GofasterFirebird

iTrader: (3)

OK, speaking closed loop only. Since the computer corrects up to the max/min blm and the capacity of the injectors, etc; can I actually cure my noxious idle smell? Even if the blms are at say 150 in closed loop changing the VE tables doesn't really effect anything, or does it? I know I can go and change the entire a/f ratio that the computer attempts to achieve. I just want to lean my idle a bit, but I wonder if I can? I am using tunercat and cm scanning software. Thanks

funstick

yes changine the ve tables will have a dramatic affect on yr idle and part thottle mixtures. with proper timming and ve you can get 128 blm's. id suggest locking them at 128 and working over the ve and spark tables. then once everthing is honky dory with the integrator right around 128 then re enable the block learn. me i i like the blm limits at 100 low 142 high. thats just me other people leave them locked.

RBob

iTrader: (1)

There are O2 window values within the calibration. These values
are defined in milli-volts. They directly relate to the O2 sensor
reading. The INT & BLM will go in which ever direction required
to bring the O2 sensor reading within this window.

Typically there are separate windows for idle vs cruise. Sometimes
the idle window cal terms will be an offset from the cruise terms.

There is a paper (747fueling, I think) that goes into this in
more detail.

RBob.

GofasterFirebird

iTrader: (3)

Funstick, I am pretty sure you are confused. I believe that even if I have my VE values off at idle, it does not matter. The a/f ratio will be corrected as long as the min/max blms are not exceeded. So, when I tune, if I have my WOT O2 millivolts at 850 (is this the recommended value?) I believe my blms are a non-issue. ??????

funstick

go read the programming 101 again.you missed some things. the Ve table Map vs Rpm is the main fuel table. you should really try to narrow down yr error in the feul. yr car will run better there is no exscuse for being to lazy to touch up the VE and main spark table. the computer is basing injector Pulse width on the VE table and the BLM & INT. when the ecu see's a mixture deviation IE a voltage of say .350 it knows the engine is lean. i look up th correct blm multiplier ( blm is sort of a slow lag filter in a way )
then it goes to the INT for a final tweak. this is a sort of simplified version but fairly close to the truth. locking the blms at 128 keeps them from filtering and changing mixture allowing you to see where you need to tune.

as for WOT thats an open loop functions that is based on the VE table and is tweaked and modified by a couple of other tables. IE VE adder and one other i can;t think of right now. but you get the point. the WOT mode ignores the O2 sensor. so what are you tunning for ?

funstick

as for yr WOT value being .850 volts i guess ths is ok ?? what does yr engine like in terms of a/f ??? you should build yrslef a good wide band O2. this will get you much further. goto the track and try different a/f ratios. there is no perfect a/f for every engine. so many things influence how the engine burns feul.

TRAXION

I looked into this awhile ago when I was trying to pass emissions. I was going to raise the A/F so that the car would run lean. But, even though I changed the stoichiometric A/F constant of 14.7 to UP TO 16:1 ... the ECM was still commanding a 14.7. I didn't look into it any futher but I would imagine that an examination of the source code would reveal the truth. I needed a 'quick fix' at the time so I used a different method to make the car run lean and never looked into it any further.

Tim

GofasterFirebird

iTrader: (3)

Ok, so funstick is wrong and I am not crazy.

Traxion, thank you for the prompt response. Would you mind telling your method?

funstick

i still want to know whats so hard about chaning the VE table. changing the a/f ratio is a cheat at best and absolutely will not fix all yr problems. FUNSTICK IS NOT WRONG. yr just to lazy to fix yr problem.

GofasterFirebird

iTrader: (3)

This above is wrong. Changing the VE at part throttle will not effect the mixture. It will change the blms. I am glad I cleared this up. Laziness is not an issue, I am just trying to get my facts straight.

funstick

exactly how do you think the ecu computes the PW for the feul in the first place ??? it bases injetor pw on the VE table which in the end affects yr A/F ratio. sure commanding the ECU to change the A/F ratio can work but the whole thing is that the PW the A/F reads from is based on the VE table.

here is the text form bruces website.


Main Fuel tables, $037C to $03C6 and
This is the main 3D fuel delivery table and its companion 2D table The value in the table is volumetric efficiency, which is used ultimately in the fuel calculation to determine the injector pulse width along with RPM, and coolant temperature, This is why this is a speed/density system.

Fuel is the easiest parameter to get right, record the Block Learn Value when the Integrator if neutral (Near 128). Divide the BLM value by 128 and you have the current error from 14.7:1 AFR.

Example:

At 2000 RPM and 50 Kpa:
BLM = 140
140/128 = 1.09, a 9% error in the lean side

What this indicates is that the BLM is multiplying the calculated value of fuel by 1.09 to achieve 14.7:1 AFR (The Stocheometric point)

To improve this situation got to 200 RPM and 50 KPA map on the fuel table and multiply the value of VE by 1.09, (46 x 50.14), we round to 50 and move on.

Make sure the total of the two table is less that 100.

Sample table from a stock 5.7l truck.


Note:
The table starts with a three byte header that defines minimum MAP, minimum RPM and the number of row /column
VE Adder Table, $03C7 - $03D7 Volumetric efficiency is expressed as a percentage, the theoretical amount of air that the engine should be pumping at a given RPM divided by the actual amount of air that the engine is pumping

Note:
The VE value used is the result of both table summed. Summed values exceeding 100% will be limited to 100%


--------------------------------------------------------------------------------

GofasterFirebird

iTrader: (3)

Hey, you can regurgitate all the facts you wish.

funstick

how many times have you broken things ????? you dont listen. dont ask for any help when you have decided before someone gives you advice to not take it.

