Lee

I must admit the theory of the twin-dump pipe sounds a winner. Certainly PE have "copied" it.

I don't think the Jap exhausts are using this method (correct me if wrong(probably)) they go for a single outlet down pipe with the cat removed.

For normal road use though I think many people stick with the original downpipe therefore their gains will be less.

GavinP

I came across this post in the Australian WRX list and have copied it here..

GP: I have added approximate bhp figures to the text below but the rest was a straight "cut and paste"

FYI
===

Greg writes......

The BPM exhaust has now undergone several independent tests in two different states and also overseas. The result showed an average increase of 13kw's (17.5bhp) at the wheels. We estimate with our new system available shortly we will push this to 16kw (21.5bhp), details of which are mentioned below.

The test undertaken at Croydon Autosports in Sydney also included tests of many other exhausts currently for sale on the Australian market including the following:

* HKS
* Hi Tec
* Greddy
* Numerours others

This test showed the BPM exhaust to give the greatest amount of power increase at the wheels. We ensured that all the following criteria were followed.

* The same car was used for the standard and modified test runs;

* Neither BPM or any representative of the company had access to the vehicle between its standard and modified runs. This means that no items of the vehicles were changed in any way;

* All tests were conducted by independent parties;

* No fuel additives were used. No ice was placed in the intercooler or anything else that may distort the outcome of the performance;

* Both before and after runs were performed on the same day and therefore at as close to possible to the same ambient temperatures.


We have gone to extreme efforts to provide as clean and accurate tests as possible to show that our product is the best on the market.

Here is what a couple of customers have said after having our product fitted:

"Good torque response, great workmanship that rivals the Japanese and the HPC coating option is a must have. The dump pipe and centre pipe are lighter than Jap ones. I love the noise."

"The increase in performance is fantastic. The car accelerates not just much quicker, but also heaps smoother with a lot more response throughout the entire rev range. The system looks like a work of art when you see it and it has performance to match."

Further news include.........

New muffler design guarnateed more Kw increase , tested and proven available for purchase in two weeks.

Sti exhaust soon to be launched and the inventory list will also strive to include the VF22, VF23 etc.

If you have any further queries , please do not hesitate to email me or we can chat online with
ICQ (45940764)

Greg Nikolettos
BPM Marketing Division
Phone: (617) 3272-8885
Mobile: 0410 678 989
Fax: (617) 3218 8880

firefox

Hi chaps...

The twin dump has been proven.... but the true benefits have only been shown on large turbo/high boost cars....due to the large amounts of gas...

For true power vent it to atmosphere... The gases coming from the turbo will be faster/more pressure.... and the wastegate gasses just bypass the turbine...

There are three stages of the twin dump system:

Scoobysport - Large open flange that fits over both the wastegate and turbine outlets. No divider. (Just one large pipe that fits over both outlets)

PE - Seperate outlets for wastegate and turbine. Join together a few inches down.

BMP - Seperate outlets for wastegate and turbine. Join together at the base of the down pipe. Has seperater plate (depending on turbo requirement).

Alot of the jap and American cars dont use the twin dump system because they use external wastegates that bolt onto the exhaust manifold before the turbo. These are seperate units.... and have their own pipes.
But require a custom manifold/header with a flange.

Hope this helps..

J.

Lee

Is the std exhaust the same as SS ?

If so, is the SS just a bigger diameter pipe without cat ?

Pete Croney

Food for thought... At full open, the wastegate valve opens approx 30 degrees.

(I'd post a picture if I could use UBB)

firefox

Hi again..

Hey Pete..

There are several differences between the SS and the original. Some of these are:

SS has bigger bore pipe
SS has less restrictive bends (mandrel bent - retains same bore)
SS hasnt got a cat
SS's flange onto the turbo doesnt "block" off the wastegate. The original Subaru pipe virtually blanks off the wastegate exit, making it instantly bend the gases through 90"'s to join the turbo gases through a 0.5" gap..This design is the same as the HKS pipe....The SS pipe is large at the top which fits over both the turbo and wastegate...allowing the gases to leave...

