will PCM give a lean code spraying NOS??
Thread Starter
Safety Car
Joined: Apr 2000
Posts: 4,326
Likes: 140
From: Weatherford, TX
will PCM give a lean code spraying NOS??
When I put in a Vararam I got a lean code that has been cleared. I'm wondering if you can use the lean code as a tuning guide. If I increase my NOS jets and go lean, do you know if the PCM will spit a code? If I go up in small steps, I could know when I've gone too far. Then it wouldn't surprise me if running WOT doesn't fire a code like normal part throttle driving. Any ideas?
Melting Slicks
Joined: Mar 2002
Posts: 2,931
Likes: 2
From: Tx
Originally Posted by Chris Stewart
When I put in a Vararam I got a lean code that has been cleared. I'm wondering if you can use the lean code as a tuning guide. If I increase my NOS jets and go lean, do you know if the PCM will spit a code? If I go up in small steps, I could know when I've gone too far. Then it wouldn't surprise me if running WOT doesn't fire a code like normal part throttle driving. Any ideas?
The stock o2 sensors are pretty much like a switch with very little accuracy for any AF ratio other than 14.7. If the ratio is above 14.7 they read lean, if it is below they read rich. This is how closed loop works; it adds/removes fuel on either side of the switch until it goes the other way. The codes get set when it stays on one side too long or the adaptive fuel trims just can't push it to the other side.
None of this really matters at WOT, since the fuel trims are no longer adaptive (open loop).
The only way to know for sure what the AF ratio is at WOT is to install a WB sensor and controller. They work on a totally different principal than the stock narrowband sensors and provide an accurate AF ratio.
Le Mans Master
Joined: Aug 2002
Posts: 8,472
Likes: 38
From: Houston TX
St. Jude Donor '11
As stated above you couldn't go by codes since the fuel trim codes don't come into play at WOT but I would say that you could use the narrow band stock O2s for the purposes of seeing if you are in the bal park, IE to make sure your fuel noid is spraying but the narrow band O2s could certainly not be used to play around with deviations from the recommended fuel and nitrous jets.
I tapped into my right O2 at the PCM and ran some stereo jacks up into the ash tray that I can stick the leads of my digital multimeter into to see the milivolts it's putting out. I use it after a jet change (IE stepping up from the recomended jets for 125 to the recommended 150 jets). I like to see very high 800 mVs to low to mid 900 mVs.
People will argue that this is not accurate and to a large extent I agree. I just use this method to ensure I didnt swap my fuel and nitrous jets or my fuel noid is stuck closed or something else like that.
I tapped into my right O2 at the PCM and ran some stereo jacks up into the ash tray that I can stick the leads of my digital multimeter into to see the milivolts it's putting out. I use it after a jet change (IE stepping up from the recomended jets for 125 to the recommended 150 jets). I like to see very high 800 mVs to low to mid 900 mVs.
People will argue that this is not accurate and to a large extent I agree. I just use this method to ensure I didnt swap my fuel and nitrous jets or my fuel noid is stuck closed or something else like that.
Last edited by 5 Liter Eater; Aug 25, 2005 at 01:55 PM.
