TDT

Ok cool thanks for the diagram.

I think there could still be an open question as to what additional monitoring might be occurring via map or otherwise.

ronbauer

I'll try to find it, but I'm pretty sure that Fabspeed or one of the other companies pulled the OAP and one of the chambers was actually empty.

Ron

jmartpr

Now that would be interesting....if you find the info please post it.

TDT

So Jamie provided a small hint at this in the latest video.
There is some additionally monitoring/sensor/sensing going on, which will need to be ‘managed’

jmartpr

Mitch from M-Engineering or John from BGB could provide more info as they already have worked on the GT4RS CS ECUs....same one used on the street cars.

Avera

What is the ‘CS’ and how does it differ from ‘street cars?’

Avera

TDT

CS is the Clubsport race car

Yep, but I expect that the race cars don’t have the same constraints for street legislation, and maybe not even the same exhaust layout.
In the 718 GT4 CS the header didn’t have a cat directly attached… instead the cat was in the OPF position. Porsche also provided loud and quiet back boxes.

jmartpr

Clubsport..the ones used for the GT4 racing class....those have been racing for quite some time now and share basically the same drivertrain as the street cars.
They don't have cats on the manifold but have them on the OAP instead.
@BGB Motorsports can you add a bit of info on this?....John would be a good source of info on this car as they not only race these cars but have done some R&D which will translate to the street cars.

jmartpr

Yes...the exhaust is exactly the way you mention but that shouldn't matter a lot for ECU programing as they share the same architecture street and race cars.
Whatever options/restriction are on the street car they are also available on the race car but probably turned OFF or adjusted...they will know how to work around them.

Avera

Thank @jmartpr and @TDT

So, Dundon just built the CS version of the headers/OAPs? Namely, removed cats from headers and placed them where the GPF resides?

Does the CS have the same rear box as the street GT4?

Avera

jmartpr

The design of the Dundon system for the 718 GT4 is exactly as the Clubsports.
Besides providing more liberty with the design of the header and collector placement moving the cats farther downstream allows them to be subjected to less stress and chance of failure.
I remember on the 981, the CS and some street cars (including mine) had cat failures...never had a problem on the 718 GT4

TDT

based on similar concept yes, although Dundon may have reached the same design independently. TBF the concept of relocating cats to the far end of the OAP is not new and is actually how the early Caysters were laid out. I had a custom system on my 981 GT4 which also had this layout… full race style header with long equal length tube and motor power collector placed as far back as possible and then catted OAP


pretty much… it’s for performance and won’t sound better or have less drone.

Avera

Thank you again @jmartpr and @TDT

Although CS and Dundon have same header/OAP design, my understanding it the Dundon pipe diameters are significantly larger than OEM pipe diameters on the GT4. . . do you know if CS pipe diameters are the same as OEM diameters on GT4 and RS? What I am getting at is the larger the pipe diameter, the more flow and TQ/HP. . . and probably more decibels?

Interesting you should state OEM rear box is the same on CS and street cars, and built for performance. I never considered the rear box anything more than for drone management, which it is fantastic at achieving.

I have heard things like valves being closed in lower RPM range builds back pressure/TQ, but it always sounded like hocus pocus or, at best, a non-appreciable degree of gains.

What I can say from experience is the TQ/HP gains from Dundon headers/OAPs is hugely underrated and, in my opinion, the best aftermarket tune available for the GT4. I have tried the setup with and without the valves held open. The acoustic benefit is real with valves held open, while I did not notice and TQ/HP differences with my butt-dyno. Valves stay held open

Avera

jmartpr

Not sure on the pipe diameters of Dundon Vs Stock vs CS but the Dundon setup does relocate the collector which is why you can only use their OAP with their headers.....

BGB Motorsports

I may be late to the party so if this has been said, disregard; the race car runs the CAT in the OAP and has holes for being able to look in there and monitor detoriation of said OPF or cat because they were asked to do so. These cars run one O2 sensor and that's it. The 2nd bung is for us to look in. The street car gets this manifold with cats in it and matains the OPF in the rear section.