I'm relatively new to the subject. I read all I can about the chip burning pratice...
I'm able to burn a new chip and I'm waiting for a borrowed laptop to start the datalogging.
I burned 3 or 4 chip only to lower the fan temp start and to raise a bit the idle due to my underdrive crank pulley.
I'm always afraid to ask something that seems stupid to you gurus, but even if (for sure) this has been discussed several times I have to ask because I have't found an answer even If I read 100 times all the Traxion posts and the Importand/useful treads, and all the old posts (Grumpy's final answers included).
I've a TPI 1990 vette Speed Density. 727 prom.
If the car in closed loop is always searching to achieve the 14,7:1 A/F ratio via O2 feedback, why I have to change VE tables in order to put BLMs to 128?
I explain:
If in part throttle conditions (no PE) at a certain RPM, KPa level the O2 sensor says the A/F is lean, the ECM commands to widen the BPW up to the time the O2 sensor "reads" again the 14,7:1 ratio. Now the car runs at 14,7:1 A/F ratio. The BLM (if datalogging is performed) in this particular RPM and Map level will be more than 128. (say 140)
Now I change the VE table at this particular RPM and Map level and I increase the VE value just to put the BLM to 128.
Now the car run 14,7:1 (without the ECM has to do any kind of correction to the BPW), but the end of the story is that the car runs 14,7:1 just like when the VE table was off.
14,7:1 before the change, and again 14,7:1 after the change to the VE table.
Where is the advantage?
The advantage is that the ECM don't perform any correction to the BPW? How many times the ECM needs to perform this correction in the case tha A/F ratio is differnent from the 14,7:1 ratio?
Is this lag in the ECM correction the differce between a perfect part throttle tuned chip and a chip not tuned?
Thanks

 

Simple math

$8D

BPW=VE *Inj const*2+BLM corr+(Int corr/2)*decel enleanment
and a batt volt offset and some AE stuff.
Or something close. I'm still learning to read code If in PE, the corr factors act different. Haven't got that far yet, but IIRC there was at least a couple posts dealing with those instances in the last year.

Reread the post:
The BLM and INT values are limited to a max and min number. Which can be changed of course. Anyway, if you reach the limit, I believe the cal cannot correct the AFR any further. Also your PE AFR is based on the VE tables to. It adds a certain amout of AFR to the current 14.7. Called commanded AFR IIRC.
If your tables are off, so is the PE afr I think. Especially with bigger cams.
Something else for me to trace in the Hac.
I hope I was close on all that. Most of the time I'm only half right.

 

You say: "The BLM and INT values are limited to a max and min number. Which can be changed of course. Anyway, if you reach the limit, I believe the cal cannot correct the AFR any further."
Are you speaking about the constants BLM value min and BLM value Max?
I have a max value on my stock bin of 160
and a min value of 108.
So, If the stock cal is so rich to put the BLM UNDER the 108 value, the ECM will be not able to compensate in order to reach the 14,7:1 AFR?
Is for this reason that I seen bins with this value decreased to 96?

You say also:"Also your PE AFR is based on the VE tables to. It adds a certain amout of AFR to the current 14.7. Called commanded AFR IIRC.
If your tables are off, so is the PE afr I think. Especially with bigger cams."
So if I'm in part throttle cruising and the cal is rich (because the VE table for this RPM and Map value is greter than required) then I do a WOT the PE mode (engaged because now I'm at WOT) starts from a richer AFR level ending on a PE mode richer than commanded?
Thanks
-Beppe-

 

I went and review my notes more.
The AFR I put in the equation is where the PE is added. AFR was easier to write. It's actually a % of 14.7(2 tables) based on rpm and coolant temp. The code also only allows adding fuel, not subing during PE IIRC. So however far of from 14.7 you are, then your at least that far off in PE.

Yes on the BLM min/max thing.

Get the ANHT Hac. Then you can ask/follow better.

HTH

Man, I gotta get to work. Going to have to run around like a headless chicken

 

The calculations are used for other items, such as EGR. Then in some codes there are PE fuel corrections based on BL that are applied to PE. And as you mention there's less delay in the AFR corrections from cell to cell if everythings at 128s.

How critical, or how your car runs at 118-128-138 is just stuff you can play with. 128s are a universally good place to be at, at least for the new guys.

Takes notes, see what makes the engine happy, look for trends.

 

I'm new too, so let me take a shot. I think the main reason you can't rely on the BLM to just take up the slack (assuming that they are within some reasonable range) is because there is not a BLM value for every single cell in the VE table.

If you look at the VE table cells, multiple adjacent ones are contained within a single BLM cell. So if the BLM in one cell wants to be 150 and the BLM in an adjacent one wants to be 140, then the BLM will be changing as you move between those cells. The car will not function at peak when you make the transition between cells until the computer readapts based on the O2 readings.

Based on this, I would conclude that if your BLMs were, say, 140 across the board, then there'd be little benefit from adjusting the VE so they said 128 instead. Of course, there is the minor issue of having to relearn all these BLMs if the power to the ECM is removed.

Like I said though, I'm pretty green, so I welcome corrections to this.

 

To try to understand what Mastiff just wrote:

Since several VE "cells" are in the same BLM cell, if you have one that needs 120, then the next needs 140 within the same BLM cell, you will have a temporarily lean condition as you pass through that VE "cell", which is aggrevated by the fact that you may be on to the next VE cell before the BLM value even starts to change. Also, I believe I've read that some codes reset the BLM to 128 when you start it up. If 128 is what the engine needs, you'll be where you need to be!

Wow. Now that I've thought about things enough to type this, I see where a WBO2 is much better for tuning, since you know the AFR at a certain VE "cell", instead of a BLM that may not have been updated fast enough. Interesting.....

