7749 using TBI firing strategy- WORKING!
09-11-2004 | 10:38 PM
#1
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From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
7749 using TBI firing strategy- WORKING!
A few weeks ago, I decided to try converting over to a 7749 ecu to control the supercharged V8 in my '89 Chevy C2500. The truck's been running the 749 for a couple of weeks but I was struggling with the batch fire mode of the 749. I dramatically increased fuel pressure to compensate for the reduced firing rate of batch mode, but was not happy with that as a long term "fix".
I've read that the 730 & 749 ecus were used in some TBI applications, but could not locate many details. I did find this post https://www.thirdgen.org/techbb2/sho...threadid=39111 that referenced a "TBI mode" and "pin 56". Pin 56 refers to the CAL56 line of the memcal. CAL56 connects to the CYL input (pin 11) of U13 & U15 (16034984) EST/Inj Driver controller ICs.
I decided to do a little more experimentation this afternoon. With the engine idling, the CYL input (pin 11) of U13 was at 0 volts. Because it was an easy first step, I decided to remove the CAL56 input to see what would happen. With CAL56 out of the circuit, the voltage at pin 11 of U13 was 2.5vdc. Low and behold....the injectors are now both firing once per two DRPs!!!!! This matches the firing rate I see when using the stock 7747! (Note: I originally stated "pattern" which is incorrect. The firing "rate" is the same.)
I then lowered the fuel pressure back to normal TBI levels (I had it up to 43lbs which just barely compensated for TPI mode firing) and calculated a new BPC using the TBI formula of 1461.5 * (VOL/RATE). Burned this to a new chip and it's running GREAT!
Now...I don't know if this change might adversely affect either the hardware or $58 software algorithms. It might be fine long term, or not. Tomorrow I'll finish up my WBO2 install, so I'll be able to begin logging my results!
I had just about given up hope on running 2-barrel TBI off of the 7749...so hopefully this works out long term.
Brent
I've read that the 730 & 749 ecus were used in some TBI applications, but could not locate many details. I did find this post https://www.thirdgen.org/techbb2/sho...threadid=39111 that referenced a "TBI mode" and "pin 56". Pin 56 refers to the CAL56 line of the memcal. CAL56 connects to the CYL input (pin 11) of U13 & U15 (16034984) EST/Inj Driver controller ICs.
I decided to do a little more experimentation this afternoon. With the engine idling, the CYL input (pin 11) of U13 was at 0 volts. Because it was an easy first step, I decided to remove the CAL56 input to see what would happen. With CAL56 out of the circuit, the voltage at pin 11 of U13 was 2.5vdc. Low and behold....the injectors are now both firing once per two DRPs!!!!! This matches the firing rate I see when using the stock 7747! (Note: I originally stated "pattern" which is incorrect. The firing "rate" is the same.)
I then lowered the fuel pressure back to normal TBI levels (I had it up to 43lbs which just barely compensated for TPI mode firing) and calculated a new BPC using the TBI formula of 1461.5 * (VOL/RATE). Burned this to a new chip and it's running GREAT!
Now...I don't know if this change might adversely affect either the hardware or $58 software algorithms. It might be fine long term, or not. Tomorrow I'll finish up my WBO2 install, so I'll be able to begin logging my results!
I had just about given up hope on running 2-barrel TBI off of the 7749...so hopefully this works out long term.
Brent
Last edited by 89C2500; 09-13-2004 at 11:40 PM.
09-12-2004 | 06:38 AM
#2
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From: In reality
Car: An Ol Buick
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Please keep the board posted on what you find. I've been trying for years to get some one to run a TBI off of a 749. Glad to see it working. I'd tried it once, *years* ago, and had limited success.
09-12-2004 | 10:13 AM
#3
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From: Bartlett, IL
Car: 92 ZR-1
Engine: LT-5
Transmission: ZF-6
Axle/Gears: SuperDana 44 4.10
Brent,
Any chance you could provide the pin-out scheme you have used? I am in the midst of trying to do the 7747 > 7749 conversion right now.
Any chance you could provide the pin-out scheme you have used? I am in the midst of trying to do the 7747 > 7749 conversion right now.
09-12-2004 | 06:43 PM
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From: Chasing Electrons
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Originally posted by Dominic Sorresso
Brent,
Any chance you could provide the pin-out scheme you have used? I am in the midst of trying to do the 7747 > 7749 conversion right now.
Brent,
Any chance you could provide the pin-out scheme you have used? I am in the midst of trying to do the 7747 > 7749 conversion right now.
So, look at the Sunbird pinout and wire one injector to each driver. As is there will be two jumpers at the ECM where the Sy/Ty has none. D5, D6; C13, C15.
This will PnH the two TBI injectors.
RBob.
09-12-2004 | 06:46 PM
#5
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From: Chasing Electrons
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Re: 7749 using TBI firing strategy- WORKING!
Originally posted by 89C2500
A few weeks ago, I decided to try converting over to a 7749 ecu to control the supercharged V8 in my '89 Chevy C2500. . .
Brent
A few weeks ago, I decided to try converting over to a 7749 ecu to control the supercharged V8 in my '89 Chevy C2500. . .
Brent
RBob.
09-12-2004 | 06:57 PM
#6
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From: the garage
Car: 84 SVO
Engine: Volvo headed 2.3T
Transmission: WCT5
Axle/Gears: 8.8" 3.73
Well bugger.... 
Thats exactly what I was planning to do this winter with Thunder. Run a 749 in TBI.
I'm planning on using the 91 305 TBI engine I have, has a LT1 cam, but swap out the intake for a crossfire and run either the crossfire lid, or make up one and use the 2BBl TBI.
Will have a 200r4 and 2:73's as this is going to be my daily driver.
Cool.. One less hurdle. Well done. Bob
Thats exactly what I was planning to do this winter with Thunder. Run a 749 in TBI.
I'm planning on using the 91 305 TBI engine I have, has a LT1 cam, but swap out the intake for a crossfire and run either the crossfire lid, or make up one and use the 2BBl TBI.
