dsddcd

Just following up. I was able to do some demo laps with some clients during a private event and the car ran very well. We ended up putting my old Header & Tune GT4 up against the car and the difference between them down the straight, 50-125MPH, was about 1/2 a car after the upgrade, previously the GT4 would easily put a car per gear! Sorry no video's of both on track but here are a few hot laps.

cobalt

We found the best you can do depending on headers is 380BHP on a mustang dyno. Doesn't matter S, or GTS, boxster or cayman. The other issue is apparently the 981 uses the same tranny as the GT4 and with the added power have seen some trannys detonate.

Looks like you were having fun,

Yogi911

If they have the same tranny why are you seeing failures if the gt4 is 385 from the factory and weight is similar?

cobalt

Track use. The GT4's are dropping 3rd gear like crazy. I know of one GT4 owner that is on his third tranny and a dozen or so who have already replaced it once. I have heard that it was a manufacturer defect and they have since corrected it. Best to break it now under warranty. I doubt the 5 HP makes a difference but when your down at 330/340 it isn't as much of an issue.

ajw45

The 3rd gear issue doesn't seem to be power related related, more just a bad batch of trannies. I have over 3k miles without issue on my 4l X51 pushing around 460+ hp and there are a bunch of others out there that are doing just fine. Plus, trannies are torque rated not hp rated and most mods aren't making a ton more peak torque. Even the GT3 3.8 making 90 more hp only delivers another 16 ft/lbs of peak torque over the GT4.