Who Runs With 02 Unplugged?
10-14-2007, 06:42 PM
#1
Pro
Thread Starter
Join Date: Aug 2001
Location: Maryland
Posts: 740
Likes: 0
Received 0 Likes
on
0 Posts
Who Runs With 02 Unplugged?
I'm asking this question because I get different answers. I have a 86 930 with headers, GHL exhaust, no cat and Fabspeed intake. I set my CO at 3% with it plugged in.
I know your suppose to set the CO with it unplugged but when I tried it ran very rough. Should I unplug it and try to set it up at 3% to see if it will settle down?
I know your suppose to set the CO with it unplugged but when I tried it ran very rough. Should I unplug it and try to set it up at 3% to see if it will settle down?
10-14-2007, 08:57 PM
#3
Racer
Join Date: Sep 2006
Location: S. Florida
Posts: 406
Likes: 0
Received 0 Likes
on
0 Posts
Mine runs better unplugged, so it is.
I got really good at tuning multiple webers with a unisyn and my ear back when I had a BMW 20002ti with 2 45DCOE's, 10:1 pistons, 300 degree BMW cam, and Stahl headers...years ago.
Tuning CIS by ear is a piece of cake.
I can tell when it's getting lean and too rich is very obvious with the oscillating idle and dropping below idle speed and then coming back up after blipping the throttle.... and the smell of the exhaust with the motor at operating temp and then fine tuning through the warm up stages.
It's best to be on the edge of lean while at idle.
Are you adding an adjustable warm up regulator to richen the top end under boost when you put on the K27S with the 1 bar spring, and headers?
I got really good at tuning multiple webers with a unisyn and my ear back when I had a BMW 20002ti with 2 45DCOE's, 10:1 pistons, 300 degree BMW cam, and Stahl headers...years ago.
Tuning CIS by ear is a piece of cake.
I can tell when it's getting lean and too rich is very obvious with the oscillating idle and dropping below idle speed and then coming back up after blipping the throttle.... and the smell of the exhaust with the motor at operating temp and then fine tuning through the warm up stages.
It's best to be on the edge of lean while at idle.
Are you adding an adjustable warm up regulator to richen the top end under boost when you put on the K27S with the 1 bar spring, and headers?
10-15-2007, 01:36 AM
#5
Rennlist Member
IF you are going to run your fuel mixture (CO%) RICHER than the factory recommended setting of approximately .60-.80%, I would leave the oxygen sensor disconnected because the oxygen sensor is going to be fighting the fuel mixture trying to bring it down to a leaner point. IF you were running a STOCK car at the factory fuel mixture setting then it is a great idea to leave it connected "IF THE OXYGEN SENSOR WAS OK". Please note: I would recommend 3.0-4.0% for your car especially since you are running no catalyst and have aftermarket headers, period.
10-15-2007, 05:49 PM
#7
Three Wheelin'
Join Date: Apr 2006
Location: London, England
Posts: 1,977
Likes: 0
Received 0 Likes
on
0 Posts
My car was set up with o2 disconnected and at 3% idle and it ran fine.
Then after some works a different garage set it up with o2 connected and 0.8% idle and it runs fine.
Dyno, boost and CO readings all steady and good.
Confused? yep, me too.
Then after some works a different garage set it up with o2 connected and 0.8% idle and it runs fine.
Dyno, boost and CO readings all steady and good.
Confused? yep, me too.
Trending Topics
10-15-2007, 07:01 PM
#8
Burning Brakes
Join Date: Apr 2006
Location: Central Washington State
Posts: 1,118
Likes: 0
Received 2 Likes
on
2 Posts
I run without the O2 sensor and set the CO to 3% at idle (900 rpm). The only drawback I can see is maybe a slightly sluggish off-the-line performance, which I attribute to being much richer than factory at idle (but then again, it may just be the fault of the low compression 930 engine). But once I get some air moving through there to lean things out, everything is cool. Check out the line to the 911Turbo Board forum on this topic.
http://www.911turbo.com/BB/viewtopic...ight=o2+sensor
http://www.911turbo.com/BB/viewtopic...ight=o2+sensor
10-15-2007, 07:45 PM
#9
Pro
Thread Starter
Join Date: Aug 2001
Location: Maryland
Posts: 740
Likes: 0
Received 0 Likes
on
0 Posts
IF you are going to run your fuel mixture (CO%) RICHER than the factory recommended setting of approximately .60-.80%, I would leave the oxygen sensor disconnected because the oxygen sensor is going to be fighting the fuel mixture trying to bring it down to a leaner point. IF you were running a STOCK car at the factory fuel mixture setting then it is a great idea to leave it connected "IF THE OXYGEN SENSOR WAS OK". Please note: I would recommend 3.0-4.0% for your car especially since you are running no catalyst and have aftermarket headers, period.
I did a complete tune up before I set the CO. I replaced all plugs, cap/rotor, fuel/air filter and new O2 sensor.
I just remembered when I tried to unplug the sensor the car did what to stay running so I plugged the sensor back in and set it to 3% at 900 RPM.
10-15-2007, 09:57 PM
#10
Burning Brakes
Join Date: Apr 2006
Location: Central Washington State
Posts: 1,118
Likes: 0
Received 2 Likes
on
2 Posts
[QUOTE=Bernard;4678098]So are you saying set it up 3.0-4.0% plugged in or unplugged? In the next week are so I'll be installing my new K27S and bigger intercooler.
I did a complete tune up before I set the CO. I replaced all plugs, cap/rotor, fuel/air filter and new O2 sensor.
I just remembered when I tried to unplug the sensor the car did what to stay running so I plugged the sensor back in and set it to 3% at 900 RPM.[/QU
Unplug it, then proceed to set the idle and the CO%. But if it's working fine for you plugged in, then perhaps you should just leave it alone?
I did a complete tune up before I set the CO. I replaced all plugs, cap/rotor, fuel/air filter and new O2 sensor.
I just remembered when I tried to unplug the sensor the car did what to stay running so I plugged the sensor back in and set it to 3% at 900 RPM.[/QU
Unplug it, then proceed to set the idle and the CO%. But if it's working fine for you plugged in, then perhaps you should just leave it alone?
10-16-2007, 03:26 PM
#13
Pro
Thread Starter
Join Date: Aug 2001
Location: Maryland
Posts: 740
Likes: 0
Received 0 Likes
on
0 Posts
10-16-2007, 09:58 PM
#14
Burning Brakes
Join Date: Apr 2006
Location: Central Washington State
Posts: 1,118
Likes: 0
Received 2 Likes
on
2 Posts
If I understand all the input offered so far, and with my own experience, set the CO with the O2 sensor unplugged at first. That will set your proper AF ratio when the engine is running through it's power band. Then, plug the O2 sensor back in and it will lean out your mixture at idle. If the sensor is in good condition, your idle should still be ok...but you'll be assured of maintaining the AF you want when running the car through it's full range. But if it doesn't idle worth a crap, then just unplug it and forget about it.