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Mountune CBE a bottle neck?

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Location
Miami
#1
I was told that my exhaust system might be a bottle neck and wanted to see what the forum thinks.

2867 gen 2
4 port aux
2j intake
Mountune 2.5” CBE with a MAP catless downpipe

What is the limit of a 2.5” exhaust? I was under the assumption that 2.5” should be able to flow more than enough. Am I wrong? I think the MAP Downpipe catless is 3” but I might be wrong.

Thanks for your help
 


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291
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154
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langhorne
#2
I highly doubt ur exhaust is restricting anything. Hell there's people on here that pushed 370whp on the stock cbe. Catbacks are simply just for sound on this car.

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langhorne
#4
If you are trying to get 100% out of the rest of your system then yes, it is a restriction. @ 2.5" though it is not a restriction by much (and is quite a bit better than the stock 2.25" by about 25%) If you want piece of mind, get a Thermal R&D 3" system.
Even though a 2867 is one of the bigger turbos for this platform, overall it's a pretty tiny turbo, back pressure isn't gonna be an issue at this size.

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San Antonio
#6
Could you make a little more power with a 3 inch? Probably. But I highly doubt it causes much restriction, if any at all. I assume you're around 300-350hp? I wouldn't see it being a restriction until closer to 400hp and at that point the bottom end would be your biggest limitation. Save your money, I got my CBE because I wanted sound more than anything
 


OP
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Thread Starter #7
I bought the Mountune CBE when I had the X37 installed. Think I picked up a little power with it, but I wanted a little more sound with zero drone.

The car is still being tuned on the 2867 E50. I haven’t been on legit dyno. The vdyno is around 360’s. I was expecting to see closer to 380 if not more. That’s where the idea of some sort of a bottle neck is to blame.

Some people with the smaller 2860 are making 380’s maybe a tad more. I would have guessed I would beat there whp numbers having a larger turbo. Not many people have the 2867 to compare to. Maybe the difference from the 2860 vs 2867 is minimal?
 


Dpro

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#8
I bought the Mountune CBE when I had the X37 installed. Think I picked up a little power with it, but I wanted a little more sound with zero drone.

The car is still being tuned on the 2867 E50. I haven’t been on legit dyno. The vdyno is around 360’s. I was expecting to see closer to 380 if not more. That’s where the idea of some sort of a bottle neck is to blame.

Some people with the smaller 2860 are making 380’s maybe a tad more. I would have guessed I would beat there whp numbers having a larger turbo. Not many people have the 2867 to compare to. Maybe the difference from the 2860 vs 2867 is minimal?
If you want Zero drone than you want a Thermal which is a 3inch. It can help a bit definitely will not hurt. lol
If you are happy with your Mountune then keep it though its not holding you back power wise . If the car had more displacement it might be a restriction but we are talking 1.6 liter with relatively small turbos even aftermarket.
 


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langhorne
#9
I bought the Mountune CBE when I had the X37 installed. Think I picked up a little power with it, but I wanted a little more sound with zero drone.

The car is still being tuned on the 2867 E50. I haven’t been on legit dyno. The vdyno is around 360’s. I was expecting to see closer to 380 if not more. That’s where the idea of some sort of a bottle neck is to blame.

Some people with the smaller 2860 are making 380’s maybe a tad more. I would have guessed I would beat there whp numbers having a larger turbo. Not many people have the 2867 to compare to. Maybe the difference from the 2860 vs 2867 is minimal?
Vdyno is pretty much bs and has alot of variables that can be messed up, plus most people haven't weighed their cars so that's a huge part of it being somewhat accurate. Are you still on the stock map sensor and what kindof boost are you running.

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OP
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Thread Starter #10
Stock sensor by the manifold and 3.5 bar on the TIP. Seeing boost 32-34 psi.
 


OP
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Thread Starter #12
Thanks to all about the consensus on the 2.5” isn’t a bottle neck. I’ll dyno it eventually, still have a lot of tuning to do before it’s done.
 


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Dyer, IN, USA
#13
Well i have a hybrid and just had a muffler delete, i was told the same thing, so i went to a 3 inch exhaust, it was a noticeable difference past 5000rpm


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