Advise on custom exhaust

[menno]

Hi guy and other forum users.

I am currently running a Fiat twin cam (2l) on twin 45's in my Westfield. I am in need of a new exhaust system.

I would like to make a stainless steel system going into a cherry bomb backbox.

Which type of cherrybomb should i be looking at and what other things do i have to keep in mind for the manufacturing of this system?

Anybody know of a good exhaust manufacturer in the UK?

Any advice appreciated
Regards
Menno

[Guy Croft]

I have never seen good results off those so-called 'Cherry bomb' exhausts so I am going to suggest you do not do that. I don't want to go into the reasons on a public forum.

The solution I would urge you to adopt is one or two (depending on how quiet you want it) of the George Polley AX891 flat oval silencers. GC race approved in every way and most 8V 2 liter engines will fly thru circuit noise test with even just one. It's - from memory - about 18 x 8 x 4"

See: http://www.polleymotorsport.co.uk/parts/exhaust.asp

Cambridge-based George Polley is a legendary NHRA driver by the way, had the privilege of meeting him once.

GC

[menno]

Thanks Guy.

The exhaust you mention AX891 is a oval shaped unit. The car my engine is fitted to is a westfield. We usually run round exhausts on these. Thought it might look a little odd having an oval one?

When making my custom exhaust manifold, Is it best to run it 4branch into 1 or 4-2-1 :?:

[Guy Croft]

Oh, OK.

A long cylindrical straight thru with 2 - 2.25" ID perforated (3.1mm holes) liner, glassfibre packed, say 2-2.5ft long, 5" OD.

Don't know the availability of things like that. Maniflow, Piper? Anyone know a source with link or photo please?

GC

[sumplug]

Try these;-
http://www.supersprint.com/a_prodotti.asp?modello=silur
http://www.powerflowexhausts.net/HOME.CFM
http://web.ukonline.co.uk/grahamf/index.htm

Andy.

[Westfield]

Hi Menno

I built a Westfield S2000S and the exhaust on it is the one you want I think! I have posted a picture of it on the car. The guys in Westfield are very helpful you should ring them they may make you up a manifold.



Gary[/img]

[menno]

WOW!,
Nice bit of kit!!

I have spoken to Westfield already, they didnt know anything about such a conversion and didn't know anyone who could help me. :?:

I have found a few writeups on the westfield forum though, but nothing substantial.

Sumplug kindly posted a few links for exhaust suppliers/builders(Thank you Sumplug)

Guy too has given some usefull advise on the backbox type i need.

All i need to know now is how to design the manifold
4-2-1 or 4-1. And incase of 4-2-1 which branches do i have to pair.

[sumplug]

Link 1&4 together and 2&3 together for manifold.
As for which type, the Twin Cam is infamous for its torque. The 4-2-1 type will enhance bottom end torque, whereas the 4-1 will enhance the top end. So i would go for a 4-1 system, as it will help you also to get your down pipes the right lengths due to the relatively short run one of these cars has.

Andy.

[menno]

Thanks Andy.

4-1 will suit me well. As the car with me in it weighs approximatly 675kg, the lower end torque wont be as important as the top end torque.

Thanks for all your input chaps, will let you know how it goes!!