Will have a 200r4 and 2:73's as this is going to be my daily driver.
Cool.. One less hurdle. Well done. Bob
09-12-2004 | 11:37 PM
#7
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From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
Ok....spent all day out in the garage...again. My wife's gonna kill me soon!
I decided to do more o-scope traces. I also swapped back all the 747 stuff to verify some assumptions.
What I found is with CAL56 removed, it is NOT firing a true TBI pattern...i.e. alternating injector pulses on each DRP.
However, it does fire both injectors simultaneously every 2 DRPs so I'm guessing fuel delivery will be identical. Is there an advantage to firing the injectors 180 degrees out of phase???
I tried different voltage levels at U13 pin 11 but the injectors always fired in phase. There must be a way to invert the trigger signal to one of the injector driver controllers....but I wonder if alternating pulses are really needed?
I really need to setup a test bench...someday.
I did get the wbo2 installed today.
Unfortunately, my homemade ALDL interface quit working so logging will have to wait a couple of days.
Brent
I decided to do more o-scope traces. I also swapped back all the 747 stuff to verify some assumptions.
What I found is with CAL56 removed, it is NOT firing a true TBI pattern...i.e. alternating injector pulses on each DRP.
However, it does fire both injectors simultaneously every 2 DRPs so I'm guessing fuel delivery will be identical. Is there an advantage to firing the injectors 180 degrees out of phase???I tried different voltage levels at U13 pin 11 but the injectors always fired in phase. There must be a way to invert the trigger signal to one of the injector driver controllers....but I wonder if alternating pulses are really needed?
I really need to setup a test bench...someday.
I did get the wbo2 installed today.
Unfortunately, my homemade ALDL interface quit working so logging will have to wait a couple of days.Brent
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09-12-2004 | 11:44 PM
#8
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From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
Originally posted by Dominic Sorresso
Brent,
Any chance you could provide the pin-out scheme you have used? I am in the midst of trying to do the 7747 > 7749 conversion right now.
Brent,
Any chance you could provide the pin-out scheme you have used? I am in the midst of trying to do the 7747 > 7749 conversion right now.
RBob nailed it....Turbo Sunbird. If I remember there were a couple of gotcha's. I'll try to post my pinout notes in the next day or two.
Brent
09-13-2004 | 08:39 AM
#9
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From: Bartlett, IL
Car: 92 ZR-1
Engine: LT-5
Transmission: ZF-6
Axle/Gears: SuperDana 44 4.10
Brent,
That would be excellent. Thanks. I'd be interested in knowing how you found the conversion of VE and Spark Tables to be going from a 747>749. Then obviously all the other calibration areas like IAC/PDC/PE/WOT controls. Brave new world.
Saturn 5,
BTW, I'm running a 350 Xfire with TFS 23D Heads and a CompCams HydRoller.
That would be excellent. Thanks. I'd be interested in knowing how you found the conversion of VE and Spark Tables to be going from a 747>749. Then obviously all the other calibration areas like IAC/PDC/PE/WOT controls. Brave new world.
Saturn 5,
BTW, I'm running a 350 Xfire with TFS 23D Heads and a CompCams HydRoller.
09-13-2004 | 03:19 PM
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OK, dug around in some old diy stuff I collected. the voltage at those pins breaks down as follows:
"quote"
> Here's how the voltages are interpreted:
> 0 to 1 volt : 8 cylinder port injection
> 1 to 2.5 volts : 6 cylinder port injection
> 2.5 to 4 volts : 4 cylinder port injection
> 4 to 5 volts : throttle body injection (any cylinder count)
looks like you are in 4 cylinder port mode right now, may be why you are seeing injector events happening at the same time? Might want to try putting like a 10K resistor to those pins(to +5v), and measuring the voltage with the key on, no engine running. there was some other info too:
"quote"
>The '727 I tested this on defaulted to "4 cylinder port" when pin 11 was
> not driven (no MEMCAL).
>
> The CPU can read out the pin 11 mode selection. Code 41 will be flagged
> if it doesn't match the cylinder selection stored separately in the
> MEMCAL's EPROM.
if 10k doesn't bring the voltage up high enough, try using a 4.7K, and so on and so forth, just go lower in value slowly. Odds are, it is just a hard pull up to +5 volts in tbi mode, but a resistor is always a safe bet.
great project, glad to hear its working.
"quote"
> Here's how the voltages are interpreted:
> 0 to 1 volt : 8 cylinder port injection
> 1 to 2.5 volts : 6 cylinder port injection
> 2.5 to 4 volts : 4 cylinder port injection
> 4 to 5 volts : throttle body injection (any cylinder count)
looks like you are in 4 cylinder port mode right now, may be why you are seeing injector events happening at the same time? Might want to try putting like a 10K resistor to those pins(to +5v), and measuring the voltage with the key on, no engine running. there was some other info too:
"quote"
>The '727 I tested this on defaulted to "4 cylinder port" when pin 11 was
> not driven (no MEMCAL).
>
> The CPU can read out the pin 11 mode selection. Code 41 will be flagged
> if it doesn't match the cylinder selection stored separately in the
> MEMCAL's EPROM.
if 10k doesn't bring the voltage up high enough, try using a 4.7K, and so on and so forth, just go lower in value slowly. Odds are, it is just a hard pull up to +5 volts in tbi mode, but a resistor is always a safe bet.
great project, glad to hear its working.
09-13-2004 | 04:21 PM
#12
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Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
Cool. I'd have done this already if I had known that the 7749 would fire the TBI injectors like GM intended.. not batch.
Grumpy told me it was worth a shot but I just didn't have the $ to just go out on a whim when I was having good success with the 8746. I also have lockers which makes switching over to the p4 even less of an "upgrade."
I would definatly like to try this out now that you got it to fire correctly.
Grumpy told me it was worth a shot but I just didn't have the $ to just go out on a whim when I was having good success with the 8746. I also have lockers which makes switching over to the p4 even less of an "upgrade."
