cfm for my motor...
03-19-2004, 11:49 PM
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Car: 91 Camaro
Engine: 3.1...not hardly stock
Transmission: 700r4....not stock either
Axle/Gears: 3.73
cfm for my motor...
what sensor on a SD car reads/senses the amount air flowing through the intake? i datalogged my car at the track thurs. night and the computer (laptop) was showing 255 grams per second the whole time i was at WOT. i found online that 1 gram/sec = 1.79 cfm. first, is that right? second, that tells me that my motor was pulling 456.45 cfm. i had been told before that this stock TB would only do about 308 cfm or something. is something not right somewhere? and, with that sensor (whichever one it is) showing 255 the entire time i was at WOT, does that mean that sensor is maxed out? is my motor pulling more air than the sensors can read?
03-20-2004, 12:16 AM
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Car: 86 Berlinetta 84 MonteCL
Engine: 3.4 MPFI 3.8 229
Transmission: 700r4 T350
255!!!
I don't think that's right. At idle our cars pull 6-8ish grams per second. That's by MAF. I forget exactly what our CFM is at wide open, but I think it's about 350ish
03-20-2004, 07:12 AM
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On the $88 mask the gms/sec value is calculated. The code uses the injector PW, commanded AFR, engine RPM, the # of cylinders, and a constant. Out pops the airflow.
RBob.
RBob.
03-20-2004, 08:09 AM
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Car: 3
Engine: inboard
Transmission: underfloor
ALan- you were able to get the computer to read the data off the 3.1 or did you swap to a 2.8 speed density system and ECM?
Eric
Eric
03-20-2004, 10:06 AM
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Car: 91 Camaro
Engine: 3.1...not hardly stock
Transmission: 700r4....not stock either
Axle/Gears: 3.73
Originally posted by eric17422001
ALan- you were able to get the computer to read the data off the 3.1 or did you swap to a 2.8 speed density system and ECM?
Eric
ALan- you were able to get the computer to read the data off the 3.1 or did you swap to a 2.8 speed density system and ECM?
Eric
03-20-2004, 10:07 AM
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Car: 91 Camaro
Engine: 3.1...not hardly stock
Transmission: 700r4....not stock either
Axle/Gears: 3.73
Originally posted by RBob
On the $88 mask the gms/sec value is calculated. The code uses the injector PW, commanded AFR, engine RPM, the # of cylinders, and a constant. Out pops the airflow.
RBob.
On the $88 mask the gms/sec value is calculated. The code uses the injector PW, commanded AFR, engine RPM, the # of cylinders, and a constant. Out pops the airflow.
RBob.
03-20-2004, 10:37 AM
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Originally posted by AM91Camaro_RS
are you saying that its possible that my motor is pulling that much or some calculation it is doing is off some where or what? why does it only go to 255 and stop there?
are you saying that its possible that my motor is pulling that much or some calculation it is doing is off some where or what? why does it only go to 255 and stop there?
If you changed injector size or fuel pressure (anything that affects the fuel flow per PW) then the calculation is off.
BobR.
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03-20-2004, 10:44 AM
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Car: 91 Camaro
Engine: 3.1...not hardly stock
Transmission: 700r4....not stock either
Axle/Gears: 3.73
Originally posted by RBob
The number 255 is the largest value a single byte can hold. I guess that GM thought that it was enough to satisfy the requirements.
If you changed injector size or fuel pressure (anything that affects the fuel flow per PW) then the calculation is off.
BobR.
The number 255 is the largest value a single byte can hold. I guess that GM thought that it was enough to satisfy the requirements.
If you changed injector size or fuel pressure (anything that affects the fuel flow per PW) then the calculation is off.
BobR.
