AIT and open loop

[01Z]

I'm trying to work through a lean condition at open throttle. What I'm looking for is some ideas and knowledge regarding open loop tuning.

My open loop air/fuel ratio is nearly 14.5:1 and I need to get that down. I have cleaned my MAF with the hope that some residue is skewing the intake volume reading but it was already nearly clean as a whistle.

My next thought is that my Air Intake Temperature sensor (which calibrates the MAF through the PCM) is faulty. In other words, if the AIT is telling the PCM a lower (less ohms) intake temp than actual then the MAF will require less milivolts to adjust its temperature resulting in less fuel to be added; causing the lean condition.

Does this sound logical? A new AIT sensor is only $15 from Autozone. I'm wondering if there is a reasonable chance this could be my problem. I'm inviting any thoughts.

thanks

[CamTom12]

Your IAT guage will tell the PCM to pull timing for higher IAT's...

You said for open throttle or WOT? just part throttle the PCM commands about a 14.5 a/f mixture. It's only at wide-open that it pours more gas into the mix

[01Z]

open loop = wot and PE or am I mistaken ???

Doesn't the PCM look at the intake air temp to also determine fuel to air or is it strictly timing?

thanks.

[01Z]

I should have given more information.

I had my 2001 dyno'd with a wideband reading. It's a/f was 14.5 at WOT. I'm trying to determine why this is the situation. The first thing that came to my mind was that the PCM was seeing less air coming in than reality. I'm now trying to determine a way to get this right without tuning around the problem.

thanks

[Chris 96 WS6]

Open loop is not the same as WOT.

OL is at cold start up....the o2's are offline.

WOT is similar in that the 02s are off line, but instead of shooting for 14.7:1 AFR the PCM uses the power enrichment table to aim for maximum power.

[CamTom12]

any exhaust leaks after your o2's?

They could have thrown the pipe-sniffer off especially with all the slip-fit connections in a LM...

[01Z]

Okay, thanks for that info on the OL and the PE.

As for the accuracy of the wideband, I can't know for sure. There's no leaks afaik. I put the exhaust on myself; it clamps up real nice. Everything seemed good and I hear no leaking that I can tell.

I've been scanning for any dtcs and so far none. I have thought about a maf translator but that doesn't fix the problem. I've been told there's more power to be had if I can richen the mix up a bit. Plus, any tuning gets blanked out with it that lean at open throttle.

thanks

[CustomSSI]

So am i misunderstood or is there no tuning yet on the car and your trying to get the correct A/F ratio without tuning?

[01Z]

No tuning at this time. The wideband O2 reads 14.1 to 14.5 a/f when on the dyno at WOT. I've been told I need it to be close to 13.

I can have it tuned to adjust the a/fr but I feel the computer should be getting it right in the first place. I don't have any significant mods to the powertrain. Consequently, I'm looking to find what is causing my lean condition rather than having the pcm tuned around the fault.

I'm just looking at things that I might be causing the pcm to think there is less air coming in than actual. I thought perhaps the IAT sensor could be one thing to consider. I could test the sensor if I could find a chart that shows ohms to temperature.

I blundered with the name of the thread; I should have called it IAT sensor and WOT.

thanks

[Chris 96 WS6]

Any mods throw the PE calculation off. The PCM can't just "get it right" w/o tuning because there's no feedback loop for it to learn under WOT.

Like I said the O2s are ignored during WOT/PE, so the PCM is just taking the MAF reading then looking up an RPM value in the PE table and adding that much fuel to the base timing.

The only fix is to tune it, period.

[01Z]

Then that is what I will do. I have already contacted someone to do this but he wants me to get another wideband reading to make sure of the lean condition and by how much. The speed shop where I had it dyno'd does not have the software to do the LS1 at this time. Also, I'm not ready to spend $500 just for this.

As you said, I must have it tuned. My next question asks what is the best, cost effective thing to do in order to get a reasonable tune up but not break my bank. I can live with a $150 mail order tune but don't want to waste it. Should I consider getting something like autotap to get some good data to send to a tuner? I'm afraid I know too little about this end of it but I'm anxious to learn.

I'm just looking for more ideas....

thanks

[Chris 96 WS6]

There's no substitute for a good on-site dyno tune. Having said that, some of the mail order tuners can get real close if you send them good data logs. With as mild as your mods are I think somebody like PCMforless could nail a tune for you.

[01Z]

How do you suggest I obtain good data logs or should I contact the pcm programmer and ask that question.

thanks

[foff667]

Open loop is not the same as WOT.

OL is at cold start up....the o2's are offline.

WOT is similar in that the 02s are off line, but instead of shooting for 14.7:1 AFR the PCM uses the power enrichment table to aim for maximum power.

fwiw the computer doesnt aim for 14.7:1 at startup...open loop is open loop whether at wot or at cold start its the same thing basically. Whatever is richer the olfa table or pe table thats what the computer aims for in a perticular situation.

[foff667]

also if you were just getting a tailpipe sniffer after cats its very possible that 14.5:1 reading was incorrect.

[01Z]

also if you were just getting a tailpipe sniffer after cats its very possible that 14.5:1 reading was incorrect.
How can I get a correct reading? The extra money paid for the f/a ratio during the dyno pulls is a waste of money then?

Although the car has no major modifications the intake has been opened by cutting away the restrictions under the air cleaner and an SLP lid is in place. The exhaust is SLP Loudmouth with resonator catback. Is this enough to make a significant difference where the factory power enrichment tables are now too lean?

thanks

[Chris 96 WS6]

fwiw the computer doesnt aim for 14.7:1 at startup...open loop is open loop whether at wot or at cold start its the same thing basically. Whatever is richer the olfa table or pe table thats what the computer aims for in a perticular situation.

I didn't mean the PCM is looking for 14.7 at startup...I was not clear. I meant that neither at OL or WOT/PE is the PCM looking for 14.7...that is only in closed loop.

[foff667]

How can I get a correct reading? The extra money paid for the f/a ratio during the dyno pulls is a waste of money then?

Although the car has no major modifications the intake has been opened by cutting away the restrictions under the air cleaner and an SLP lid is in place. The exhaust is SLP Loudmouth with resonator catback. Is this enough to make a significant difference where the factory power enrichment tables are now too lean?

thanks

if at all possibly when im tuning someone I have an extra bung welded in before any cats so I can get a true a/f reading.

[foff667]

I didn't mean the PCM is looking for 14.7 at startup...I was not clear. I meant that neither at OL or WOT/PE is the PCM looking for 14.7...that is only in closed loop.

correct...you had stated that the computer will look to the PE table to get commanded afr...yes it will look at it but the computer will make a decision to use it or not depending on other tables like the olfa & cot tables to figure out what to command at wot. It will take the richer of the tables depending upon a few variables to determine commanded a/f