Any feedback on my theory?

 

I'm not at all certain of this, but I think programs like WinALDL might not log all the BLM values generated while in a given VE cell. If the INT is still big, this indicates that the BLM has not converged and the it really shouldn't be used.

Because, as you say, the BLM's aren't much use if you just pass through a VE cell and the ECM hasn't converged yet.

I'm new though, so I gladly accept corrections to this.

 

not sure if this of any value but when i had a lean or rich VE cell it appears it took several burns to enrichen or enlean that VE table cell. the fact of a "BLM" showing 138 or 118 and my subsequent adjustment of the VE table with a correction/burn did not get me to 128. just got me closer. seems like i was sneaking up on 128 rather than just nailing it first time. something tells me each datalog the conditions were different in the environment the car was operating in. i was not aware that a BLM cell covers more than one VE cell location? i was of opinion 30 map/ 2800 rpms was one in same for VE cell(tunercat) and BLM cell (winaldl). please explain that point.

 

I forget how many BLM cells there are in a normal 7747, but it's far fewer than the number of VE cells. The ECM estimates BLM's to cover a section of VE cells, say a 3x3 grouping or something. I assume this is why it's called "block" learn mode.

Regarding only getting a little closer each adjustment, one thing is that there are two VE tables. If you only multiply the main VE table by the BLM adjustment, I think you'll come up short. Say your VE1 in a cell is 20%, but VE2 has 40% at that RPM. If you need to increase your VE by 1.1, I think you should multiply 1.1 by(40+20) and add the difference to VE1. In my bin, VE2 is much bigger than VE1 most places, so the error would seem to be significant.

1.1 times 20% would only add 2%, but you really want to add 6%.

 

i am aware of two tables. i got tired of changing both so i combined them. took table 2 and added to table 1. table 2 zeroed out. seems to have made no difference(1 table vs two. after doing so i got some comments that that was not the best thing to do. not sure why however!. you are correct however in your point, both need to be changed to be affect the net change. thanks for the explain "block learm mode". makes sense. is a block covers 3 cells(?) i assume the high/low BLM will affect all cells in that block. this must be some compromise (GM) as it would be nice to affect change only in a specific VE cell. maybe since all thiose cells are close by (map/rpm) changing all (one BLM)may be adequate.

 

I'm not sure about 3x3. Actually, I'm not sure if it's always the same. I think GM did it to save memory.

Here's a pic I'm linking from customefis.com:



I think the dark lines indicate the BLM boundaries. So in this case, it's a 2x2 section covered by each BLM, except at higher MAP where it's 2x3.

 

The "Standard" is a 4x4 set of BLM cells, giving a total of 16. The last pic that Mastiff posted puts it into perspective. The cell boundaries can be adjusted so that they are more useful, so if a big cam keeps you out of the lower end cells, the low end boudaries can be changed to get all your cells functioning.

There are some masks that only use 2 BLM cells, though, one for idle, and one for non-idle. IIRC, $58 is one of them.

 

I don't understand.. There are 2 VE tables??
I use Tuner pro as editor and for my $8D I have 3 VE table but basically it can be considered as one.
I explain: I have
VE lower table (from 400rpm to 1600 with 5 Kpa increment from 20 to 100)
VE upper table (from 1600 to 5600 with 10 KPa increment from 20 to 100)
then I have an Extended table from 1600 to 6400 filled with 0 values across the board)
With the exception of the 1600 rpm row, there aren't VE cells with same MAP and RPM value to del with...
..So I don't understand your VE1 and VE2 statement.
What I want to say is that If I need to change a value in the 2400 rpm / 60 kpa there is ONLY one VE cell to modify and it is in the VE Upper table (1600 rpm to 5600 rpm)
Maybe the 730/727 is different from a 7747?
Thanks
-Beppe-

 

Yeah, I'm talking about the extended table. It has no MAP axis, just RPM. If yours is all zeros then it doesn't matter. In the factory bins I've seen, the extended table has big numbers in it, like 40%.

I only know about 7747 though.

 

The extended table to 6400 is not enable (used) in the bin.
It is for additional change later if desired and was added by Traxion and 69Ghost IIRC.
I don't know all the items that need to change to use it .
(not YET anyway )

 

Which bin are you talking about? 7747? All the factory bins I looked at for 7747 had FL2 in there with non-zero values.

 

They're talking about the S_AUJP bin and the Super_8D ecu. The S_AUJP is not a stock bin its a modified $8D 730 bin. There is a large post on it that is probably on the first or second page.

 

Balck 91 Z28 is right, I was speaking of the S_AUJP and the Super8_dm2.ecu files.
The tuning stickie at the top has many good articles to help you along.
Here is the link to it.
https://www.thirdgen.org/techbb2/sho...hreadid=200256

I read them till my eyes hurt, and then read them again.
I ALWAYS find something that makes more sense than the last time I read them. Tuning is not a matter of only adjusting one thing. Everything works together at some point, more timing more fuel, less IAC response, change AE, PE etc.
As a good example, I thought having enough power to burn rubber right from the getgo was a good thing. Then after ready Grumpys timing "final answers" it becomes clear to me that I'm pulling in too much timing before my converter can build power to move the car and lighting the tires. I've lowered my timing which caused me to remove fuel and the car launches better without spinning (not as much anyway ).
One thing always leads to another.

I guess I lost track if you were running the $8D 730 or the 7747?
Anyway, IIRC the VE tuning stuff seems to be fairly the same for speed density applications.
Jp

Edit: Also if you are running #8D and using datamaster to do some logging, there is a program called VEmaster that can help make the adjustments on your bin VE tables.
I've had pretty good luck with it.
It's available at moates site IIRC.