Dyno'd the NPI Automatic

d98gt

Founding Member
Mar 14, 2002
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Went to a gathering at a local shop and decided to put the little automatic NPI on the dyno:rlaugh: I put in two runs with the second being the better of the two, though not by much.

This dyno was a MUSTANG dynamometer aka "the heartbreaker". When I found out it was a mustang dyno I was pretty hesitant to even pay money to see such low numbers :rlaugh: Regardless I decided to throw the high-miled mustang up there to see what it had.

The first pull had a small error since we didn't exactly pick a great mph to start from, so the car downshifted and didn't get a good looking graph. It put down 200 horsepower and I don't recall the torque since I didn't get the graph but I beieve it was in the upper 230s. The second run was a bit better and I still only revved the car to 5600 (not that it exactly matters) though resulted with a 201 horsepower and 242 torque.

Now I recall that mustang dynos read lower, though I don't know how to go about recalculating to even get an idea of what I would put down on a dynojet. I was thinking I was going to put down 175 :rlaugh: so not bad to break the 200 mark.

I'll post the graph tomorrow :nice:
 
That's what I thought aswell, as I figured I would put down 195 on a dynojet. The car surprised me a bit :)

The car has a mac prochamber, weld-in magnaflows, gears (though that doesn't mattter) and pulleys. So not "stock" though not modified much.
 
Did they do those runs in the Dyno-Jet Simulation mode? Otherwise the Mustang Dyno was calibrated incorrectly. Your numbers are close to what 99 - 04 GT Auto's put down on a properly calibrated Mustang Dyno. Your estimate of 175 is close to what it should have put down.
 
It wasn't calibrated like a dynojet because the operator even said that the car would put down quite a bit more on a DJ. It was a group gathering and there just so happened to be a guy there with a turbo fox that dyno'd 3 weeks before on a different shops mustang dyno and he ran again. He said he put down 607 previously and when he was on the dyno today, the car put down 599. Car was definitely a sleeper as it was quieter than my mac prochamber/magnaflow setup until he got on it :rlaugh:

I don't believe I am losing the 20% that most autos lose since this transmission was rebuilt not too terribly long ago. So for a 98 GT with no programmer currently, a lovely CAI, steeda pulleys, 3.73s, and exhaust--the car is decent. I don't believe in "factory freaks" by any means, though the car has always surprised people even at the track with the low 14 second passes.
 
I will also be getting it dyno'd again in a matter of 2 weeks to ensure the nitrous is dialed in for the track so i'll find a different shop to see what's up. As for now--I'll stick with my 201 horsepower.
 
i'm betting that the 3.73 gears are what caused the dyno to show high numbers. with the gears, you have no true 1:1 ratio gear. i'm betting the operator did not correct for that.
 
I mentioned having gears which is why we had problems on the first pull since it downshifted. I also had no real control of o/d as it would shift into it before redline.

This car as it sits is a 13 second car and that will be done on the 11th when the track opens (if the weather isn't 80* :() I will be getting more runs done in a matter of weeks so that I can dial in my A/F ratio. I need to get my xcal2 back from JMS before that however.
 
If the car was shifting on the dyno, that will affect the numbers as well. For a dyno pull with an auto to be accurate, the transmission needs to be in 3rd the entire pull with the Torque Converter locked, otherwise you have bogus numbers...