Exhaust

[kcsun]

I have been talking to a firm about a custom exhaust. They say you do not need cats as they restrict flow (leave the legalities out)But cannot give an answer to the question - what happens to the sensors - oh just leave them disconnected sir! surely the ECU looks at these and alters settings accordingly?

Any advise would be appreciated

kc [img]images/graemlins/s4anogaro.gif[/img]

[Taipan]

Ken,

I went through that, by incident, with the M Coupé and had a legal expert audit the car so maybe this can be a first hint.
I asked him if the missing cat could have damage the engine, especially since the disconnected "alpha" sensor wasn't reporting anything to the Ecu. His answer : no, the ECU returns to standard default setting so it basically means your pollution level isn't controlled anymore.
They also plugged in the computer analyzer to check and found no significant defective incidents in the memory (something like 6 months).

Now if true for a stock ECU, it maybe something to check when someone gets a Stage I ECU.

Eric

[kcsun]

Thanks Eric

I already have the MTM chip perhaps someone else knows if that sensor has any effect on the MTM chip?

kc [img]images/graemlins/s4anogaro.gif[/img]

[Nige_RS4]

I believe you will get the occasional DTC, but there are ways round this .... 1) you can supress the O2 sensor DTC via ECU s/w (however I don't think MTM do this), there are O2 dummy loads available which fool the ECU into thinking everything is OK, or finally, keep resetting the DTC with VAG-COM [img]images/graemlins/033102bad_1_prv.gif[/img]!

My advice would be to use sports-cats and keep all the sensors in place to ensure you ECU has a chance at getting the mixture right.

[kcsun]

Sorry I am thick - whats DTC? [img]images/graemlins/stupid.gif[/img] [img]images/graemlins/idea.gif[/img]

kc [img]images/graemlins/s4anogaro.gif[/img]

[Nige_RS4]

DTC: Diagnostic Trouble Code [img]images/graemlins/thumbs.gif[/img] Your ECU (and other computers in the car) log all error codes (DTC's) - serious problems will cause the ECL: engine check light (orange light on your tacho) to come on. You will need a VAG-COM or VAG 1551 to read/reset these.

Nige.

[BRETTCOLLINS]

HAVE REMOVED THE CATS ON MY S4 WHEN TUBE TORQUE MADE THE EXHAUST, THEN THE CAR WAS REMAPPED BY AMD. THEY TOLD ME THAT IT WOULD BE OK AS LONG AS THE CAT WERE REMOVED B4 THERE WORK WAS DONE.

BEEN 9 MONTHS, ONLY PROBLEM THAT EPC LIGHT HAS COME ON 3 TIMES NOW.