L Jet Mixture question
01-30-2004, 06:23 PM
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L Jet Mixture question
The idle appears to have stabilized. I replaced the seal at the bottom of the AFM which seems to have helped the fluctuations. I then checked the timing which was right on, and the o2 sensor which also checked out fine.
Given all that stuff was ok, I cranked the idle fown from 1100(!) to 750 which is at spec. Boy does it sound better now! I then checked out the mixture via the O2 sensor. The sensor reading at idle was right at 0.5v. So far so good. I hooked up my new A/F sensor and went for a spin.
Under WOT, I pretty much peg the sensor. This corresponds to an AF mixture of around 12.5:1 which is very rich. At idle the AF mixture is 14.7:1.
It seems like idle is fine and at WOT it is pretty rich. So here is the question: should I care? Is there any reason not to run that rich at WOT? Do I need to lean out the mixture a tad? The car was up to operating temperature, but I have no idea how hot the exhaust was which can change the top end of the O2 sensor readings.
TIA
Given all that stuff was ok, I cranked the idle fown from 1100(!) to 750 which is at spec. Boy does it sound better now! I then checked out the mixture via the O2 sensor. The sensor reading at idle was right at 0.5v. So far so good. I hooked up my new A/F sensor and went for a spin.
Under WOT, I pretty much peg the sensor. This corresponds to an AF mixture of around 12.5:1 which is very rich. At idle the AF mixture is 14.7:1.
It seems like idle is fine and at WOT it is pretty rich. So here is the question: should I care? Is there any reason not to run that rich at WOT? Do I need to lean out the mixture a tad? The car was up to operating temperature, but I have no idea how hot the exhaust was which can change the top end of the O2 sensor readings.
TIA
01-30-2004, 06:27 PM
#2
Rennlist Member
Re: L Jet Mixture question
pegging the sensor, which is very crude by the way, is fine. you are probably around 13.5 if I was to guess, even though the meter is reading 12.5. (you are talking about a 1/10 volt differnce. and again, the o2 sensors are very crude, but great at keeping the mixture in the right range for emissions and fuel mileage.)
mk
mk
Originally posted by Marc Schwager
The idle appears to have stabilized. I replaced the seal at the bottom of the AFM which seems to have helped the fluctuations. I then checked the timing which was right on, and the o2 sensor which also checked out fine.
Given all that stuff was ok, I cranked the idle fown from 1100(!) to 750 which is at spec. Boy does it sound better now! I then checked out the mixture via the O2 sensor. The sensor reading at idle was right at 0.5v. So far so good. I hooked up my new A/F sensor and went for a spin.
Under WOT, I pretty much peg the sensor. This corresponds to an AF mixture of around 12.5:1 which is very rich. At idle the AF mixture is 14.7:1.
It seems like idle is fine and at WOT it is pretty rich. So here is the question: should I care? Is there any reason not to run that rich at WOT? Do I need to lean out the mixture a tad? The car was up to operating temperature, but I have no idea how hot the exhaust was which can change the top end of the O2 sensor readings.
TIA
The idle appears to have stabilized. I replaced the seal at the bottom of the AFM which seems to have helped the fluctuations. I then checked the timing which was right on, and the o2 sensor which also checked out fine.
Given all that stuff was ok, I cranked the idle fown from 1100(!) to 750 which is at spec. Boy does it sound better now! I then checked out the mixture via the O2 sensor. The sensor reading at idle was right at 0.5v. So far so good. I hooked up my new A/F sensor and went for a spin.
Under WOT, I pretty much peg the sensor. This corresponds to an AF mixture of around 12.5:1 which is very rich. At idle the AF mixture is 14.7:1.
It seems like idle is fine and at WOT it is pretty rich. So here is the question: should I care? Is there any reason not to run that rich at WOT? Do I need to lean out the mixture a tad? The car was up to operating temperature, but I have no idea how hot the exhaust was which can change the top end of the O2 sensor readings.
TIA
01-30-2004, 06:40 PM
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Cool. Then it's done! 
Time to declare victory over the strange idle demons.
Before I start on the steering rack or the synchros I think I'll bask in the glory of the moment.
Time to declare victory over the strange idle demons.
Before I start on the steering rack or the synchros I think I'll bask in the glory of the moment.
01-30-2004, 06:52 PM
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Marc,
You could convert that to a hot wire MAF and the car will run a lot better. I did my turbo 928 with this and it runs like a champ!
I still like the simplicity of the AFM though.
You could convert that to a hot wire MAF and the car will run a lot better. I did my turbo 928 with this and it runs like a champ!
I still like the simplicity of the AFM though.