03-20-2004, 12:39 PM
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Originally posted by AM91Camaro_RS
i ddint' change anything in the fuel system. stock injectors and fuel pressure. what can i do? won't this number maxing out effect/hurt my performance? do i need to cut a little fuel at higher rpms or something? at one point, the target AFR dropped to 11:1 for a sec or two. shouldn't i try to get it to stay up around 12:1? anything you can tell me is greatly appreciated! THANKS!
i ddint' change anything in the fuel system. stock injectors and fuel pressure. what can i do? won't this number maxing out effect/hurt my performance? do i need to cut a little fuel at higher rpms or something? at one point, the target AFR dropped to 11:1 for a sec or two. shouldn't i try to get it to stay up around 12:1? anything you can tell me is greatly appreciated! THANKS!
A stock 3.1l will hit 255 gms/sec at 2900 RPM, 91 KPA MAP with 42% TPS. Injector PW of 8.1 msec.
The WOT fueling is calculated from VE% (table lookup), MAP, CTS/IAT term, commanded AFR, and closed loop correction terms.
The WOT commanded AFR is a lookup which can be affected by the cat-con protection routine. It is normal for it to be commanded rich in order to protect the cat-con from melting.
RBob.
03-20-2004, 04:22 PM
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Car: '99 Trans Am, '86 Camaro
Engine: LS1, Scrap
Transmission: T56, T5
Axle/Gears: 3.42 Stock ZT, 3.42 Open
Originally posted by RBob
A stock 3.1l will hit 255 gms/sec at 2900 RPM, 91 KPA MAP with 42% TPS. Injector PW of 8.1 msec.
A stock 3.1l will hit 255 gms/sec at 2900 RPM, 91 KPA MAP with 42% TPS. Injector PW of 8.1 msec.
03-20-2004, 08:53 PM
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Originally posted by TechSmurf
I'm guessing it's not calculating actual gm/sec airflow then, because a stock 3.1l will never truly do 255 gm/sec without blowing up
I'm guessing it's not calculating actual gm/sec airflow then, because a stock 3.1l will never truly do 255 gm/sec without blowing up
Code:
37 AIRFLOW ENGINE AIRFLOW
GRAMS/SECOND = N And AM91, I missed one of your questions: I have gms/sec X 1.787 = SCFM. Same as what you have.
RBob.
03-20-2004, 11:06 PM
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Car: 91 Camaro
Engine: 3.1...not hardly stock
Transmission: 700r4....not stock either
Axle/Gears: 3.73
Originally posted by RBob
The engine fueling was AM91's priority. This airflow calculation does not affect WOT fueling. I was giving an example of what a stock 3.1l f-body reported.
And AM91, I missed one of your questions: I have gms/sec X 1.787 = SCFM. Same as what you have.
RBob.
The engine fueling was AM91's priority. This airflow calculation does not affect WOT fueling. I was giving an example of what a stock 3.1l f-body reported.
And AM91, I missed one of your questions: I have gms/sec X 1.787 = SCFM. Same as what you have.
RBob.
03-21-2004, 07:53 AM
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Originally posted by AM91Camaro_RS
so is there anything i need to change or worry about? i might have understood all of what i just read if it wasn't as late as it is. then again, i might not...
so is there anything i need to change or worry about? i might have understood all of what i just read if it wasn't as late as it is. then again, i might not...
As for WOT fueling, it isn't affected by the gms/sec calculation.
RBob.
03-21-2004, 12:32 PM
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Car: 91 Camaro
Engine: 3.1...not hardly stock
Transmission: 700r4....not stock either
Axle/Gears: 3.73
Originally posted by RBob
I don't believe it is anything to worry about. If the gms/sec calculation was changed it would affect too many other items. They too would then need to be changed/recalibrated.
As for WOT fueling, it isn't affected by the gms/sec calculation.
RBob.
I don't believe it is anything to worry about. If the gms/sec calculation was changed it would affect too many other items. They too would then need to be changed/recalibrated.
As for WOT fueling, it isn't affected by the gms/sec calculation.
RBob.
