No power gain from Underdrive Pulley?...

[Nine8Six]

VJ should have included a before dyno run in the same environmental conditions as he tested the UDP afterward. I think you loose 10~15HP between seasonal air densities. It can be difficult to track small power gains sometimes.

My Boxster gains about this +10hp... when the wind blows from behind loll

Perhaps he forgot to install the shorter serpentine belt required to make the kit working?

[thstone]

Originally Posted by Nine8Six

VJ should have included a before dyno run in the same environmental conditions as he tested the UDP afterward. I think you loose 10~15HP between seasonal air densities. It can be difficult to track small power gains sometimes.

My Boxster gains about this +10hp... when the wind blows from behind loll

Perhaps he forgot to install the shorter serpentine belt required to make the kit working?

+1 ^^^^

The dyno baseline test was on 10/22/16 whereas the UDP test was on 11/26/16. The temp and humidity correction (or poor correction) could easily result in a margin of error equal to the magnitude of the difference under test (3-5hp).

He needed to do a baseline and the UDP test on two consecutive days at the same time of day when the weather was generally constant to be able to accurately measure the difference.

[WorkInProgressK]

Originally Posted by thstone

+1 ^^^^

The dyno baseline test was on 10/22/16 whereas the UDP test was on 11/26/16. The temp and humidity correction (or poor correction) could easily result in a margin of error equal to the magnitude of the difference under test (3-5hp).

He needed to do a baseline and the UDP test on two consecutive days at the same time of day when the weather was generally constant to be able to accurately measure the difference.

Considering the difficulty of the change. This could be planned on the same day. Then again we are talking inertia change. Just like a lightweight flywheel but at a microscopic scale. Engine will rev faster without load. That's if the parasitic drag of the equipment doesn't increase from the pulley size change. With load, nothing will change.

Hey if you are looking for most horsepower output, try running a lighter oil both in the engine and transmission. You will have way less parasitic loss and more income loss.

To be honest, I feel my boxster would benefit from a beefier flywheel looses revs too fast for my taste which makes up shifting a rev match fest(6 speed).