Hi I have a 1990 touring 325 i with a cat which I want to get rid of. Anyone know which section is the cat as apposed to the silencers.
Also I do NOT want the car to be any noisier, and would this be worth it, how much BHP does the cat restrict?
Anyone decatted there touring?
Cheers
K
decat a touring how?
Moderator: martauto
I think the Cat is built into centre box, so you would need to get hold of a non Cat front section. Should just be a straight swap, although you will need to weld in a threaded bit for the Lambda sensor - you will still need this even though you are removing the Cat.
Being a 1990 325i, you will have no problems with the MOT. August '92 is the date for that.
The noise shouldnt be any louder, although the tone might change a bit I guess.
I dont know how much BHP having a Cat will lose or whether you will notice a difference. Ive only deCatted my old Cav SRi, and the engine was shagged on that so I didnt expect much
Being a 1990 325i, you will have no problems with the MOT. August '92 is the date for that.
The noise shouldnt be any louder, although the tone might change a bit I guess.
I dont know how much BHP having a Cat will lose or whether you will notice a difference. Ive only deCatted my old Cav SRi, and the engine was shagged on that so I didnt expect much
James
'91 325i Sport
'93 318i touring 16v
'91 325i Sport
'93 318i touring 16v
The Lambda sensor will be located somewhere in the downpipes, between the manifold and Cat. Im not 100% sure where, cause Ive never seen one on an E30.
The Lambda sensor is part of the engine feedback loop. It monitors the oxygen content in the exhaust gas as unburt oxygen and then the ECU knows if the engine is running rich or lean. It then richens or leans the air/fuel mixture accordingly, to keep it at the optimum point, 14.7:1.
On your car it would mainly be there to protect the Cat - it doesnt like unburt fuel, but also to keep the engine running cleaner and more efficiently.
If your car is Cat equiped car then yes, you will need the Lambda. You can remove it by using an ECU from a non Cat car, but if you keep the original ECU, you will need to keep the Lambda sensor, otherwise the ECU will not receive the signals its expecting and run in 'Limp mode'.
There is no problem with keeping the Lambda sensor once the Cat has been removed. The engine will not run any different. Ive removed both Cats from my new engine, but still have both Lambda sensors cause there isnt anyway of bypassing them.
The Lambda sensor is part of the engine feedback loop. It monitors the oxygen content in the exhaust gas as unburt oxygen and then the ECU knows if the engine is running rich or lean. It then richens or leans the air/fuel mixture accordingly, to keep it at the optimum point, 14.7:1.
On your car it would mainly be there to protect the Cat - it doesnt like unburt fuel, but also to keep the engine running cleaner and more efficiently.
If your car is Cat equiped car then yes, you will need the Lambda. You can remove it by using an ECU from a non Cat car, but if you keep the original ECU, you will need to keep the Lambda sensor, otherwise the ECU will not receive the signals its expecting and run in 'Limp mode'.
There is no problem with keeping the Lambda sensor once the Cat has been removed. The engine will not run any different. Ive removed both Cats from my new engine, but still have both Lambda sensors cause there isnt anyway of bypassing them.
James
'91 325i Sport
'93 318i touring 16v
'91 325i Sport
'93 318i touring 16v
-
glenn
- Engine Transplant Services
- Posts: 2198
- Joined: Sat Jan 29, 2005 11:00 pm
- Location: blackwood, south wales
james,I dont know how much BHP having a Cat will lose or whether you will notice a difference.
on the m5 (e39), the cat's restrict 20bhp on each bank!
that's a total of 40bhp
i had a look in the one's i cut off and how the hell the
engine breath's through them, god know's
20bhp each 
I didnt realise it would be that much.
That means you got to be looking at 440bhp in yours then??
I guess the M5 has Cats like that for the USA emissions laws and its cheaper for BMW to leave as is for all countries.
Im assuming there wouldnt be that much of a restriction on an M20 with a Cat though, Ive heard figures of around 5-8bhp and some say 8-10bhp, but nothing that can confirm.
The only deCat experience Ive had was on my old Cav SRi. It rusted through and fell off one Sunday night and I was driving upto Heathrow to pick up a mate on Monday morning.
5.30am on the Monday morning with my car on the ramps welding in a section of pipe
I didnt notice a difference without the Cat really, but then I never had a way of telling and the engine was roasted. 150K miles, of which I did 30k and I never serviced the engine, just made sure there was some oil and water - was waiting for it to go bang so I could drop a V6 in there, but the bloody 2.0ltr kept going and going
Then I bought the E30......
Without the Cat the Vaux engine did rev better and the noise was crisper and deeper at low revs, and it also developed a nice pop on overrun.
I didnt realise it would be that much.
That means you got to be looking at 440bhp in yours then??
I guess the M5 has Cats like that for the USA emissions laws and its cheaper for BMW to leave as is for all countries.
Im assuming there wouldnt be that much of a restriction on an M20 with a Cat though, Ive heard figures of around 5-8bhp and some say 8-10bhp, but nothing that can confirm.
The only deCat experience Ive had was on my old Cav SRi. It rusted through and fell off one Sunday night and I was driving upto Heathrow to pick up a mate on Monday morning.
5.30am on the Monday morning with my car on the ramps welding in a section of pipe
I didnt notice a difference without the Cat really, but then I never had a way of telling and the engine was roasted. 150K miles, of which I did 30k and I never serviced the engine, just made sure there was some oil and water - was waiting for it to go bang so I could drop a V6 in there, but the bloody 2.0ltr kept going and going
Then I bought the E30......Without the Cat the Vaux engine did rev better and the noise was crisper and deeper at low revs, and it also developed a nice pop on overrun.
James
'91 325i Sport
'93 318i touring 16v
'91 325i Sport
'93 318i touring 16v
Could just be some air getting into the exhaust somewhere - you should hear the XR3i Ive been driving lately, it leaks quite badly at the join just before the backbox, but its great at popping on overrun when it revs down from 3k rpm.chu346 wrote:My car does that with the cat fittedjmc330i wrote:it also developed a nice pop on overrun.
Might be worth checking yours out though, if its overfueling it could damage the Cat.
The Astra V6 conversion Ive just finished for a mate was overfueling so badly it was popping flames at the MOT test
Looked cool as fcuk, but the MOT tester wasnt very happy Im just glad we didnt bother refitting the brand new Cat that was on the Astra
it would of been toast.James
'91 325i Sport
'93 318i touring 16v
'91 325i Sport
'93 318i touring 16v
-
glenn
- Engine Transplant Services
- Posts: 2198
- Joined: Sat Jan 29, 2005 11:00 pm
- Location: blackwood, south wales
20bhp each
I didnt realise it would be that much.
That means you got to be looking at 440bhp in yours then??
you warrior!!!!!!!!!The only deCat experience Ive had was on my old Cav SRi. It rusted through and fell off one Sunday night and I was driving upto Heathrow to pick up a mate on Monday morning.
5.30am on the Monday morning with my car on the ramps welding in a section of pipe