Okay,

the twin dump has two pipes for its mouth where it bolts to the turbo.

When you look at the turbo exit, it has one large seal round its outside and two holes, one exiting from the spiral of teh exhaust housing itself, and the other from the wastegate.

These are set back from the seal round the outside of the turbo.

The scoobysport downpipe has one large hole which mates to the seal, and both holes feed into the ovel shaped downpipe mouth.

Twin dump designs such as the BPM have a dedicated tube for the exhaust from the impeller, and fromt he wastegate. the idea being keeping these two "exhausts" separate for longer, means that the turbulence caused when they rejoin is much further away from the exit of the turbo, impedes scavenging less than generating the turbulence just after the impeller.

What greg is talking about is effectively a tongue that protrudes from the end of the DP, into the recess in the turbo. It tries to ensure that the gases really are completely separate from right when they leave the wastegate and impeller exhaust (otherwise there is a gap, before the gases reach down pipe since the holes are recessed).

The tongues vary in design for Mitsubishi turbos and ihi turbos.

I am not convinced tehy make much difference as the fit of the tongues is less than exact and there is still plenty of gap to allow the gases to mix.

There is a site where one aussie guy reports before and after gains of around 4bhp (I think) purely as a result of fitting this tongue

If you are really concerned about this, you can make a beautifully fitting tongue that is permantly secured to turbo and not to the downpipe, separating the two exits. In doing this, you can make sure there is no leakage between them.

 

Thanks for that Adam -makes perfect sense

 

I have a complete BPM GT system with the down pipe,mid pipe, single exit BB. MY01,I love it. Brought the car to life. It is not loud, though it is louder that my friends MY01 with BPM down pipe, mid pipe and Apexi N1 BB. But with the baffle inserted, my car sounds just like stock. And the power is excellent.

Ken

 

Adam you seem to really understand exhausts so can you help me out .I have a SSDP on my car with standard STI mid and BB.I want to replace these standard parts and want maximum performance with least noise but of course and happy to meet somewhere in the middle.I am considering a SS BB and Magnex mid with res,how much restriction to flow do you think the mid with res will make.I d'ont want to buy a setup that ends up giving me no real flow gains and therefore would rather suffer the extra noise of a straight through mid pipe than have a mid with res that saps all the power.On the other hand if the res only marginally restricts flow than I would accept this for the benefits of less noise.Any thoghts on my rather long winded question?

 

Deep,

I am no expert on exhausts, I have just changed from SS to BPM so have back to back comparisons, however these only relate to MY car.

Forget the resonators, there is little in it. noise will be softened by a centre high flow cat such as the BPM or Power engineering but I am not entirely by sure how much.

If I were you I would just buy the straight through SS centre and backbox. I cant imagine you will be unhappy with them.

Noise is not obrusive, but gains with the downpipe in place should be noticable.

If the worst comes to the worst then after some time you can sell it if bothers you, without losing much money, although I doubt this will be the case.

I love the sound of the scooby sport, and never found it obtrusive.
For knowledge of quiet exhausts you are better off asking other people. But as I said before, I would never mix SS components with other aftermarket makes again (magnexs centre excluded).

 

Greg, massive diameter pipes for 1200 bhp are all very well, but they are not optimised for cars that are only going to flow around 3-400 bhp, so why bother in our market?

 

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by Adam M:
<B>so why bother in our market?[/quote]

In marketing terms, bigger = better. Pure and simple. People buy cars based on BHP, and modify to increase BHP, therefore this one must be great

(Tongue firmly in cheek)

 

Adam,

The X series system will spool up faster than a 2.5" and provide a superior top end and best overall HP gain AND torque gain...

Sounds unrealistic but you can have the best of both worlds and the sad truth is sometimes fiction becomes fact.

It is not only the diameter of the pipe but other factors including coating, bend usage, different collectors within the X series Twister and so on that will make this a race system. It is not aimed at the average owner.


Greg Nikolettos
Australia 1300 850 BPM
International +61 7 3272 8885
Facsimile + 61 7 3272 8045
bpm@bpmsports.com

 

Amazing to think what debates will occur when the BPM X Series system is released in 6 weeks..

4.5" Extreme Coat Twister Series system that will flow 1200hp

Further details to follow

Greg Nikolettos
Australia 1300 850 BPM
International +61 7 3272 8885
Facsimile + 61 7 3272 8045
bpm@bpmsports.com

 

Greg..

Has my CC been credit/refunded ?

It better had!

J.