Idle AFR inconsistent W/BS3

[jpwalt1987]

I have been noticing that my AFR at idle isnt staying the same from day to day. One day it will be about 14.2-14.7 and then the next it will have -22%correction and be at 12.xx. I have the VE table for idle at 7. This is with 95lb injectors @45psi static and a 224/224 solid roller cam. The idle RPM is @850 There is no temp correction influencing the VE table when it acts up. Is it realistic to expect this combo to idle at 14.7:1 ?? I hate to go lower on the fuel pressure because I would think that the higher pressure would help with atomizing the fuel a bit better. I may be wrong though. I need to check and see at what RPM closed loop operation happens, but I know it is not at idle. I am thinking about going down to a smaller hydraulic roller cam and some smaller injectors to help with the driveability but that cost money I dont have right now. I want to make the best of what I have.

I am at a loss for now. Any ideas?

 

[lazaris]

Try raising the rpm to 950.

 

[TurboBob]

the BS3 is just a computer. so something is happening that is making the unit deliver more or less fuel.

You need to compare data from a good day and a bad day, and go over it with a fine tooth comb.

Watch for enrichments being triggered or not, differences in MAP readings, granularity in the VE, battery voltage compensation, drive cycle changes (hot engine, hot injectors, hot fuel). Watch the injector pulsewidth very closely.

Bob

 

[S2V6RACER]

Raise the idle and I'm leaning on a issue in the tuneup. I would never consider touching the fuel pressure when you can change the tune.


I think what Bob is saying is to maybe pull a replay log when it is running good and then one when it is running poor. You will have some useful data on gross injector PW and base injector PW. I would expect you will see what's going on right there.

 

[jpwalt1987]

I raised the idle rpm to 950 and tried playing with the VE figures. The VE was at 7 but I dropped it down to 4. The AFR leaned out a little bit but not to 14.xx. I looked at the closed loop turn on RPM and it was set at 850rpm. I changed it to 2500 just to take that out of the equation. Of course the O2 correction went to 0. The injector pulse width was at 1.3 MS with both VE settings(4 and 7). I think I may have some oil smoke fooling the O2 sensor. I looked closer at the color of smoke coming out of the tail pipe and it is more of a blueish color than black/gray. I am going to go drive around and see what my cruise AFR is. I am wondering if the oil is getting past the turbo seals at low RPM but not at higher (turbo)rpm. I have a restrictor built into the oil fitting for the turbo that is about .120 big. Could be the valve guides too. Time for some testing

P.S. What rpm should I set the cosed loop operation at? It has an ON and OFF. The OFF has to be lower than the ON from what I read. Thanks, Jeremy

 

[norbs]

I have the same cam and injectors and it will run with no issues with a 14.7 a/f. But my pw is at 1.5 ms@ 900 rpm. I would set the closed loop rpm to be about 50 rpm lower than the idle rpm in gear so if the idle drops below that value it goes into open loop and runs a bit richer so it doesn;t stall. Try another o2 sensor and check for any exhaust leaks.