andyr

I've seen things mentioned about decatting a classic but having searched I've not really found info I could rely on.
I need to replace the centre cat in my exhaust (it's rusted) and it's either a case of getting hold of a cat or replacing it with a non-cat pipe.
Is it safe to do without the cat wrt boost levels etc : I'd thought that leaving just the cat in the up-pipe woudl potentially give rise to excessive boost levels. Car is a std 1995 JDM WRX with a P1 backbox.
Have knocklink fitted and always run V-Power plus NF Race OB. Never normally see any Knocklink activity.

myblackwrx

iTrader: (1)

Early imports only have 1 cat (downpipe) centre section is a resonator and there isn't one in the upipe (this is only going by all the early imports i've seen)

My 93wrx is decatted and runs fine (running the same ecu you are).
Imo you are also wasting money on octane booster if you are running V power as that fuel has a higher RON rating then what the ecu was mapped for.

andyr

Re V-Power/OB, I thought the fueld was only 98RON whilst the JDM fuel was 102 ?

Anyway, I haven't removed the cat/centre pipe-thing but it has what appears to be a heatshield below it which made me think it was a cat.

myblackwrx

iTrader: (1)

JDM fuel in 1995 was nowwhere near 102 RON ,the higher octane fuel started coming in about 1997 onwards and even then imprezas may not have been specifically mapped for it.

i run my 93wrx on Tesco 99 ron and it's fine,i've used BP ultimate 97ron (car didn't like that),Optimax 98ron fine now obviously V power and Total Excellium 98 ron and the only difference i've found is mpg.

It may very well be a cat but i've never seen one on an early car (but since subaru did **** about with the early cars who really knows)

andyr

Anyone else care to comment on the safety of removing the centre cat (assuming the box in the centre pipe is a cat and not just a resonator that is ?!) ?

p1u

i run a 95 jdm wrx and have a 3in exhaust from the down pipe back and running with no probs i did notice the turbo spooled up a bit faster but not much.
p1u

edit to say i run cheap fuel and give it death and never had a prob lol

w13dle

iTrader: (5)

as said above the centre section has a resonator not a cat, im running a full decat but with a polar performance chip & mines overboosting just ordered a dawes device to control that, running on tesco 99 & everything seems fine apart from that

dj219957

ive run with a full decat (no cat or resonator) in my old 95 wrx before with no issues at all. the centre section only reduces noise. it does not hurt to take it out.

stop wasting money on octain booster. shell optimax or tesco 99 ron is more than enough for a 95 wrx. your knocklink should proove that (mine did).

andyr

Sounds good - best/cheapest place then to replace this rusty box currently located in the centre of my system ?

Jamz_

iTrader: (12)

Got pretty much a straight through pipe on my 93wrx from headers to rear, no problems what so ever... got the pipe from ebay cheap

No boost problems (dunno why you would think there would be any)

mach

the statements on the quality of jap fuel before 97 are spot on but it's allways best to run the 99ron stuff.the centre box on my 94 sti was a cat but now i run with a sports cat(in up-pipe, won't actually pass a uk mot on emissions but import pre-97 are exempt,didn't find out till after i'd bought and fitted it but turns out they are designed for the uk one's),centre pipe with sound deadening box in it(try and keep the vosa men happy but still didn't and caused all hell) and a race box rear,all came from scoobyworld and were really good fit,i got an esl motherboard fitted and mapped and have had no trouble with overboosing and am getting 8mpg more than before.

andyr

Wonder if this is a decent way of replacing my centre cat/resonator ?

SCORPION IMPREZA TURBO CLASSIC WRX STI DE-CAT PIPE on eBay (end time 24-Jul-09 19:17:59 BST)
SCORPION IMPREZA TURBO CLASSIC WRX STI DE-CAT PIPE