I've just purchased myself a 7747 ECU...without a PROM chip (or that little one, whatever its called). I've got two questions. 1)Where can I find a good .BIN file for a V8 (305 or 350) automatic to get started in the tuning process. 2)Where do I need to get the little chip, or do I really need it? I've got the little chips out of my 8063 ECUs, they won't work will they?

-Mark W.
<A HREF="http://www.angelfire.com/al3/thegreycar">'88 SC Camaro w/ 305 TBI</A>

 

Another question, I just started it with a random chip I downloaded. It started and ran real rich...Tried to check the scanner to see what the O2 sensor was reading and it wouldn't scan "Vehicle not Responding". What do I need to configure my scanner to, is it PROM dependent rather than ECU dependent?

-Mark W.
<A HREF="http://www.angelfire.com/al3/thegreycar">'88 SC Camaro w/ 305 TBI</A>

 

There are bunch of bins at ftp://ftp.diy-efi.org/pub/gmecm/ . A dealer will have the little chip (the limp home calibration). Get one as close your app as possible.

You will have to scan using the vehicle the prom came from. Your car is now a truck.

 

you need that little chip, its called the cal pack, get it from the dealer it cost me something like 15 or 20 dollars, just ask the parts counter guy for a calpack for a 92 chevy truck with the 7747 ecm and a 305 or 350

also
when you scan you need to use the engine code from a truck.

Is your SES light on while its idling rich? or flashing rapidly?

If not, what injectors do you have? and what is the rest of your combo

 

there is a very important setting called BPW or base pulse width, its the result of this equation
TBI:
; Val = 1461.5 * (VOL/RATE)
; VOL = Vol of 1 Cylinder in liters, (0.7125l)
; RATE = Injector flow in gms/sec
: 5.7l = 7.71 gms/sec (61.2#/HR)
; (VOL/RATE) = 0.0924 l/gm/sec
; LD2B4: BPW = 135

Definately important to get you started, youll also need to know the injector flow vs pressure formula incase you have increased the pressure from a stock setting of 10 psi on GM tbi injectors or 15 psi on the chrysler injectors Holley TBI units use (those are the pressures they are rated at)



Fn = New Injector Flow Rate, ml/min
Fo = Original Injector FLow Rate, ml/min
Pn = New Baseline Fuel System (rail) Pressure, psi
Po = Original Baseline Fuel System (rail) Pressure, psi
Once you get BPW nailed you need to start tuning the VE of the main table

Pablo

 

I think I discovered the problem. The .BIN files are not being written to the PROM. You can load a file, move it to the PROM, and when you verify it, all FFs (blank). I need some help, if anyone has used this PROM writer...help me.

-Mark W.
<A HREF="http://www.angelfire.com/al3/thegreycar">'88 SC Camaro w/ 305 TBI</A>

 

Guess it helps to tell you what PROM writer I'm using doesn't it? It's the Pocket Programmer, I've got the their eraser as well that I've used to wipe the PROMs clean. TRAXION, you use this don't you? Any help would be appreciated.

-Mark W.
<A HREF="http://www.angelfire.com/al3/thegreycar">'88 SC Camaro w/ 305 TBI</A>

 

I've had some difficulties with the pocket programmer, but it was associated with the 'Cypress Semiconductor' 27C128 chips I was using. Very fast (70ns), but they were like backwards or something, inverted bit defaults, so that blank was 'FF'. Used the AM27C128's @ 150 & 155ns without problem though. Maybe irrelevant to your case, but worth offering up.

 

Mark,

I ran into a similar problem when I started burning chips with the PP. But, it had nothing to do with the PP and everything to do with the EPROM I was trying to use. It was toast. After trying a new EPROM everything worked great.

Can your read PROMs OK? After reading to they verify to buffer OK?

Are you using Fileprom or eprom?

Is the PP plugged in and is the power cord functioning?

Have you tried a different computer?

Are you inserting the EPROMs into the programmer correctly? Pin 1 has to go into a particular slot on the programmer.

How long does it take to fully program the EPROM?

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Yes, it will read the PROMs just fine (I've never verified, though)

I've used the FILEPROM and EPROM programs and neither one would write to the chip. The FILEPROM returns an error when it tries to write, EPROM seems to think that it's writted ok, but upon verification...FF.

It's plugged it, as far as I know it functional.

I've tried it on two different computers, a 600 MHz PIII and a 200 MHz P(I or II). Not only that, I've gone into CMOS and set-up the LPT1 port on every available setting on both the computers.