I would definatly like to try this out now that you got it to fire correctly.
09-13-2004 | 05:33 PM
#13
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From: In reality
Car: An Ol Buick
Engine: Vsick
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Originally posted by 89C2500
but I wonder if alternating pulses are really needed?
but I wonder if alternating pulses are really needed?
Crossfire, I don't see how.
Single plane small plenum, none heated, might.
V6, would.
Using just Batch fire, that one experiment that I did years ago had a good idle.
Might be *fun* to plug a stock ecm in, and see what the difference is from batch to this TBI mode.
09-13-2004 | 08:05 PM
#15
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From: the garage
Car: 84 SVO
Engine: Volvo headed 2.3T
Transmission: WCT5
Axle/Gears: 8.8" 3.73
Originally posted by jwscab
OK, dug around in some old diy stuff I collected. the voltage at those pins breaks down as follows:
"quote"
> Here's how the voltages are interpreted:
> 0 to 1 volt : 8 cylinder port injection
> 1 to 2.5 volts : 6 cylinder port injection
> 2.5 to 4 volts : 4 cylinder port injection
> 4 to 5 volts : throttle body injection (any cylinder count)
looks like you are in 4 cylinder port mode right now, may be why you are seeing injector events happening at the same time? Might want to try putting like a 10K resistor to those pins(to +5v), and measuring the voltage with the key on, no engine running. there was some other info too:
"quote"
>The '727 I tested this on defaulted to "4 cylinder port" when pin 11 was
> not driven (no MEMCAL).
>
> The CPU can read out the pin 11 mode selection. Code 41 will be flagged
> if it doesn't match the cylinder selection stored separately in the
> MEMCAL's EPROM.
if 10k doesn't bring the voltage up high enough, try using a 4.7K, and so on and so forth, just go lower in value slowly. Odds are, it is just a hard pull up to +5 volts in tbi mode, but a resistor is always a safe bet.
great project, glad to hear its working.
OK, dug around in some old diy stuff I collected. the voltage at those pins breaks down as follows:
"quote"
> Here's how the voltages are interpreted:
> 0 to 1 volt : 8 cylinder port injection
> 1 to 2.5 volts : 6 cylinder port injection
> 2.5 to 4 volts : 4 cylinder port injection
> 4 to 5 volts : throttle body injection (any cylinder count)
looks like you are in 4 cylinder port mode right now, may be why you are seeing injector events happening at the same time? Might want to try putting like a 10K resistor to those pins(to +5v), and measuring the voltage with the key on, no engine running. there was some other info too:
"quote"
>The '727 I tested this on defaulted to "4 cylinder port" when pin 11 was
> not driven (no MEMCAL).
>
> The CPU can read out the pin 11 mode selection. Code 41 will be flagged
> if it doesn't match the cylinder selection stored separately in the
> MEMCAL's EPROM.
if 10k doesn't bring the voltage up high enough, try using a 4.7K, and so on and so forth, just go lower in value slowly. Odds are, it is just a hard pull up to +5 volts in tbi mode, but a resistor is always a safe bet.
great project, glad to hear its working.
Bob
09-13-2004 | 11:18 PM
#16
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Joined: Mar 2004
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From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
Originally posted by jwscab
looks like you are in 4 cylinder port mode right now, may be why you are seeing injector events happening at the same time? Might want to try putting like a 10K resistor to those pins(to +5v), and measuring the voltage with the key on, no engine running. there was some other info too:
"quote"
>The '727 I tested this on defaulted to "4 cylinder port" when pin 11 was
> not driven (no MEMCAL).
>
> The CPU can read out the pin 11 mode selection. Code 41 will be flagged
> if it doesn't match the cylinder selection stored separately in the
> MEMCAL's EPROM.
looks like you are in 4 cylinder port mode right now, may be why you are seeing injector events happening at the same time? Might want to try putting like a 10K resistor to those pins(to +5v), and measuring the voltage with the key on, no engine running. there was some other info too:
"quote"
>The '727 I tested this on defaulted to "4 cylinder port" when pin 11 was
> not driven (no MEMCAL).
>
> The CPU can read out the pin 11 mode selection. Code 41 will be flagged
> if it doesn't match the cylinder selection stored separately in the
> MEMCAL's EPROM.
Your info confirms that I must be running 4cyl port mode. What's odd is I've driven about 70 miles with this config, and so far no SES codes. Oops, just checked the .bin....malfunction flag 41 is disabled by default!
Actually, when I was using the scope Sunday, I soldered on some test leads to my Moates G1 adapter so I could test different inputs to pin 11. I only have a 2 channel o-scope and I was viewing both injector pulses to see if could get the injectors to fire out of phase with each other. I tried 1v, 1.5v, 2v, and 5v(using a 10k resistor to Vcc - pin 58 on the memcal socket). No matter what, the pulses always occurred at the same time. FWIW, I noted the second injector driver controller U15 has its pin 11 "hardwired" to 5v.
With U13 pin 11 at 5v, injector pulse rate increased but I did not see them alternate. I need to test that again and also note the relationship to DRPs.
I wonder if "true" TBI mode requires not only setting U13 pin 11 to 5v, but also inverting the INJS input to U15. The schematics on Ludis' page show some some logic gates in the path of INJS.
Thanks, Brent
09-14-2004 | 12:23 PM
#17
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yeah, I knew I had that tidbit squirreled away somewhere. when I see some technical info, I usually try and archive it....
as for the injector pulses, it might be that the code also needs to reflect that its in tbi mode(I forget if you mentioned if you changed any code parameters), which would possibly change the signal routing due to that combinational logic you saw on the schematic.
so, in other words, you've altered hardware, but the firmware may need to change also to make the injector controls change function completely.
as for the injector pulses, it might be that the code also needs to reflect that its in tbi mode(I forget if you mentioned if you changed any code parameters), which would possibly change the signal routing due to that combinational logic you saw on the schematic.
so, in other words, you've altered hardware, but the firmware may need to change also to make the injector controls change function completely.
