Hi Guys, I have 3.4 991, looking for some information on how hot your exhaust gets without any driving. I installed a Speedtech X-Flow Exhaust (the second one on this page: http://www.speedtechexhausts.com/ast1_041.htm). After installing I noticed the exhaust was extremely hot (as in will singe your fingers if touched). Even the tips and exhaust gasses were scolding hot. This is with zero driving and the car idling in the garage for 5 minutes. I don't remember the stock exhaust ever getting this hot but hoping I am mistaken.

For comparison I started my Lexus IS350 and idled in for 5 minutes, although the exhaust gasses were warm I could easily touch the exhaust and exhaust tips without burning myself.

I would love some input. FYI the X-Flow exhaust employs louvers, right after I received the exhaust I noticed them and was concerned. Could these be causing the extreme heat? Anyone else have experience with louvered exhausts or this particular Speedtech exhaust?

 

ak78, It is normal for all Porsche exhausts on the rear engine 911 models to get extremely hot. This is due to the fact that the exhaust is very short in make-up vs. a full length exhaust for a front engine car with mufflers at the rear. 911 exhausts are bolted directly to the headers, which literally get red hot during hard driving and very hot, even at idle. When you have temps in the 2000 degree range at the headers and the exhaust is comprised of just a few feet of pipe on each side, the entire exhaust will get extremely hot and definitely too hot to touch, even the tips. The louvered muffler internals have nothing to do with the heat level, they are simply a sound attenuation method. Our 991 exhaust is all 2.5" pipe, which is larger than the OEM pipe diameter and there are no restrictions such as baffles or resonance chambers, so it flows better. I think you were asking if the louvers were causing the heat you felt by holding heat in and that is not the case. You are not holding any abnormal amount of heat in the system due to the louvers, it's just the design of the rear engine 911 and the proximity of the exhaust to the motor that makes the entire system very hot when the car is running.

 

Thanks for the quick reply John, certainly makes me feel much more comfortable.

 

You're welcome...my pleasure.