Basic question on knock sensors and fuel mixture
02-17-2010, 07:18 AM
#1
RL Community Team
Rennlist Member
Rennlist Member
Thread Starter
Basic question on knock sensors and fuel mixture
I tried a search (on rennlist, on google, other forums, etc).
This is what I want to know. When I unplug an injector on my '84 it produces less emissions. When I unplug an injector on my '93 Audi V6, the emissions go WAY up. Why? The only thing I can think of is that the knock sensor senses a misfire (because there is no fuel in that one cylinder) so it changes the fuel mixture (rich? lean?) in an attempt to stop the knocking. I figured on knock sensor because my audi has one and my 944 doesn't.
If this is indeed the reason for the higher emissions with an unplugged injector, could I then unplug the knock sensor to bring the mixture back to normal?
Help/insight greatly appreciated.
This is what I want to know. When I unplug an injector on my '84 it produces less emissions. When I unplug an injector on my '93 Audi V6, the emissions go WAY up. Why? The only thing I can think of is that the knock sensor senses a misfire (because there is no fuel in that one cylinder) so it changes the fuel mixture (rich? lean?) in an attempt to stop the knocking. I figured on knock sensor because my audi has one and my 944 doesn't.
If this is indeed the reason for the higher emissions with an unplugged injector, could I then unplug the knock sensor to bring the mixture back to normal?
Help/insight greatly appreciated.
02-17-2010, 10:01 AM
#2
...knock sensor? or just the DME in closed loop with the o2 sensor?
i doubt the knock sensor would sense a misfire..cause there would be no fire coming from that cylinder. there would be no knock. and i don't think the DME would change AF due to knock. it would most likely retard igntion when knock is sensed.
what emissions go way up on the audi? HC CO or NOx? i'm imagining that the audi V6 with a dead cylinder and tries to use the other 5 cylinders with increased load to keep it running. so prob pushes more air and more fuel into the other 5. still don't see how it's related to knock unless it pushes the 5 cylinders so rich that it starts to knock.
i doubt the knock sensor would sense a misfire..cause there would be no fire coming from that cylinder. there would be no knock. and i don't think the DME would change AF due to knock. it would most likely retard igntion when knock is sensed.
what emissions go way up on the audi? HC CO or NOx? i'm imagining that the audi V6 with a dead cylinder and tries to use the other 5 cylinders with increased load to keep it running. so prob pushes more air and more fuel into the other 5. still don't see how it's related to knock unless it pushes the 5 cylinders so rich that it starts to knock.
02-18-2010, 07:29 PM
#3
RL Community Team
Rennlist Member
Rennlist Member
Thread Starter
I guess I figured running on 5 cylinders would make the knock sensor think it was knocking, for some reason.
On the Audi the HCs are too high. In this county they don't check for NO. I forgot to look at the CO.
I just remembered though that disconnecting the knock sensor would trip the check engine light so maybe I should get a spare sensor to plug in and let dangle to the side or something if I want to try this.
On the Audi the HCs are too high. In this county they don't check for NO. I forgot to look at the CO.
I just remembered though that disconnecting the knock sensor would trip the check engine light so maybe I should get a spare sensor to plug in and let dangle to the side or something if I want to try this.
