birtywrx

got a 95 wrx import, is it worth a decat?! or do i need to do other stuff aswell like a remap?

jaytc2003

iTrader: (1)

decatted mine yesterday (downpipe only as already had a decat sys on), makes one hell of a difference, feels a lot livelier and the sound is awesome

Journeyman

As I understand it, (my limited knowledge) just a decat may well increase your bhp but might well reduce your torque due to the fact that removing the cats will reduce exhaust back pressure to the point were your turbo will not spin up as fast.
A remap on a decat will increase bhp and torque respectively. Am I right?

flat4_ire

pretty much correct yeah, get those gases out as quick as possible, open neck downpipe way to go, the sound is somethng else also

DaveD

iTrader: (2)

Quite the opposite - the turbo will spin up more freely. My 93 WRX started to pick up at 3,500 rpm rather than the 4,000 rpm before the decat - makes the engine a lot more responsive.

You'll also like the subtle whistle too

Tidgy

might need to reset ecu to get best result (check that with mecanic first not sure if it helps or is a good thing on all models)

brunny42

yes is worth it the engine throttle response is brilliant, the sound and turbo whistle is great, well worth doing, really quickens the car,no remap needed at all,just try and get the top heat shield back on the turbo, you will need to cut some off tho to get it on, just helps with under bonnet heat mangement

Scoobynodd

iTrader: (1)

definately worth it fella! ohhhh yes lol!

i've got a uk 1996 turbo, it came with a 2 and a quarter (maybe 2.5) inch diameter system with an oval backbox, it sounded nice but was a little too tame for me.

So then i went back to powerflow (Mikey there built my last system for me on my jap import 2.2 vtec prelude (which was a 2.5 inch system) and a great job, it took a little arm twisting to get him to build me a 3 INCH system tho as he had'nt done one b4 - had had to borrow the dies used to bend the 3 inch pipes from another garage lol! But after tht it was great - i opted for a 5 inch slashcut jap style backbox, set at an angle so the gases get out a little faster. It sounded way better and ran far better too.

Then about 3 weeks later i manged to find a 3 inch downpipe tht exited in 3 inch too! (not the common ones tht reduce to 2.5 grrr! took some finding tho!)

Took me a few hours fighting with some bolts and removing some knuckle skin lol, but i got it on.............AND NOW THE GROUND SHAKES!!! its class!!

I sometimes drive with the window down and the radio off bcos i can actually hear everything the turbo does - spinning up, spinning down etc, its great! far more repsonsive too - a whole different car! and i hav'nt remapped either.....i will do at somepoint but i'm not remapping (to have to remap again later) just because i've changed my pipes grr, but i will when i've done some more work - like a FMIC etc then it would be far more worth the job!

Its been done now for about 2 months nearly and i drive it everyday (my only car!) and its been from Teesside to Norwich and back and Huddersfield and back and not one single issue! Faultless.......but i do need to clean my boost control solenoid now as i was a little 'generous' with my oil lol (miss read the dipstick oops) but thts totally un-related.

Summary: do eeeeeeeeeeeeeeeeeeeet!!! lol u won't b dissapointed fella gd luck

Journeyman

Hmm, well I lost 10lbs of torque just by removing the center cat with a
new cat back system.
It's a Jap Kakimoto Hyper Mega N1 -

http://www.kakimotoracing.co.jp/image_BF1302.html

I have not changed anything else on the car and got it rr'd on the same rollers before & after. Can anyone account for this then if it's not due to loss of back pressure?

I was also lead to believe that removing the downpipe cat was dangerous if the car was not remapped after due to the ignition timing altering etc?
Can anyone clarify this as I would like to decat my downpipe but don't really want to remap the car but also don't want to loose torque...

jaytc2003

iTrader: (1)

Since mine has been decatted, I also took the time to fit a knocklink at the sametime. On maximum sensitivity I have so far had 1 bright green led light up (using esso sul). The only other time I have had more was when I start the car (picking up noise from the starter motor) so a remap would not imho be needed.
I dont understand how the ignition timing would be altered as the ignition has already taken place, the downpipe is just getting rid of the gasses.

Roojai

You probably wont need a remap. The only reason some people say you should is that it is possible to get beyond the tolerances of the ECU with a decat.

More air passing through the system as a result of decat, the ECU sees it's max volume of air passing through, 'X' amount of air, but actually 1.2'X' is passing through. So the ECU is fueling for X but more air is coming through hence the car will run lean.

You are unlikely to get beyond the limits of the ECu with a decat so don't worry too much.

Journeyman

Cool.
So will I see my torgue figure rise again if I decat the downpipe even without a remap?

crispyduck

iTrader: (1)

birtywrx,

I had to do a lot of research around this a while ago and captured a number of FAQs. I've since linked to them on my personal site for days like these. Take a look at the Downpipe FAQ on this page as there is a lot of good information.

Hope this helps,
-Steve.

dmnbrm

ive got a scoobysport back box and de-cat center pipe,which was very good,ive just recently fitted a de-cat downpipe and boy oh boy does it make a difference
i would recomend it to any scooby owner,by the way,your turbo will sound amazing too as you can hear it spool up,my turbo also spools up 1000rpm quicker.

birtywrx

cheers peeps! i read a post and it worried me a bit!! think i will get it done then!!!! next question . . . . . . is the CAT a pain to change?! and i was going to get a Blitz NUR - SPEC system, can i get a decat for this?!