jrussell

Anyone know why there is a difference between the two? I know one is inertia and the other load, but wondering why they would use different gears?

trik396

Never been back to dealer.... can you blame me?

Guess I've been wasting my time... should I remove my numbers in my sig?

jrussell

It would be interesting to see the difference, if any.

Don't feel bad. I've wasted plenty of time (and a little $) on dyno runs. Did you see the post where I got 405hp on one dyno and 570hp on another dyno a few weeks later (with all the same mods/programming)? I would definitely call that a waste.

trik396

Ouch...

Well I've only been on a Dynojet and the first pull I did the operator wanted me to try to keep her in third... which I did by letting off throttle right as it shifted into OD. I think I hit 380hp... and one wasted pull...

And I don't understand the difference in Dyno's either. Why would a third gear pull differ from a OD one? My thought is that it would be actually harder to make a better number on an OD pull because if your engine isn't producing serious numbers, you won't accelerate as quickly as you would in 3rd gear... make sense? Gears multiply torque... that's all they do really. So first, second gear the torque multiplication is MUCH greater than 3rd at 1 to 1 and OD which is obviously less than 1 to 1.

OldSmokey

I dont know much about dynos, but from what I understand mustangs are load dynos, so you should make your pull 3rd or 1:1. While on a dynojet you dont get the same load so you need a higher gear to help load the motor and make some boost.

I may be way off but thats what I have gathered

rahtok

What's the 1:1 gear on the 6 speed then? Is it 6th?

TNLoneWolf

5th gear is 1:1....I think that is correct, but saying that, this last weekend the dyno operator had us all run in 6th for manuals and 5th for 48RE's. He said something about loading up the Dyno? I'm still not sure which is which or why....

trik396

I wish there was a 5th gear in the 48re....

jrussell

Lol...wouldn't that be awesome!

Swayse

I've only dynoed on a Dyno Jet, it was fun, but a waste of time IMHO. Guys at high elevation love to use the correction factor too

If the Mustang Dyno is anything like the load dyno I use to dyno my tractors, I would love to try it. We hooked up the PTO on the tractor, went full throttle, and pulled the rpms down with the dyno. Then out came the tools, and a 3/4 turn of the screw later, the 8.3 Cummins was making 20 hp more. I had a blast.

jrussell

That makes sense to run in 4th to help increase the load, but aren't the numbers then skewed because the gear ratio isn't 1:1. If running in 4th skews the numbers on a Mustang it seems like the same would happen on a Dynojet?

If the Dynojet is seeing lower HP due to the lack of load, and then people are running in 4th to help inflate the numbers back up, then that doesn't really tell you squat about the true power output. If that's the case you might as well estimate the numbers yourself.

purduepurdy

Thanks for the insight guys, got my smarty jr. today and have been playing a bit. Thing is something else...

trefling

With enough practice and patience you can calibrate your dyno to get you good accurate #'s and use 3rd (non OD) when on a dyno. Many shops do it simply not to break stuff. But just like anyone here knows how at 52mph where the converter simply lock you get instant more power and the turbo's really get a change to push with proper engine load.

4th gear gives you more true HP # simply because your engine has more load to work with, but things break too

TexasCTD

I have dyno'd quite a bit. And, I have always had very good luck with Dynojets. My consistent experiences and numbers on several DJ's show to run the truck up to about 70+ in 4th gear/od............and then hammer it up to about 120mph. It won't shift down and you will get a good positive run.

..

purduepurdy

Well, the dyno event was pretty fun. I went with a group of mustang and pontiac gtp guys so i was the guy smelling up the place. Couldnt get a good reading on the dynojet there in 3rd so we used OD. The guy there said he had had a few diesel guys there before(they left their mark on the ceiling thanks to stacks) and said most had to use higher gearing to get realistic numbers???
Ended up using the 100hp tune and got about 386hp with 707ft/lbs. Anyways love the smarty jr! Got almost 1.75 mpg better afterwards driving home for easter.
Happy Easter everyone!