Quote Originally Posted by Yoinkers View Post
Wes, why does your dyno chart show a loss of power, I understand the goal of midrange power, but I cannot understand why the prodigy power line dips under the stock line.


Also, can you give your position on axle gearing with dynos?


What tranny gear was prodigy's dyno done in?

When the vehicle is turbocharged, load is a huge factor. Graphing the lower RPM band is the most difficult. We ran the vehicle in 4th gear and slowed to the lowest point we could maintain a wide open throttle pull. So picture yourself in 4th gear and slowing down to like 2k and then give it wide open throttle. Not really ideal...
We use the dyno as a tuning device to hold the vehicle stationary. We then make adjustments while recording data from the vehicle and the dyno. This helps determine what adjustments are needed next. When its all done the street is where the fine tuning comes into play.

We used 4th gear for our pulls and also tested with 3rd gear. They were close enough where it didn't matter.

As for axle gearing on dynos, I personally have not seen this as a real issue. When I am taking the time to dyno a car I would start with a baseline, make the modification and retest to see the results of the modifications. If you are looking to compare something then the variables need to remain the same all the way down to how they are tested. What gear they are driven in, tire size, weather etc..

Gear ratio just changes how quickly the engine pulls through the RPM band. A gear change can deliver faster acceleration but will also get less fuel economy as it cruises at a higher rpm on the hwy. Turbochargers like load and I find ratios closer to stock work best. Over gearing may deliver adverse affects like poor fuel economy and surging on the highway.

Typically over gearing is done just to make up for the overall lack of power. If the Jeep performed great stock and you changed the tire size why wouldn't you just install the gear that puts you closest to stock? Choosing a different gear than this could give improved acceleration but would also change the rpm at cruise. The reason the performance went away is due to the weight of the tire and wheel combination. To get the performance back you will need more power.