Dyno conversion...rear wheel to real HP ?

[hdheritage97]

I just came back from my dyno tuning trip and I'm kinda bewildered. The stats came in well below what I had thought they would....or am I wrong about the outcome. After I left, probably when the shock was worn off, I realized that I didn't ask if the #'s were rear wheel #'s or true HP/Torque #'s. My guess would be that they are rear wheel since it's on a roller right ? And if so, what would the real #'s be if that is the case ? The #'s are as follows......313.8 HP @ 5850 RPM's and 323.4 Ft/#'s @ 3350 RPM's. I expected WAY bigger #'s than this but then I thought that the adjusted #'s MAY be in the range I was expecting IF these are rear wheel figures. We also did a couple of 1/4 mile simulations and those #'s would kinda back up what I was thinking. They did the first run, drove VERY conservatively, no hard launch, and pulled a time of 13.196. I got behind the wheel, made a hard launch, power shifted through the gears, and pulled a 12.059. If these #'s are correct, the HP/Torque can't be real HP could they ? If anyone has any real experience with this, let me know what you think, I'm going crazy here.....lol.

Cliff

[keithw]

Good rule of thumb is divide by .85 to get crank HP.

Keith

[Hal Copple]

By coincidence, i was asking about dyno's and hp and torque at the Charlotte Autofair this afternoon, with the Roush engine consultant for Superformance, down from Livonia, and another automotive engineeer. They both have lots of dyno experience, both engine and rear-wheel.

We talked, i listened, for about a half hour.

The Roush engine man said he uses 17% for drivetrain losses in the SPF cars, he has done many dyno's on them, with the same engines. He basically told me my rwhp with a stroked, strong Windsor, at 350-360 hp twice, two different Dynojets, was about 450/460+ or so hp at the engine, if the exhausts and such were on.

They test engines two ways, just the motor, open headers, no air filter, and with all the stuff hooked up. My guess is that you have about 400'ish engine hp.

Stout, too.

[mstngjoe]

If you don't have any prior experience with a chassis dyno, it can be a humbling experience for most people.

What kind of dyno was it? SuperFlow, DynoJet, etc.

Where you able to do any tuning of the carb and/or timing adjustments?

Was the air/fuel ratio monitored?

Depending upon your original state of tune, I've seen as much as 50 hp improvement (at the wheels) thru carb and timing adjustments.

[hdheritage97]

The unit they used was called an MS.....Mustang Systems I believe it stood for. Yeah, they tuned it while it was there, reduced the jet sizes, adjusted the MSD distributor with a spring and advance change, and adjusted the timing also. It did improve quite a bit from what we started with but still isn't where I thought it would be. So now I need to figure out why it isn't, which of course is killing me.....lol. This was supposed to be the big bad engine from the glory days and it's not living up to it's rep....lol. Actualy, we picked up 60 hp through tuning so it wasn't a total loss at all...and as I said, it turned a fairly respectable 1/4 time on the dyno. I just want to find the missing horses, if they're truly missing, and see what kind of times it could pull then.

Thanks,

Cliff

[mstngjoe]

There's some hp/tq right there.........Mustang Systems dyno.

They typically run 10%-15% lower than say a DynoJet. This is because the add in some "drag" factors that others do not.

Check out this article:

http://www.mustangdyne.com/Articles/...article-03.htm

I also saw you were contemplating a cam change. Are you running a mech or hyd now?

[hdheritage97]

I just expected better results than what I got really. The car runs VERY strong but the #'s don't seem to back it up. As for the cam...I'm running a solid lifter cam right now. I'm not married to a soild, but have no troubles staying with one either. The cam change is brought about by the #'s really. Besides, I bought the engine set up as is, except for the carb, and I never leave anything alone.....lol. I'm gonna try and find the rest of this article and read the entire thing and see if I can't figure out what's going on.

Thanks,

Cliff

[mstngjoe]

At the bottom of the page I linked, you will note that it's a 4 page article. You should be able to see them all.

You might also consider a custom cam. Tech has come a long way since the tp hit the street.

I had a custom cam spec'd by Buddy Rawls. I'm EXTEMELY happy with it and will use him on my next engine too.

Here is a link to some of Buddy's theory:

http://www.wighat.com/fcr3/camtruth.htm

Good luck.

You sure have a nice ride there.

[hdheritage97]

Thanks...I like it and I'll like it better when I bumped some mnore go out of it. Thanks for the cam info and the link and I LOVE your ride...I have a thing for the pony. Before this car I owned a 68' GT500KR so I know a thing or two about the ponies....lol.

Cliff

[mstngjoe]

Cliff,

KR to Cobra........sounds like a natural progression to me.

And thanks for the props on my Mustang. It's been a blast doing all the mods and it goes pretty good.

[Mr.Fixit]

Dyno numbers are irrelevent, unless you are mid-process in an engine development program. It takes more than HP to get around a racetrack quickly.

[mstngjoe]

Originally posted by Mr.Fixit


Dyno numbers are irrelevent, unless you are mid-process in an engine development program. It takes more than HP to get around a racetrack quickly.

Quite right. The track is where the results matter for the cars that are raced.

IMHO, the chassis dyno is the best tool for dialing in a given combination and for evaluating different set-ups.

Lots of "also rans" have bigger hp numbers than the winner might. It's the well thought out total package and the skill of the driver that will produce a consistant winner.

That and a little luck from time to time.