So if the BLMs are correcting for improper tuning, what is wrong with that?? I am really new at this so bear with me.

 

Someone mentioned that BLM is locked at WOT? Is this true?? Also, could someone tell me what integer is??

 

BLM's of 128 mean the ECM is not having to do any corrections. Or simply put, the current bin file in the EPROM is close to perfect. The integer is a smaller step in correction, once the integer exceeds its max (-/+ 8 i think) the BLM changes up/down one # and the process starts again. Someone please correct me if I am mistaken. Bob

 

The important part is when the ECM goes into WOT (wide open throttle). If the fuel tables are not right at 14.7 AFR, then the ECM stores that info...BLM, block learn memory. So you can cruise around with a BLM of 115 (too rich) and be ok. This means the fuel tables are not at 14.7 AFR but the ECM is correcting for that. When the ECM goes into WOT is *assumes* (hence the BLM going to 128 when you mash the gas) the fuel tables are 14.7:1. If they are not this is where the big problems occur.

That is my best understanding.

 

So what are the problems at WOT, if the part throttle BLMs are off some but the WOT AFR is close working with a wb o2?

Why tune for 14.7 at part throttle? Is this best for throttle response?why not tune the part throttle at an AFR that provides best responce/and power for the particular setup? If you dont have to worry about emissions.

 

128 means the ecm isn't making any corrections to the AFR, and that the calibration is close.

While the AFR is being corrected to **right**, none of the other fueling stuff is. So proportionly the accleration enrichment etc is off.

14.7 just happens to generally line up that there are a min of unreacted chemicals in the exhaust.

The ecm, cycles rich and lean of 14.7 to keep the converter happy.
Long story told in a short way

 

"While the AFR is being corrected to **right**, none of
the other fueling stuff is. So proportionly the accleration
enrichment etc is off. "


COULD YOU EXPLAIN THIS??

 

It means, that while the ECM (in conjuction with the O2 sensor) will correct the fuel mixture to 14.7:1 (hence you get a different reading than 128/128), all the other "fuel aspects" of the ECM, the "Pump Shot", "PE Fuel Enrichment", "Deceleration", etc are all off too - and NOT corrected.

Thus, if you want to add 15% more fuel when in PE to get an AF Ratio of around 12.5 (i.e. 14.7 x (1-.15) = new AF Ratio), this will ONLY happen if your BLM/INTs are already at 128/128. If they are off, you are just adding 15% to an incorrect figure.

If the BLM/INTs are generally around 120 (about 8% off), then you are a further 15% off. It starts to "compound" the problem.

Having your BLM/INTs as close to 128/128 when in part throttle, will make the likelihood of adding 15% more fuel when in PE, much closer to your desired 12.5:1 (if that is what you want) than if it wasn't 128/128.

PS: You really need a WB O2 sensor to confirm your real AF ratio when in WOT btw. I was just illustrating why you should strive for 128/128....it just makes life so much easier when you do additional tuning to the other fuel parameters.

 

I've always tried to tune for the 128 but at idle the motor just doesn't like it. My cruising and part throttle is around 130-135 but at idle it only likes to be around 140-145. I know this sounds stupid, but ask Craig Moates. We tuned some on my computer one night and we tried getting the BLM to 128 but the exhaust about knocked us out it was so strong. Also, with the BLM at 140 or so, the idle is much smoother as well. I'm curious to see what my WOT is. I will be putting a wideband on it in the next month or so and tune it on the dyno....but right now with this tune the car runs very well!

 

What is happening when the exhaust burns the eyes like you mention? Lean? Incomplete combustion?

 

When it smells really strong and when you walk away from the car and you reek of exhaust.....it's definitely on the rich side. I can tell a big difference in my exhaust b/w the two different BLM's.

 

Ever have it burn your eyes? Sure it smells, but like literal stinging in the eyes?? What is that?

 

Yes I have, I hate when that happens!

I think it's when a faster car is trying to signal a slower car in the garage next door that it's about to get it's ***!

 

Say most of your lower blms are 108 thru 114. If this throws off PE because they are not close to 128. What would happen when the car did go into PE with the lower blms of 108 thru 114. Would it be rich or lean in PE mode?

 

yuppers...sure will tear up the ol eyes when rich, stand next to a fueler with upswept headers and the good stuff, you'll really cry..hehe

 

You've got something else going on in the background.

140-145, or 128 you're still at 14.7:1 at idle.
A vac leak., opil containated intake charge, IAC being off, can all contibute to weird problems.

If you have to tune to other then 128 for reasonable street engine there is a problem, that you're covering for.

BTW, the problem can be internal to the engine, ie cam with too much self egr'ing.

 

Originally posted by MikeH:

I can personally answer from experience, then you go REALLY RICH and that's VERY bad.
You gotta look at it like this, the maximum that it can pull out fuel is 108 BLMs and 70 INT I think. If you are at those values that means you are hella rich. You enter PE mode and just think of what is happening....I think gas washing the cylinder walls maybe???

Brian P
89 IROC-Z 355

 

My problem is it will ALWAYS run around 115-123 on the highway. No matter what I do.

But when I hit the gas (no PE) the BLM will go to 135-140 and then after a sec it will plummet to 113.

I gave up on trying to get 128...I'm gonna start tuning the VE tables after I do my cam.

 

Thanks brian...IM going to try and stay out of PE untill I get the rest of the stuff to burn proms. I have the PPII and tuner cat, just waiting on proms and an adapter. When IM driving and enter pe at part throttle The car just bogs down, must be going pretty rich.

At Idle the BLMs are 108 and the intergrator is 94 or so. Pretty close to setting a code I guess.