Corvette's Throttle Response, 7.0L Z06 vs 6.2L SC ZR-1

[dudejo]

Long story short, which of the two has better throttle response?

My theory is that while the Z06 has less power, the fact that it doesn't use forced-induction means the internals are be lighter, making for a more responsive engine than the ZR-1's supercharged engine.

Is this accurate?

 

[Bopop4]

You also have to remember that the ZR1 has an 800cc smaller engine, so the internals are lighter on it.
And a supercharger doesn't really add any lag, you'd have to drive both to see for yourself.

 

[dudejo]

We're talking about a ~11% difference in displacement. How big of a difference would it make?

 

[Bopop4]

You can't really say, it also depends on the intake, exhaust, too many factors to be able to make up a formula. Driving it is pretty much the only way to tell.

 

[Slash]

You'd be really surprised.

 

[Rotary Junkie]

You also have to remember that the ZR1 has an 800cc smaller engine, so the internals are lighter on it.

Not necessarily.

We're talking about a ~11% difference in displacement. How big of a difference would it make?

Nothing huge actually. Definitely wouldn't surprise me in the slightest if the LS7's rotating assembly is in fact lighter than the LS9's though.

 

[Slash]

Well LS7's rod's are hardly worth their weight in scrap, I can tell you that much.

 

[Rotary Junkie]

And their strength is relative to this discussion... How?

 

[Slash]

And their strength is relative to this discussion... How?

You were talking about weight. Not strength.

 

[dudejo]

You were talking about weight. Not strength.

How are we supposed to interpret "They're hardly worth their weight in scrap"? It felt like a criticism of its durability to me. :/

Back on topic, I looked over my question again and I considered I could word it better.

Assuming the ZR-1 turns out to have overall heavier internals after all the moving parts are taken into account, how well does its torque deal with the inertia compared to the Z06's torque and its own inertia?

 

[Slash]

You really need to drive them both to really get an understanding I think. I haven't however.

 

[savage388]

Well LS7's rod's are hardly worth their weight in scrap, I can tell you that much.

OK first the ls7 used the best stuff gm could come up with and calling a motor that can take a 200 shot of nitrous or quite a few pounds of boost crap is by no means correct. They are actually very stout pieces which is irrelevant in this thread but needs to be said regardless.
Back on topic though while I would bet all my money on the internals of the ls7 being lighter as the ls9 has beefed up pieces for the boost lighter internals only accounts for part of the throttle response equation. If lighter internals were the only thing that counted ferrari v8's would be phenomenal, but they aren't because of the second factor which is torque. Torque comes from displacement which makes internals heavier which seems counterproductive to throttle response because more weight has to get moving but in most cases this is fairly irrelevant except for extreme cases. The third factor in this question is the supercharger which creates "instant" torque as a substitute for the missing displacement changes everything. That said the high revving ls7 should't have as good throttle response as the ls9 in theory, but all that goes out the window once you drive both.

 

[playnthru]

^^ That's what I was thinking! The torque produced in the low RPM range would overcome whatever RPM speed advantage the lighter rotating assembly (LS7) would have. While the LS7/Z06 makes great power and torque. Seat of the pants feel, I think the LS9/ZR-1 would feel more responsive.

 

[Bopop4]

I found a way to decide this once and for all, just get me a Z06 and a ZR1, and I'll tell you which one is more responsive.

 

[Slash]

I think it depends on how you look at it. How he wants to look at it. Which one you hit the power band first in or which one takes longer to respond from the movement of your foot on the pedal.

 

[savage388]

^^ That's what I was thinking! The torque produced in the low RPM range would overcome whatever RPM speed advantage the lighter rotating assembly (LS7) would have. While the LS7/Z06 makes great power and torque. Seat of the pants feel, I think the LS9/ZR-1 would feel more responsive.

Exactly. Light rotating assemblies and valvetrains were never built to achieve the best throttle response,only as a means to achieve higher rpms and in doing so many of them sacrifice throttle response from low and mid rpm. Take the 2.0 liter Honda s2k, it is a complete dog below something like 4k yet it has an extremely light rotating assembly. On the other hand I know my trans am has very good throttle response even with a carb ( another factor entirely ) and the rotating assembly is an anchor in comparison and there's no chance it'll spin past 5.5k. The only time the weight makes a noticeable difference is in engines that are otherwise identical, yet that rarely happens because of so many other reasons(titanium valves yet stock heads?!) That it will be a fair comparison.

 

[dudejo]

So at best, the only inertia to be noticed will be when you stop accelerating and put the car in neutral?

@ savage388, when you mention extreme cases, would that include diesel engines? I've heard they have particularly heavy internals due to their design and that it affects response in spite of their amazing torque.

@ Slashfan, it would be the second one, how long it takes for the engine to react to driver input.

Either way, thanks a lot for the responses. If I understand well, the quality of a car's throttle response is mostly determined by its torque and powerband, right?

 

[PAPPACLART]

If we are talking about throttle response "in Gear" then also we must consider the gear ratio's of each car. Gears are a multiplier of torque and play an extremely important role in how responsive a cars' engine is in each gear.

 

[savage388]

So at best, the only inertia to be noticed will be when you stop accelerating and put the car in neutral?

@ savage388, when you mention extreme cases, would that include diesel engines? I've heard they have particularly heavy internals due to their design and that it affects response in spite of their amazing torque.

@ Slashfan, it would be the second one, how long it takes for the engine to react to driver input.

Either way, thanks a lot for the responses. If I understand well, the quality of a car's throttle response is mostly determined by its torque and powerband, right?

For the most part that is correct, lighter internals will cause an engine to rev faster in neutral than one with heavier internals all things being equal.
And yes diesels are exactly what I was thinking of when I meant extreme cases, however because they are so different from gasoline engines in their induction I can't really count them as a proper example.

If we are talking about throttle response "in Gear" then also we must consider the gear ratio's of each car. Gears are a multiplier of torque and play an extremely important role in how responsive a cars' engine is in each gear.

See the problem is there is a line between throttle response and acceleration and once you get into talking gear ratios you are speaking more in terms of acceleration than the second or less it takes to notice throttle response. A higher numerical gear could give the perception of much better throttle response in engines that typically don't have a good throttle response but the only thing that is different is the acceleration after you hit the throttle, the initial tip in is usually the same.