Calibrating MAF sensor.

[beestoys]

Ok here are the questions. Based on a 93 LT1 running and wired professionally for a 95 computer. Engine has a BBK 58mm 1000 cfm throttle body. Coolant bypass, ported to manifold, K&N cold air kit, Stock 95 Pontiac TA MAF sensor with screen intact. Stock boots and elbow. Bailey ENT LTCC kit. Headman Elite Headers (not long tube) 1 5/8 primary's 3 inch ball flange collector. 3inch exhaust to bumper with 2.5 crossover and 3 inch flowmaster Delta force 2 chamber silencers (can't prove that by the local car alarms).

1. Is it neccessary to recalibrate the MAF sensor.

2. If so how do I go about doing that?

Asking these questions because search hasn't pinged anything and by advice from a learned member starting this thread so that it may help out someone else down the road.

[dave w]

Stock 95 Pontiac TA MAF sensor with screen intact.

1. Is it neccessary to recalibrate the MAF sensor.

2. If so how do I go about doing that?

The stock MAF calibration for the 95 Pontiac TA MAF sensor is what I would program into the LT1 computer.

dave w

[steveo]

if you want stock maf cals like that, and you're using my XDF, you can go into the presets section and patch them in.

if your blms show as fairly far out due to engine modifications, but only in some areas, i'd recalibrate the maf for sure.

if it's across the board, just scale your injector constant a bit more.

first off they're sensitive to changes in intake plumbing. notice that the f-body and y-body MAF sensors are calibrated differently, even though they are the same sensor.

sure, closed loop will compensate for the maf being out a little bit, once it catches up, but that doesn't help open loop very much, does it?

do you want it to be perfect or not?

[beestoys]

Dave
Thanks for the tables I am pretty sure that is what's in there but now I can verify.

Steveo
Yes I am using the new 2.4 with the patch capability.
I'll log some more and check them I know the idle is out some and from the last work run they were around the 108 rich side still. Still going to drop in the WB and be sure my O2's aren't fried. this thing was running without the VSS input for a long time.
If I find it is out in as you state in some areas then would loading the stock cal work or would I need to do something else?
Yes open loop will be checked and reworked with the WB once it's in for sure.
And yes I am a bit OCD when it comes to my toys performance.

[steveo]

well, an ocd guy just has to tweak his maf table a bit, that's just how it is.. if for no other reason than to be one step ahead of closed loop operation, so it doesnt take any time to correct your AFR. and hell, this thing is used as the metering device for power enrichment, so when you go to tune that, if you have your maf table nailed so you get 14.7:1 at higher rpm out of PE, you can hit your final power enrichment targets way more easily.

once you tune your maf wideband in open loop properly, your blms WILL be pretty much garunteed to be close, unless the o2 sensors are screwed.

so your BLMs, are they 108 the entire time, or are they 108 only in cruising cells? that's kind of important.

always remember what a BLM value really is. you're working with a 4x4 grid of cells, each one specifying a range of operating, rpm on one axis and MAP on the other. the data in these cells is based on averaging the short term trims.

the value itself isn't as important without a frame of reference, knowing what cell you're in, and what range of operating it covers, for example if you're hitting 108 in cells 17 and 18 (fairly common) it doesn't matter. i made this chart so you can visualize an LT1's BLM system:

http://resfilter.net/files/carstuff/...ell%20Grid.pdf

the boundaries between the cells are tuneable, my XDF has two tables in air fuel metering > block learn mode, BLM cell RPM and MAP boundaries, and they're labeled appropriately to that chart so you can figure out where you stand as far as what cell is what, and how you can improve them.

it's also worth viewing a datalog to see how many log events happen in each blm cell. if you're only getting a few events in a cell, you should move your cell boundaries so all cells are being used for something. having a good range of operation is a good thing; that means if you have a lean area next to a rich area, they wont average into the same cell

[beestoys]

well, an ocd guy just has to tweak his maf table a bit, that's just how it is.. if for no other reason than to be one step ahead of closed loop operation, so it doesnt take any time to correct your AFR. and hell, this thing is used as the metering device for power enrichment, so when you go to tune that, if you have your maf table nailed so you get 14.7:1 at higher rpm out of PE, you can hit your final power enrichment targets way more easily.

once you tune your maf wideband in open loop properly, your blms WILL be pretty much garunteed to be close, unless the o2 sensors are screwed.

so your BLMs, are they 108 the entire time, or are they 108 only in cruising cells? that's kind of important.

always remember what a BLM value really is. you're working with a 4x4 grid of cells, each one specifying a range of operating, rpm on one axis and MAP on the other. the data in these cells is based on averaging the short term trims.

the value itself isn't as important without a frame of reference, knowing what cell you're in, and what range of operating it covers, for example if you're hitting 108 in cells 17 and 18 (fairly common) it doesn't matter. i made this chart so you can visualize an LT1's BLM system:

http://resfilter.net/files/carstuff/...ell%20Grid.pdf

the boundaries between the cells are tuneable, my XDF has two tables in air fuel metering > block learn mode, BLM cell RPM and MAP boundaries, and they're labeled appropriately to that chart so you can figure out where you stand as far as what cell is what, and how you can improve them.

it's also worth viewing a datalog to see how many log events happen in each blm cell. if you're only getting a few events in a cell, you should move your cell boundaries so all cells are being used for something. having a good range of operation is a good thing; that means if you have a lean area next to a rich area, they wont average into the same cell

Point one on the tweaking.
Yes I agree and part of my thinking if I can adjust the factory to work like the original with my nods then I can then leave it alone and let it do what GM designed it too with maybe a little better refinement.

I'll log some more runs as it sets right now. I can't remember to be honest where they where at. it seems to be correcting now that the injector flow has been corrected for my size of injector and rail pressures. But I plan to mod the log dash you have with the 3.8 adx. Along those lines the low D2 D3 D4 are for auto trans gear position right? I planned to remove those if that is the case and drop a BLM monitor in there instead. I am also noticing the BLM trim is going active a lot and it seems to be coinciding with the 108 indications on the LT BLM's.
Again I am planning more log runs to build up a good reference to go back too. All the points your mentioning are all very good ones and something that I would not have thought to look at closely thanks for the insights for sure.

[steveo]

Along those lines the low D2 D3 D4 are for auto trans gear position right? I planned to remove those if that is the case and drop a BLM monitor in there instead. I am also noticing the BLM trim is going active a lot and it seems to be coinciding with the 108 indications on the LT BLM's.

you lost me here, are you talking about the dash display/logger thing i've built? you can display whatever you want... it's very configurable.. but it sure doesn't use adx files..

[beestoys]

you lost me here, are you talking about the dash display/logger thing i've built? you can display whatever you want... it's very configurable.. but it sure doesn't use adx files..

Yes that is the file I meant and sorry for all of the confusion. I was able to change the BLM from an indicator to the actual cell count. Again sorry I asked a question before trying it. It's all new and have to admit I am tripping over myself.