Running Lean? Problems?

[1stGENracer]

It seems to me that I am running a little lean. My O2 sensor voltage is high under acceleration, and I'm running about 12-14 knock sum on NGK BPR7ES plugs, running stock boost. How would I make my car run a little richer? Why would my car be running so lean? What problems could I check for that would cause me to run lean?

Thanx

 

[CanadianTSi]

You could always rewire your stock fuel pump or buy a new high flow unit

 

[jw]

If you say your O2 is high, then why you said it's running lean? You can be running rich and still get knocks. The turbo could be spinning much higher rpm than it should to maintain stock boost if you have a boost leak. Also, if the intake temperature is too hot, it will cause detonation also.

 

[1stGENracer]

my voltage reading off my O2 sensor is up around .88 volts and higher when I am on the throttle, which means there is a lot of oxygen, which means I am running lean maybe not to lean, but I am not running rich enough. I need more fuel.

 

[jw]

The lower the voltage, the leaner it gets

 

[1stGENracer]

ok, well how low is youre oxygen sensor voltage suppose to get? mine will drop all the way to 0.00 at times also. is that right?

Also are you sure on that O2 voltage thing? I thought it was the other way around? Maybe I need to read up on O2 sensors a little more.

I haven't checked for leaks yet. Maybe thats my problem. I want to figure this out before I put my boost controller on.

 

[CanadianTSi]

Yep, the lower the voltage, the leaner you are running.

At what RPM's are you seeing your 12-14 knock sum and what is your timing like?

 

[jw]

The reason why it go to 0v at times is because it's in close loop operation. When in close loop, the ECU uses the O2 feedback to control fuel (injector pulse width to be exact). When the O2 reads too lean (closer to 0v), it will try to rich things up (closer to 1v), then it goes on and on. That's why the O2 cycle around 0v and 1v when your are cruising/idling. While doing that, it updates the fuel trims so it remembers what to do the next time you start the car. The fuel trims are constantly changing based on the O2 readings. The conditions for changing fuel trims are mentioned in another thread already by me, so I wont repeat it here again.

Now, on the other hand, there is the open loop operation where the ECU dont use the O2 and fuel trims as feedback anymore. What it need is airflow (hz), baro pressure and intake air temperature. With these three variables, it calculate air mass and determine the injector pulse width (IPW). So, in open loop condition, it dont care if your O2 is reading lean/rich or even broken, all it knows is air mass and with the air mass gives IPW. What you are trying to tune for is this WOT open loop condition.

The car is always in close loop operation
during idle and cruising until it go above 4krpm, big change in throttle position or WOT where it go open loop.

For 1G, generally you want it to be at least .86v-.88v. Every car react differently with the voltage so you have to find the sweet spot. However, use the O2 reading with a grain of salt because our stock O2 is not accurate and vary widely with the change in temperature.

 

[1stGENracer]

Ok, I will go and look all this over again.

I start seeing the highest knock at about 5500 rpm's. Under that it will only go to about 3-4 knock. But once I get to about 5500 it will go way up.

I use to hit 36+ knock sum before I bought my NGK BPR7ES plugs.

 

[4WARND]

Have you checked your base timing ?

 

[IPT]

Your O2 voltage will also read 0.0V on deceleration (compression braking) the stock ECU shuts down the injectors to help slow you down.

 

[1stGENracer]

How do I check my base timing?

Bear with me here, I know how to work on cars and stuff, but DSM's are new to me, and a little different. I really need to get a shop book, anyone know where i can buy one?

 

[jw]

You can get Hayes manual from Pep boys. Or better yet, VFAQ.com has these info for free

 

[4WARND]

>>> How do I check base timing ?

http://www.plymouthlaser.com/timin.htm

This is the VFAQ on how to check timing. I would not bother with re-marking the Crank pulley, you should be able to see the mark with the timing light. The plug it refers to is behind the battery.