robmypro

Great job guys. Couple questions for you.

If stock is 475 hp (not at the wheels), given what your baselines were on this car, what are we looking at for crank hp with cats now? I know this isn't an exact measure, but what would your estimates be? Same question for torque.

Second, since I live at higher altitude would you expect that I would have more benefit or less, given the additional breathing capabilities?

Thanks guys!

Maxi_z

I would also be interested if someone can let me know what are the averege corrected crank hp on a dyno of a std 991 gt3.

We put mine on a 4wd dynaflow dyno with bmc airfilters and side mufflers delete valved pipes and it was a little low at around 451 bhp but keep in mind it was filled with 10w60 racing oil and only a big front vent on the dyno nothing for the air intake.

I would also like to know if to do the tune you need the ecu to be sent to you or
is there another way?

Thanks

Charles@dundonmotorsports

Technically the 991 gt3 is 475DIN HP Which is 468 SAE hp which is the correct HP number to compare to.

With a 15% drivetrain loss, (which the dyno we use shows consistent 14-15%) 468 x .85 = 398whp which is what ours have been base lining at. With that 15% loss, that means 424whp = 500crank SAE HP which is 507 DIN HP. Or a 32 crank HP gain At peak

We will have a way to tune without needing your ECU once we are finished with the tune process.

At higher altitude I would expect the gains to be slightly less as there will be less cylinder pressure

STG

Charles, so you think the actual higher flowing cats are causing the mid range loss, or the header pipe design?

robmypro

Thanks Charles!

Charles@dundonmotorsports

From ALL of the 991 testing I have done I would say the midrange loss is not due to the header design or the cats but more the entire system length and design. There are waves that flow from bank to bank across the exhaust system and with the added length needed to retain similar header design to the race cats, that length is too long to allow proper wave cross talk between banks and this is why there is a slight power loss

From what I have learned with this catted setup I am going to try and redesign it to eliminate this loss.

I fairly confident with full ecu tuning and exhaust cam timing adjustment we can eliminate that loss, just need time on the dyno. I am not sure we will get to the same power as the race header setup but I think we can have 2 setups that are close in relation to power outputs and curves after extensive tuning and adjustments to collaborate with our exhaust

STG

Well, amazing work and documentation. It really shows who the enthusiasts and guys who love what they do are. It's not just not about a paycheck.

Charles@dundonmotorsports

Honestly I consider this my hobby. It's what I love to do. I have spent about 30-35hrs on the dyno this year. None of it was making me any money, just money going out so that's about $2000 out of my pocket just in R&D. But invaluable and sometimes it's the only way you learn and can be able to improve. Before this year, time was my biggest limiting factor. I do all of this on my own personal car (when and if I have time) so why not on everything else. It's just time, effort, and being able to stay outside the box.

911_RS

Almost switched the O2 sensors backwards!
Thanks for the help Jamie!


Very impressive results on the catted headers, even there's a slight dip at mid range you still got 30whp max gain! That's a lot if you ask me, I doubt if some other aftermarket headers can even match this. I'm sure you can work out something about the small power loss with a right tune. Keep it up guys!

Jamie@dundonmotorsports

Heading to the dyno with our 997.2 RS D3 setup (Headers, CF airbox and 4.0RS IM) and the 991 Race and Catted headers.

Will be getting some more time to tune the 991 Race setup and test the Catted system with the existing tune and with some cam timing tweaks in the midrange.

loungedog

Very exciting news and can't wait for the updates on the 997 RS

Jamie@dundonmotorsports

I'll put up some quick hits as they come in tomorrow!

loungedog

Jamie...Just dropped off my RS tonight at the dealer to install your headers on my 2016. Can't wait to hear what the RS will sound like live and to see what power I would feel once I have a little room.

Jamie@dundonmotorsports

Let us know how you like it! 911_RS (from the Philippines) and Slip (from Australia) were some of the first to get it on their RS. You and EarlierApex might be some of the first in the US!

Excited to hear your feedback!

Jamie

GT3 KSA

Is it a good idea letting the dealer know you are installing this? Won't it void your warranty?