3" Overpipe Clearance issue
 

Hi. I am getting the Treadstone turbo installed and also a Tomei Expreme Ti Type 80 3" exhaust. I am going with the cat-less setup and the shop is fabricating a 3" stainless steel frontpipe. However, for the overpipe the shop is saying that there isn't enough clearance between the engine and cross member for a 3" overpipe and that I will have to go with a 2.5".

Can anyone advise if this is true? I am seeing some options for full 3" exhaust systems and 3" overpipe.

Thanks in advance.

Zee

It's possible but its a VERY tight fit.

I had a custom full turbo kit and full turboback exhaust done by a local shop 3". Never had a rattle, but I know for a fact it was a very tight fit.

Thanks man. I appreciate the feedback. I will relay this to the shop and see what they think.

I believe JDL makes 3" overpipe

JDL 3" over-frontpipe equipped. Nameless also makes (or made?) a one-piece 3". It has to be exactly right, and probably requires lifting the motor to get it through the gap.

C

I believe that one of the problems is having a 3.0in overpipe with a flange on it to connect to the front pipe. JDL solved this with having a vband connection, and then Nameless just made it a true one piece if I remember right. Definitely needs to be precisely made so I wouldn't trust any exhaust shop around me at least.

I actually have a 3" overpipe built by Treadstone installed on my car right now. I took it loose and wrapped it with heatwrap. It was a PITA to do, but I was able to get it mostly out to do it. So yes a 3 overpipe will fit.

Thanks everyone!


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Does anyone have any advice on going with the 2.5" instead? With the turbo and Tomei 3" and a 3" front pipe, will I see a significant power loss going with a 2.5" overpipe instead of a 3"?

JDL delivery time is 4-6 weeks and Nameless can't guarantee that they front/over pipe combo will fit with my system. The shop that is doing the turbo work said they won't fabricate a 3", only 2.5".

Thanks in advance.

Zee

Decided to go with the Tomei 2.5" overpipe and the Tomei 3" frontpipe. Hopefully the 2.5" overpipe isn't a big bottleneck and loss of performance.

Shouldn't effect performance too much. From what I've seen people have reported around 30whp increase from going full 2.5in to full 3.0in on a turbo setup. Definitely a good gain but with only the overpipe being 2.5 i'm curious if it would be that much of a choke on it.

I'd be interested to see one brands 2.5" and 3.0" back to back on a dyno tune.

Also I *think* the MXP(?) is a 2.7", so it would be an interesting data point to see the dropoff.

Contact from Treadstone sent a note saying due to 2.5" overpipe power loss at max would be 10-15hp. Said it's no big deal but tell that to the $15k I'm spending on turbo, clutch and exhaust...

O well, will have to find a 3" overpipe for next summer.

Is your downpipe 3 inches? I hear lots of claims of huge 25+ gains from 2.5 to 3 but I have yet to see a dynograph that supports this. I was just looking at midnight23's build journal, he has a Greddy setup and his 2.5/3 inch overlay graph showed gains, but nothing in double digits, and only between the 5k to 6.5k area.