The exhaust was built for SCCA Autocross “Stock” class competition. This means it can be replaced from the catalytic converter backwards, and must comply with a 95 db sound limit. It must exit the stock exhaust location.
We went from a dual to a single setup. They used thick wall aluminum with their welding expertise, retained the factory resonator and went with a single muffler. The header collector is 2.5" so the exhaust bottleneck is up there, and I wasn’t going to see any power gains by going larger, so the piping is 2.5". Power is useless in autocross anyways.
As you can see, the weight savings are substantial.
The sound is wonderful and completely streetable/easy to live with. If you’re familiar with RX-8s, most exhaust setups sound like a robot fucking a sewing machine. This is just a nice, rich somewhat exotic gurgle. Minor little pop-pops on throttle lift off.
STM was a pleasure to work with, and stand by their work.
I say this because several people have informed me that this setup is absolutely 100% going to fail, but so far its been great.
I’m really curious as to how much an Al set up would differ in sound to steel. Aside from weight, were there any other benefits that made you go with aluminum? Also, does this car get winter duties?
People probably say the aluminum would fail since most aren’t braced and break at the seams/welds. They must be a weaker metal/weld? BTB5A4 Phil’s has broken a few times around the muffler. That bracing should help yours stay together.
Looks like a nice setup! I know you’re trying to save weight, but why not make a second tip go to the left side? Being aluminum it would have add like 5 lbs.
But would have looked a lot better in my opinion (which if course doesn’t matter lol) I guess I just hate the dual exhaust outlet bumpers with only a single exit tip.
That’s not true at all about adding 5 lbs. I have a dual exit aluminum STM on my X and the single exit is like 9 lbs and my dual is 11 lbs. the aluminum exhausts from STM sound amazing and are worth the price especially if you’re looking to shed weight.
i think i heard a video of your car when the exhaust was first finished. it actually does sound really good and not horrible like most RX8’s do. exhaust looks great
Fab work looks great. I know aluminum is a pretty controversial choice for exhausts due to durability and thermal expansion but it’s always interesting to see them in use. MotoIQ did a cool article a few years back using an aluminum exhaust on a bike powered Miata and explained the pros and cons.
