AKS Racing

I spoke with the Mustang Dynamometer operator/tuner, and he said the conversion is 12% (he says it may be more like 15%) between the Mustang and the DynoJet. All of my past runs have been on the DynoJet. If indeed it is 12% (or 15%) additional then I am happy with the runs. If the Mustang and the DynoJet are roughly equal (which I don't think so), then I am back to where I was roughly 4 years ago.

So.... if anyone knows the conversion factor, you might provide some relief or just lead me to further frustration.

Jeb, TJ, BTF, chime on in.

Aaron

SloRvette

I can tell you my car dyno'd at 358 at the wheels on a MD 1750 DE and ran 123 mph in the qtr at 3400 lbs. Exact to the byte tune in similar conditions. On this particular dyno I think the difference is closer to 20%.

AKS Racing

Hmmmm... Nobody has mentioned a 20% difference between the Mustang Dynamometer and the DynoJet. I do not want to get my hopes up to have them dashed. Though I would like to think that the additional port work and intake/TB change made a difference.

Hmmmm....

Aaron

black_89_vette

I have heard of a 10% difference between the 2 with the Mustang reading lower than the Dynojet.

Alvin

I wouldn' tworry about it too much.

A dyno is good for before/after runs or seeing trendlines in power/torque curves.

vader86

I wouldnt worry about it either, 10-15% might be the average but there are always variances. If theres a problem with the engine, it should show on the curve, not necessarily the numbers.

Best thing is to just get it tuned, and find out where your power peaks end up.

DieL

depends on what the dyno operator wants them to be

snootworks

Agreed. We run a Dyno Dynamics (load) dyno in our shop, and started out supplying customers with straight-up numbers. Despite months of attempting to educate the masses on a) the slew of important and valid information we could provide them regardless of peak numbers and b) the differences between intertial and load dynos, we ended up caving in and using a 17% correction factor. (17% since the closest dyno to us, which happens to also be a DD unit, uses 17% as well.)

AORoads

What is the "correction factor"? What is it correcting for?

AKS Racing

The conversion factor is important to me, as it will show me where I stand vs all of the other runs that I have made on my '87. The curves looked good, but I would just like to know that I have not gone backwards with all of the changes I have made in the last 3+ years. My peak numbers on the MD almost matched the DJ numbers from before the intake, TB, portwork, and much tuning.

Thanks,
Aaron

Fastmax32168

I dont think there is a correct answer to your question. You can get substantial differences between same brand dynos when running the same car. It can be altered by the input the operator puts in when he runs your car. Lots of things can cause them to be different.
So what you are really wanting to know is what is the correction factor between this particular mustang dyno the way it was set up vs the Dynojet I ran on before and the way it was set up?
IMHO anything you use is just a guess and really doesnt have any validity other than easing your mind.
Roy

vader86

The dynojets can't simulate aerodyamic and rolling resistance load that the Mustang can. Dynojet uses a drum of fixed mass, Mustang uses electromechanical resistance to apply the load.

Neither reads wrong, they just read it differently. Dynojets are better for bragging numbers.

C4DC

Sounds like you need to find a dynojet to run on.

tjwong

Here in my area I have a dyno jet nearby. I have had customers tell me that its about 12% to 15% higher than what my Mustang gives them.

dizwiz24

And that is the type I will run on.

If I'm talking with my friend that has a mustang GT or WRX, Id rather be the one talking the higher #'s.

ninetyfivevette

That's insane... That means on a DJ, my car would have put down between 387 and 397 at the wheels, with basically an LT4 hot cam and stock heads... Plus your tuning. I guess it really is all in the tune!

ANDREWS

What I Was Told Was The Same Thing With The Super Flow Dyno, That Typically The 10-12% Factor Is Added To Get Close To Other Dynos. Stock Run Was 351 On A Hot 90 Degree Day And Two Weeks Later Put Heads And Cam In And Ran 431. So About 80 Hp Was Gained And If 10-12% Is Added It Is Right On Par With Those Getting 470-480 On Other Dynos. Still Got A 80hp Gain For Heads And Cam,"at The Rear Wheel."

AKS Racing

I think the question has been answered. The difference between the Mustang Dynamometer and the DynoJet is ~12%, with the DynoJet reading higher.

As an aside, the dyno operator said that he can adjust the MD to read the same as the DynoJet, but then when you run in the 1/4, the trap speed will not match up with the HP that is indicated by the dyno. He feels strongly that the MD is a more accurate indicator of "real HP".

Thanks for all of the input.
Aaron

AORoads

Thanks for the explanation.

snootworks

If you want to dig into the nitty gritty then yes, Dynojet's read wrong. They're popular because they're less expensive, not because they're better.