Making a Custom Exhaust

[Tom Bourn]

Hi All,
Cant decide on an after market exhaust for the car, so.....................
I'm going to make one (with help from an uncle who made a custom titanium one for his kitcar - including manifold!), it will be de-catted, with just a re-packable backbox to suit track noise limits.

Has anyone else done this? thinking of going for 2"/2.5" stainless throughout.
Any help/advice welcome............

 

[EngineerDaisy]

I've been looking into doing this on my 182 as I have a cherry bomb end silencer to use up. I'm leaning towards buying a pre-made cat to rear axle section from ebay and then just making the piece from the back axle to the cherry bomb.

 

[Chrisgti6]

lol at cherry bomb, have I gone back in time to the late 80's early 90's?

Personally i'd say 2", maybe 2.25", 2.5" will be overkill. I'm looking to upgrade the exhaust on my S40 at somepoint, and that's only likely to be 2.5" and that's for something turbocharged and 300+ bhp.

 

[Tom Bourn]

Oreca's system and the KTR ones use 2.5" tubing, was thinking along the lines of something like this

Only difference will be that the backbox will be riveted so they can be drilled out and it re-packed

 

[Saner]

the ol' Supersprint system was 2.75", That was loud.

 

[M.C..]

2.5" for N/A and 3"inch for turbo.
Pure motorsport use 2.5 on their exhausts.

 

[Tom Bourn]

Nice one @M.C..
Anyone have a pattern for one? Or am I making it up as I go along?
The plan at the moment is to get the car up this weekend take some measurements and order the tube and bends! Might even do a build thread when it happens....................

 

[M.C..]

I assume you are going to TIG the pipe together?
Try and use V band clamps too as they are much better.

 

[Tom Bourn]

TIG yes, and thinking of sleeving the tubes, welding lugs on and then using exhaust springs to pull them together.
Thats how my uncle did it on his system. Seals really well and less weight etc...........
I'll grab some pics over the weekend, easier than trying to explain it:yum:

 

[M.C..]

I know what you mean my Akrapovic on my bike uses the same system but you will need a good fit, don't think the normal tube expander will be good enough, I may be wrong though.

 

[Tom Bourn]

You're right dude. Gonna use a specially made mandrel and fly press to expand the pipe to make perfectly formed slip joints. Should be far more accurate than a normal pipe expander.

 

[Dan@SJM]

2.5" is pretty unnecessary in terms of performance on these. I'm on a 2.5" exhaust with 400bhp being blown through it.

 

[Tom Bourn]

Anyone know what size the manifold down pipe is into the exhaust?

 

[Dan@SJM]

2.5"

 

[Tom Bourn]

So if the down pipe is 2.5" how is a 2.5" system excessive? Surely all it will do is aid in flow....... As long as the back pressure is ok.............

 

[Dan@SJM]

Just saying it doesn't need to be 2.5", having a smaller bore can work better as it can create a Venturi effect.

 

[Gray]

Just saying it doesn't need to be 2.5", having a smaller bore can work better as it can create a Venturi effect.

Ace Venturi?

 

[Dan@SJM]

Like a glove.