Ru$$Rip

Had a scoobysport de-cat pipe and the other centre section replaced on my MY02 WRX and the car feels like its running slower! The car simply doesnt 'feel' as quick and the boost although correct doesnt seem as noticeable as it was with the standard exhaust on. I have an STi7 BB which when fitted made a noticeable difference to performance - now with the SS centre sections in place it doesnt feel as good.

Does anyone have any ideas whats going on here?


Cheers

Ru$$Rip

Just had a thought - does anyone think that the Sti7 BB may be restricting the extra flow of gasses or something? Do de-cats only work in conjunction with higher-flow BB's?

gareth

How long have you had it on?

It took my WRX a couple of days (about 300 miles) to work out what to do with my scoobysport uppipe & downpipe.

Cheers,
Gareth

Ru$$Rip

Its only been on a couple of days. I thought the ECU on the MY01+ 's learned within a matter of minutes? I will wait a while but I do think that the STi7 BB cannot cope with the additional flow of gasses......

mega_stream

I found this when I decatted my MY99 UK scoob
Seemed to lost its kick and it sorta flattened it's acceleration.

Does make you think if after all the R+D that's done on these cars only for people to start messing by decatting and such without having the map altered....

Put the cat back on I say, stop buggering the ozone

john banks

It is common with a decat system not to feel the same punch during spool up since the turbo comes in earlier and smoother. Only a (semi ) objective test in the form of AP22, Road Dyno or similar, or chassis dyno would tell you. There was an Autospeed article which suggested that exhaust systems do not add power to the WRX. Looking at the maps I can see why - when you stray off the standard areas of the map with higher airflow the ECU pulls timing and throws in fuel by the truck load. A remap would unlock the gains, unless of course there is some other issue on your car which would need checking with datalogging.

stevejohnson511

I also noticed this on my 01 wrx,the sti 7 back box seemed to improve things but I was never convinced about the de-cat centre,
and adding the wrsport back box made it seem even slower.When I put the centre cat back on to p/x the car at the dealers it was noticably quicker low down the revs.To me it seems as though a slight decrease in back pressure helps, ie sti7 back box ,but any more slows it down.People on here will tell you the sti7 bb and the standard wrx bb are equally restrictive but adding the sti7 bb
on its own was the best mod i made to my wrx.
Steve.

Ru$$Rip

Steve I agree, the Sti7 BB really made a difference to my WRX. The gamble is wether I go for a Scoobysport BB or stick the cat and resonator sections back on?

stevejohnson511

I found adding the prodrive bb to the de-cat centre made my car a noisey slug,I have been in a wrx with just the prodrive bb an it sounded and drove better than mine,so from experience I would say if you want the scoobysport bb, put your cat back on first or you will have increased the flow too much and need a re map as John
said to increase performance.
Steve.

Fizz

iTrader: (1)

the sti7 back box made no improvement what so ever on a friends car (dyno results showed) The replacement on mine of centre section and back box with Scoobysport made a dramatic difference (felt like a classic again)....

stevejohnson511

Fizz
you must be lucky in that your car responded well to exhaust mods.
I timed mine with a stopwatch on the same stretch of road and it was definately slower even after allowing a few days to settle.
Steve.

Ru$$Rip

Is there anyone else out there that has experienced this, I dont want to fork out on a SS BB on a gamble.

Pete Croney

There is no question that removing the centre will help, which is why Prodrive do it in the PPP.

The main thing is that, as John said, you get an earlier and smoother boost build, so whilst being quicker, the car can feel less frantic.

There are plenty of dyno figures of 01's with various levels of exhaust replacement, none are producing less power and a full decat will normally produce over 255bhp.

You certainly do not need a remap, but if you knew what the car was like with one, you would have it done immediately

Ru$$Rip

Pete,

If I go for a SS BB will this improve the flow of gasses and improve power as opposed to retaining my STI7 BB?

Cheers

Pete Croney

The STi backbox will not be flowing any more than your WRX one.

A good straight through silencer will flow much more gas and should provide better performance throughout the rev range.