FastLane

So I have the RD Sport Mufflers and X pipe, and I need to get custom piping to install the quad exhaust. I have been told numerous times I need a shop that does Mandrel piping so that there's no bends, for a variety of reasons (better flow, performance, etc.). When I went to a shop to get a quote, they told me that it would be much more expensive to go the mandrel bending done. When I probed further, he indicated there would constraints at the bends, but it would not make much of a difference compared to the pressure bending.

This was a specialized muffler shop, and they had the ability to do the mandrel bending, but the difference in price was $800 versus $500 just due to labour / time.

I'm not getting a quad exhaust for performance gain, it's more for the sweet sound and the fact that I'm getting the M5 rear installed. After that, I'm looking for the best price, so I would think that going with the pressure bending would be good enough for my needs.

Before I make the call, I wanted to get some views on whether I should be concerned about the pressure bending from the experts.

pjinca

Well, as has been well documented, all quad exhausts lose HP unless you HAVE a V-8. That said, the pressure bending increases turbulence (because bends are not smooth) and therefore reduces HP even more because of increased back pressure, save $$$ if you want but you will probably be less than happy overall.

acuteperformance

+1

FastLane

Thanks. I do have a 545i V8, does that change anything? I mean I won't be happy with some huge loss in performance, but if were talking 5 hp that I will barely notice then, I can live with that. Actually, I thought I had read that the RD sport quad conversion was one of the few quad setups that gained hp, so if I gain some from the quad setup, and lose some from the bends, is it a wash??

pjinca

With a V-8 you will probably gain from the quads, however that and the sound will be dampened by using pressure bent tubing. Mandrel has been the hallmark of quality exhausts for some time, gotta figure there has got to be a reason for it.

acuteperformance

You drive a 5 series, don't go cheap just to save a few bucks! Mandrel bend is the way to go for any exhaust system if you're looking for performance.

Michael

FastLane

I guess it goes back to the age old saying 'you get what you pay for'. Sound dampened is probably not what I'm looking for, but is it worth the extra $... I suppose mandrel would also be the way to go from a resale perspective...

Nice rims, I have the same ones, although they suffer from severe curb rash...

FastLane

Yeah, you're probably right, I just keep thinking I need to save $ where I can to make up for the $2400 I'm out from quad m last year... I'm still soooo biter...

I wish I could hear the dif.

pjinca

Thanks, I wanted something a little different than the norm here.
Yes, if you want the full effect of an upgraded exhaust go with mandrel bending, and shop around, maybe you can find another local shop that can do it for a better price.

acuteperformance

Sell the exhaust and get the RPi one.

Michael
Acute Performance