I'm putting the chips in with the notch facing up (the power cord side) all the way down in the slots.

It takes just a few seconds on either of the computers to program the chips...

I've ordered some more chips, in case these are somehow bad (maybe ruined in the process of removal from their plastic carriers). They should be here tomorrow or Tuesday maybe. I'm gonna call the company tomorrow and see if they can provide any useful insight. Thanks for your help.

-Mark W.
<A HREF="http://www.angelfire.com/al3/thegreycar">'88 SC Camaro w/ 305 TBI</A>

 

Mark,

A few seconds to program the entire chip?? You mean like 1 - 2 - 3 - and it is done?! If so, then that is most likely the problem.

Once you are in the PP type '88' to access the special menu. Type '6' to access the programming pulse. INCREASE your programming pulse. The chip should take anywhere from 20 seconds for NEW TECHNOLOGY chips to a couple minutes for the older chips.

Not having enough pulse time means that the PP will not pulse each memory location enough to move the bit from 0 to 1. If your chip is still blank then I would suspect that you may not have enough pulse time. Increase your pulse until it takes you about 2 minutes to program the chip. Then try it

Let me know if this works for you!

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

I increased the pulse timing to max, FILEPROM doesn't even start to program the chip (or it doesn't get very far into it) before it returns an error. EPROM still only takes about 20-30sec. at full pulse timing, and they're still blank. Only thing is, I checked this morning before class and I didn't have time to check and see what the LPT1 CMOS setting was. When I get home in a few hours, I'm gonna call 'em and see what they say.

-Mark W.
<A HREF="http://www.angelfire.com/al3/thegreycar">'88 sC Camaro w/ 305 TBI</A>

 

Mark,

Something is wierd because if I increase the pulse to a high pulse time (i.e. > 20) then the programming takes longer and longer. If I set it REALLY high the EPROM will take MANY minutes to program. Wierd - very wierd. Which EPROM do you have selected? Also - post the options listed at the top after entering the special menu (option '88').

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

I called 'em this afternoon when I got home from class. I described the problem to them and they decided that it was a bad programmer. Said something about a batch that had bad "caps?" and that I must have gotten one of those. Had me UPS it back to 'em. So, I'll be waiting for a new programmer for the next couple of days. BTW, you wouldn't know how to tell what kind of car an ECU came out of would you, without the PROM or the little chip (mem-cal?)?

-Mark W.
<A HREF="http://www.angelfire.com/al3/thegreycar">'88 SC Camaro w/ 305 TBI</A>

 

Sorry Mark ... determining the type of ECU is one thing but determining the actual car it came out of without having the PROM is practically impossible without the sticker on the ECM

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.587 @ 107.97mph (1.710 60ftr) on the long runner setup.
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels. Stock Wheels. No Weight Reduction.
Gunning for NA 11's with the MiniRam II and Hooker LT Headers.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Damnit...
I guess that leaves trial-and-error...

-Mark W.
<A HREF="http://www.angelfire.com/al3/thegreycar">'88 SC Camaro w/ 305 TBI</A>

 

Mark, I don't think you should worry. A 1227747 is a 1227747. The only differing factors are the prom and the cal-pack. All you need is a prom .bin and cal pak from a similar engine. This page should get you a bin that is close, http://www.diy-efi.org/gmecm/ecm_info/1227747/

You will probably have to change the BPW to adjust for your injectors, as trucks ran a 55lbs/hr unit. Tune from there......

 

I'm not worried about the PROM work, I've got a scanner that I can't get to work because the scanner won't see the computer.

-Mark W.
<A HREF="http://www.angelfire.com/al3/thegreycar">'88 SC Camaro w/ 305 TBI</A>

 

HMMM. I wonder where the scan tool gets that data from... the calpak maybe?

 

Scan tool reads the data stream as the computer is working. Doesn't "get" it from the chip... Just "reads" the data, ie, TPS, RPM, MAP, spark, spark knock... etc. Basically, you are watching the computer program run...

 

Regarding the bpw calculations from Pablo...

First, what units is the bpw in, usec? If I used the value I calculated my motor would be extremely over-fueled unless I move the decimal place to the left one digit. In other words I have values that are working fairly well at nominal operating temps of 8-10 usec, not my calculated value of 98.66.

Second, does your ecm/pcm use the bpw as a global variable that scales the calculations made from the ve tables?

