JeepLab Prodigy Install LIVE

[UselessPickles]

I think the 4.88 gears on Jesse's Girl could have significantly affected the dyno results, especially because it was run with stock 32" tires, and because of the nature of how a turbo works.

The overall gear ratio of 4th gear on that setup is close to 3rd gear with 3.73 gears, and is like something between 2nd and 3rd gear with 3.21 gears. This means that Jesse's Girl did not have as much load on the engine when run on the dyno as compared to Prodigy's dyno runs. This would lead to lower dyno numbers for 2 reasons:

1) The already-discussed issue of quicker acceleration on the dyno leading to lower dyno numbers because more torque is lost to accelerating the drive train more quickly.
2) Less load on the engine and quicker acceleration causes the turbo to spool up more slowly with respect to engine speed, so boost increases "later" in the rpm range, resulting in a lower peak torque that occurs higher up in the rpm range.

Additionally, common dyno practice is to use the transmission gear that is closest to a 1:1 ratio. 5th gear is a 1:1 ratio on the Wrangler, so it's possible that Prodigy's results are from a 5th gear dyno pull, meaning that Prodigy's dyno pull had even that much more load on the engine for slower acceleration, allowing the turbo to spool up at lower rpms, and giving up less torque to accelerating the drive train.

To get as close to Prodigy's conditions as possible, we need to find out what transmission gear they used for the dyno pull, then run Jesse's Girl one gear higher with stock tires. Even at one gear higher, Jesse's Girl will still be geared overall a little shorter (numerically higher), plus the driveshaft will be accelerating more quickly than the stock jeep (using up some of the torque), so I would still expect the numbers to be a bit lower than Prodigy's results.

[JeepLab]

I think the 4.88 gears on Jesse's Girl could have significantly affected the dyno results, especially because it was run with stock 32" tires, and because of the nature of how a turbo works.

The overall gear ratio of 4th gear on that setup is close to 3rd gear with 3.73 gears, and is like something between 2nd and 3rd gear with 3.21 gears. This means that Jesse's Girl did not have as much load on the engine when run on the dyno as compared to Prodigy's dyno runs. This would lead to lower dyno numbers for 2 reasons:

1) The already-discussed issue of quicker acceleration on the dyno leading to lower dyno numbers because more torque is lost to accelerating the drive train more quickly.
2) Less load on the engine and quicker acceleration causes the turbo to spool up more slowly with respect to engine speed, so boost increases "later" in the rpm range, resulting in a lower peak torque that occurs higher up in the rpm range.

Additionally, common dyno practice is to use the transmission gear that is closest to a 1:1 ratio. 5th gear is a 1:1 ratio on the Wrangler, so it's possible that Prodigy's results are from a 5th gear dyno pull, meaning that Prodigy's dyno pull had even that much more load on the engine for slower acceleration, allowing the turbo to spool up at lower rpms, and giving up less torque to accelerating the drive train.

To get as close to Prodigy's conditions as possible, we need to find out what transmission gear they used for the dyno pull, then run Jesse's Girl one gear higher with stock tires. Even at one gear higher, Jesse's Girl will still be geared overall a little shorter (numerically higher), plus the driveshaft will be accelerating more quickly than the stock jeep (using up some of the torque), so I would still expect the numbers to be a bit lower than Prodigy's results.

I have never heard of a 5th gear dyno.

Ive also been told by separate people that the gearing doesnt matter with a tumbler style dyno machine.

Im not an expert, these points, I have heard from different people. The power comes thru the drive train, and the rear wheels roll the tumbler. The tumbler dosent know what the gearing is, and im not sure the number of teeth in the ring alters the power from the driveshaft thru the wheels.

Maybe I can get someone from dynojet to tell us exactly.

[UselessPickles]

Ive also been told by separate people that the gearing doesnt matter with a tumbler style dyno machine.

The math might work out so that it doesn't really matter for N/A or supercharged engines, where there is a direct relationship between engine speed and torque output. But we're talking about a turbocharged engine here. It takes engine load and time to spool up a turbo. Just compare a 3rd and 4th gear run from Jesse's girl and you'll see how much of a difference the overall gear ratio can make.