09-14-2004 | 12:41 PM
#18
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From: In reality
Car: An Ol Buick
Engine: Vsick
Transmission: Janis Tranny Yank Converter
Originally posted by Dominic Sorresso
Bruce,
Isn't Synch Mode on a Xfire alternating pulses?
Bruce,
Isn't Synch Mode on a Xfire alternating pulses?
09-14-2004 | 02:12 PM
#19
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From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
Originally posted by Dominic Sorresso
Brent,
Any chance you could provide the pin-out scheme you have used? I am in the midst of trying to do the 7747 > 7749 conversion right now.
Brent,
Any chance you could provide the pin-out scheme you have used? I am in the midst of trying to do the 7747 > 7749 conversion right now.
Here's my pinout:
Code:
747 Harness 749 ECM
------------------------------- --------------------------------------
A1 (Fuel Pump Relay) A11
A2 (Not Used)
A3 (Not Used)
A4 (EGR Cntl) E9
A5 (SES lamp) E7
A6 (IGN/ECM +12v) A6
A7 (TCC solenoid/A4) F4
A8 (ALDL Serial Diag) A9
A9 (ALDL Diag Term) E12
A10 (VSS {buffered}) C6
A11 (MAP Sensor GND) B6
A12 (Sys. GND) A12
B1 (BATT +12V) B1
B2 (Fuel Pump Signal) E13
B3 (EST Ref Low) D9
B4 (Not Used)
B5 (EST Ref High) D8
B6 (Not Used)
B7 (ESC Signal) F9 (req ESC jumper between pins C & D)
B8 (A/C Signal) C9
B9 (Not Used)
B10 (Park/Neutral Sw Signal) D16
B11 (Not Used)
B12 (Not Used)
C1 (Not Used)
C2 (AIR Valve - Converter) not required
"C3 (IAC ""B"" Low)" E5
"C4 (IAC ""B"" Hi)" E6
"C5 (IAC ""A"" Hi)" E4
"C6 (IAC ""A"" Low)" E3
C7 (4th gear switch) D14
C8 (Not Used)
C9 (Crank Signal) not required
C10 (CTS Signal) E16
C11 (MAP Signal) F15
C12 (Not Used)
C13 (TPS Signal) F13
C14 (MAP/TPS +5v ref.) A5
C15 (Not Used)
C16 (Battery) C16
D1 (Sys GND) D1
D2 (CTS/TPS Sensor GND) B5(also for new MAT sensor GND)
D3 (Not Used)
D4 (EST Ctrl) C8
D5 (EST Bypass) C7
D6 (O2 GND) E15
D7 (O2 Signal) E14
D8 (Not Used)
D9 (Not Used)
D10 (Not Used)
D11 (Not Used)
D12 (Not Used)
D13 (Not Used)
D14 (Injector B) C11
D15 (Not Used)
D16 (Injector A) C10
Add MAT sensor - signal connection to F16
MAT ground to B5
Add injector jumpers: C13 to C15
D5 to D6 Oh, I'm not running EGR, so I did not implement the EGR connections shown in the list. I reused the EGR wiring for the new MAT sensor.
Hope this helps.....Brent
10-01-2004 | 06:16 PM
#21
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From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
Originally posted by Dominic Sorresso
Brent,
Any further update on this?
Brent,
Any further update on this?
I've been struggling with knock...at idle and any load condition. I didn't have this with the 747, so I know it's related to the swap. I was comparing $42 & $58 fueling parameters(injector & AE constants/tables) and noticed many similarities. So I decided to replicate all the $42 TBI injector & AE settings in the $58 code. I also migrated my VE tables from my last $42 chip. This has eliminated knock counts at idle, but it's still running too rich and VE settings are WAY off....BLMs are very low 105 to 115. As my min BLM is set to 105, I think some areas are much lower.
I desperately need to fix the VE tables, but my logged MAP values are way off. The BARO value looks right but ALDL MAP kPa is about half of what I'd expect. When my boost/vac gauge shows 0, equal to atmospheric pressure, I'm logging a MAP reading of ~42kPa. At cruise on a level highway, it's showing 21-23kPa. It looks like the MAP value reported has scaled the 2-bar voltage to a 1-bar kPa value. I'm going to try having ALDL report on memory location 0x003E which is commented in $60 as "SD map, 20 - 200 Kpa".
I also found that I need to adjust the BLM kPa learn thresholds as they track the "lower" ALDL reported kPa values. I'm not sure how important this is as I read $58 only uses 2 BLM cells????
It's been frustrating at times, but I'm learning a lot in the process. Once I get these basics under control, I'm going to port over to $60 code.
10-01-2004 | 11:11 PM
#22
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From: SE Michigan
Car: 81 Turbo Trans Am
Engine: 301 T
Transmission: 200-4R
Originally posted by 89C2500
The BARO value looks right but ALDL MAP kPa is about half of what I'd expect. When my boost/vac gauge shows 0, equal to atmospheric pressure, I'm logging a MAP reading of ~42kPa. At cruise on a level highway, it's showing 21-23kPa. It looks like the MAP value reported has scaled the 2-bar voltage to a 1-bar kPa value. I'm going to try having ALDL report on memory location 0x003E which is commented in $60 as "SD map, 20 - 200 Kpa".
The BARO value looks right but ALDL MAP kPa is about half of what I'd expect. When my boost/vac gauge shows 0, equal to atmospheric pressure, I'm logging a MAP reading of ~42kPa. At cruise on a level highway, it's showing 21-23kPa. It looks like the MAP value reported has scaled the 2-bar voltage to a 1-bar kPa value. I'm going to try having ALDL report on memory location 0x003E which is commented in $60 as "SD map, 20 - 200 Kpa".
I'm not sure how important this is as I read $58 only uses 2 BLM cells????
