Tom W

FWIW, I had some dyno runs done at the last track weekend. We ran a number of runs with some tweeks to the MoTeC after we had a baseline. By changing where the flapper in the air intake opens and closes there were minor improvements.

The intake and headers limit the power the engine can make, so we didn't expect much gain from any tweeks. Another car in my class was run the day before - we were within 3 hp but he had about 8 more ft-lbs of torque. The rules appear to be accomplishing the objective.

I also had a run done that looks at power train loss. It appears I lose about 20 hp at 110 mph with my G50/32. All runs were done in 4th gear.

Christer

I have a 9M intake, but run standard headers....I don't think the headers are such a problem until you get to around 350+ HP.....

Do you run bigger injectors?

Greg_L

Tom, are those figures at the crank or the wheels?

Seaflat

Warning Stupid Question: When you do a dyno run does how fast you get up to speed have anything to do with it? Are you running the car like you are trying to beat you best 0 - top speed time if you were on the track? Or are you just looking for your max hp in any gear and that gets you the curve?

Tom W

Christer: I believe the injectors are stock. Class rules require the stock intake system and I beleve the header is 1 5/8" max diameter.

Greg: Wheels. It runs about 300 at the flywheel on the Jerry Woods engine dyno (but they don't worry about calibration, it's simply used comparatively).

Seaflat: It's measuring the power at wide open throttle. It's not a measure of how fast you get up to speed (in that a certain speed is not an end-point), it's a measure of the power the car produces to accelerate. More power means faster acceleration given a fixed resistance on the dyno. You car about the shape of the power and torque curves.

Seaflat

So if I am on a dyno and I floor the car to red line in 1,2 or 3rd I would get the same reading for each gear? Or Even if I took 1 minute to get from 3000 rpm to red line in 2nd???

Bill Verburg

No, a dyno measures torque, the torque in lower gears is massively more than in higher gears as are friction losses.

Here you can see the torque at the wheel curves for 6 speeds and the hp curve which of course is the same for each gear


to get as nearly correct results as is possible, the gear ratio, final drive ratio and for drive on dynos the tire rolling radius need to be inputs to the program that comes up w/ the hp #s, the more any of those #s are off the more fictional the results. I strongly suspect many posted dyno runs are inflated by intentional or inadvertent errors of this sort

most runs are done in a gear which is as close to 1:1 as in possible., usually 4 or 5

The best chassis dyno date comes from Dyna-Paks which eliminate the tire from the equation all together, as a result the output is by far the most realistic.

Geoffrey

It depends on the dyno whether or not it will read the same power in all of the gears. The Dynapack dyno I use will produce the same power reading in all gears.

race911

Funny to see Kevin's dyno chart.......I'm sitting in my garage next to his shop right now, getting the cars ready for tomorrow. He's sure getting a LOT of automotive experience with the installation of that dyno! When he first moved in, I heard stories of his Salt Lake bike engines. Little 50cc stuff that made 38-39hp and could get up to some amazing speeds.

Bill Verburg

yes, when you input each individual ratio, the only thing missing is then the difference in friction losses which apparantly is below threshold of measuring sensitivity.

but if you do the run in say 5th and enter the ratio for 4th the resulting hp curve will show as higher than it should.

Geoffrey

For that particular dyno, yes.

Seaflat

Thanks for the answers!

Tom W

The dynomometer used was a brand new Dynojet. I have no info on the model in the printouts or data files (you still up there Ken?).

Tom W

I was talking to the folk at Jerry Woods today - I have larger injectors (part number ends in 803) that are sufficient for up to 400 hp or so. These were used instead of the stock injectors as MoTeC control of the stock has more issues than if the bigger ones are used. I also have non-stock cams to provide a mild boost over stock.

For comparison, a couple years ago I posted the dyno numbers for the original engine with a performance chip, cat bypass and secondary bypass and it showed 245 rwhp. Changing the exhaust and chip did not improve on the 245 hp (I actually lost some). So this engine is providing about 33 hp more than the original. Old dyno showed 225 ft-lbs max at 5k rpm. That original thread is here