03-22-2004, 07:28 AM
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Originally posted by AM91Camaro_RS
ok, thanks. can i do anything to change it to keep it from going all the way to a 11:1 afr? i like the 12:1 but i think 11:1 could be a little too much fuel. i don't really know. i am still trying to learn about chip tuning. i have all the equipment for it and have done a few chips but any advice you can give me on it would really be helpful and appreciated.
ok, thanks. can i do anything to change it to keep it from going all the way to a 11:1 afr? i like the 12:1 but i think 11:1 could be a little too much fuel. i don't really know. i am still trying to learn about chip tuning. i have all the equipment for it and have done a few chips but any advice you can give me on it would really be helpful and appreciated.
There is a bunch you can do to make that ECM run the engine better. As for fueling the cat-con protect, the PE enrichment, and PE AFR can all be changed. Later tonight I'll post again.
RBob.
03-22-2004, 12:28 PM
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Car: 1991 CAMARO 1968 FIREBIRD
Engine: CAMARO 3.1L FIREBIRD 455
Transmission: CAMARO 700R4 FIREBIRD TH-400
What do i need to show info on my 91 3.1? I have the laptop but what program/connnector do i need.
03-22-2004, 04:34 PM
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AM91, here are some items to change/consider for WOT fueling.
To disable the cat-con over temperature code set these four locations to 255 ($FF):
$83E7, $83E8, $83E9, $83E7A
The cat-con overheat changes a lot of items, things such as TCC lockup, PE mode TPS% PE thresholds, spark timing, are all affected by the cat-con temperature.
This next one is strange and I have no idea why GM implemented it this way, but change this location to 0:
$8B05
It reduces the AFR after a certain amount of time in PE mode. Setting it to 0 prevents this reduction.
Then the AFR vs RPM table:
And the TPS% required to go into PE mode:
The location addresses are in ECM addresses, subtract $8000 from each to get the EPROM bin file address.
The data shown in the tables are from AZTY, an $88 maskID ('90-92 f-body, 3.1L, '730 ECM, SD system).
RBob.
To disable the cat-con over temperature code set these four locations to 255 ($FF):
$83E7, $83E8, $83E9, $83E7A
The cat-con overheat changes a lot of items, things such as TCC lockup, PE mode TPS% PE thresholds, spark timing, are all affected by the cat-con temperature.
This next one is strange and I have no idea why GM implemented it this way, but change this location to 0:
$8B05
It reduces the AFR after a certain amount of time in PE mode. Setting it to 0 prevents this reduction.
Then the AFR vs RPM table:
Code:
; -------------------------------------- ; ; PE AFR vs. RPM ; ; tbl = AFR * 10 ; -------------------------------------- $8B06: ;----------------------------- ; AFR ; RPM ;----------------------------- FCB 125 ; 0 FCB 125 ; 400 FCB 125 ; 800 FCB 125 ; 1200 FCB 125 ; 1600 FCB 125 ; 2000 FCB 125 ; 2400 FCB 125 ; 2800 FCB 125 ; 3200 FCB 120 ; 3600 FCB 120 ; 4000 FCB 120 ; 4400 FCB 120 ; 4800 FCB 120 ; 5200 FCB 120 ; 5600 FCB 120 ; 6000 FCB 120 ; 6375
Code:
; -------------------------------------- ; ; TPS% required for PE ; ; -------------------------------------- ;----------------------------- ; ; tps ; øC ;----------------------------- $8B17 FCB 141 ; 44 55% FCB 154 ; 56 60% FCB 154 ; 68 60% FCB 179 ; 80 70% FCB 179 ; 92 70% FCB 128 ; 104 50% FCB 115 ; 116 45% FCB 90 ; 128 35% FCB 90 ; 140 35% FCB 90 ; 152 35%
The data shown in the tables are from AZTY, an $88 maskID ('90-92 f-body, 3.1L, '730 ECM, SD system).
RBob.
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