10-07-2004 | 04:46 PM
#24
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From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
Knock issues solved....finally! I wasn't having much luck "tuning" out the knock so I went back to basics. Pulled the 3.9k sensor I installed with the 749 swap and replaced it with the original 100k sensor & a 3.8k bias resistor. BINGO...no more false knock.
For the 3.9k knock sensor I used a GM#10456126 (ACDelco 213-92) which is listed for 90-92 5.7l F on ACDelco's parts database. Maybe this was the incorrect part or I received a defective part???? Either way, the old sensor/bias resistor solved the problem.
Now I can get back to tuning the VE tables & solving a lean tip-in problem.
Brief (sort of) list of changes up to this point:
For the 3.9k knock sensor I used a GM#10456126 (ACDelco 213-92) which is listed for 90-92 5.7l F on ACDelco's parts database. Maybe this was the incorrect part or I received a defective part???? Either way, the old sensor/bias resistor solved the problem.
Now I can get back to tuning the VE tables & solving a lean tip-in problem.
Brief (sort of) list of changes up to this point:
Code:
Fuel Delivery: - remove FMU - set fuel pressure to 14psi. Constants: - change KNUMCYL from 6 to 8 - change KREFANGL to 8.1 from 0.0 to match base timing - change KEGRTEM1 to 150.5 from 59.8 Deg. C (disable EGR) - changed KLCLDLO to 20kPa from 50kPa (allow BLM learn in lower kPa ranges) - change KAPLH to .793 from 1.068 to match $42 value - change KAPLL to .504 from .793 to match $42 value - change KAPMAX to 11.993 from 5.997 to match $42 value - change KAPMIN to .504 from .793 to match $42 value - change KMAXADV2 to 41.84 from 46.76 to match $42 value - change KDISFS to 5.8 from 4.9 (assumes TBI 70pph feeds eqiv 2 cyls firing once per 2 ref pulses vs. TPI 30pph feeding 1 cyl firing once per 4 ref pulses) - change KLCTCLL to 65 from 80 Deg. C - change KLCESTHU to 3600 from 3200 RPM - disable KKMASK2_M32 Malfunction Flag 32 - disable KKMASK2_M31 Malfunction Flag 31 - change KRSHNTHK to 55.0 from 32.0 MPH - change KRSHNTLK to 50.0 from 30.0 MPH Tables: - change F28 to .082 (from .089) which corresponds to BPC=120 (for injectors running at 70pph) - change F4 to all zeros & change KEGRBIAS to 0 (remove EGR SA) - change F80 to all zeros (remove all PE SA) - change F92 entries to .397 from std values to match $42 Injector Bias value NOTE:**changed to .793 ($1A) same hex value at $42 code entries** - change F33 to match $42 "Volt Comp vs. Batt Volt" table - change F21 to match $42 "AE vs. Diff. MAP" table - change F22 to match $42 "AE vs. Diff. TPS" table - change KAEISCN to .244 from 0 to match $42 value - change F37 to match $42 "AE vs. Coolant" table - change F38 to match $42 "AE vs. RPM" table - change F30 reduce all entries by 25%
10-08-2004 | 05:08 PM
#25
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Joined: Mar 2004
Posts: 66
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From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
Originally posted by 1981TTA
I just put together a test bench and noticed a similar "problem" with MAP values. For example, when I have the MAP voltage set to 2.5v, I expect a value of MAP of ~101kPa. The value in $003E/$003F is ~0x81. (Which would seem like a "good" value for 2.5v.) But, using the MAP conversion in the ALDL, (kPa = N*0.369 + 28), I get ~75kPa. This value max's out at ~122kPa with a 4.6v input. I'm still investigating the problem. But, I wanted to mention this since you're seeing something similar... I wonder if anyone else running $58/$60 has seen this too???
I just put together a test bench and noticed a similar "problem" with MAP values. For example, when I have the MAP voltage set to 2.5v, I expect a value of MAP of ~101kPa. The value in $003E/$003F is ~0x81. (Which would seem like a "good" value for 2.5v.) But, using the MAP conversion in the ALDL, (kPa = N*0.369 + 28), I get ~75kPa. This value max's out at ~122kPa with a 4.6v input. I'm still investigating the problem. But, I wanted to mention this since you're seeing something similar... I wonder if anyone else running $58/$60 has seen this too???
Using the above formula with your example, the MAP reading would be ~58kPa. If the value in $003E/$003F was 0xFF, then the calculated MAP reading would be ~104 kPa which is max for a 1-bar MAP.
Now, what about a 2-bar MAP reading....
I found the following equations in the archive found at http://www.diy-efi.org/gmecm/ecm_info/1227749/749.txt
MAP1volts out = Vref(.01059*[Kpa] - .10941)
MAP2volts out = Vref (.00500*[Kpa] - .04000)
Also, the AYBN hac lists the following info for ALDL byte 30:
Code:
;-------------------------------------- LC7AA FCB $0039 ; 30 MAP, n/51 VDC ;--------------------------------------
n/51=5.0(.00500*[kPa] - .04000)
Solve for kPa and we get:
kPa=.78431*n + 8
Using this new equation for a 2-bar MAP, if we try a max value for "n" of 0xFF, the calculated MAP reading would be 208kPa. If we use your register scan value of 0x81, the calculated MAP value would be 109kPa. The "MAP2volts" formula from the archives indicates that the MAP output voltage at sea level (101.3kPa) would be ~2.33v so at 2.5v a slightly higher kPa than 101 would be expected.
Please let me know if I'm on the right track here.
10-10-2004 | 09:10 PM
#26
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Joined: May 2004
Posts: 289
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From: SE Michigan
Car: 81 Turbo Trans Am
Engine: 301 T
Transmission: 200-4R
89C2500,
I think you've nailed it! I found another transfer function for a GM 2-bar MAP sensor that's approximately 0.1 to 0.3 volts offset from the equation you listed below. Since I don't know the specific sensors that each equation was meant to fit, I wouldn't be surprised if the difference is simply a function of sensor-to-sensor (or voltmeter-to-voltmeter) variance.