GofasterFirebird

iTrader: (3)

I took 'trax's advice. I have yet to see yours. If you were to give advice I would gladly take it. I am a beginner by far and need all the help I can get. Later

funstick

ok here it is

set the A/F for 14.7 at all engine speed except WOT
lock the BLMS at 128
use the intagrator values to figure out yr a/f ratio as well as yr O2 sensor. i wish i had some chart for you to use but i don't
generally a cruise O2 sensor voltage should be .550 to .650 or slightly leaner like .500 is ok to the 14.7:1
adjust yr VE table to get the thing as close to 128 intgrator as possiable. its gonna take some time. dont be affriad to add/remove advance either.

then once youve got everything hondy dorey re enable yr blms to there factory setting.

thats the best way to get the part throttle tune.

for WOT yr gonna have to tweak some where you can get good accurate reulst liek the dragistirp.

also command the ecu to 11:1 for WOT and then carefully lean it out. do some plug reads as well.

this will get you started reading the link i posted can help alot to .

RBob

iTrader: (1)

RBob.

GofasterFirebird

iTrader: (3)

OK, now that is way over my head. Could you tell me what that means?

goneracin

i believe that is the O2's rich/lean threshold setting for toggling over 14.7 vs map reading. If you could change the o2 r/l threshold mv number, you could in effect change the a/f ratio for any given map reading. At least thats how i interpret that.

RBob

iTrader: (1)

In order to control the AFR the ECM will toggle the
O2 sensor above and below 1 or 2 trip points. These trip
points define the actual AFR in use. With a regular
old O2 sensor and trip points of 390mV and 510mV
the AFR will be ~ 14.7:1.

For a richer AFR set the trip points to 560mV and
620mV. Now the ECM will use the O2 sensor to run
a lower AFR (say 14.5:1).

Basically speaking the trips points (or window) define
the calibration of the O2 sensor. The window can be
and is fudged for different running conditions. As
the O2 sensor is very non-linear this technique can
only be carried so far. But it works.

Some masks define the window against the airflow
('8746). The $8D mask define the window vs MAP.
There is a correlation between MAP and airflow.
So the results are similar.

To help put this in perspective there is an early
turbo Buick (factory) chip that would not pass
emissions. The recall chip lowered the mentioned
O2 trip points. This allowed the vehicles to pass.
The kicker is that the early chip had much better
driveability.

RBob.

TRAXION

First and foremost - I gave no advice in this thread. I just answered a question. Here are the facts:

1) The VE tables do not control the A/F mixture in terms of trying to achieve a specific AFR. However, if your VE tables are off then it is possible to produce some wierd AFRs in OPEN LOOP.
2) The ECM uses the target AFR for adjustment purposes in CLOSED LOOP. So, if you are running an AFR of 12:1 at idle in open loop because your VE tables are wrong then when the computer enters CLOSED loop the BLMs and INT will adjust to attempt to reach the target AFR of 14.7:1 (stock)
3) There is absolutely NO reason to adjust the target AFR that is worth discussion with regard to the this topic. Leave it alone.
4) I wanted to FORCE a lean condition (which is very dangerous!) in order to pass emissions. I raised the injector constant and set the CLOSED LOOP enable temp to 255. This basically put the ECM in a place where it would NEVER adjust for bad fueling.

BTW - AWESOME post Rob!

Tim

GofasterFirebird

iTrader: (3)

OK, great information. But this still leaves my idle smelling horrible. I must edit source code to remedy this? Trax, why do you say there is no reason to adjust the target afr? You must mean across the entire rpm band? How is the car coming? Any new times? Problems?

RBob

iTrader: (1)

One thing to make sure of is that there are no exhaust leaks pre-O2 sensor. Even the slightest amount of leakage will cause a false O2 reading and drive the AFR rich. I've been finding out that w/o a cat the exhaust can also stink. And I mean to the point of feeling sick due to it.

From what I can tell you are most likely running the $8D mask. Here are the locations to change for the idle O2 window. These are from the ANHT bin. Note how idle is run a bit on the rich side of stoich.

Keep the fast R/L threshold between the upper and lower boundries.

RBob.

GofasterFirebird

iTrader: (3)

OK, yes I have the 8D mask. All I have is tuner cat to edit my bins and will have to research to look at the source code changes. I also have no cat, yet all the carb cars I smell dont stink like mine. Hmmmm?? Can an idle stink due to a lean condition? High combustion tempertures producing different by-products? Thanks for all the help.

Why would GM run the idle on the rich side of stoich?

RBob

iTrader: (1)

You may want to ask Tunercat to add these parameters to the TDF.
These are not changes to the source code, but to the calibration
portion of the bin.


Engines tend to idle better when on the rich side. Although this is
not a universal truth.

RBob.

leirch

My car idles right at 13.0 afr, I'm using a wideband to note this of course. The VE tables seem to be right in line of where they need to be.

It idles very well at the 13.0 but the BLM's peg all the way up to 160. I'm running a 383, afr 195's and the lpe 219 cam, with a miniram also.

I'm trying to figure out what exactly needs done here. Do I need to increase the Lower and Upper 02 Thresholds?


I can stand looking at the 160 BLMS on the scanner being that I have the wideband to tell me whats really going on. I also notice that the car is staying in Cell 6 while driving alot of the time.

Any idea guys?