M5Pilot wrote:You cant just make an exhaust. it needs to be tested.
These custom exhaust places just stick on what ever bore size pipes they want without knowing the effect it will have on back pressure which in turn is going to effect BHP and torque.
Your better off buying something like a Mongoose. At least we know it doesnt lose you power!
Problem with buy an off the shelf system is the M30 downpipes are in a different place and have different bore sizes so mating it becomes tricky, I also REALLY want twin exit twin pipe. I think 70mm will flow ok, I know that they are supposed to be pulse matched to the engine displacement to generate standing wave low pressure and high pressure areas to maximise scavenging, but with a standard manifold and downpipe, I really don't think it will make a toss of difference. Might get that book on 4 stroke tuning, supposed to have lots of header/exhaust info in it. If I can work out what I need I will just tell them to build to that.
Adammcf wrote:Powerflow is pure scrap. Might look good for while but will soon rust away. They use decent stainless for the tail pipes but really crap low grade stuff for the pipes.
Yes heard the same thing but a couple of friends of mine have them and they are not rusting, it's supposed to be 304 grade stainless, which is what more or less everyone uses, if it isn't then it is against Trade Descriptions and you can get a refund/replacement. On that all the systems come with lifetime warranty, if it rusts I will get them to replace it FOC, full new system every year for free sounds good to me.
JonnyDrift wrote:Which Powerflow did you use Jos?Ballymena one is very good but as Adam says they do use inferior steel for the inner pipes.Depends on how long you plan on keeping the car.
Nope, Dee's Exhausts in Newtownabbey, whilst I haven't heard anything directly bad about Gilbert, the boys in Newtownabbey are supposed to be much better.
Moofles wrote:- When i had a similar exhaust made for my old e30 I could choose different grades of steel for the exhaust (not just tailpipes). Might be worth investigating (better steel was more but not a lot more).
- The relative power gains (or losses) from an exhaust are not *huge*. So you might be willing to [possibly] sacrifice a bit for the look you want. I probably would
304 is normal grade for exhausts the next one up is 321 grade, then 347. there is also a 316 which is used in marine applications because of salt, hmm that would be the choice for here on the roads too

Powerflow advertise 304 as what they use, so they damn better. 321 is aircraft grade and the price is quite scary..