This all started (for me) from trying to sync the ALDL MAP reading with the results of the main spark table on an ECM bench. I'd change the calibration so that spark would only change with MAP. All the columns of RPM were kept constant. I noticed that the results of the table vs. the reported MAP were off by about 5 kPa. While not the end of the world, I can see this causing a lot of confusion during the process of tuning. I think this is similar to what you were describing in an earlier post......
Thanks for your help!!
I think you've nailed it! I found another transfer function for a GM 2-bar MAP sensor that's approximately 0.1 to 0.3 volts offset from the equation you listed below. Since I don't know the specific sensors that each equation was meant to fit, I wouldn't be surprised if the difference is simply a function of sensor-to-sensor (or voltmeter-to-voltmeter) variance.
This all started (for me) from trying to sync the ALDL MAP reading with the results of the main spark table on an ECM bench. I'd change the calibration so that spark would only change with MAP. All the columns of RPM were kept constant. I noticed that the results of the table vs. the reported MAP were off by about 5 kPa. While not the end of the world, I can see this causing a lot of confusion during the process of tuning. I think this is similar to what you were describing in an earlier post......
Thanks for your help!!
10-21-2004 | 01:59 PM
#27
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Joined: Mar 2004
Posts: 66
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From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
I got the non-PE tuning pretty close and started in on WOT stuff. I found that the injector pulse widths exceeded the time available at higher RPMs and the AFR was leaning out. Logs showed 10-12ms p.w. at 4k rpm. At that rpm, there would only be 7.5ms available between injector pulses. Ok...now what???
Well, back to testing "TBI mode", that's what!
A while ago I wired up a toggle switch to connect CAL56 to 5vdc (TBI mode) thru a 10k pull-up resistor. So, I burned a chip with a 50% reduction in VE and toggle on TBI-mode. Inj. p.w. are WAY down...logged 5.0ms @ 4400rpm this morning. So "assuming" TBI-mode is firing the injectors twice per crank rev, then the pulse widths are not exceeding the time available.
I'm gonna ask Santa for an ecm test bench!
WOT issues aside, the truck's running very well. My wife & I took a 300 mile Sunday drive a couple of weeks ago. 80+mph on the interstate and a mountain road drive over a 10,000' pass......17.7 miles per gallon. Not bad for a blown sbc in a 3/4 ton pickup!
Well, back to testing "TBI mode", that's what!
A while ago I wired up a toggle switch to connect CAL56 to 5vdc (TBI mode) thru a 10k pull-up resistor. So, I burned a chip with a 50% reduction in VE and toggle on TBI-mode. Inj. p.w. are WAY down...logged 5.0ms @ 4400rpm this morning. So "assuming" TBI-mode is firing the injectors twice per crank rev, then the pulse widths are not exceeding the time available.
I'm gonna ask Santa for an ecm test bench!
WOT issues aside, the truck's running very well. My wife & I took a 300 mile Sunday drive a couple of weeks ago. 80+mph on the interstate and a mountain road drive over a 10,000' pass......17.7 miles per gallon. Not bad for a blown sbc in a 3/4 ton pickup!
10-21-2004 | 02:25 PM
#28
Senior Member
Joined: Oct 1999
Posts: 6,621
Likes: 2
Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
So let me get something straight. You've gotten it to fire the TBI injectors twice per engine revolution but they fire at the same time right? Where as in all of GM's TBI fireing strategies (that have 2 injectors) they alternate fire while in sync mode.
If this is the case, why not just go with a 94-95 TBI computer that'll have all the advantages of a fully documented hack, pcm controls, fast aldl, and true TBI firing strategies?
If this is the case, why not just go with a 94-95 TBI computer that'll have all the advantages of a fully documented hack, pcm controls, fast aldl, and true TBI firing strategies?
10-21-2004 | 04:53 PM
#29
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Joined: Mar 2004
Posts: 66
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From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
Originally posted by JPrevost
So let me get something straight. You've gotten it to fire the TBI injectors twice per engine revolution but they fire at the same time right? Where as in all of GM's TBI fireing strategies (that have 2 injectors) they alternate fire while in sync mode.
So let me get something straight. You've gotten it to fire the TBI injectors twice per engine revolution but they fire at the same time right? Where as in all of GM's TBI fireing strategies (that have 2 injectors) they alternate fire while in sync mode.
Is it possible to properly verify injector timing without simulating load conditions using an ecm bench?
If this is the case, why not just go with a 94-95 TBI computer that'll have all the advantages of a fully documented hack, pcm controls, fast aldl, and true TBI firing strategies?
Last edited by 89C2500; 10-21-2004 at 05:23 PM.
10-21-2004 | 05:59 PM
#31
Senior Member
Joined: Oct 1999
Posts: 6,621
Likes: 2
Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
Forgot you were running with your own atmosphere, lol. Probably better of with the 7749 . Although with the hack and high resolution tables you could run a 2 bar map and just shift the tables like we used to do with the 730.
The only thing I don't like is the firing both injectors at the same time like in async. I never liked the way TBI ran in all async mode and I'd rather not experiment just yet.
. Although with the hack and high resolution tables you could run a 2 bar map and just shift the tables like we used to do with the 730.The only thing I don't like is the firing both injectors at the same time like in async. I never liked the way TBI ran in all async mode and I'd rather not experiment just yet.
10-21-2004 | 09:10 PM
#32
Supreme Member
Joined: Dec 2001
Posts: 1,996
Likes: 11
From: Bartlett, IL
Car: 92 ZR-1
Engine: LT-5
Transmission: ZF-6
Axle/Gears: SuperDana 44 4.10
Jon,
Are you saying that if you're not using boosted inducton, you wouldn't use a 7749? I can tell you asynch is for the birds.
Are you saying that if you're not using boosted inducton, you wouldn't use a 7749? I can tell you asynch is for the birds.