My questions depend from the fact that the $0D pcm has a temperature scaled table for bpw. Presumably (according to Tunercat) this value is used for startup. Do you know how the pw algorithm generates pw from the ve tables and how the block learn cell is incorporated to quantify load on the motor?

 

To be honest I dont know what it is (along with alot of other things in the chip), I know its a scaler of some sort that will increase your fueling or decrease your fueling as a whole like say if you change your bpw by 10% it generally would be close to say that your fueling would change 10%
ive never seen a real good explanation of how it works

and to your last question, I wish i knew how that worked (the internal math of it all) it would make changes so much simpler

 

I'm sure it's safe to say that the ECU uses the BPW in all of its calculations. ie, the ECU can calculate how much fuel an engine, say a 350, would need but the last calc in the chain would be how long does the injector have to spray to get the req'd fuel. Ie, in Open loop (7747, anyway) there is no fuel map table but an Air Fuel Ratio specified. Theoretical fuel required is calculated and further transformed into pulses for injectors w/BPW...

 

Ramsey,
I think I can answer the last part.
I'll cut and paste from an earlier post.

"BLM is block Learn multiplier
It is Long term fuel trim. Values range from 0-255, 128 is perfect +/- 5 is where you want to be. The range of 0-128 and 128-255 are equal to 100% add or subtract fuel. High numbers add fuel due to a lean condition; low numbers subtract due to a rich condition.

How BLM works: One BLM value is stored in the ECM for each cell in the fuel table, and fuel is therefore modified.

How BLM is calculated:
The oxygen sensor constantly fluctuates back and forth across 450 or 500 mv (I forget which) the ECM counts these, you may notice a monitor named "cross counts" You should also notice the Sensor voltage as displayed fluctuating as I said, each of these values is added up and averaged using cross-counts... thus giving an indication of rich or lean, this value is represented as the "Integrator" or short term fuel trim again, a 0-255 monitor with 128 as the value that equates to 14.7:1 air/fuel ratio. BLM is Calculated from the Integrator.

Use BLM as your tuning aid for part throttle / idle closed loop operation. Use this value only when the integrator value is at or very near 128."

So given all that, the ECM knows what the map voltage is (manifold pressure or load) while its recording that oxygen sensor data. It saves the data in memory against the appropriate cell in the fuel table and applies the correction whenever the engine is operating in that cell on the fuel table.

 

Thanks for the primer , but the stuff I'm looking for is how the block learn cell is determined and how to modify the afr target of the block learn. In other words, what is the mathematical algorithm the pcm is using to combine input from the TPS, MAP, O2 sensor and VSS.

Further, most of the GM boxes max the BL at 105 on the leaning out side. It is possible to change the code so that BL can have a greater range of fuel trim but more commonly a tuner will change the actual AFR that 128 in the BL points towards. In other words, the BL at 128 is a state of stochiometry for the fuel and air (14.7:1). It is possible, for instance, to generate a lean cruise state which changes the afr value at 128 when the block cell is in a low load value, like 7. This is much like when the block cell reaches 15 and PE mode is enabled and the calculation of pw is pointed towards attaining the values in the wot table.

Re: the bpw, Pablo, what box are you running. The table may be using different units. My bpw is indicated in usec and my setting for std op temps (68-80*C) is around 10usec for startup. Could the 135 value possibly be 13.5usec? Its not clear to me how my 16197427 box uses the bpw. I have the bpw at startup table as well as a table of choke values that subtract from the stoich value, but it is not clear how the bpw is incorporated in the pw calculation. I think this would be a mechanism to allow manipulation of the block learn target afr. Does your box have an injector constant? That could take a similar role as your global? bpw value (135) that you mention.

 

BLM of 128 is not always stoichiometry. BLM will change based upon the ECU addition/deletion of fuel to get the exhaust gas to stoichiometry. Ideally, your VE tables are setup so that your BLM is running at 128, (no BLM correction necessary) like the factory did/tried. You cannot "change" BLM. BLM moves around based upon the richness/leanness of the engine at existing rpm/load in an existing BLM cell.

I believe ther are several BLM "cells" that the ECU uses. ECU will look at MAP and RPM values and use last BLM when you get back into that cell but BLM can still change when you are in that cell. The last BLM value that the ECU used is "stored" when you leave that BLM cell. Pablo may be able to better say what I am trying to say. Also, I bet a good programmer COULD change the AFR that the BLM signals around, ie make it a little richer/leaner, but that's what lean cruise and Power Enrichment (PE) values are for.


