heard alot about them, power eng do one and apparantly prodrive do one for their rally cars.heard they give an extra 30-40 brake.is this true and does anyone else do them?
please help
nutter

 

BPM, MRT, scoobysport/hayward+scott, zero sports, jun all do replacement manifolds, to name but a few.

As with everything, there is compromise involved... you will tend to find that a manifold that gives better breathing in the top end and hence more top end power will loose torque and driveability in the low and midranges. Similarly, you could get a manifold that improves midrange torque and driveability that doesn't give quite as much at the top end.

I was impressed by the MRT headers when a friend fitted them to his car, they gave a healthy improvement in the midrange and changed the exhaust note without loosing the off-beat boxer sound completely.

 

i recently saw an owner's website at http://www.steve.ukmail.org/car/index.html

looking at his dyno plots, he got pretty incredible torque gains throughout the rev range and he is using the standard ecu.

of course, the sound of the car will change considerably.

the other option is to get the standard manifold ported and flowed thus keeping the sound but improving breathing

 

Porting your own headers seems the cheapest option - by a long way! and is supposed to produce noticeable gains

 

are they equal?

 

moray
u r very helpful, please give me web address for the companies u stated?

 

NUTTER
If this helps you, I'll send you a mail with the most famous manifolds for Scoobys. Check your mailbox!
Cheers
JIM

 

does anyone know anything about the HKS one?

 

I' ve got a JUN manifold on my WRX and I have to tell you that I expected more for the price I paid. Nevertheless, it gives the most noticable improvement compared to other external bolt-on modifications. You get significant gains if you change the turbo or have the ECU reprogrammed- otherwise you don't get more than 10- 12 bhp. Low-end torque on my car was affected a bit but I saw considerable improvements at mid and top end torque. The car for sure breathes better now between 4 and 7 thousand revs and pulls better as well. If the money is no object, then go for it.

[Edited by piravlos - 11/30/2001 12:57:51 AM]

 

thats why I went for porting the headers rather at minimal cost than paying over £1k.

On a back to back test, if I'd changed to Jun or something similar I doubt my peak power would have been different..

Just glad I took everyones advice and did'nt waste my money

 

I have the HKS item. It certainly made the same difference as going from OME d/p -> magnex d/p but at what a price! HOWEVER it brought boost down ( i never see more than 1.05 bar and that only in 5th) and it brings exhaust gas temps down.
For the HKS low down torque is more or less the same but the car gains top end and revs faster to the red line.
FYI PPP+ magnex d/p+APS induction =277 cv=281 bhp @ 6100rpm

 

Steve,

I reckon in a back to back test the appropriate aftermarket manifold would beat the matched standard item no problem, assuming map is adjusted accordingly.

Moray

 

i always though un-equal was the way to go?

 

christian,

unequal gives the impreza its sound

equal gives better performance

depends if you want to trade the sound off against a bit more performance

bear in mind that the standard unequal manifold can be improved considerably by porting and flowing

[Edited by milo - 11/30/2001 2:57:40 PM]

 

Moray

Yeah - but I doubt by much

It cost me about £150 to get the headers ported. That includes getting them off and putting back on.

So take a HKS item - say about £1200,then theres the fitting cost - add circa £100

Gain say 5bhp over standard headers say - thats one heck of a cost for a little gain... hmmm then again I dont seem to have got much of a gain to date on my car anyway

ChritianR
Unequal length - no I think it depends on the design - you may well lose power over the standard headers with some of them

The reason I went for porting the ones on there was that there was no definitive answer on the subject - if there was a product out theere that was proven to give me noticeable gains I would have gone for it - but there was'nt and still is'nt

I know people who have had problems putting on aftermarket headers