum ratios for fuel efficiency.

You could do that too... Never said you couldn't.

You need to understand that the engine performance numbers that affect fuel economy are not the peak power numbers. They are part throttle numbers. Many people seem to confuse that. Peak power and WOT conditions don’t mean anything when we are looking at part throttle cruising conditions.

I understand that perfectly however you must understand that an engine is most efficient at WOT. Therefore WOT BSFC ratings are not meaningless they give you the absolute best the engine can do.

[hightower99]

There's no need to do that, however, since percentage variations can be easily calculated and compared. When we do that (see below), we see that the Camaro's torque curve, in terms of percentage deviation from its average, is FAR flatter than the Porsche's.

Camaro: ~ 300 FT-LB +/- ~25 FT LBS = +/- ~ 8.3% DEVIATION

Porsche: ~ 284 Newton-Meters +/- ~54 Newton-Meters = +/- ~ 19% DEVIATION.

In other words, the Camaro wins by a landslide. Furthermore, the Camaro's torque curve is smoother and far more robust.

Umm you need to get your eyes checked!

In the same rev range for both engines the Camaro goes up from about 275ft-lbs to 329ft-lbs (54ft-lbs difference) then drops off back down to 290ft-lbs (39ft-lbs. drop)

The porsche goes up from 188ft-lbs up to 248ft-lbs (60ft-lbs difference) and that takes it to 5400RPM.

The porsche has a flatter torque curve.

The Camaro makes more engine torque though.

[hightower99]

Both gearing and engine efficiency are the biggest contributors to how fuel efficient a car is (amongst other things). The corvette has taller gearing because it has tons of usable torque. Of course the corvette would have a slightly worse fuel economy using the Ferrari gearbox. However looking at those EPA economy figures I would say that the corvette would still be a far better fuel sipper........so that really leaves the engine!!!!!!!!

I have already shown the BSFC figures... It is not an efficient engine.

Engine wise, the corvette has a better engine (engineering wise).

No it isn't how could you possibly come to that conclusion. The Ferrari revs higher, has a higher thermal efficiency and much better specific output aswell as a better torque curve shape... All that is because of the better engine design.

Ferrari F430
EPA Fuel Economy mpg: 11/16 – 13 combined
Gear Ratio: 3.29:1, 2.16:1, 1.61:1, 1.27:1, 1.03:1, 0.82:1

Corvette ZO6
EPA Fuel Economy mpg: 16/26 – 18 combined
Gear Ratio: 2.97:1, 2.07:1, 1.43:1, 1.00:1, 0.84:1, 0.56:1

You forgot one of the biggest factors... the final drive ratios...

Here is what the final ratios are for both:
Ferrari:
1st = 3.29:1 X 4.30:1 = 14.147:1
2nd = 2.16:1 x 4.30:1 = 9.288:1
3rd = 1.61:1 x 4.30:1 = 6.923:1
4th = 1.27:1 x 4.30:1 = 5.461:1
5th = 1.03:1 x 4.30:1 = 4.429:1
6th = 0.82:1 x 4.30:1 = 3.526:1

Z06:
1st = 2.66:1 x 3.42:1 = 9.0972:1
2nd = 1.78:1 x 3.42:1 = 6.0876:1
3rd = 1.30:1 x 3.42:1 = 4.446:1
4th = 1.00:1 x 3.42:1 = 3.42:1
5th = 0.74:1 x 3.42:1 = 2.5308:1
6th = 0.50:1 x 3.42:1 = 1.71:1

Even in 6th the Ferrari will be running a total ratio that is lower (numerically higher) than the Z06's 4th gear. That means in 4th gear the Z06 is saving fuel... 5th and 6th help get all that extra mileage.

Note: it seems that we have different information for the 'vette... where did you get your info?

[harddrivin1le]

Umm you need to get your eyes checked!

In the same rev range for both engines the Camaro goes up from about 275ft-lbs to 329ft-lbs (54ft-lbs difference) then drops off back down to 290ft-lbs (39ft-lbs. drop)

The porsche goes up from 188ft-lbs up to 248ft-lbs (60ft-lbs difference) and that takes it to 5400RPM.

The porsche has a flatter torque curve.

The Camaro makes more engine torque though.

Are you on drugs? Anyone with a pair of eyes can see which of these two torque curves is flatter, and it's not the Porsche's:
http://members.cox.net/harddrivin1le/CamaroDyno.jpg
http://members.cox.net/harddrivin1le/PORSCHEDYNO.png

[color]But for the sake of objectivity, I'll use YOUR figures and run them as PERCENTAGES of their respective averages.[/color]

CAMARO: (275 + 329)/2 = 302 FT-LB average

54/302 X 100 = 17.9% total variation from average

Porsche:

(188 + 248)/2 = 218 FT-LB

60/218 X 100 = 27.5% total variation from average

You are BLINDED by unjustifiable bias!

Furthermore, you tell others than it's the engine and transmission that are responsible for producing drive wheel torque and any given wheel speed (a correct observation), but discount the significance of the transmission altogether when it comes to fuel economy (a ludicrous oversight)!!!!!!!!!!!!!!!!!!!!!!