We all know the S2000 engine puts out lots of horsepower in Vtec. What it doesn't do is put out full horsepower at all rpms. We only have a narrow spot in the rpm range where we get maximum horsepower.

Inorder to maximize the horsepower and torque output we must generally go to the redline before shifting thus ensuring the engine remains in Vtec at the subsequent lower rpms of the next gear.

Taking advantage of Reverend's Garage (thanks Rev) http://reverendsgarage.net/index.php?conte...7a14b156ce3bee2
and charting hp vs speed [rpm in gear] I came up with the following numbers.

These numbers are unique to my car and you will have to do your own calculations using your HP, tire size and final drive gear ratio. My final HP is more than most at 363 and tire size 245/50/16, 9300 rpm peak with 4.44 gears. I use a 9500 redline but seldom push it so I used 9300 here instead. The actual Vtec in my setup is 5200 rpm to 9500 rpm, a wild 4300 rpm range.




It passes through 200 hp with 180 ftlbs torque at 27 mph and never sees that low of a number again. It drops to 210 hp at 43 mph, 250 hp at 65 mph, 280 hp at 90 mph and a low of 310 hp at 115 mph and 137 mph
Torque is 180 ftlbs at 6000 rpm, 195 ftlbs at 7000 rpm and 216 at 8500 rpm.

These numbers were produced with a Vortech centrifical supercharger. Turbos would tend to have more midrange boost thus higher midrange hp numbers. I would think that leads to the shift drop being less significant with the turbo. That is, less peak hp number with a higher midrange hp number (like moving the HP numbers down on the chart.) Maybe someone would chart out some turbo numbers and let us know.

Now I know why it goes from 115mph to 135mph in 5th gear so very, very quickly.

Thanks again Reverend.

 

Good analysis. I think I'll do the same with mine to determine if I should get the 4.57 gears or stay with stock 4.10.

I like to have top end power for highway encounters. The 4.57 gears pull great down low, but after a certain speed, they actually accelerate slower than 4.10 gears becuase it's one gear up. This will help me decide based on my driving habits.

BTW, your S puts out good HP. What other work have you done besides headwork?

 

Why would the 4.57 accelerate slower? It's just a mechanical advantge right? You will be top speed limited, but it should pull harder all the way to the top speed versus 4.1

 

You have HP labeled on the right, like it is correlated to the Y-axis, but I don't see anyway for this to have anything to do with HP. If the lines that you have there had anything to do with HP, they wouldn't be straight, they'd have a curve to them, similar to your dyno chart.

It seems you've over-simplified this analysis. Your graphs should look something like the ones in this thread:
https://www.s2ki.com/forums/index.php?showtopic=162249

Hopefully, you can re-work them. I'd be interested to see the real results.

 

Acceleration in any gear is proportional to torque output, not HP. Try plotting wheel torque ( = engine torque * overall gear ratio) vs. rpm for each gear; then the optimal shift point will be obvious.

 

[QUOTE=mxt_77,Sep 21 2004, 03:45 PM]
You have HP labeled on the right, like it is correlated to the Y-axis, but I don't see anyway for this to have anything to do with HP.