Dyno chart analysis

[Brentis]

Hello, I am a new member who has always loved the z06, but couldn't find a way to have one of those and a gs400 at the same time. Anyway bought a mint rx7 and am upgrading it and found a review of an rx7's dyno chart comparing a straight pipe and a highflow cat.

I've posted this question on the rx7 board, but don't feel they appreciate the relationship of broad torque band vs. peak hp. I thought you guys would have a good appreciation of extracting which is better for most of the time.

Anyway here are the dyno links - thanks!

http://www.efini.net/tqcomparo.htm

http://www.efini.net/hpcomparo.htm

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excerpt of what I sent on the rx7 board.

Can someone on this board give me your interpretation of these graphs. One shows the delta of the horspower between a hf cat and a midpipe and the other shows the delta between the torque curves.

I guess what I am interested in is which is faster in a 1/4 mile or track situation, how much, and why. I would suppose gearing would come into play somewhat, but I am not that familiar yet to have a good understanding.

Likewise, I read somewhere that someone had the same 1/4 mile time with a trap speed 1 mph slower with the hf cat. In my world they are effectively the same and the hf cat isn't as loud and will pass inspection.

[ZO6/Les]

Power under the curve looks a lot better with the high flow cats in. Peak power is meaningless. Clearly these graphs say go with the high flow cats, the car will pull stronger and go faster.

BTW next time your dyno shop runs the graphs use the same scale for HP and TQ.

Les

[Brentis]

Good deal - I wound up going with the high flow cat - just wanted some insight - I had heard one guy say that he had run both and had the same et but 1 mph faster with the straight pipe - so I went with the cat to be somewhat environmentally conscious, save the ear drums, and better streetability.

Sorry if this sounds a bit dense - but specifically what does "power under the curve" mean?

thx.

[Brentis]

^^^ Anyone else? thanks for your insight!

[Roland]

Basically, it's the power that the engine makes in the range of RPM's that the engine will be in while racing.

Like Les said above you have a much better power curve with the high flow cat, unless I'm reading the graph wrong. You have way more torque at 5000 RPM to redline. With the midpipe, your torque is much lower at 5000 to 6000 rpm, and at 6000, your torque jumps up and drops off real quick.

When you shift with the midpipe, your power will drop off considerably if the engine spins back down below 6000 RPM. Thiis means that you don't get to use the peak power as effectively because you have to shift soon after the RPM's get high enough to make the power. However, if you had the gearing to keep your revs above 6000 though all the gears, then you'd want to keep the midpipe.

So assuimg your rev's fall to about 5000 after a redline shift, the high flow cat gives you much more useable power under the curve.