Confusing findings with oxygen sensor.
Thread Starter
Instructor
Joined: Sep 2001
Posts: 209
Likes: 0
From: Seattle WA
Confusing findings with oxygen sensor.
I just installed headers and new exhaust, its running really well. I also had a heated oxygen sensor put in the collector close to where cylinder 1 dumps. I am using a voltage meter to measure the findings. The sensor reads about 900mv when just idling and cruising, but when I give it full throttle it drops down to as much as 700mv. It didn't make sense that it should get leaner when I am at full throttle so I didn't pay too much attention since it was working great.
I just changed the jets down 4 points(80 to 76 secondary and 72 to 68 primary) and the results are identical except all the readings are lower(leaner) which is as expected.
This is just really confusing because its supposed to be richer when at WOT and its significantly leaner. With the leaner jets it gets down to like 200mv after a few seconds at full throttle.
I am thinking its a possible fuel delivery problem, I did pick up quite a bit of high end when I put in a new holly 120 gph fuel pump. Its not detonating and the timing seems about right. Could it possibly be that my power valve is open all the time and I have been jetting it leaner to fix that at idle?
Any ideas or comments are appreciated, thanks guys!
I just changed the jets down 4 points(80 to 76 secondary and 72 to 68 primary) and the results are identical except all the readings are lower(leaner) which is as expected.
This is just really confusing because its supposed to be richer when at WOT and its significantly leaner. With the leaner jets it gets down to like 200mv after a few seconds at full throttle.
I am thinking its a possible fuel delivery problem, I did pick up quite a bit of high end when I put in a new holly 120 gph fuel pump. Its not detonating and the timing seems about right. Could it possibly be that my power valve is open all the time and I have been jetting it leaner to fix that at idle?
Any ideas or comments are appreciated, thanks guys!
Race Director
Joined: Oct 2000
Posts: 15,037
Likes: 79
From: central FL, near the beach.
Re: Confusing findings with oxygen sensor. (inqbus383)
once you tune it with the sensor, you will wonder how you lived without it.
look for 880mv at idle and WOT. i'm not sure what the exact a/f is at 880, but the c5ers use this voltage so it must be close
look for 880mv at idle and WOT. i'm not sure what the exact a/f is at 880, but the c5ers use this voltage so it must be close
Racer
Joined: Mar 2001
Posts: 372
Likes: 1
From: Ellicott City MD
Re: Confusing findings with oxygen sensor. (inqbus383)
Also, make sure you have good power and ground to the sensor. I had my sensor temporarily hooked up to the cigarette lighter and never got good results until I found a more permanant power source.
Thread Starter
Instructor
Joined: Sep 2001
Posts: 209
Likes: 0
From: Seattle WA
Re: Confusing findings with oxygen sensor. (inqbus383)
Thanks Matt for the help, but the problem seems to have fixed itself. Perhaps the oxygen sensor hadn't been heat cycled fully or something, or else maybe my carb decided to meter properly. Who knows. Thanks
Racer
Joined: Aug 2001
Posts: 356
Likes: 0
From: Glacier County mt
Re: Confusing findings with oxygen sensor. (inqbus383)
The voltage is dependent upon the O2 sensor.
I use a Holley Commander 950 injection system, and they say .500 volts
on the O2 sensor is 14.7:1 air / fule ratio..
The answer is is check with the manufacturer of the sensor / gauge
:cheers:
I use a Holley Commander 950 injection system, and they say .500 volts
on the O2 sensor is 14.7:1 air / fule ratio..
The answer is is check with the manufacturer of the sensor / gauge
:cheers:
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Race Director
Joined: Mar 1999
Posts: 10,258
Likes: 1
From: Calif.
Re: Confusing findings with oxygen sensor. (gdh)
Please make sure to take out a couple of degrees initial timing if you jet down, especially if you reduce the jet size to something smaller than what was installed in your carb when it came out of the box.
You've been warned...
You've been warned...
Race Director
Joined: May 2002
Posts: 14,376
Likes: 1
From: Check this riff........
Re: Confusing findings with oxygen sensor. (shawn_cake)
The voltage is dependent upon the O2 sensor.
I use a Holley Commander 950 injection system, and they say .500 volts
on the O2 sensor is 14.7:1 air / fule ratio..
The answer is is check with the manufacturer of the sensor / gauge
:cheers:
I use a Holley Commander 950 injection system, and they say .500 volts
on the O2 sensor is 14.7:1 air / fule ratio..
The answer is is check with the manufacturer of the sensor / gauge
:cheers:
--marc