JHM longtube headers and STaSIS cat-back
The parts we were waiting on came back from the machine shop and we were able to complete the exhaust installation. The headers sound great with the cat-back; angry outside of the car while reasonable inside the cabin. The piping is 2.5" through and everything is connected with v-band clamps. You can click the video for a higher quality version.
Three exhaust videos: JHM headers, GMG resonated midsection, and straight pipes
Here are three different videos of the car testing various exhaust options. These two videos are of the JHM headers with the GMG resonated midsection, there are no mufflers attached. This video shows what the car sounds like with only the JHM headers.
Stern control arms and completed headers
Today we put the transmission back into the car and buttoned everything back up. If everything works out tomorrow the brakes and cat-back should go on!
Below you can see the high-flow cats mate up to the new headers. JHM offers a pre-lengthened set of O2 sensors since the O2 bungs have been relocated on the longtube headers.
Some "better" photos of the JHM/Stern motor mounts.
Here the Stern control arms have been installed.
The S4 goes under the knife…
Monday the S4 went under the knife to receive the first round of performance modifications. Take a look at the OEM exhaust manifolds. Proceed to cringe.
To gain access the exhaust manifolds we had to lower the motor. Pictured below, the transmission has already been removed.
The motor is supported so it can be lowered down enough to gain access to the exhaust manifolds.
Here you can see the JHM longtube headers installed.
This version of the headers uses v-band clamps.
GMG 2.5″ RS4 exhaust with Labree mufflers
The last piece of my exhaust puzzle was the cat-back exhaust; having previously run a 2.25" APR downpipe and exhaust I needed something a little larger to mate up to the 2.5" JHM longtube headers. After poking around I found S-Fore, a local forum member, parting out his S4. He had originally purchased a GMG RS4 exhaust, but found that the internal drone was too much. To rectify this little problem he replaced the GMG mufflers with Labree mufflers and hasn't looked back since. When I asked S-Fore to describe the sound, he said hands down it was the best sounding S4 exhaust. Ever. Once the headers and exhaust are on I'll see how the quad tips fill the RS4 bumper; if it doesn't look right I'll have ...
Ceramic coated longtube headers
My JHM longtube headers have made it back from Performance Coatings! They've recieved a satin black ceramic coating to dramatically reduce radient heat.
We're looking at a 110-120 degree temperature reduction in the engine bay; this should be good for a 11-12% increase in engine efficiency. Gotta love free horsepower!
For a 450-500HP motor we can expect a gain of 50-55HP. Show me a better mod for the money!
Thanks to Performance Coatings and JHM!
JHM longtube headers have shipped!
I received word from JHM that my longtube headers have shipped. The JHM longtube headers replace the OEM headers and downpipes; other cars have been seeing both 20-50 ft/lbs and 20-50 AWHP gains throughout the powerband. JHM reccomends wrapping the headers with an exhaust wrap, I choose another route.
Performance Coating in Auburn, WA will be coating the headers with their satin black ceramic coating; we expect to see a temperature drop of 110-120ºF.
Read more about the headers on JHM's site.
Stock B6/B7 headers:
JHM prototype headers:
034 Motorsport dyno of stock headers and JHM headers; note the vehicle dynoed was an auto. Click image for fullsize.