John D II

We just finished fabricating another complete 991.2 system, pictured below - call us for special Rennlist member discounts on our 991.2 valved X-Pipe, 991.2 HJS Hi-Flow cat sets or both....




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991.two

John, Your welds look perfect and your finished X-Pipe is beautiful. I have one of your X-pipes but some resent discussions about the X section of the exhaust seems to have a negative effect on the performance for the 991.2 engines. Before I install it, can you elaborate on the performance gains if any?

John D II

Hi Mark,

Our X design with straight through plumbing and HJS Hi-Flow cats has picked up considerable HP on the 997 twin turbo cars. The donor design car owner did not want any dyno pulls, so we were not able to measure the gains, so I can only offer the following. The owner did however go to the 1/4 mile and improved his time over stock once our system was installed. The 991.2 has smaller turbos than the 997TT's, so I would not expect the improvement to be a great as on the 997 turbo cars, but from our experience, whenever you reduce the back pressure via hi-flow cats and provide a straight through pipe design on a turbo charged car, there is always a bump in power, as well as improved throttle response and quicker turbo spool up, which are the other side effects that help transform the driving experience and quicken acceleration. Also, extremely similar, nearly identical "X" designs with HJS cats are making substantial dyno HP claims. I personally drove the test car before and after and could certainly identify the overall improvement. All that said, we could also easily build this pipe in a non-X design by request, where the two sides barely "kiss" (keeping the full pipe diameter throughout the system), however, the sound quality would degrade and drone would surface that is otherwise eliminated by our current sound engineered design.