DataMaster Noob question.

Can someone please confirm? Theory only, no specific model.

High count INT = lean fuel mixture

to compensate, the BLM reduces it's count below 128 = rich fuel mixture

Result should be that the INT counts closer to 128.

So a steady middle to high count INT and steady low count BLM in most cells indicate signs of lean fuel mixture due to lack of fuel or excess air?

any help appreciated,
thnx

 

No. An INT or BLM value of 128 is neutral. Not adding or subtracting fuel.

If either is higher then 128, the ECM is adding fuel. IOW, the ECM found that the exhaust AFR was on the lean side and is bringing it back to stoich (or there abouts').

A value lower then 128 (INT or BLM) is removing fuel. the ECM found that the exhaust AFR was richer then stoich, and is trimming it back to the proper value.

RBob.

 

Thnx, I think I get it. If INT's go down due to a rich AFR, then BLM's decrement and the INT goes back up to 128.

In my Datamaster snapshot below a large number of BLM's are running rich. I had it backwards, it's not rich to compensate for lean mixture, it's just rich period. I can rule out low fuel pressure.

http://i1196.photobucket.com/albums/...man1/test4.gif

 

Yes, the BLM follows the INT. In the case of the snapshot, the BLM is at 113 and the INT is at 134. So shortly before this the INT was lower then 128 (minus a few points) and pulled the BLM down.

Then went to a different area of RPM & load which is now on the lean side, so the INT increased to add some fuel. The BLM will follow upward shortly.

RBob.

 

So the BLM cells are a representaion of the actual AFR, not a value that the ECM has calculated as an offset for correction. So in my example, the ECM see's past ARF results in a BLM cell and calculates a compensated AFR to hopefully achieve an INT of 128?

 

No, the INT is an adder/subtractive to the current calculated PW.

The BLM is a multiplier to the current calculated PW.

Basically, the difference between 128 and the current INT or BLM values is used as the PW modifier.

RBob.

 

Thnx for your patience.

 

Last question (i think). Given that my INT's are steadily hovering around 128, do I really need to care that my BLM's are rich? Anotherwords, if I am troubleshooting a problem, can I rule out the rich BLM's?

thnx

 

In closed loop the resulting A/F is at stoich or approx 14.3 for E10 and 14.7 for good gas.

Neither lean nor rich. Stoich. ECU is contantly monitoring 02 sensor feedback maintaining stoich.

You could place tune so that BLM is 128 with an ambient temp of 90F. The next day say temp is 50F(happened a couple weeks ago WI) you will see BLM drop adding fuel.

Mechanical issues can also affect BLM reads. Barometric as well. Elevation change as well.

 

yes.

since BLM and INT work together to make up for fueling differences, if you have your BLM at say 108 and INT is moving around 128, you are still running rather rich before O2 correction.

get your BLMs to be consistently near 128 and then you're in better shape.

 

i have been wondering to, i think lowering my fp would bring BLM numbers higher,but it would also disrupt fueling at WOT,right? if thats the case,it would be better to use some program like VEMaster to get BLM's in shape below like 3k rpm?

 

Yup! Or math...

 

generally, the programs, while they will work flawlessly in steady-state conditions, don't always work well when transient fueling comes into play, or should come into play.

it takes what feels like a decade, but i step through my logs and only make fueling changes when i know the engine is in a steady state, watch the INT to make sure it's swinging around 128, then base the amount of VE added/sub'd off of the difference between my current BLM and 128.

it's a pain, but it works.