Optimum exhaust bore diameter

[cliokongen]

Planning to build a stainless custum exhaust for a soon to be hybrid'ed Valver. Decat with straight through silencers.

Engine mods:
2L Willi BE
Devil manifold
Wössner pistons
AngelWorks head
Piper cams
CatCams verniers
CatCams connecting rods
Lightened and balanced BE

Which bore size would you recommend?

Michael
http://www.renaultklubben.dk/forum/forums/thread-view.asp?tid=1641&start=1

[cliokongen]

BUMP! :(

Michael

[MAXIBOY]

most are around 50mm but my system a mongoose is 62mm. why custom build one. just use an off the shelf system. can,t see you needing anything bigger than that running n/a

[cliokongen]

Thanks.. :)

51mm = 2" which is what I had in mind actually.
Although 63mm = 2,5"is said to work very well on the 172/182 - also with a 2L displacement.
This gets me wondering if a 63mm system would work on a hybrid.

I can understand that you need 63mm for a turbo application.
Especially for your beast Maxiboy.

What does the Hybrid and TB'ed cars on here use?

I want to do this because I can.... errmmm - with a little help from a good friend. :D
I think the satisfation of doing something your self and get a nice result is great.

In general IMO the quality of an off the shelf system is not very good.
And I can get all the parts for a system in 304 SS quite cheap.

Michael

[MAXIBOY]

most cars on here run a 51mm magnex or similar system. only mongoose use the larger pipe but there systems are designed with performance in mind above all else. they dont fit as well as others. need heating up and tweaking to fit properly but do a good job on power. most turbo,s run 75mm systems so will see how it goes.

[arj256]

I would say 2" As thats what Devil ran, and Devil products where used on the rally and cup cars.
And being with a straight through, you will still retain some back pressure.

Most aftermarket systems are 2.25" other than mongoose which is 2.5"

[stew]

id go 2.25"

depends on silencers and power output obviously though, and what diving conditions will be.

mine is a 2.5" and seems to work well for my track car. maybe loose some low down torque but gain higher up the rev range for sure.

[cliokongen]

Isn't the std. Valver/Willi system a little bit larger than 2", but smaller than 2,25"? Anyone ever measured?

Unfortunately I find it very difficult finding 2,25" materials.............
2",2,5", 3" is easy enough though.

With the material sourcing problems in mind i might stick with the 2" option. But 2,25" might be better? Will try and optimize flow using high flow silencers and avoiding 90deg. bends where possible.

Looking for exhaust velocity with the least amount of back pressure. Thats the difficult part finding the best compromize between diameter/velocity/backpressure.

My car is not a daily driver - more like a semi track slag.


Michael

[stan]

your not going to go wrong with 2-2.5"