can an exhaust make an engine run rich?

[bozothenutter]

noticed my exhaust tips were black on the inside (sooty)
this wasn't happening before with the oem exhaust, could the exhaust be causing the engine to run slightly rich?
Car is going for a remap in march so that should take care of it.

if it is not normal, what could it be lambda sensor? (how do I check it?)

 

[Jimbo_M]

Yes it could, i have found it to be the case in the past, has the car still got the cat on? no cat normally makes cars run 'richer'.

 

[Chip-mk1]

Its very dependant on the car and specifically how the management works.

If you are looking at a speed/density based engine management system like the clio for example (ie it primarily uses a map sensor and the rpm to work out how much to fuel) then anything that makes the exhaust more restrictive will result in a drop in volumetric efficiency of the engine which the ECU will have no way of seeing when its in open loop mode (ie not lambda controlled) so wont be able to adjust for.

During closed loop operation though the ECU should be able to catch varations and allow for them by adjusting the injector pulse width accordingly.

Since the removal of lead from petrol, its normal for all exhausts to be black inside IME.

 

[bozothenutter]

thanks it is about my 182, and the exhaust is a milltek with the original cat.

 

[pug_leg]

If it helps, I found a load of soot on my old lambda (pre-cat) when I removed it recently. The faulty sensor was causing the car to run too rich - got to the point where it was struggling to run at all when cold.

http://www.cliosport.net/forum/showthread.php?619547-Lambda-sensor-causing-fault-or-just-a-symptom-!

 

[Chip-mk1]

thanks it is about my 182, and the exhaust is a milltek with the original cat.

Use a wideband lamda sensor to see what the richness is, not guess from looking at the tailpipe.

I would wager it will be marginally leaner now than before you fitted the milltek.

 

[bozothenutter]

Use a wideband lamda sensor to see what the richness is, not guess from looking at the tailpipe.

I would wager it will be marginally leaner now than before you fitted the milltek.

that's what I would have thought.....strange.
been working on the car today and found something....the exhaust to cat coupling had a slight leak (telltale soot track) I understand that that can make the car run badly (hadn't noticed anything though)

can the standard ECU handle a wideband lambda?
is the standard one a narrow band?
My car is being mapped in march (with an RS2), would the mapping be more accurate with a wideband lambda?

like johnny 5 said...need more input!

 

[Chip-mk1]

You are misunderstanding me.

I am not saying get the ECU to use a wideband, I am saying use a stand alone one with a guage to see what your fuelling is doing rather than guess that it is rich from the colour of the exhaust.

Any leaks after the cat shouldnt effect how the car runs greatly, although obviously if there is enough of a blow to cause turbulance it can then lead to a decrease in VE wish could push the car slightly rich

When you car is mapped it WILL be done on a wideband, you cant possibly map a car without a wideband really.

 

[Chip-mk1]

PS

Is the RS2 already fitted?

If so your fuelling will be well out in places.

 

[bozothenutter]

nope, RS2 will be done next week, mappoing in march...

thanks for the info, I understand the first sensor (front) is the one that controls the engine, and the second is only a control for the first?
I really should read up on engine management, my knowledge kinda stops at L-jetronic :S

 

[Chip-mk1]

Second one is just there to check operation of the cat, serves no purpose other than that, only does anything if it detects a fault.

 

[danh90]

mine runs rich. but seems to run fine cold and warm i also have alot of sut inside my tailpipes :/

 

[Chip-mk1]

mine runs rich. but seems to run fine cold and warm i also have alot of sut inside my tailpipes :/

What sort of afr are you calling 'running rich' mate?