I think i going to go against the advice given. I want to put a new bb on, nothing too loud, and also to delete one cat.

I cant afford 1250 for a remap/new ecu. Leaving the one cat in place (keeping some back pressure) should be sufficient to not totally screw it over right?

1250 on a 3k car just doesnt add up. I m thinking run without an ecu upgrade, if the engine goes bang, can probably get another engine for 1250!

SO does anyone run a 1 decat with different back box without a remap on a classic v4 imported STI running on 99 tesco jungle juice?

 

Classic sti only has 1 cat.

 

hi gang,

this is v interesting for me as my v3 sti has failed mot today. the centre section is rotten and I'm going to replace it, but the thing that worries me is that most of the 'zorst companies will quote a de-cat pipe, there is a small bulge of a box that the centre section has in it, so is this another silencer?

If so, I can 'whip it out' (oo-eer) and throw in a stainless H&S centre section with no worries??... perhaps a bit more noise, but that's not a bad thing...

Mikey

 

On mine centre was only a resonator. Think only uk cars have a centre cat. I run a ninja sports cat downpipe and a straight through centre on my v5 with no problems.

 

ok. anyone got a diagram of the system. only ones i can find have downpipe decat center decat another center with a box on and a back box section.

flames would be nice so downpipe decat prolly. also gotta be less than 100db.

should probably fit a knock sensor if i dnt remap.

 

early classic sti car do have 1 cat only (the 1st cat downpipe) mid cat was not fitted it should have a resonator box, you can get away with fitting it without a re-map but you will not get the best results out of it, but also some cars do suffer boost spikes after a de-cat as far as i know its v3 on cars that can suffer this i was told the cars with 3 port boost solenoids (early v1-v2) dont usually have a problem but some later 2 port solenoid cars can suffer i think this can be helped by drilling the restrictor pill to a slightly larger size hope this helps

 

Interesting. Although im afraid i dont know much about what your talking about.

What is a resenator box? Im basically after the scooby burble. Currently have a 22b back box and std everything else, and its really quite. Doesnt really sound like a scoob at all.

I would imagine the most back pressure to be caused by the cat? Im not sure why back pressure is needed and how that would affect boost. I can only assume with the back pressure removed the turbo can spool more easily/faster so a little more boost. ?

I shall be going up to scoobyworld to get a few fitted see what i like. But would like to turn up with an understanding of what needs doing.

The car will be tracked every month, without the map is it likely to cause pinking or other bad effects?

Just trying to gauge the seriousness of the mod. Some people seem to think i will destroy the engine really quick without a remap. However im sure tons of people run decats without a remap.

its a v4. No idea what boost solenoid i have, and i dont know what a restrictor pill is. Would you mind explaining a little. Ill google so feel free to write a technical answer if you wish.

THanks

 

Ok is the boost solenoid what controls the boost by opening and closing a port real fast?

 

Resonator box keeps the exhaust quiet removing it will give the car a more distinctive burble

The boost solenoid is on the drivers side suspension turret you will have a 2 port solenoid iirc
Boost Solenoid Plumbing
this is a 3 port solenoid yours i believe will only have the bottom 2 connections (i may be wrong)

In the early cars if the restictor pill is removed it will cause boost spikes and quite violent fuel cut but i think in yours it has the opposite affect (limited boost)

 

anyone experience any negative effects running a downpipe back system with cat removed without a remap or porting this restrictor?

I have a compliment of gauges so i could try it and revert back if i have troubles.

 

also im assuming a decat is required to get any flames/pops so the unburnt fuel ignites later in the zaust rather than in the uber hot cat?

 

thanks for this.. I shal go for the stainless centre section from xtreme scoobies or TSL then... thanks

Mikey

 

i am running a full decat and have been for nearly 3 years and had no running issues whatsoever (MY96 WRX)

I have not had any kind of remap at all, and many of my friends also run with ll decat and no remaps with no ill results.

I appreciate that a map will get better results from the decat/backbox upgrades, but it shouldnt be detrimental and will sound great.................!

All you need is a friendly MOT centre

My car also pops and bangs like chinese new year on over-run, but IIRC to get flames, you will need a vent to atmosphere dump valve - but that is a whole other story..........

Jason

 

Im running full decat on my sti v3 type r and I am changinging back to the standard downpipe. I get alot of spiking and boost surge but because I have to plans to modify Im just going to run cat back.

 

hmm perhaps sport cat is the way to go then.

Or perhaps ill start cat back then adjust later on when i can afford/justiy some ALS.