PSA: The MBRP 3" Exhaust is not 3" all the way through

[iso100]

I just received my box today and opened it to make sure things arrived undamaged. I pulled out the resonator/muffler because it was the shortest item (I am installing it tomorrow so I didn't want to have to figure out how to repack it) and looked at the flange.

It didn't seem like 3" so I measured it. The flange hole (that attaches to the downpipe) is only 2.25" in diameter. This seems to be an odd decision. CP-E ships with two gaskets... one that mates to the factory downpipe and another that is a full 3". It's odd that MBRP went this route.

It's not just the flange either... the baffling inside the resonator/muffler sticks into the flow path, making it effectively smaller than 3" in my estimation.

I'm not too broken up about it since I have the stock downpipe. But for those of you wanting the ultimate performance and have a 2.5" or 3" downpipe already, having it open up from the turbo then neck down for the downpipe and then neck down again for the flange and muffler then open up to 3" after that seems sub-optimal.

Despite the smaller inlet size, they do claim +10hp or so with the stock downpipe... so there's that.

 

[TheStig]

Curious, thanks for the leg work.

Let us know how she sounds and what the butt dyno says.

 

[rooSTer]

Great idea on measuring it...weird why they did that. +1 repped

 

[Sekred]

Interesting, so they have made it to fit a stock down pipe or after-market down pipe. Looks like you can't really open up the flange either by grinding.

 

[me32]

I wonder if there is a reason for this.

 

[LT Berzerker]

Wondering if it might have to do with resonation/drone...Random guess

 

[iso100]

Might be a performance decision made for those running a stock downpipe. It doesn't get to 3" until the resonator outlet. They might have discovered something special about letting it expand inside the housing instead of before.

 

[razorlab]

You could blow out gaskets if you went 3" flange to 2.1"

 

[iso100]

You could blow out gaskets if you went 3" flange to 2.1"

Even with the downstream being 3" and upstream being 2.18"? I can see it happening going 3" -> 2.18" but the other way doesn't seem logical (not saying you're wrong).

At any rate, I'm off to go install this bad boy right now...

 

[razorlab]

Even with the downstream being 3" and upstream being 2.18"? I can see it happening going 3" -> 2.18" but the other way doesn't seem logical (not saying you're wrong).

More a chance the other way around like you are saying but vibration blows out gaskets too. If the edges of the gasket are barely sealing it doesn't take much...

 

[iso100]

Bloody hell this exhaust system is loud. Uh oh...

 

[Sekred]

Bloody hell this exhaust system is loud. Uh oh...

So its got a Res and a muffler?

 

[iso100]

So its got a Res and a muffler?

No. It's literally just a resonator / muffler. I can't tell the difference by looking in the end but it's mounted where the stock resonator was.

 

[iso100]

To clarify, this is what's out back:

 

[lessard.dcj]

Ok so how am i going to fare as i just ordered the 2j Race DP (3") and now you tell me that the MBRP (3") exhaust isnt 3". wtf. will it still work as i have already ordered them both.

 

[iso100]

I'm sure it will bolt up but there will be a "wall" where the 3" DP outlet hits the smaller opening in the exhaust inlet. From the outlet of the resonator to the tips it definitely is 3".

 

[RAAMaudio]

One more reason I built my own DP and exhaust, full 3", less bends than any, to many compromises on all others I have seen.

 

[iso100]

One more reason I built my own DP and exhaust, full 3", less bends than any, to many compromises on all others I have seen.

Certainly a great option if you have the skills, tools and time to do it yourself.

They're definitely on to something with the asymmetrical resonator inlet/outlet and the stock downpipe. This thing makes a noticeable amount of additional power throughout the RPM range. Wasn't expecting this.

 

[RAAMaudio]

Another thing I have seen over the years and on at least a couple of XT exhausts, single inlet, dual outlet, muffler with very poor internal flow design. I also do not like most single in, dual out, tips as they are usually not good flowing either. I could not find what I wanted so spend a few hours on one then realized I made an early error and did not want to start over so now I just have single all the way, turbo to tip but the tip is oval for a bit of Ford Style

I also made sure the tip was light and very free flowing, it came with rolled edges that would be quite restrictive so I cut it off at the right angle for the car.

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I would not be able do this with work without a well setup shop due to injuries in the past, etc....it was more about the totaly build of the car to maximize everything about it than the money saved as it was not a huge amount and took many hours.

 

[re-rx7]

Im going with the Ford Racing exhaust. I cn get a gd deal on it. An exhaust is only as big as its smallest point. That being said 2.5" has shown to be more then adequate for these cars.