Thanks for giving your input, I appreciate the added thoughts.

BLM's register 128 on dataloggers when our cars go into PE mode, but they do not necessarily do. The best theory I have heard is that if the last BLM in the cell was below 128, the computer will use 128 because the car is already running rich. If however the BLM is above 128, the computer utilizes the last BLM to compensate for the lean condition and thus protects the engine. This matches on the rich side with what I found when I tested on the wideband.

This somewhat is what 97Z said below.

A guy named Christian Millard used to frequent this board. Being a programming wiz, he made this small program that goes into your downloaded .bin file and modifies a portion of the hex program so that the computer always goes to 128 when PE is enabled. takes literally about 5 seconds to do.

Hmmm, I don't have my laptop with me to look at my old Datamaster logs to see if this was the case for me. I am checking on Monday. Going to cell 18, as I remember would only apply in open loop any time other than these conditions:

Cell 16: idle
Cell 17: DFCO (Decel fuel cutoff)
Cell 18: In open loop, anything other than above.

Otherwise, I remember cell 15 only being used in these runs. Well, when I am above 2800 RPM, but I am being simplistic as I can be in PE mode within cell 13, 14 or 15. It is just a matter of where your cell boundaries are when you finally go into PE mode. However, if in say cell 14 and you go to PE, when you cross to cell 15, the computer will use the last BLM in cell 15 that is being utilized...as far as I remember. Don't want to take anything away from you.

You do bring up a clarification and that is ALL my testing was done in closed loop only.

Another note, I can only comment on a 95 OBD-1 computer, not a 97.

Yes, I you are right here. Maybe someday TC will hack that part of the code that allows us to modify the time before the car enters closed loop.

Ben

 

Dan,

Why would you sell the Z?

 

What you both are saying is partially correct. When BLM's aren't 128, the computer doesn't use 128 necessarily. If BLM's are LESS than 128, cell 15 is used, and it is reset to 128 for PE mode only (it will go back to it's previous value). This is used because if the computer knows it is running RICHER than the 128 setting, it knows it can start from that baseline and add the AFR. This is why you were seeing a lower AFR (richer) than you thought you would 95blackhawk. When BLM's are HIGHER than 128(ie LEANER THAN HELL), it reverts to cell 18 to attempt to richen it up.

Jonota

 

Did this theory die?
Very intersesting.
And would assume that mods that affected air flow the MAF would have to be recalibrated?

 

you got it backwards. blms<128 resorts back to 128 and uses cell 18.

blms>128 it holds that blm and used cell 15, ive got several scans that show it

 

as do I..... my way...

 

I am bringing this thread back from the dead because I am going to be testing this theory soon and want to report my findings. Also I believe the reason for the difference in results between jonota and 97Z-M6 is OBD-I vs. OBD-II. I think this may also be the reason for the VE tables vs. MAF tables argument. I spent several days trying to tune my VE tables and couldn't get them to affect BLMs, but 2 adjustments to the MAF tables have gotten the BLMs to 126-128.

Some things to note: my car is stock, with only the mods in the sig. I have done part throttle and cruise tuning, up to about 100 AFGS only. I am planning on leaving the MAF tables 3 and 4 stock and using the Datamaster dyno function to estimate power. Then I plan to adjust the PE tables to hit 12.5 -13.5 targeted AFR, and again use the dyno function to estimate power. Then I will disable PE mode, and adjust the MAF tables to attain <=128 BLMS through the upper RPMs. Then I will enable PE mode, get a baseline Datamaster dyno, and again adjust the PE tables to hit 12.5-13.5 and get estimate power at each AFR.

I am new to tuning, but have been doing a lot of reading and datalogging and tuning over the past couple of weeks. If any of this sounds incorrect or dangerous (mainly the 12.5-13.5 AFR, is that too lean?) please let me know.

 

Interesting you bring this back. I am about to go back on the dyno this Tuesday after being away from tuning for a few years. I had to think about and reread this stuff again that I wrote, hehe.

Here is what I have done to make sure I have limited the factors affecting the wideband results:

Injectors pulled and serviced to put all within +/- 2% flowrate

MAF sensor cleaned

Find all exhaust leaks prior to O2's

Recalibration of MAF

Same fuel from same gas station used to dyno and with calibrating MAF – to avoid variances in fuel BTU values.

BLM locker programmed in


I too will post my results. Maybe I can get a better idea why my AFR was off on the lower RPM ranges only but dead on when higher.

DropZ, My personal feeling on the datamaster dyno is that it just cannot show the accuracy you need. In addition, the ultimate goal is to get AFR corrected. The only way to be sure is to put it on a wideband.

 

That is true, I will have no way to truely verify if my targeted AFR = actual AFR. I will only know which setting produces the most estimated power, which is limited by the accuracy of the Datamaster Dyno.

I have noticed that my INTs in PE/WOT now are at holding steady at +/-0% until I hit around 3000 RPM, at which point they steadily climb up to +40% or more! I assume this is because I tuned the MAF already for the sub-3000 RPM range, but shouldn't the extra fueling from PE mode make the INTs read rich? Seems odd that the fueling would be spot on both in and out of PE mode at the same RPM.

I have adjusted the PE vs. RPM table to lean it out 80%, which actually made only minor changes in the calculated AFR. Saw no difference in my WOT Datamaster Dyno tests. I then adjusted it to have a steady calculated AFR of 13.5 from 4000-5600 RPM. This seemed the make the car lose power, approx. 10-13 hp.

I now plan on disabling PE and tuning the upper range of the MAF tables. Then I will put the PE tables back to stock and enable PE mode, and do more tests with stock and altered PE tables.

Results to follow.

 

Why are your INT's changing in PE mode? Once you go to WOT, they should lock and be constant. I could be wrong, because it's been a while since I messed with O2's (I run an open loop tune).

 

I don't know honestly. I believe they have always done that. The BLM's definitely lock at 128 (or 128+whatever extra fuel was necessary in the cell before PE mode was entered), but the INT's have always fluctuated. I have verified that prior to tuning the MAF tables, the INT's started moving around as soon as I hit the gas and entered PE mode. Now that I have tuned to 126-128 BLMs the INT's stay rock solid until ~3000 RPM. It seems strange that the tuning I did without entering PE mode gives ~128 INT's, and then once I enter PE mode it still shows ~128 INT's. I assume this is because the stock PE vs. RPM table modifier at those RPM's is very low, however the PE vs. Coolant Temp modifier is 15.6 which I think would be enough to alter the INT's...

 

Do you know what cell(s) your in @ WOT? This can verify your going in PE. I think the INTS may still report the oxygen levels, the BLMS definatly do lock, and just ignore the ints for that. If your running lean... the BLM's will lock @ what ever the previous cell closest to WOT for that RPM is (i think). Keeping the car from using the PE tables propelry.
If your running a bit on the rich side (< 128) it'll enter the PE tables. THis might explain the results your getting with the ints still bouncing around 128, they should be bouncing way higher (or probably more likely pegged) since its supposed to lean out in PE.

 

Cell 15. Definitely going into PE as far as I can tell. Not running lean at all, I was until I tuned the MAF tables. Now BLM's are 126-128 at all times. The INT will stay at 128 on the nose when I first enter PE, until I hit about 3000 RPM. Then they increase up to 167 or higher as I pull to ~6000 RPM.

I expect when I disable PE, tune the MAF, and then reenable it, the INT's will stay close to 128 from 3000-4000 RPM, and then start going up until I hit 6000.

 

Im having a hell of a time finding a blm locker program that the link actually works. anyone got something they would mind updateing this post with.

 

It is now part of Tunercat. Please start another thread.