Powerflow exhaust 2 questions

[dva99999]

hi all, after the questions of how to fit the Powerflow exhaust last week I've now come to a dilemma or 2.

The bore/pipe diameter of the original exhaust is wider from the cat to the back box than the Powerflow one. The Powerflow was taken from a 2.2 (with mine being a 2.8). Circumference of the original is about 17cm, the Powerflow is roughly 13cm. Would there be a reduction in power if I changed over to the Powerflow one?

There is from what I've seen an electric valve at the end of the original exhaust. Can this be removed and would it be needed on the Powerflow one? What is its function and is that limited to the original exhaust?

Thanks
D

 

[GazHyde]

There is from what I've seen an electric valve at the end of the original exhaust.

This is too keep it quiet when pootling around, but opens up when booting it for more sound. Usually find the actuator is broken and it doesn't do anything, or someone has wedged it open

 

[Rha]

Hi dva9999, GaZ is right and the valve built into the OEM exhaust works off the engine vacuum system, if or when you decide to change the exhaust all you need to do is plug the vacuum pipe leading to this valve. As for your Powerflow exhaust off a 2.2 being smaller bore you may loose some power because your going to restrict the gases exit after the cat. If you can't use it Im sure another 2.2 owner will be along to take it off your hands.
I'm currently runnering a Powerflow cat back exhaust on my 2.8 and the only difference it made when first fitted was the great exhaust note. Obviously now playing a bigger role with all the other mods +remap. Hope this helps.

RHA,Roy.

 

[dva99999]

Hi dva9999, GaZ is right and the valve built into the OEM exhaust works off the engine vacuum system, if or when you decide to change the exhaust all you need to do is plug the vacuum pipe leading to this valve. As for your Powerflow exhaust off a 2.2 being smaller bore you may loose some power because your going to restrict the gases exit after the cat. If you can't use it Im sure another 2.2 owner will be along to take it off your hands.
I'm currently runnering a Powerflow cat back exhaust on my 2.8 and the only difference it made when first fitted was the great exhaust note. Obviously now playing a bigger role with all the other mods +remap. Hope this helps.

RHA,Roy.

Thanks for that. It does answer my question. I do want a good exhaust note but not at the expense of less power. Having modified the air inlet last year I was planning on getting that increased gobfull of air back out again via an aftermarket exhaust but this one probably won't do it.
Unless anyone has any other ideas I'll put it up for sale once I've cleaned it up.
Thanks all....

 

[oldcarman]

I agree with @Rha that by reducing the diameter of the exhaust pipe you will be creating a bottled up system which will not breath properly. Selling off is your best bet then get a custom exhaust designed and made up! Some shops will allow you to try out different back boxes so you get the sound you want! JIM

 

[Antm72]

Speak to Powerflow and ask, the exhaust should be an awful lot more free flowing than stock and it may well breath fine.

 

[Lee]

Thanks for that. It does answer my question. I do want a good exhaust note but not at the expense of less power. Having modified the air inlet last year I was planning on getting that increased gobfull of air back out again via an aftermarket exhaust but this one probably won't do it.
Unless anyone has any other ideas I'll put it up for sale once I've cleaned it up.
Thanks all....

Might take this off your hands when It comes available

 

[dva99999]

Might take this off your hands when It comes available

Thanks Lee, I'll keep you informed.

 

[Ianmc]

I'm no expert on this but understand that exhaust bore (amongst other things) is optimised in design to best suit the engine characteristics. Larger (or smaller) is not necessarily better, and no doubt cost is a factor for the OEM solution. Getting it wrong aftermarket could certainly lose power. Guess "fine tuning" could increase power - I'm sure the aftermarket suppliers would likely say this. I would personally stay OEM unless convinced to do other.
Didn't know about the electronic valve, is this fitted to all cars do we know?

 

[Lee]

Didn't know about the electronic valve, is this fitted to all cars do we know?

Facelift models.

 

[Ianmc]

Interesting, thanks Lee. You learn something every day!

 

[Lee]

Interesting, thanks Lee. You learn something every day!

It works on the vacuum, don't get mixed up with electronic

 

[Antm72]

Mine had one and its prefacelift but right on the year of turn.

 

[Lee]

I've seen this a few times when we remove the exhausts. Never seen one before 2000 though. Must of been what ever they had in stock

 

[Lee]

Mine had one and its prefacelift but right on the year of turn.

Guy I work with ex BMW tech just told me 2.8 only. I'll get back in my box

 

[Ianmc]

Are we thinking just 2.8 (pre face lift) now?

 

[Lee]

Are we thinking just 2.8 (pre face lift) now?

I would say Facelift as well because Ants is a facelift with the same valve

 

[Ianmc]

So the thinking is all 2.8/3.0? Don't think the M has such.

 

[Antm72]

I would say Facelift as well because Ants is a facelift with the same valve

Mines prefacelift
Back box now changed but i have the old one and the valve was in the right side pipe.

 

[GazHyde]

I doubt anyone could tell you which had the exhaust valve with any certainty. Had one on my '99 2.0, and I've seen them on both pre and post facelift.

One thing you could rely on with BMW is that they were rather inconsistent with what they fitted to the Z3. Not sure if this happened with other models, or maybe it's because the main assembly plant was relatively new to BMW...