Hello-

I am still new to all this stuff, and have what will probably be a few pretty basic questions.

My fine fuel correction varies between 111 and 152, but averages at 128.5. My "course BLM's" vary between 158 and 122, and average at 143. Do I tune for optimal coarse BLM, or the fine BLM? If it is the fine BLM, I assume that I don't need to tune the MAF tables to get them better, since the average is at 128. Is that correct?

Also, my understanding of the BLM and INT relationship is this: BLM varies based on what the o2 sensor tells it. INT then goes back and fourth between 108 and 160 to bring the BLM's down to 128. When INT hits 108 or 160, the BLM's can no longer be corrected in that direction. Is this right?

I have been reading up on fuel tuning to correct this, and it seems that the MAF tables are the way to go for fine tuning. Is this right? I really don't see any other way to change the inj. PW based on RPM or LV8.

As far as ECU selection goes, it seems like $6e offers alot more options, but I really like the way the 32B tunes fuel. Is there any way to combine the 2 ECU's together and have it actually work?

The car is an 87 IROC with 305 TPI and 700R4. My mods so far are pretty minimal. I've gutted the airbox, added shorties and true duals, and removed all the A/C, P/S, and smog stuff (except EGR, that comes later)

I have read Trax's write-up at least a few times, read all the stickies pertaining to the 165 ECM, and read everything else I could get my hands on. I just need a little clarity with these q's please

Thanks guys

 

you will want to shoot for having your coarse fuel close or on 128 Blms.

 

no, you can't combine 32 and 6E ECUs (or bins) and have it work.

Sounds like you have the concepts of BLM and INT down.

I personally think of it like this. BLM is the actual fuel trim. INT tells you the rate and direction that BLM is changing. An example:

BLM = 112, INT = 130 ... this means that the BLM is increasing slowly, as 130 isn't far from 128, which is centered

BLM 120, INT = 145 ... this means that BLM is increasing pretty quickly and that the BLM isn't close to where it needs to be

BLM 122, INT = 128 ... this means your BLM is exactly where it needs to be and is not moving.

For those of you with a math/physics background, think of BLM as speed and INT as acceleration (or, BLM is the 1st derivative of INT). Of course, if you think like that, you probably already figured it out. :-D

 

i like sandpaper analogy. int fine course and blm rough.

 

Thats incorrect, though. INT is not fine course.

 

lets try this again. a locked BLM is "fine" working with INT only. slower process an open BLM is "course". faster process. working with BLM and INT. does this seem accurate?

 

So a BLM of 128 is not always optimal for the engine?

Also, I was almost exactly 9% lean thru the entire scale, so I increased my MAF tables 9% on every number. This brought me to exactly 128 BLM in all but a few spots. BUT, the top two numbers in each of my 6 maf tables are now topped out. Do you have any tips for playing with the scalars to up the scale a bit more to get my optimal BLM's?

Another quick one. When I play with my highway spark (and a couple other spark tables) I see that they have numbers like 9.25 and such. Is that based on a 20.04 bias also like the main spark table? Where that 9.25 is actually retarding the timing 10.75 deg? Or is it addative, where the 9.25 deg is actually 9.25 deg on top of my other tables and base timing?

Thanks guys, you've been a great help so far

 

Also, after diving in and playing with the MAF tables, this seems to be a much better way to tune anyways

So are there really any benefits to tuning with the 32b over the $6e?

 

Would you mind elaborating on this a little more? I've heard reference to what you are saying about locking the blm's and tuning only with int, but don't really understand how it would work. Is this just a method of removing one of the variables from the equation?

 

no, 128 BLM across the RPM/Load range is optimal. thats waht you're targeting.

 

from what i learned a open BLM it takes a change of 5 in INT to move the BLM 1. this takes time as there is a sampling rate time factor. with locking BLM at 128/128 the INT moves the fueling changes more quickly. this was my understanding. correct me if i am off on this. i have not locked BLM yet as have been tuning only this past 2003 season but will have at it aagain 4/04. my 20 or so burns have got BLM 126-130 so pretty close. with changing air temps it appeared the BLM was moving day to day. i ran winALDL every day and watched it as temps dropped to 40 F then i quit.

 

The fueling routine is a PID loop. The Proportional gains are set high for two reasons: to force the loop to oscillate (for the cat-con) and to get the fueling back on center quickly.

The Integral gain is the fine trim adjustment to fueling. It integrates any error over time.

The Derivative term are the resets that occur such when AE become active, BLM cell in use changes, a crosscount happens, items such as that. Terms that are reset may include the Integral and Proportional gains, the integrator and proportional gains delay timer(s), BLM and delay timer, O2 error term.

The BLM is an offset adjustment. It is the big-control-**** in the scheme of things. It comes into play whenever the integral term is X distance from the desired fueling. The goal of the BLM term is to center the PID loop about the desired set point. It has the longest time constant (slowest to change).

The desired set point of the PID loop is defined by the O2 constants. To close the loop the O2 sensor value is used as the feedback term. The PID loop error term is created from the actual O2 value and the O2 constants from the calibration tables.

RBob.

 

:hail: WOW, some of that is still floating above my head a little out of grasp

What's a PID loop, and what's it do?

Also, I'm getting 2 counts of knock right as I fire my car. Is this most likely just false knock from all the movement and viberation going on while the car is cranking? If it turns out to be actual pre-ignition, should I pull more timing out of the crank tables, or should I add more fuel to them?

Thanks for the help so far guys, I'm making great progress. My BLM's are almost constantly at 128, except at idle where they vary from about 130 to 135. But I'm reading that a lean idle might do more help than harm anyways, so I might not tinker with that. According to everything I'm reading, my next step is timing. I bumped my low RPM timing 6 deg to help keep it from bogging so much off the line, and bumped it up top about the same and had good results so far. Especially in the seat of the pants dyno