Cal Club Autocross Forums

Just got off the phone with tech support at FlowMaster. Was looking for design info on the Hushpower and learned some interesting stuff.

The HP-2 has been redesigned and is now available in a more compact case with the same internal size. The case ears are now gone. And a longer one is available so you can get 12" and 18" case lengths in 2.5". A single 2.5" system is recommended for up to 250 flywheel hp.

The HP is not a chambered muffler. It has two perf cones which meet in the center of the can at the cone bottoms. So the flow goes in the cone, passes into the can, and back into the second cone. They claim no pressure loss compared to open pipe on a flow bench.

And they have a larger version of the same technology available called a DBX. His suggestion was to run a DBX or an 18" HP in the rear location and then after trying it, add a 12" or 18" HP mid-pipe if more silencing is required. Quoting him, with this technology you could make up an entire exhaust system with HP's connected end to end over the entire length of the car and it would still flow like an open pipe. Remember, he said it, not me.

Part No's: 12512409, 12518409, 12514310

I ran the old HP2 on my Yaris and it was stupid loud and the new mufflers any better?

Probably not for the same size. A bigger version should be quieter. I wouldn't go this way for a street system. But <93dB @ 50' is what I'm after.

You want to sell your old one?

No its still on the car, just had to add a second muffler to be at 92db at 50ft.

Kinda stuck with packaging on this car not a whole lot of muffler I can fit in the center tube.