A question has been pondering on my mind. I was thinking about making a fully custom straight pipe out of a pipe bender i have. Has anyone done this, how loud would it be, and would i have any power loss. I do have forced induction, i imagine it would only free things up. I really don't care how loud it is (cop wise) but would i have power loss is my main concern.
(i already deleted my cat)

 

You would not have any power loss from a straight pipe. It would be ear bleedingly loud on an N/A, it might actually be somewhat less painful with a turbo to soak some of the exhaust energy/sound. Don't forget about the change to the pre-post pressure ratio on the turbine if you end up with a freer flowing exhaust than you have. Usually all benefit, but make sure you account for the change.

What do you currently have on there?

 

Well my cat got clogged, so i put it on a lift and took it off and just got a crowbar and started chipping away, then i put a Borla catback on it. It just isnt loud enough for me haha. other than that i have a greddy turbo kit, upgraded hybrid turbo, running 10 psi, upgraded seals (forget the name of them at the moment) and a hks intake

 

Yeah, the exhaust bits i was curious about. I'm surprised you were running a cat with a turbo. They don't last long and can cause all sorts of problems on an already risky endeavour. Keep in mind that just gutting the cat has changed your pre-post turbine pressure ratio significantly.

My advice is to not just go cheap, and go get a BHR midpipe. A straight pipe will be louder and flow better than your gutted cat, but probably be far more annoying to live with. Your ears though (and everyone else around you).

 

How would i go about adjusting the pre-post turbine pressure ratio?

 

The pressure before the turbine is dictated by the amount of energy/mass the engine is dumping into the exhaust. More load = more pressure.
The pressure behind the turbine is dictated by how freely flowing the exhaust is. A restrictive exhaust will increase pressure behind the turbine, an open exhaust will decrease it.

The bigger the difference between these two, the faster your turbine will spool up, but it's not something to just go ***** nilly on, since you have to account for things like boost creep if your wastegate isn't big enough, running the turbo too fast, etc...

You should really understand these things if you run a boosted rotary... I highly recommend you start digging for some deeper reading. Start here: https://www.rx8club.com/series-i-maj...itrous-122645/

 

Alright, well i have a gutted cat, so i was thinking about keeping my borla that i spent money on, and fitting exhaust pipe in the cat, so it looks like i have a cat but its straight through, which will help flow. Is that a good idea?

 

Sorry I didn't read the thread, just the topic and first post.

I work in a welding shop, we slowed down a bit, so I made mine out of 3 inch ID 409 SS. 1 pipe, header back only 3ish bends in the entire pipe.




aaaaaaaaaand!






You can't even drive it.

It was like attacking a tin shed from the inside with a chainsaw.

It shatters your ear drums.

And I noticed what felt like power loss from 1,000-4,000 rpms.


So unless your going to drive with ear plugs.

I couldn't even stand it. And I like it loud.

 

I first heard an open exhaust rotary in 1980. In IMSA they had RX2 & 3's (Bridgeported 12A's) in the Champion Spark Plug Challenge and RX7's in GTU (P port 12A's). The noise was so loud, as the cars went by, it was painful. Covering your ears was not sufficient. Ear plugs were required. The next year, IMSA required the rotaries have a spec muffler. One of the teams, local to me, was sponsored by a ear plug company. Even with the muffler, the free ear plugs that were given away were helpful. The rumor was they gained 15 hp with this change. My RX7 race car had a muffler and 2 resonators.