shanegs

hi iv only had my impreza uk turbo 97 about a week and its backfiring when i let of the throttle an it seems mainly in the lower gears after giving it just a little bit of beans!! 1 chap on here said its prob because the chap b4 has put a decat exhaust, induction kit and dump valve with out it having a remap? does any 1 else agree with this and could any 1 plz let me know if this is causing any damage or could it cause damage as i cant afford a remap for at least a month possibly 2!! any comments and advice welcome plz

bugeyejohn

iTrader: (11)

Does the exhaust blow anywhere this will also cause that,If not id check to see if the ecu is still standard and if so stay of the boost and you should be ok

Terminator X

iTrader: (7)

IMHO you shouldn't be driving a decat car without a remap!

TX.

shanegs

exhaust is not blowing as far as i can tell, and i believe its got a standard ecu ill have a look at it in a sec and see not that im sure ill be able to tell lol

shanegs

only had this car a week an did not fit exhaust my self, is it going to cause much damage if i keep driving the car b4 remap?

Terminator X

iTrader: (7)

You might get away with driving off boost but I'd just not drive it if possible. FYI I got some mods done to my Spec C a few years back one of which was a decat zorst ... Bob Rawle advised me to drive dead slow straight from the garage over to his place to get it mapped!

TX.

bugeyejohn

iTrader: (11)

Im not to clued up in remapping but i know if you decat youve got to stay of boost until its mapped as you will have fueling issues which will cause engine damage,I was told that if you drive of boost and steady its ok but remap as soon as poss.If you have the old catted pipe fit it back on and you shouldnt have any problems

shanegs

thanks guys as only had car about a week have been putting my foot down lol but guna keep it slow an smooth now till remaped luckily iv got a work van i can use instead also as been told i cant remap my standard ecu so guna cost me about a grand!! any 1 know of any second hand ecu's which would suit my car to help make things a little cheaper or if looking for a second hand ecu which 1s i should look for?

shanegs

dont have old cat pipe any idea ware to get a cheap 1 from?

bugeyejohn

iTrader: (11)

Proberly on here or ebay,I wouldnt have thought they would cost much as most people want decatted ones which leaves a lot of standard ones left over

shanegs

if i get a standard cat pipe will this fit to my stainless scorpion exhaust an this should sort the prob for now?

bugeyejohn

iTrader: (11)

Btw the decat youve got which part of the exhaust is it,as long as you have the original down pipe i think you should be alright,as i think classics only fitted one there anyway at least imports did

shanegs

dont have standard pipe im not that clued up on my car as only just got it an dont know which cat part i shoud order to fix prob to be honest

bugeyejohn

iTrader: (11)

Look at the down pipe the one that connects to the turbo. If its only like a tube type pipe its decatted and if its big around like a silencer its not

shanegs

exhaust is def a de cat. so i need to get a cat in the down pipe of exhaust then an will it fit strait on to my scorpion exhaust?

bugeyejohn

iTrader: (11)

Yes,and it should do is it a 2 1/2 system ie the pipe

bugeyejohn

iTrader: (11)

http://cgi.ebay.co.uk/1998-genuine-S...item3cb4e15cb5 That what you want something like that,if you system is a 2 1/2 it should be a straight fit. If its 3 inch you might need a adapter but someone on here will know for sure

bmposer

iTrader: (3)

Mine does this alot to, i have the same mods as you.
It has had the fueling checked which is fine.
I was told its the dump valve that causes it as it lets the metered air out which causes a sudden rich mixture which is unburnt as you are off of the throttle but then ignites on the hot exhaust.

shanegs

cheers every 1 uv been very helpful im guna get the cat back on for now till i cant afford ecu an remap

shanegs

yer 1 chap said it could be dump valve but im guna go with every 1 on here for now till i get remap

bugeyejohn

iTrader: (11)

Its proberly better safe than sorry,although a decatted classic is proberly less affected than a newage wrx as they dont have 3 catts in them to start with,but i would have thought you could end up with boosting/fueling probs at least thats what mappers say and they know a lot more about it than me,so i wouldnt take a chance

P1Drifter

iTrader: (7)

if i were you i would leave the decat on, take a trip to alan jeffreries and get the fueling checked, it will probably be fine and if your worried just drive it sensibly and off boost. The 'back firing' is very likely due to the dump valve and just a bit of unburnt fuel burning in the exhaust. For what its worth there are a large amount of classics running around with decats and no remaps !

The king

Dont listen to much on hypoconders decatting their car and dont dare hitting the throttle until some tuner can ripp them off on a remap.

You have a little thing called a air flow sensor in your intake (by the air filter). When decatting, you get more exhaust out of the cylinders, so therefore you can get more air in. More air requires more fuel. Without the air flow meter this would be bad. very bad. But that little sensor reads that you get more air in, and therefore increase the amount of fuel injected.

The "problem" with this little sensor though, is that even small leaks, from intake pipes, intercoolers, BOV`s etc also reads as air into the engine. Some FI systems wont allow fuel cut with a certain amount of air flow through the MAF. They then inject fuel as if the air flow enters the engine. This cause backfireing, even flames when enough ignities on the hot turbo.

So have fun. Pedal to the metal. Invest in a wideband AF meter if youre worried about running into problems with fueling.


Oh, just for the fun of the examples, a Nissan 200SX, with virtually the same fuel injection as your scoob, can handle a boost increase of over 100%, 3" exhaust, FMIC, and even mild camshaft replacements without a remap. So dont tell me removing a cat will blow up a scooby engine.

Terminator X

iTrader: (7)

^^ Note to self - don't buy a car from you!

TX.

Maz

iTrader: (34)

Of course he did and relieved you of some money too. I'm not knocking mappers or mapping but a bit of overfuelling whilst not ideal isn't going to blow this bloke's car up. I had a 97 MY UK Impreza with the exact same mods and that never had problem on the standard map. I reverted back to the standard dump valve when the popping (not backfiring) got a bit much. The decat and induction kit stayed though at no detriment to the car. Infact Rich Wilding of Jap Innovations got 380 bhp out of his 97 Impreza on the standard map. I hasten to add I'm not knocking mappers but a remap isn't always necessary. An AFR monitor is a far more useful tool.

Terminator X

iTrader: (7)

FMPSL you'll warrant my car then will you with a decat zorst

TX.

shanegs

nice to hear it aint that bad the first few posts had me ****ting my boxers that id already given it a fair amount of beans lol

shanegs

think im just guna take from this:
dont rag it like my life depends onit!!
no need to drive it like im 80 cause the engine will go!!
and car will be happy enough for a couple of months till when i was hoping to have a biiger turbo and remap done any way!
plus im going to this exeter meet next sunday an can hear wat every 1 saze there!!

Maz

iTrader: (34)

Not on an original Spec C map no. For the record MY97 UK cars do not have mappable ecus.

Maz

iTrader: (34)

I would put the re circulating original dump valve on. It will save you a few quid on fuel.