J.

Bob Rawle

Greg, losses are circa 25% not 40-50% as you quoted, these numbers confirmed by Subaru.


Bob

BPM

Bob,

I totally disagree it is a minimum of 40%.
Post this question on an Australian, New Zealand group and that will be the result you get, that is why a 155kw standard Impreza turbo generally registers 85kw at the wheels.
It is a 4WD drivetrain hence the loss is so great.


If you have any further queries , please do not hesitate to email me or we can chat online with
ICQ (45940764)

Greg Nikolettos
BPM Marketing Division
Phone: (617) 3272-8885
Mobile: 0410 678 989
Fax: (617) 3218 8880

Lee

My MY99 registered a 32% loss due to transmission when on the rollers.

Bob Rawle

Greg, I said circa ... I stand by the post. it is not 40-50% !!

firefox

Hi guys...


I agree with Lee... I have seen various results from various dynos.... they all come out at around 30'ish percent...

50% is too bloody high (try putting some oil in the diffs)!!

15-20% is for 2WD...

J.

J.

Lee

(A massive off-topic post but couldnt resist..)

would explain why, in a straight line, the scoob is not as quick as you might believe.

Compare with a Pug 306 GTI-6. Lighter car, better gearing, 2WD so less loss.
I would estimate that 176bhp less 20% is 141bhp..my scoob was pushing 157 at the wheels..not much in it really !
(unless we make him choose low revs and the scoob shove-ya-in-the-back-torque gets the advantage!)

BPM

Just a note on the first leading thread, the figures that were quoted were at the wheels ie not the flywheel.
Figures at the wheels result in 40-50% decrease through drivetrain loss.
If we had quoted flywheel results, they would have obviously been much higher.

If you have any further queries , please do not hesitate to email me or we can chat online with
ICQ (45940764)

Greg Nikolettos
BPM Marketing Division
Phone: (617) 3272-8885
Mobile: 0410 678 989
Fax: (617) 3218 8880

BPM

Bob,

I have just called Subaru and the figure of 40% is true. The fact is you can easily equate this if you converted flywheel figures to at the wheel figures. You will see there is a pattern of 40-50%. Sounds high but facts are facts.
How is it that a 160kw at the flywheel Subaru MY99 only registers 85-92kw at the wheels?


[This message has been edited by BPM (edited 11-10-1999).]

R19KET

Guys,

Unless we know in which gear the Aus'/NZ/Subaru are basing the 40/50% on, the arguement is pointless.

PE do the runs in 4th (5th for 2door)the results would be totally different if the run was in 3rd, bhp wheels > bhp fly.

Also depends which way you work your equation.My car consistantly gives circa 200 'sh bhp at the wheels, which equates to 300 'sh bhp at the fly, correct me if I'm wrong,BUT !!!!.

Our figures are calculated from bhp at the wheels, not the flywheel.

Mark.

Bob Rawle

Mark's made the point I think!! the numbers tell the story.

Stef

Even so guys, BPM's system would equate to an increase of about 24/28 bhp at the flywheel.
Doesn't sound too bad to me compared to the competition.
BTW Greg, is this a full system inc downpipe or a cat-back?

Stef.

[This message has been edited by Stephan (edited 11-10-1999).]

Darren Soothill

But that sort of figure is not unusual!

My Type R with Scoobysport down pipe and backbox is putting out 308BHP with the standard center section which is known to cause a drop in torque!

Unfortunately I didnt have the car on the rollers before the test but I would guess at the car producing 280ish before which gives a gain of 28BHP at the top end.

The gains lower down are far larger.

Darren

BPM

Guys,

It would equate to 30Hp without our new muffler which we showcase on the dyno day in the UK Dec 11th.
All queries to Subaru Manchester for now.

If you have any further queries , please do not hesitate to email me or we can chat online with
ICQ (45940764)

Greg Nikolettos
BPM Marketing Division
Phone: (617) 3272-8885
Mobile: 0410 678 989
Fax: (617) 3218 8880