2.5" OMP single pipe exhaust good for 3.5 rover? or cus

[reanimation]

Is 2.5 inch exhaust bore on a OMP exhaust any good. 3.5 Rover Holley carb and edelbrock intake IIRC.

I can probably take my car to JP exhausts, ( http://www.jpexhausts.co.uk/ ) and comback with one of their mild steel custom pipes in 3" fitted £260+vat w/o down tubes (from my decent cast manifolds), after down tubes from there and transport costs, i expect it costing me about £400


Of course if its worth doing, its worth doing properly! and this also looks like a reasonable option. what you you's think? Cheers





Designed for Cosworths, i have eyed up a selection of OMP pipes. ready to go all i need is to get two 2" bends made for down pipes.

stainless steel item shy of £300 offers 30% weight saving over steel
racer style


"ONE BRAND NEW OMP INOX SS EXHAUST SYSTEM TO FIT:



FORD SIERRA COSWORTH 2WD



> Stainless Steel Construction

> 50/63mm Tail Pipe Diameter

> 2 Sections

In collaboration with well-known tuners OMP produce a complete range of exhaust systems for competition use. Units for Group N/A cars are designed to take the place of the catalyst where applicable.



Fabricated entirely of high quality stainless steel by highly skilled craftsmen.

Reminder: the FIA Group N noise limit is 98 ±2 db.

OMP exhaust systems have significantly lower back pressure values than the original system. In order to achieve the most power from the exhaust system, it will be necessary to tune the air-fuel mixture appropriately."



or this pretty item, £200 steel


http://www.ybracing.co.uk/images/exhaus ... bfo594.jpg
"In collaboration with well-known tuners OMP produce a complete range of exhaust systems for competition use. Units for Gr.N/A cars are designed to take the place of the catalyst. Entirely made from mandrel bent aluminized steel treated with heat-resistant resins, they are engineered for the best torque and horsepower outputs. The torque outputs of these systems also make them suitable for road use.

Reminder: the FIA Group N noise limit is 98 ±2 db.



OMP exhaust systems have significantly lower back pressure values than the original system. In order to achieve the most power from the exhaust system, it will be necessary to tune the air-fuel mixture appropriately.

Section plan of an exhaust system

1) Rear pipe in chromium plated steel
2) High performance damping system: internal drilled tube in aluminized steel AISI F4P8 combined with deadening materials with 2 layers in stainless wool
3) Bottom made with aluminized steel hot-pressing, increased thickness (2 mm)
4) Central muffler pipe and final pipe in aluminized steel Ø: 130 mm thickness: 1,5 mm, treated with thermoresistant resins
5) Welding by means of first quality weld materials "

[Lewis]

Ello Reanimation Fancy meeting you in a place like this.

I think the general rule of thumb for exhaust systems (not manifolds) is for 200BHP, you want around 2.75", 300BHP, 3.5" and 400BHP 4.25". If it's a twin system then each induvidual pipe should be 80% of the above.

It varies so much from vehicle to vehicle though.....The OMP system might not be a bad starting place but I guess it depends on what else your exhaust guys can make for you. I'd take stainless over mild steel any day.....I reckon for your application 2.5" would be bang on and see you with some overhead

[reanimation]

Hi mate, i used to go on the old site a fair bit then the v8 project got accidently shelved , so i not bin around much! Really keen to sort thits car now.

2.5 should be ok, guy who built it amed to put a standard cossie back box on. might have a word...

[ian.stewart]

Dont worry about 2.5", I am running a 3,9, producing 285hp and revs to 7k without a problem on a 2.5 system, I suppose the only real difference with mine is I run a single steel baffled rear box, [Flowmaster], so dont ecxpect any problems with a 3.5, and its not quiet either as you would expect from a smaller pipe, If I am giving it stick my son has heard it over a mile away
The only thing with stainless pipes they do sound, for want of a word "HARSH" compared to a M/S system

[reanimation]

Thanks ian, thats pretty much what my mate mentioned ages ago, and he has spent some years running drag race yank tanks. Plus i have done sound courses, I guess with all that bass rumble the thin stainless item will rattle like tin can. So the steel item may not be a bad buy. Also Cossies are very rarely under 200BHP, and i'd guess race ones are meant to make more. Yeah it should fit the bill.