Hi all -

I hope everyone had a good Thanksgiving.

I was over at a friend's place on Sat helping him get his car set-up. He has a turbocharged Miata that he wanted to dyno to see how much power it was putting out. Since he was going over to the shop and I had the S2000 with me, he tried to convince me to take the car over to the shop. Ok, twist my arm.

On the way over, we met up with his cousin and another friend and ended up with four cars to dyno.

I went first with the S2000, thinking it would be pretty straight forward, and wouldn't take very long.

If you've never been to a dyno, it's pretty impressive. The shop backs the car onto a lift, which raises the car about 5 feet into the air. Then they back to car so the drive wheels are on these large (~1500 lbs) drums and strap the car in place.

They attach an inductive coupling on the #1 spark plug wire to have the computer be able to track RPMs. This turned out to be a big problem since the S2000 doesn't have plug wires. They tried to find a main high voltage line to tap into, and that didn't work either since the car has coil-on-plug instead of any type of distributor.

They finally removed the spark plug cover and were able to get a signal from the control line to the coil on plug #1.

Once they had the RPMs measured, I climbed into the car, put it in gear, and slowly accelerated and up shifted until I was in 3rd gear at about 2500 RPMs. They handed me a control box and told me to punch the throttle and hit the green button at about the same time. This would start the data logging. Once I hit the rev limiter, I hit the button again to stop logging.

So I ran it up to the limiter in third, which had the drive wheels going at about 115 MPH. Let me tell you, in a closed garage with the engine screaming at 9000 RPMs, it sounds incredibly impressive.

I did three runs total, the first two in 3rd gear, and the last in 4th gear. Results of the runs:

Run Peak HP (@8250 RPMs) Peak torque (@6500 RPMs)
1 194.6 130.3
2 193.4 129.2
3 185.9 126.2

I'm not sure if the engine was starting to heat soak or the numbers are really lower in 4th vs 4rd gear.

The results of the dyno runs looks very similar to the ones at http://albums.photopoint.com/j/ViewPhoto?u...9833&p=32538927 but a few HP lower. I would associate this with the fact that it's still a new car and only has about 1800 miles on it. When we get up to 5000-6000 miles, I think we should pick up about 5-10 HP as the engine breaks in.

I'll post my charts when I have a chance to scan them in. But look at that chart as an example and please help me try to answer a couple of questions:

1. The cam switch occurs at ~5800 rpms. Is this correct? I though I remembered reading that it occurs at 6200 rpms.

2. The rev limiter comes on at about 8700 rpms. Again, is this correct? I thought the redline was at 9000 and the limiter a bit above that.

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This morning I took the results and put them into an Excel spreadsheet and graphed the results from the dyno run. I took the gear ratios from the sales brochure and graphed the wheel torque vs MPH.

Doing this resulted in a maximum speed in 2nd gear of 77 MPH. From actual testing, the top speed is actually around 66 MPH. I rechecked my numbers on several web sites and came up with the same results.

Does the S2000 have an additional gear reducer that is not mentioned anywhere? It would need a ratio of about 1.17:1 to correct the speeds I've actually seen on the road. I guess the answer has to be yes, but I'd like some verification.

I looked at the results of graphing wheel torque vs MPH trying to determine where to up-shift. Normally, the wheel torque for each gear will eventually cross when the engine runs out of breathing near the rev limiter.

With this engine, though, the result is that there is such a reduction in wheel torque when changing gears, it is never worth up shifting. The engine flows so well that if we could rev past 9000 rpms, the engine would still produce enough torque to justify staying in the lower gear.

Bottom line, when racing rev it to the limiter in each gear unless other circumstances dictate a short shift (slalom, offsets, etc).

I posted the Excel spreadsheet in the files section on egroups. Take a look and let me know if I missed anything or screwed up on the conversions.

Brad

PS My friend's Miata was putting out 271 HP at the wheels. Not bad for a 1.8L engine.

 

All reports I have seen show VTEC at 6000.

The rev limiter seems to be just over 9000 which is the stated redline.

Yes, there is a secondary reduction of 1.16.

Yes, Honda publishes a chart showing force exerted in each gear, and shifting at the red line clearly gets you down the road fastest

 

could you throw out a link to the spreadsheet? i'd like to take a gander

 

Sorry about not giving a link. The S2000-motorsports egroups list requires that you be a member before you can access the files section.

I posted the files on my web site at:
http://www.xnet.com/~lamont/racing/torque.xls http://www.xnet.com/~lamont/racing/comparison.jpg

-Brad
'01 Spa yellow S2K

 

I assume your HP and torque numbers are also off by 16%, right? They surely must input the overall gearing ratio to calculate HP and torque.

 

No, I fixed the ratio in the excel spreadsheet and the comparison graph.

-Brad
'01 Spa S2K

 

Great charts, Brad.

What is the rated max HP and torque for the Eclipse?

 

Come to think of it, it's probably measured and not inputted.

 

The Eclipse is rated at 210 HP @ 6000 rpms and 220 ft-lbs @ 3000.

All of the data points in the chart (both S2000 and Eclipse) are based on the actual dyno print-outs (S2000 every 250 rpms, Eclipse every 200 rpms).

The measurements for the Eclipse were not of my actual car - there aren't any 4wd dynos in Chicagoland. I got the dyno numbers from someone else who has a FWD turbo model. They should be accurate since there are no other difference between the cars other than the drivetrain.