Rear Wheel Horsepower on a Stock GTS 4.0 ??

[WillyDaP]

Having searched various Forums and the Web, I seem to have come up with a goose egg on what a stock GTS 4.0 produces at the rear wheels. I figure someone has dyno'd their GTS 4.0 even if for just a baseline prior to a tune or other mods, but for the life of me it appears no one has posted it on You Tube or just listed the info on a Forum. I am just trying to get a RWHP ballpark so I can determine what mods I may or may not want to run in NASA Time Trials. I think I will be able to run TT3 with 200 TWR tires , considering the weight of the car and a rough guess on the horsepower. My dilemma is that everyone is telling me Porsches usually come out close to their posted flywheel HP , but at the rear wheels. If anyone has done a base dyno run please post the results or just list. I am figuring a 394 HP rating at the Flywheel will likely come out in the 330-345 range , but since the car is not broken in I will likely wait till Spring for a the required Dyno certification NASA requires, but a ballpark will help me possibly decide on some of the mods I want. Thanks for reading this and I hope someone can give me an example of what they or a friend tested at.

[996C438]

A general rule of thumb I have heard is 15 - 18 percent driveline loss . Some say 20 % . That gets you a ballpark figure .

[WillyDaP]

Thanks 996, I am well aware of this and that is what I have been basing my guesstimates on, but I figured someone has actually done a Dyno prior to a tune or for NASA requirements. It figured someone had done it for various reasons but it may be I have to post my numbers next year for others as I have not been lucky enough to get a run actually done on a 4.0 GTS. Appreciate your comment.

[J-Dub]

Hey Bill,

Play around with the APR charts, they offer 91 and 93, at the wheels, at the hub etc. They show on 91 at the wheels 363 hp and 285 Tq for the GT4 and 342Hp and 285Tq. As you know the lower HP on the GTS is only due to tuning, the factory does not open the throttle all the way. All the popular tunes fix that and after a tune a GTS and a GT4 make the same HP, it does make the GTS tune a better value in hp/dollar.

GT4
https://www.goapr.com/products/software ... 0L-GT4-982

GTS
https://www.goapr.com/products/software ... 0L-GTS-982


Looks like you need official numbers to see how you will qualify for NASA events, can't help you there. Hopefully the details from APR will give you a good estimation.

[WillyDaP]

Thanks J-Dub , my concern has been based on the fact that quite a few Porsche friends have mentioned the mid-engine Cayman/Boxsters see less driveline loss due to engine placement and that makes sense. Your data from APR and 996C438's reminding me of the rule of thumb is likely all I am going to get until I can nail down a Dynojet run in 24. Since Dynojet often runs higher than a Mustang Dyno in my past experience I will likely just have to be patient. I think since the PDK is now a penalty add on, I will likely have to run Bridgerocks instead of my hoped for Hoosiers. No biggie, but the RE71RSs will hopefully last a little longer, ha.