[This message has been edited by FastBroker (edited September 20, 2000).]

 

YES there are BLM cells, and no it doesnt assign bLM to the same cells as your main fuel table, this is why im always saying to use an O2 LED meter or DMM to get your part throttle right rather than BLM, heres how it works straight from the 1227747 Hack
(sorry it might not look right, the chart that is)
LD2AA FCB 147 ; 14.7 AFR (STOCH)
;
LD2AB FCB 8 ; Freq of blk learn update, (450 Msec)
; VAL = (N * 20)+1
_______|______|_______|______
| | |
12 | 13 | 14 | 15
_______|______|_______|______ HI MAP 80 Kpa
| | |
8 | 9 | 10 | 11
_______|______|_______|______ MID MAP 60 Kpa
| | |
4 | 5 | 6 | 7
_______|______|_______|______ LO MAP 26 Kpa
| | |
0 | 1 | 2 | 3
_______|______|_______|______
| | |
750 LO RPM ______| | |
| |
1800 MID RPM _____________| |
|
2600 HI RPM _____________________|
LD2AC: FCB 30 ; 750 RPM, BLM Cell boundry
LD2AD FCB 72 ; 1800 RPM, BLM Cell boundry
LD2AE: FCB 104 ; 2600 RPM, BLM Cell boundry
;
LD2AF: FCB 20 ; 17.7 Kpa, BLM Cell boundry
LD2B0: FCB 128 ; 57.6 Kpa, BLM Cell boundry
LD2B1: FCB 192 ; 81.2 Kpa, BLM Cell boundry
LD2B2: FCB 3 ; 75 RPM BLM cell Hyst
LB2B3: FCB 8 ; 3.3 Kpa BLM cell Hyst

 

True the BL set to 128 does not exactly mean the engine is running stoich. It actually means there is no fuel trim added or subtracted to the calculated pw the box generates based on sensor data and ve values. The BL is actually always trying to drive towards stoich even when you are in open loop or in PE. However, the box sets the integrator and by consequence also the BL to 128 when in cell 15 (PE mode) so the learn control is disabled. The box still uses the fuel trim generated by other cells when learn mode is enabled to aid in calculating how to reach the pe afr. There are 15 cells in the block learn, most likely arranged along two axes: vehicle speed and manifold vacuum. That is what the box uses to index the load the vehicle is under.

The means to change the AFR that the BL is driving towards is what I keep talking about. I guess I'm not being clear enough.
Second, there is no such thing as lean cruise (except in hacked code) on cars sold in the US. The NOx (IIRC) that is generated in a lean running state is disallowed for vehicles in the US. In Europe many vehicles do incorporate a lean cruise mode because these particular emmisions are not considered as bad as the additional wasted fuel from running at 14.7 when cruising.

 

I thought some US cars had lean cruise, oh, well.

I hear what you are saying about BLM and different AFRs. You want the Integrator/BLM to shoot for, say a 14.0:1 AFR instead of 14.7, right???

Pablo, I am going to use a scan tool to operate at an RPM and MAP, read the BLM (when it steadies) and adjust the VE table accordingly (ie BLM 140, add 9.375% [140/128]to the VE value in said table cell). Not sure what you meant about BLM and main fuel table...

[This message has been edited by FastBroker (edited September 20, 2000).]

 

ok

you know how everyone starts making changes to their main fuel map right according to what their blm says right? well thats not the best way to do it
because bLM doesnt use the same areas as the main fuel map to determine what blm its running at, it might be several boxes in the main fuel area for one cell of the blm, as you can see, it has three rpm cells, and three KPA cells
thus dividing the main fuel table by 9 cells (actually i think its 12, but the 9 cells are the juicy ones anyway the ones on the extreme ends you wont really be in anyways, and for that matter the high rpm cells you wont use either so it will be in reality 6 that you are really dealing with)

so if one of the cells in the main fuel table is extremely rich, and say its in cell 6 of the blm, that whole cell will appear rich, even if the other cells on the main table are fine thus giving you a skewed view of the whole cell (i believe it takes an average of that cell, if the one cell on the main table is rich it wil lmess up the average)


this is how I understand it


the 7747 hack is chock full of information

 

Holding steady state will change BLM to existing conditions. I think what Pablo means is that learned BLM can be made by a rich cell if that cell is the last cell operated in when just leaving a BLM cell block. When you get back to that same BLM block, BLM will be low, say, for a second but Integrator will change BLM pretty quick when in there. Ever use a scan tool???? easy to watch it happeneing...