10-21-2004 | 09:15 PM
#33
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Joined: Feb 2000
Posts: 1,416
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From: Johnstown, Ohio
Car: 84 Z28
Engine: 355 (fastburn heads, LT4 HOT cam)
Transmission: 700R4
Axle/Gears: 9-bolt, 3.27
Originally posted by Dominic Sorresso
Jon,
Are you saying that if you're not using boosted inducton, you wouldn't use a 7749? I can tell you asynch is for the birds.
Jon,
Are you saying that if you're not using boosted inducton, you wouldn't use a 7749? I can tell you asynch is for the birds.
The only reason I would right now, is because I'm going to be running $8D or $58 when I get my car injected, and I have a TBI application that I can use to get familiar with the mask.....
10-21-2004 | 09:53 PM
#34
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Joined: Oct 1999
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Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
Boosted = 7749, everything else I'd look do a pro/con chart. The 8746 and 7747 have there own little issues and the p4's have some of there own. If I didn't have lockers you can bet I'd be running a 94-95 truck pcm for the faster aldl and it's got a commented hack. Not to mention it has trans control code if you ever want it.
I wish I had more time because I'd like to try out those truck pcms on my car so I could either condone or dismiss there usage on an f/y-body TBI. I'm just hoping somebody else will do it and let me make suggestions.
I wish I had more time because I'd like to try out those truck pcms on my car so I could either condone or dismiss there usage on an f/y-body TBI. I'm just hoping somebody else will do it and let me make suggestions.
10-22-2004 | 08:36 AM
#35
Supreme Member
Joined: Dec 2001
Posts: 1,996
Likes: 11
From: Bartlett, IL
Car: 92 ZR-1
Engine: LT-5
Transmission: ZF-6
Axle/Gears: SuperDana 44 4.10
Jon,
Well I have been following the threads regarding the adaptation of the 7749 to a TBI motor. 89 has done yeoman's work for a number of us. As you know I have been having my own issues with the 7747. The ideal '47 would have hi speed ALDL with greater granularity and more extended VE tables. Guess we'll wait for the Speedreader. I use EASE as my scantool and with the purchase of a PIV Micron, lost the use of serial ports. EASE has a USB adapter for their cable, BUT I don't have USB 2.0 controller, SO, now my scan rate has been reduced further by about 35%. DOH!
Well I have been following the threads regarding the adaptation of the 7749 to a TBI motor. 89 has done yeoman's work for a number of us. As you know I have been having my own issues with the 7747. The ideal '47 would have hi speed ALDL with greater granularity and more extended VE tables. Guess we'll wait for the Speedreader. I use EASE as my scantool and with the purchase of a PIV Micron, lost the use of serial ports. EASE has a USB adapter for their cable, BUT I don't have USB 2.0 controller, SO, now my scan rate has been reduced further by about 35%. DOH!
11-03-2004 | 09:27 AM
#38
Senior Member
Joined: Oct 1999
Posts: 6,621
Likes: 2
Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
Originally posted by contactpatch
Why is 'TPI' mode, different than "TBI mode, with the
injector drive wires hooked in parallel'?
Why is 'TPI' mode, different than "TBI mode, with the
injector drive wires hooked in parallel'?
11-03-2004 | 11:26 AM
#39
Supreme Member
iTrader: (2)
Joined: Jan 2002
Posts: 9,962
Likes: 3
From: Moorestown, NJ
Car: 88 Camaro SC
Engine: SFI'd 350
Transmission: TKO 500
Axle/Gears: 9-bolt w/ 3.23's
Not only that but only one injector fires each time teh ecm recieves a reference pulse with them alternating back and forth. This keeps the manifold topped off with fuel.
11-03-2004 | 11:34 AM
#40
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Joined: Jan 2002
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From: Moorestown, NJ
Car: 88 Camaro SC
Engine: SFI'd 350
Transmission: TKO 500
Axle/Gears: 9-bolt w/ 3.23's
Originally posted by JPrevost
Boosted = 7749, everything else I'd look do a pro/con chart. The 8746 and 7747 have there own little issues and the p4's have some of there own. If I didn't have lockers you can bet I'd be running a 94-95 truck pcm for the faster aldl and it's got a commented hack. Not to mention it has trans control code if you ever want it.
I wish I had more time because I'd like to try out those truck pcms on my car so I could either condone or dismiss there usage on an f/y-body TBI. I'm just hoping somebody else will do it and let me make suggestions.
Boosted = 7749, everything else I'd look do a pro/con chart. The 8746 and 7747 have there own little issues and the p4's have some of there own. If I didn't have lockers you can bet I'd be running a 94-95 truck pcm for the faster aldl and it's got a commented hack. Not to mention it has trans control code if you ever want it.
I wish I had more time because I'd like to try out those truck pcms on my car so I could either condone or dismiss there usage on an f/y-body TBI. I'm just hoping somebody else will do it and let me make suggestions.
11-03-2004 | 12:56 PM
#41
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Joined: Oct 1999
Posts: 6,621
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Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
Originally posted by dimented24x7
The tbi ecms definatly have teh ease of use as a pro. I jsut about know my $4D inside and out by now which is a huge help when writing new code and tieing things together. Now, if only the hardware didnt suck so bad. Slow stock ALDL, slow cpu, and nowhere near enough inputs and outputs. *** forbid if I ever have to be 100% smog compliant. Wont have any outputs that are free to use.
The tbi ecms definatly have teh ease of use as a pro. I jsut about know my $4D inside and out by now which is a huge help when writing new code and tieing things together. Now, if only the hardware didnt suck so bad. Slow stock ALDL, slow cpu, and nowhere near enough inputs and outputs. *** forbid if I ever have to be 100% smog compliant. Wont have any outputs that are free to use.
The slow ALDL is the biggest hang-up. I was talking to RBob and he thinks it might not be that hard to modify a p4 to fire injectors like a TBI. My other idea was to take the injector driver circuit off of the c3 and hook the "pulse width signal" (I dont' know what or where it is) from the p4 into the c3. Then again why can't the p4 just be programmed to fire the injectors alternately and twice a revolution (half the pulse width)?
