How would a dodgy lambda probe affect power??

[JMC 0]

Here's a question for all you engine experts. About 6 months ago I had my G60 custom mapped, and felt a huge increase in mid range torque, and (again) it felt more powerful at the top end as well. Went to the Surrey rolling road day recently with high hopes for an increase over last year, and the peak power and torque was almost identical to the previous run, but with an obviously increase in mid range torque. So, mixed results.

 

On the way home I noticed that my AFR, had stopped doing the usual cycling on idle, and was basically stuck on the rich side of things, even when accelerating, and the car was feeling a bit sluggish. Changed the lambda probe, and (not surprisingly) the car feels more lively again, and the AFR has gone back to cycling.

 

Sooo, the question is - would a dodgy lambda probe cause the car to go into some form of 'limp home' mode, making the mixture rich, and would that have resulted in it feeling sluggish, and the (mediocre) rr day result??

[Kevin Bacon 5]

I didn't think the G60 ECU has a limp mode? Darren will know for sure....

 

If the Lambda is dead, the open loop power shouldn't be affected, it's only when you're on closed loop part throttle that things get messy. Lack of power, too much fuel, etc etc.

[JMC 0]

Ah, so the lambda should only really be used when on closed loop with a partially open throttle, and not at WOT. The lambda was definatly dead, as replacing it has made the AFR go back to cycling on idling and part throttle.

[Henny 0]

G60 DOES have a limp mode which is normally triggered by low battery voltages... ;)

[JMC 0]

Cheers Henny, Is the limp home mode reset as soon as the voltage returns to the high value though?? (I seem to recall mentioned that unlike the VR6 ECU the G60 one don't need to be specially reset).

[Kevin Bacon 5]

Ah, so the lambda should only really be used when on closed loop with a partially open throttle, and not at WOT.

 

Yep ;-)

 

At WOT, the ECU just bungs in fuel at the ratio set in the MAP and ignores the lambda. In closed loop, the lambda takes care of the fuelling.

[flusted 0]

so where does the co pot come into it then?

[CoxyLaad 0]

G60 DOES have a limp mode which is normally triggered by low battery voltages... ;)

 

is that limp mode or just not working properly ;)

[GazzaG60 0]

the co-pot allows fueing to be trimmed. this trimming is based around lambda correction as far as i can remember. basically it changes the partial fuelling.

 

do you have an af gauge. if you do the best way i could see the changes was here. when i put the sns in it was rich basicaly harly moved from rich. as i adjusted the co-pot ohm up (up =leaner) the fueling started to react where it would cyucle and only go rich when on boost or at WOT. as needed. AF gauge can help diagnose easier.

 

in your case jmr its possible that you are runnig slightly rich and the probe was on its last legs or another is that the exra power finished off the front engine mount and ragged the o2 wires about a bit.

[flusted 0]

Im actually enjoying how it all works.

Im running mine with lambda unplugged and the WOT switch taped pressed.

Strange thing is,if i plug lambda back in,it runs like a dog even with WOT switch pressed?

Surely with switch pressed,it should ignore lambda readings?

[JMC 0]

do you have an af gauge. if you do the best way i could see the changes was here. when i put the sns in it was rich basicaly harly moved from rich. as i adjusted the co-pot ohm up (up =leaner) the fueling started to react where it would cyucle and only go rich when on boost or at WOT. as needed. AF gauge can help diagnose easier.

 

in your case jmr its possible that you are runnig slightly rich and the probe was on its last legs or another is that the exra power finished off the front engine mount and ragged the o2 wires about a bit.

 

I have a narrow band AFR attached to the lambda for the ECU. It was that the alerted me to the fact that the old lambda was dying/dead, as it had stopped oscillating on idle and partial throttle. Hopefully the front engine mount is OK (it's a solid one), although the old lambda has been intermittent over the last few months. New one seem happy though :D Think it was just bad timing that it gave out on the rolling road day :(

[MNuTz 0]

would limp mode result in higher emissions than normal?

[JMC 0]

would limp mode result in higher emissions than normal?

 

Wouldn't surprise me as I understand it richens up the mixture AFAIK.

[flusted 0]

think it dumps 25% more fuel in

[MNuTz 0]

this may explain why my G60 is running an emissions rating of 9%. Its been sitting in my driveway for 12 months now. Hopefully im going to be getting a start on before winter!