Dyno testing...different results????

[forensicsteve]

Just took my car for dyno testing in New Orleans
They gave me 3 runs

On setting 1 the results were
at 5250 rpm max power 372.3
at 3500 rpm max torque 423.5

The technician said these were real world numbers.

Then he switched the machine to setting 5 which was the same as a DynoJet test

at 5500 rpm max power 497.7
at 4500 rpm max torque 515.2

He said that the trade publications etc use the DynaJet numbers

Previous owner had upgraded the car but the Merc dealer I purchased vehicle from, didn't know to what extent, other than it sounded much louder than normal.

 

[GR8_ASP]

I am not aware of any trade magazine standard. OEM's use engine dynamometers and not chassis dynos to determine an engines rating.

I am skeptical because
- The rpms differ for when peak power and torque occur. I cannot understand a reason for that discrepancy
- The differences are much more than a Dynojet versus a Mustang dyno.

Stock Dynojet SAE corrected numbers for a stock GTS should be around 400-410 RWHP. Exhaust alone (assuming no headers) only nets 5-15 hp.

 

[forensicsteve]

Ron

The testing machine was a Mustang Dynamometer

The latter numbers could be inflated. But I don't know what upgrades have been performed. Think I will take it to another Dyno shop and compare results

 

[GR8_ASP]

I should have mentioned that the 370 hp figure for the Mustang dyno is reasonable for a stocker. Especially if tested in hot conditions.

 

[forensicsteve]

Thanks Ron

Think I will work from the lower numbers then for my modest upgrade plans.

 

[Russ M]

Just took my car for dyno testing in New Orleans
They gave me 3 runs

On setting 1 the results were
at 5250 rpm max power 372.3
at 3500 rpm max torque 423.5

The technician said these were real world numbers.

Then he switched the machine to setting 5 which was the same as a DynoJet test

at 5500 rpm max power 497.7
at 4500 rpm max torque 515.2

He said that the trade publications etc use the DynaJet numbers

Previous owner had upgraded the car but the Merc dealer I purchased vehicle from, didn't know to what extent, other than it sounded much louder than normal.

Mustang Dyno's are bugged for the most part, a good friend of mine got their top of the line unit with a promise that it is accurate as can be. After installing it they quickly realized that their numbers were anything but accurate.

That is when the **** hit the fan, Mustang dyno technicians spent a good 1/2 a year trying to figure out why their dyno was NOT delivering as promised. And finaly after all that they admited that they had been having problems with one of their computer modules and that they were developing a new one which was going to be tested on my friends asap. After another 1/2 a year they finaly delivered the new components, and this time it actualy delivered as promised. Their dyno pulls are within 1% of their dyno jet consistantly, and they seem to be happy with the unit now.

 

[Dave Dugal]

Hi Steve.

As mentioned above, 400-410 corrected RWHP is probably about right for a stock GTS. Figure approximately a 12% driveline loss on a Gen II, so that's around about 448-460 HP at the crank. [Yes, I know; this is totally over-simplified]

Dynos do vary, though. Here are two dyno runs from my '97 GTS (notably "hot" from the factory that year) with high-flow cats, a Corsa cat-back system and drop-in K&N's installed:

and three years later with no modifications (other than another ~20,000 miles on the odometer):

The first was done on a DYNOJET on a dry day in October. The second was done on a Land & Sea dyno on a damp, cold rainy day. It's possible that weather conditions varied the results, but it's more likely that different dynos read differently.

IMHO, stick with one set of settings on a dyno at a particular speed shop. Get a baseline, do your mods, then go back to the same shop/dyno/settings. The delta change should be pretty accurate.

 

[davem]

Steve,
Several things could be happening here. One thing that you can fool with is the correction factor. If you look at Dave D.'s dynosheets, you can see the impact of this.

A dyno measures the power that a car is making that day. Most apply a correction factor to that power number to compensate for air temp and barometric pressure. This way you can compare numbers on the same dyno for different days, as they all are mathematically forced to a standard temp and pressure.

Dave's dynojet graph is shown with SAE correction, and the Land and Sea graph is shown with STANDARD correction. We own this Land and Sea dyno and had wondered for a long time why we were slightly diff. than the Dynoject when the dyno's have about the same intertia and wheel diameter. Turns out we had the dyno set on STANDARD correction which reads 20 hp and 20lb-ft of torque higher on the same run than SAE. You can see that the shape of the curves are the same, just one is a little higher. We now correct all our graphs to SAE and compare very well to a dynojet.

Your operator probably showed you the uncorrected data, which may be what he meant by "real world numbers" then applied the SAE correction. However, it looks to me like he changed a lot more than that, as Ron pointed out, corrections should not move where your peaks are. I think that mustang dyno has problems in their calcs too (you can fudge numbers quite easily with a dyno, looks like Mustang dynos may be playing some games). Did both graphs have hp and torque cross at exactly 5250 rpm?

good luck,
Dave.