Or why not go with the $0D mask, it's TBI, memcal (all code on chip), and if you ever needed a "e" trans control you'd have it. That's got a lot more outs and ins, makes it worth a try. I figure if they were able to get the 7747 to run EFI in cars with those crumby adder tables and only 12k or memory then I'm sure the $0D mask ecms could be setup to work evey better.
And dim I'm sure you're waiting for the speedreader. I hope that comes out soon.
11-08-2004 | 06:28 AM
#43
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Joined: Jun 2000
Posts: 7,554
Likes: 1
From: In reality
Car: An Ol Buick
Engine: Vsick
Transmission: Janis Tranny Yank Converter
Originally posted by dimented24x7
Not only that but only one injector fires each time teh ecm recieves a reference pulse with them alternating back and forth. This keeps the manifold topped off with fuel.
Not only that but only one injector fires each time teh ecm recieves a reference pulse with them alternating back and forth. This keeps the manifold topped off with fuel.
11-10-2004 | 03:04 PM
#44
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Joined: Mar 2004
Posts: 66
Likes: 0
From: Monument, Colorado
Car: 89 C2500
Engine: ZZ838, MPFI, Whipple, & 7749 ECU
Transmission: 700R4
Axle/Gears: 4.10
Originally posted by 89C2500
Also, the scope work I did earlier was at idle, with some revs to 2k, while in park/neutral. Now I'm not sure if I was in sync mode, or the ecm was in async due the smaller pw required at no load conditions?? I believe this really needs to be tested & verified on a bench.
Also, the scope work I did earlier was at idle, with some revs to 2k, while in park/neutral. Now I'm not sure if I was in sync mode, or the ecm was in async due the smaller pw required at no load conditions?? I believe this really needs to be tested & verified on a bench.
With the 4500 pound test bench fired up, I checked synchronous injector firing in TBI-mode....HOLY COW....both injectors fire on EVERY DRP! Well, at least this explains why I had to set my VE table values so low.
I also verified sync injector firing in 4-cyl port mode (two firings per revolution). Same as earlier, both injector fire on the same DRP....not alternating. I messed around with the hardware some, but could not find the combo to alternate injector pulses.
Honestly, I believe you can successfully run TBI off a 749 without having the alternating injector firing pattern. I haven't noticed any issues....but I am FAR from an expert. I'm back to using "4cyl port mode", as TBI-mode as resulted in some very small pulse widths at idle and cruise.
My apologies for incorrectly stating I had tbi-mode working properly. I need to test a little longer before posting.
Thanks to all the real experts here at TGO and diy-efi.org! The knowledge that has been shared is invaluable!
Last edited by 89C2500; 11-10-2004 at 03:06 PM.
11-10-2004 | 03:22 PM
#45
Senior Member
Joined: Oct 1999
Posts: 6,621
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Car: 91 Red Sled
Axle/Gears: 10bolt Richmond 3.73 Torsen
Still good info. If it works good it works good, even if they do fire together. It shouldn't make any bit of difference if it's on a dual plane intake but with a single plane you might want to keep the alternating.
It's funny that you're trying to get a p4 to control TBI while I'm over here working on getting a c3 to control PFI . I think I'm stuck with hardware mofications to get the ecm to fire every other drop. I need to spend some time looking into it. Either way I've got more important things to do right now like getting my romless c3 working. Then I can be all ready for playing with the test bench and not my car (car doesn't like winter too much).
It's funny that you're trying to get a p4 to control TBI while I'm over here working on getting a c3 to control PFI
. I think I'm stuck with hardware mofications to get the ecm to fire every other drop. I need to spend some time looking into it. Either way I've got more important things to do right now like getting my romless c3 working. Then I can be all ready for playing with the test bench and not my car (car doesn't like winter too much).
11-10-2004 | 03:35 PM
#46
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Joined: Dec 2001
Posts: 1,996
Likes: 11
From: Bartlett, IL
Car: 92 ZR-1
Engine: LT-5
Transmission: ZF-6
Axle/Gears: SuperDana 44 4.10
Originally posted by 89C2500
... Honestly, I believe you can successfully run TBI off a 749 without having the alternating injector firing pattern. I haven't noticed any issues....but I am FAR from an expert.
... Honestly, I believe you can successfully run TBI off a 749 without having the alternating injector firing pattern. I haven't noticed any issues....but I am FAR from an expert.
Perhaps that would be the case with a single plenum manifold. Not so sure that with a Xfire type manifold simultaneous firing of injectors would be very useful. Regardless, thanks for all your pioneering work.
11-15-2004 | 04:08 PM
#47
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Joined: Sep 2003
Posts: 1,409
Likes: 1
From: Texas
As far as using a 730 for tbi, the 8D has a doubler for the PW IIRC in the code. And there is something for DRP's too, can't remember. Somebody has an assembled aujp IIRC. On Craigs site? Just need to replace the double code line with a nonop command. Can't remember the correct term. There are 2 or so of them. One pauses for a clock cycle IIRC. I'm sure somebody beside RBob can figure it out.
Been too busy to work on anything car related for the last 3 months. 2nd son should be here next month so I'll have the 3yo most of the time. He made it to the "what u doin daddy" stage last Saturday. Didn't help my concentration any....especially after the 10th repetition or so.
Been too busy to work on anything car related for the last 3 months. 2nd son should be here next month so I'll have the 3yo most of the time. He made it to the "what u doin daddy" stage last Saturday. Didn't help my concentration any....especially after the 10th repetition or so.
11-15-2004 | 05:35 PM
#48
Supreme Member
Joined: Jun 2000
Posts: 7,554
Likes: 1
From: In reality
Car: An Ol Buick
Engine: Vsick
Transmission: Janis Tranny Yank Converter
Originally posted by Z69
....especially after the 10th repetition or so.
....especially after the 10th repetition or so.
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