Question About BLM's
Thread Starter
Drifting
Joined: Jul 2009
Posts: 1,258
Likes: 98
From: Ashland PA
2021 C4 of the Year - Modified Finalist
Question About BLM's
I have been trying some data logging and have a question about BLM's.
Cruising down the Highway the blm's are at 135
Running around on twisty back roads, pulling steep grades, accelerating, decelerating, the blm's are up and down 138 to 154.
idling the blm's are at 131
This is with everything warmed up.
The car is a 90 with Bosch 3 injectors, no precats otherwise motor is stock with about 185k on it. the car seems to run real well ecept for a rough idle.
My question is is this normal for BLM's I am sure I read something that they should be around 128. Also what should I look at in the data for diagnost the rough idle. Thank You
Cruising down the Highway the blm's are at 135
Running around on twisty back roads, pulling steep grades, accelerating, decelerating, the blm's are up and down 138 to 154.
idling the blm's are at 131
This is with everything warmed up.
The car is a 90 with Bosch 3 injectors, no precats otherwise motor is stock with about 185k on it. the car seems to run real well ecept for a rough idle.
My question is is this normal for BLM's I am sure I read something that they should be around 128. Also what should I look at in the data for diagnost the rough idle. Thank You
Burning Brakes
Joined: Mar 2005
Posts: 1,082
Likes: 115
From: Richmond Hill Ontario
If you can post your datalog to analyze that would be helpful. I suspect your Injector Flow Rate needs to be corrected in your BIN for the new Bosch Injectors. A BLM of 154 is pushing it on the high side of AFR around 17.6.
Last edited by FrankieD; Jul 4, 2015 at 06:53 AM.
Thread Starter
Drifting
Joined: Jul 2009
Posts: 1,258
Likes: 98
From: Ashland PA
2021 C4 of the Year - Modified Finalist
these are 2 logs that I have I am not shore if the files are ok or not but that is what is in aldldroid.
https://drive.google.com/file/d/0B5d...ew?usp=sharing
https://drive.google.com/file/d/0B5d...ew?usp=sharing
https://drive.google.com/file/d/0B5d...ew?usp=sharing
https://drive.google.com/file/d/0B5d...ew?usp=sharing
Thread Starter
Drifting
Joined: Jul 2009
Posts: 1,258
Likes: 98
From: Ashland PA
2021 C4 of the Year - Modified Finalist
the bosch 3 injectors have been in there over 3 years they all ohm good hot and cold, 15 cold, 17 hot, I checked the fuel pressure and it was good, I may tape the fuel pressure gauge to the windshield when I have a chance and check it wile I am driving. the rough idle started about a month ago wile I was driving down the interstate one of my spark plugs came off, since then the idle has been very rough, the spark plug wires have been on there about 3 years. I went to check the ignition module in the distributor and found the module loos so I changed it out with a new one to play it safe along with the coil. this engine has over 180k on it and valves tick when worm so the rough idle may be mechanical, if I can swing it I may do a rebuild in the fall but I would like to eliminate any problems before then rather than chase problems with a fresh motor.
Safety Car
Joined: Sep 2001
Posts: 4,157
Likes: 554
From: Glenbeulah Wi
To clarify this it means if there was no fuel trim correction it would be around 17.6 AFR, but the computer can correct for AFR variations up to a BLM of 160 so the AFR is still at 14.7 to 1. Can it be better, yes, is it dangerous no.
Thread Starter
Drifting
Joined: Jul 2009
Posts: 1,258
Likes: 98
From: Ashland PA
2021 C4 of the Year - Modified Finalist
I am more interested in fixing the idle problem, after that maybe I will get a tune to correct the blm's or adjustable fuel regulator. thanks for the replies.
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Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
There are 16 BLM cells, so saying "my BLM is X" means nothing without knowing which cell held that number. This BLM map is from my '86 and the thresholds were adjusted in later years and if you had MAP vs. MAF (basically you idle in cell zero and run in cells 10 and 15):
Code:
; Block Learn Multiplier cell matrix at L001C: ; ; 700 1200 2000 ; RPM RPM RPM ; | | | ; --------------------- ; | 0 | 1 | 2 | 3 | ; ---------------------- 12 gm/sec ; | 4 | 5 | 6 | 7 | ; ---------------------- 22 gm/sec ; | 8 | 9 | 10 | 11 | ; ---------------------- 34 gm/sec ; | 12 | 13 | 14 | 15 | ; ---------------------
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
There have been many cases on this forum of people installing Bosch 3 injectors ,then having their cars run lean...I personally don't think Bosch 3 injectors are plug and play like advertised..The guy that did the tune on my new engine a few years ago , said any car with these injectors installed should be checked and retuned if the tune is thrown to far off from these injectors....
...WW
...WW