Rally Exhaust
We learned a pretty hard lesson at Oregon Trail this year. Due to unseasonably 100+ degree weather in April, heat management became a pretty serious issue for us, and the car was found largely deficient.
Basically when you get hot, your brain doesn’t work as well as it does when comfortable, which can and did impact our performance.
The floor of the car ran around 140 degrees, due to the fact that the catalytic converter was positioned in the stock location. Interesting thing about catalytic converters: the exhaust that exits them is actually more hot than the exhast before it hit the catalysts. Many rally teams deal with this by relocating the catalytic converter to the very rear of the vehicle–this improves performance as well as reduces the in-car temperatures drastically.
We ended up fabricating a complete stainless exhaust using pre-fabed 2.25″ midpipe from Dynomax (WLK-38212) as a starting point. It came with several hangers, flanges and an inline resonator–and was less expensive than buying the raw materials.
We bought some flanges from Vibrant and basically put a Dynomax 2.25″ Race Bullet Muffler (WLK-24234) where the stock catalytic converter was located. Our intention was to run the two resonators and the catalytic converter with no additional muffler.
The custom rear “axle-back” component was all that needed to be completed to finish up the system. It was composed of 2.25″ stainless bends, a Vibrant 200 cell 100% metal core high flow catalytic converter joined up to the Dynomax DNX midpipe with a Reid Washbon Racing v-clamp (very nice peice of kit).
Intial testing revealed that the car was LOUD. It sounded great idling and under heal-toe downshifts, but was obnouxious the rest of the time, especially when decelerating off throttle (compression braking). It probably would be legal for rally, and I’m pretty sure it would have passed most road racing requirements with the addition of a exhaust turn-down tip. But at a rally, communication is very important–even though we use intercoms, noise can be very problematic. Futhermore, we spend a ton of time in the car over a rally weekend, and I could easily imagine getting a headache (not to mention potential hearing damage) from exposure.
We use a Supertrapp Wavetech muffler on the CRX with pretty good success. The nice thing about Supetrapp components is that they are completely tunable. The added bonus was that we already had a bunch of Supertrapp discs and a open tip, etc. We opted to go for a 2.25 ID, 4″ disc only muffler (SUP-444-2503), which also is a United States Park Service approved spark arrestor, which is often required when we compete on federal and state land. Remember: only you can prevent forest fires. The muffler has to be one of the smallest, lightest, effective mufflers out there, and it definately did the trick. The exhaust note is agressive but not obnoxious–and we’re not stuck with it. We can add additional discs to increase flow, or remove them to reduce it.
Overall I’m pleased with how it turned out. I’m pretty sure it is lighter than the system we had on the car, and the heat has been reduced to a far more comfortable level. Before, if you touched the exhaust tunnel with a bare hand it was very uncofortable, perhaps enough to burn. Now it is warm to the touch but not hot. I will take a infrared temp, I’d estimate it is around 100 degrees.
Mission accomplished.
Tags: catalytic converter, Civic, exhaust, muffler, Rally
