Looking at my dyno sheets it looks like almost peak hp at 4500 and stays about the same through 6k+. Head restriction? (rect ports) Porting? Carb? (1000hp) Jets? Exhaust? (3 1/2" pipes)...looking for answers MY69WEBSITE (http://www.fast69chevelle.com)

tia

Frank

where does the peak tq and hp cross? also is this an engine dyno or chassie dyno?

Chasis dyno 5250...

HP is a derived figure.

HP = (TQ x RPM) / 5252

HP and TQ are always the same at 5252RPM. Where is your graph on the website?

Andrew

Here is a link to a dyno run: dynorun (http://www.falconrc.com/dyno1.jpg)

from what i see in your combo, your dealing with a short duration cam and lower compression ratio everything looks good in short order as you have it now, since your dealing with a 496 motor its not going to be a high rev motor if your looking for more rpm you will need a bigger cam in the 270 range and 12 to 1 compression to move that power band up..............other wise i think all looks fine from what i see.......

Looks like a regular old dyno test to me. The multiplication of the torque converter affects the lower end of the torque curve, causing a falsely high peak. The tuned frequencies of the various engine components will create small peaks and dips in the curve.
One thing I find unusual is that you are losing 225 hp from your engine dyno test to your chassis dyno test. I would expect an engine with 653 hp at the flywheel to present at least 520 of them to the wheels. How does the setup differ between the two tests?

Yes, everything below about 5k on your chart is increased from torque converter multiplication and can't be correlated to FWHP really. Nothing looks too strange. A/F looks decent except I'd agree you are losing a lot compared to the engine dyno or never had what the engine dyno said.

You have to remember on the engine dyno you do not have power steering pump, alternator, fan, etc hooked up to it. I am also using a th400 and 9" with a locker both of which consume more hp. There is a mag (car craft or ?) that recently published an article on hp consumption. They have a car that uses some of the same parts as mine and consumes an average of 35%hp from engine to chasis. I did not think your hp would flat line for 2500rpm?

I checked out your website..nice car and some impressive performance at the track too graemlins/thumbsup.gif

It looks to me like your converter is mulitplying/not approaching minimum slip until about 6000 RPM. This gives the appearance of a "flat" HP curve.

I see this effect with my own car on the chassis dyno when I run on the engine and with 100/125/150 shots of nitrous. NA my converter flashes to 4000 and with a 150 shot it gets closer to 5500 RPM.

Here's a link to a dyno test of a similar motor/tranny/chassis setup that only loses 20% to the drivetrain. I think 35% is way beyond normal expectations.

http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=4;t=014258

Thanks Chris :cool:

Doug, thanks for the input, that sheet was on motor alone. It looks like my Torq curve peaks and then just slides down. Is this normal or do I need to find a way to broaden the descent? tia

onova, I agree. I do not know the setup on the engine stand (I do have the dyno sheets though). I can't help but hink there is something I can do to recover the lost hp.

Wonder what would have happened if you snugged down the lash a bit.

I've never dyno tested, nor do I care to. Thats a sweet quick ride. I wouldnt mess with it. Converter seems a tad small to me.

Originally posted by onovakind67:
Here's a link to a dyno test of a similar motor/tranny/chassis setup that only loses 20% to the drivetrain. I think 35% is way beyond normal expectations.

http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=4;t=014258 True the Redline Oil Chevelle only lost 20%. But they used a 5 speed tremec 3550 manual transmission. I assume the tranny lost somewhere between 16 and 18%, and the rest of the loss was exhaust system, and air conditions.

I agree that 69bigblock's car is losing more power through the drivetrain than expected. But like he said, he engined dynoed his engine without any accessories, the Redline Oil's 540 was engine dynoed with alt and waterpump connected. I personally would have figured a ~475 rwhp for his combo, but who knows how much power each component is robbing.

69bigblock, have you considered putting some synthetic transmission and diff lube in? Also perhaps some underdrive pullies, and/or an electric fan setup. This surely will gain you some ponies at the wheels. Also, if you ever go back to the dyno, you could try unhooking your exhaust, and see how much power is being lost there.

That is a pretty normal curve for a car with a very high stall converter. My comment about nitrous was just to try to indicate that an engine with a lot of torque, like a BBC or a SBC with nitrous with a very loose converter, will give you a printout like you see. I've seen dozens of dynojet printouts and I don't see a problem with the shape of yours. If you had a manual trans or a real tight converter you'd see a more "normal" curve.

Your converter must flash very high with the nitrous.

Let me suggest that your torque converter is no longer efficient, that it's internal clearances are too far out of spec.

Easy enough to compute given the right data.

Theoretical MPH = (RPM x tire diameter x 2.96) all divided by (gear ratio x1,000)

Compare theoretical mph to actual mph observed at the same rpm through the lights. The difference in loss represents your efficiency percentage. A good non-lock up converter will achieve ~ 3% to 7% loss. Marginal up to ~ 15% loss. Beyond 15% and your real performance awaits a converter upgrade. I have measured up to 18% efficiency loss between input and output rpms on my own tired converters in the past - yet they still get off the line excellent.

A cross check calculation can be done by rpms.

Theoretical rpm = (MPH x gear ratio x 336) all divided by tire diameter. Compare as shown above.

Thomas