Zeus993

Hey - I drove a buddies 997.2 GT3 RS with a straight pipe in place of the center exhaust and it sounded AWESOME.

Has anybody tried this on a TT? Crazy idea?

rijowysock

I have it on mine now and swapping to something quiet next week, it's not as loud as you would think, the turbo's are loud and sound amazing, my problem with the setup is drone at low RPM on highway.. i get chronic migraines so it's not a good setup for me personally.

if you wanted to do it, the cats+straight pipe are usually 2k.. i could sell you my setup when i remove for far less to try out...

jhbrennan

Maybe someone with some exhaust knowledge will chime in - I think a certain amount of back pressure is good - not sure how much straight pipes provide...if needed.

rijowysock

i have talked to EVOms about this in length, they said you HAVE to run cats... the systems that eliminate the cats are very bad for the turbo.. 200cell w/ 70mm piping was their recommendation.

Zeus993

Hey - good idea. I do understand the drone - the GT2RS had one to at around 6K rpms. Predicable - what rev range is yours coming in and out?

I was going to go custom on this at the local Bullet Racing shop but let me know what you'd like for it. We can ship it to my Washington address.

rijowysock

pm'd you back...

so jealous of the GT2RS... that's my dream car.

Nick Wong

You have to run cats?

I don't.

Why do you have to run cats?

Why are catless systems supposedly bad? That goes against pretty much everything I know about turbocharged engines, and I've been playing around with turbocharged cars for over 20 years.

rijowysock

i've heard it several times, and they confirmed it.. they said without running cats you start to have premature issues with the turbo's.. obviously for power, better flow=more power.. but for reliability some back pressure is needed. i'm not a turbonologist, but i listen to specialists when they suggest something for the longevity of the car versus a few extra HP.

i guess HAVE was a strong word, i will replace it now with SHOULD...

i would personally sacrifice 5% power for some longevity.

Nick Wong

Well, the specialists I have talked to- actual turbo manufacturers, not street car tuners- have all said back pressure is bad.

If the tuner says they need back pressure for turbocharger life, find another tuner. The issue isn't back pressure, the issue is proper turbo design.

The other issue is whether or not you are even approaching the rpm limits of said turbo. I highly doubt a stock engined, stock turbocharger equipped 997 Turbo approaches that limit with or without a pair of catalysts. If you are not at the turbocharger limit what would cause premature failure? Vibration (poor balancing, bad tuning)? It sure as heck isn't heat because cat deletes would only lower pressure in the manifolds, not raise them. In fact, lowering the temps substantially by deleting cats may increase life instead.

Unless you have 60k+ miles on your car I seriously doubt any issue of turbocharger life comes into play concerning catalysts, unless the goal is to lower output from clogged cats, and thus lower the rpm they operate at. That is the only way the catalysts can help lengthen turbocharger life.

TT Surgeon

Catless straight pipes are gonna stink, be loud as hell and drone like a ******, be ready and buy plenty of Advil.

Leo997TT

How much more power can you get from going 200cells to catless?

Nomak

Catless = more flow = help to decrease vgts damn overheating

EVOMS

Our recommendation is on a street car to run, at a minimum, either cats or mufflers. Or both, if you drive the car on the street and value your hearing/sanity.

Running neither gives so little back pressure that the tune has to be extensively rewritten to keep the turbo spool in check. Without it, on a tune that was designed around running an exhaust, you'll get severe overboosting and driveability issues as the car tries to correct itself. We've written tunes for track/race cars that deal with it appropriately, but they were essentially custom tunes due to the other modifications they had going on and drove very aggressively. For a street car, the slight amount of back pressure that cats or an exhaust provides makes the car more driveable at partial throttle.

Edit: Had a customer bring this thread to our attention, sorry for the necro-post.

Sam

montreal911

Hey i put straight pipes on my 997tt for one day!!! I love loud cars but all it made was noise not sound and it was physically painful! On the highway the drone makes u wanna rip your head off! Thought i would share

John@Fabspeed

A high flow muffler and 200 Cell sportcats are a MUCH better tone and sound than doing a muffler bypass. An X-pipe design like the Fabspeed pictured below is a much higher quality of sound because it allows both banks of the engine to be joined into one exhaust system creating a more unison sound.