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Thread: My split blm problem
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06-04-2020, 09:37 AM #11Xtreme Member
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Supporting Member2021 Charger Scat 392
1994 Firebird Formula 381 stroker - Carrying the torch! - 9.90 @ 134.3mph on a 200 shot
The wrench/driver for LTConvert's 94 Z28- Ellwein 383/LE Trickflows/ D1SC / CPT Ultra Pro Race 4L60E
10.78 @ 125mph. Shooting for 9.99 for Frank Cahall!
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06-04-2020, 06:40 PM #12
Ah. Yes there is an open breather on the ds valve cover.
1991 Z28
Engine: '94 355 LT1, GM hot cam, 1.6 RR's, Ported Heads, Dyno Don's headers, #30 SVO injectors, stock internals with skirted pistons.
Drivetrain: '95 T56, pro 5.0 shifter, hayes clutch, Stock 10 bolt with 3.42's
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06-05-2020, 09:07 AM #13Xtreme Member
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Supporting Member2021 Charger Scat 392
1994 Firebird Formula 381 stroker - Carrying the torch! - 9.90 @ 134.3mph on a 200 shot
The wrench/driver for LTConvert's 94 Z28- Ellwein 383/LE Trickflows/ D1SC / CPT Ultra Pro Race 4L60E
10.78 @ 125mph. Shooting for 9.99 for Frank Cahall!
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06-05-2020, 10:21 PM #14
Hmm.. I plugged it and reset my BLMS. It almost seems as though it got worse. Bank 2 was slightly better, but bank 1 went straight to 108. in cell 16 and 18. (still not driving).
I wonder if I need to do a reset of the IAC ect, and I also wonder if this tune tried to compensate for the rich condition and an earlier tune would be better. I'll load up a previous tune with this breather blocked and see if that helps.1991 Z28
Engine: '94 355 LT1, GM hot cam, 1.6 RR's, Ported Heads, Dyno Don's headers, #30 SVO injectors, stock internals with skirted pistons.
Drivetrain: '95 T56, pro 5.0 shifter, hayes clutch, Stock 10 bolt with 3.42's
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06-06-2020, 07:39 AM #15Xtreme Member
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Supporting Member2021 Charger Scat 392
1994 Firebird Formula 381 stroker - Carrying the torch! - 9.90 @ 134.3mph on a 200 shot
The wrench/driver for LTConvert's 94 Z28- Ellwein 383/LE Trickflows/ D1SC / CPT Ultra Pro Race 4L60E
10.78 @ 125mph. Shooting for 9.99 for Frank Cahall!
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06-09-2020, 09:27 PM #16
Ok so I reset the PCM, and I switched the injectors sides, both didn't seem to have any positive effect. Here is a data log i took tonight
https://drive.google.com/file/d/17w1...ew?usp=sharingLast edited by BCdawg57; 06-09-2020 at 10:29 PM.
1991 Z28
Engine: '94 355 LT1, GM hot cam, 1.6 RR's, Ported Heads, Dyno Don's headers, #30 SVO injectors, stock internals with skirted pistons.
Drivetrain: '95 T56, pro 5.0 shifter, hayes clutch, Stock 10 bolt with 3.42's
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08-05-2020, 01:36 PM #17
bump
1991 Z28
Engine: '94 355 LT1, GM hot cam, 1.6 RR's, Ported Heads, Dyno Don's headers, #30 SVO injectors, stock internals with skirted pistons.
Drivetrain: '95 T56, pro 5.0 shifter, hayes clutch, Stock 10 bolt with 3.42's
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08-05-2020, 03:49 PM #18LTx Guru
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Guess I forgot about this one, or I figured I didn't want to interfere with with SlowBoat.
Downloaded it, and a quick look shows some really strange stuff.
The first thing is that the LTFT's (BLM's) in several cells (16=idle, and the mathematically derived cells 17 and 18) drop below 108. They go as low as 88. 108 (subtracting 15% fuel) is the factory programmed minimum allowable value. 88 is pulling 18.5% fuel. Either someone has altered the stock programming to permit LTFT's lower than 108, or there is something else hidden in the PCM that allows it, but I haven't seen this in 100's of data logs I've reviewed for people. Maybe Solomon can explain it to us.
Those three cells are the only place the "split" (Cell 16: 91 left/131 right) shows up. In some other cells, The right LTFT is lower than the left, and in others there is a very small and acceptable difference. I need to spend more time picking up the values for more of the cells to see if there is a trend.
When you go into power enrichment (PE) mode in cell 15, because one of the LTFT's was subtracting fuel, the PCM locks the LTFT's at 128, and both banks are showing very close, and appropriately rich (allowing for the accuracy limits of the narrow band sensors at those rich levels), in the low 0.900's. There is no imbalance at WOT. The second thing that happens is you get a huge amount of knock retard, up to 12.5-deg.
I need more time to look at it, above is just from a quick look.
I will note that the way the TPS voltage works, as long as the PCM sees a value roughly between 0.25-0.90 volts at closed throttle at startup, it sets that voltage as the baseline, and prorates the throttle position % upwards from there. Yours is 0.69 volts and that is within the range of typical unmolested stock throttle body readings that I have seen. I need to learn more about the benefits of shooting for a specific TPS closed throttle volts reading. It does make a difference in the 3rd Gens, but according the the GM factory service manual, the 4th Gen PCM incorporates the method I described, hence the reason the TPS sensor is not adjustable, and per the manual, does not need to be.
I'm a bit backed up with data logs right now, and NJ is totally F'd up by the tropical storm - 1,000,000 households without power, internet service out, or fading in and out, trees down blocking roads all over the place. 2020 really sucks so far.Last edited by Injuneer; 08-05-2020 at 03:52 PM.
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The Following User Says Thank You to Injuneer For This Post:
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08-11-2020, 07:37 AM #19
Wow. Ok I will ask him why he thinks the blms could be going so low. Is the knock retard just at wot?
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08-11-2020, 09:22 PM #20Xtreme Member
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Supporting MemberMost tuners lock blms to 128 in power enrichment mode, then tune off the o2 millivolt readings. .900 is rich as hell. are you running stock injectors or larger? i have seen him "tune" a car and not change the injector constant from stock, causing a member here to literally wipe his motor on first start, fresh build.
I gotta get some time to see what @Injuneer is talking about. nj has been rough lately, today finally had some time to breathe. Ill dig my laptop out tomorrow night.
Knock retard should be brought down, do you have roller rockers?
Fred thank you for your great read of the log.
Sent from my SM-N975U using Tapatalk2021 Charger Scat 392
1994 Firebird Formula 381 stroker - Carrying the torch! - 9.90 @ 134.3mph on a 200 shot
The wrench/driver for LTConvert's 94 Z28- Ellwein 383/LE Trickflows/ D1SC / CPT Ultra Pro Race 4L60E
10.78 @ 125mph. Shooting for 9.99 for Frank Cahall!
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