Ive tried to search. I have found nothing I am looking for. Does any know at what hp level the racing beat midpipe back exhaust becomes a exhaust restriction?

I would like to keep this exhaust, but at my hp goals im thinking the mufflers would be too much of a restriction.

 

you have to compromise sometimes. If you're looking for the best flowing exhaust then get any straight piped exhaust (3"+). The midpipe and mufflers will be a restriction since it needs to muffle the sound.


I know there are several 400+hp guys on here with the RB turboback so just wait a lil longer and see what they say.

 

Lots of people have made the 450RWHP that is your goal with the Racing Beat turbo back exhaust.

From my experience a larger exhaust really helps spool up and therefore low end power and not really top end power.

I have found it is the RB downpipe/presilencer that is really the restrictive part of the system with its many cheated radius cuts and not their "Y" pipe and mufflers.

I use a JIC Spec 90 3 1/2" front pipe to the RB "Y" pipe and mufflers and it helps with low end power as the turbo spools more easily in the low RPM and full boost 2-500 RPM sooner than the full RB turbo back.

 

my plans is to go 3.5in dp reduced to 3in to the mid pipe.
BLUE TII, are you saying that the midpipe and back are the most restrictive. if so how does 3.5 all the way to the Y sound? has it been done. are the rear mufflers still a big restriction?
I'm willing on just going with 3.5 all the way with 2 borla mufflers, one as presilencer and the other as a muffler. Ive seen that quit often used by the Fd guys.

 

phoenix7 yes i will wait and see what more members thoughts are about this.

 

Any exhaust is always a restriction, it's just a matter of how much. At double the horsepower you're talking about 8 times as much restriction. So a couple horsepower lost to restriction suddenly becomes over 10 horsepower. But do the 400wHP guys care enough to upgrade their exhaust again? I guess not. I'd think that would be a good time to get ridiculous with the mufflers.

The midpipe is not restrictive compared to the mufflers. At 450wHP you'll gain maybe a few more HP (if that) by going from 3 to 3.5. But if you're squeezing out everything you can, go ahead with the 3.5.

 

On the exact same turbo set up I have used

1) Racing Beat 2.5" downpipe/presilencer to JIC Spec 90 3 1/2" catback

2) Racing Beat 3" turbo back

3) JIC Spec 90 3 1/2" front pipe (first 57") to RB 3" turbo back "Y" pipe and mufflers

4) JIC Spec 90 3 1/2" turbo back (one "muffler" in entire exhaust)

I have not dynoed the car but every one of those exhausts felt like they had very close to the same top end HP but dramatically different low end power. The larger more free flowing the exhaust the more low end power.

1) turbo could not quite achieve full boost due to restriction of exhaust

2) full boost ~4,000 RPM, no boost/power below 2,000 RPM

3) full boost ~3,400 RPM, boost/power from 1,000 RPM idle

4) full boost ~3,300 RPM, a little more boost/power from 1,000 RPM up but couldn't really drive above 2,000 RPM without being arrest me loud.

I am saying the downpipe and presilencer are the most restrictive. The presilencer itself is a very good design, but the many cheated radius cut bends between the turbo and the "Y" pipe create the restriction.

3.5 to the "Y" is what I currently run and it is a good compromise between spool up and noise control.

RB rear mufflers are not a big restriction as they are straight through and have mandrel bent tubing with the flanges square to the tube. One forum member dynoed his 20B with full RB system and then disconnected the "Y" and mufflers and dynoed the same HP.

I disagree about the RB downpipe/presilencer combo- see above :P

A few HP PEAK will be gained going with a larger exhaust, but many more HP will be gained before peak HP due to the earlier spooling turbo. Think of a 400hp 4 cylinder versus a 400hp V8. They both make the same power, but which has more power over its rpm range.

-edit- spelling