[This message has been edited by FastBroker (edited September 20, 2000).]

 

http://www.geocities.com/ecmguy.geo/tuning/do_tune.html

thats the 7747 hack btw along with a few others

as for lean cruise mode, the 746 ecm has it i know that much. I dont know if its active in the stock programming but I know its there. It might be one of those things thats there but was never used by gm like Highway spark (cause the epa disallowed it) Course now that we have the power to play with that

 

wouldnt it HAVe to be an average of what is in the cell? thus making your steady state argument correct, if it wasnt an average of whats in the blm boundry why even have it?

must be some sort of algorithm in the code that simply finds the average for that blm cell boundry

 

If it was averaged, then you'd run rich/lean at certain points, right? BLM is ALWAYS changing but "stored" when you leave a BLM cell and returns to that stored value when you get back to that BLM cell. Doesn't realy matter much cause it get's change so fast. It's best to have little variance in BLM so you have optimum operability. Ie, always right near stoichiometry and don't need computer correction...

 

I agree that the averaging has a negative effect as you roll through the values that constitute a cell. As far as scan tool monitoring, unfortunately I haven't run my truck without my AutoXray hooked up in almost a year. I have definitely noticed, especially when coming off the throttle that as you enter a new cell the BL will blip to a different number before settling down some. I too take this as an indication that the fuel trim correction of the bl creates a state at the boundary of a cell that does not conform to performance in the cell generally.

I think especially with larger camshaft profiles the arbitrary boundaries of the cells delineate areas that are not as regular fuel requirement-wise as with the stock cam. Likewise with bigger intakes and tb that create the common need for a big pump shot. The average value of the bl provides for a fuel trim that is appropriate once the engine reaches the "meat" of a cell but seems to generate the mild flat spots that are difficult to smooth out even with minute adjustments to the ve tables.

Pablo, have you found a means to "turn on" or utilize the lean cruise mode? I think you can artificially induce such a state by running your ve values so low in the appropriate areas that even with maximum bl fuel trim added the engine still runs lean. Likewise if you have a problem with a lean spot and no means to compensate with an injector constant you might be able to run so rich that the integrator shows the need to pull out more fuel than the 105 value that the bl maxes out at.

 

no i dont think you would run rich lean rich lean per cell
because to have an average you have the element of time involved
hence amount of time spent in X boundry produced these o2 readings as an average
so say you cruise through that boundry and it hits each cell of the main table for fuel the exact same amount of time included in that boundry once and one of those cells is extremely rich, say 12 12 12 38 12 its gonna see that 1/5th of the time it was in that boundry it was extremely rich hence pushing up the blm

but if you were in that boundry a real long time to where it was constantly seeing the area of VE that was 12, its gonna see that say it passed the 38 on the way to that 12 but the longer you are at 12, the lower those blm values drop
so say for instance you enter that cell and pass by the 38 and are at that 38 for 1 second, but continue driving in that same blm cell but have moved on to another area of the main fuel map to where its 12 and stay there for several minutes of driving, the average will decrease the longer you drive simply because its being refreshed with the same amount of fuel correction for 12 many more times than it saw the correction for 38

this is how i see it working i dont see how it could work any other way really because if not then why even have the cells?

[This message has been edited by Pablo (edited September 20, 2000).]

 

BLM changes based upon existing conditions. Last BLM in a cell block is stored for that cell block and reinitiated in the ECU when you get back to that cell block, as Ramsey eluded to by using his scantool. Pablo, have you used a scantool??? Very easy to see this happen. Yeah, you could be operating in a odd very rich area, which would lower BLM to say 100. Then hit gas sharply to get out of that block. BLM would stabilize to say 128 in the new block. Let throttle of slowly while watching scan tool. BLM will be around 128 (hopefully) and then all of a sudden go to 100 when you get into the new (actually the old) block but will start changing immediately, depending on engine conditions, get it?

Cells were derived as a way somewhat seperate different operating conditions of the engine but I disagree that they don't seem too useful. ie, if your entire BLM block is truly off by a lot, ok, and you get back into that block, it would be better for driveability if BLM was pre-corrected instead of correcting itself, which would create short-term rich or lean conditions because Integrator/BLM changes only happen so fast. make sense?

 

.

[This message has been edited by Pablo (edited September 21, 2000).]

 

ok i see what you are saying, and I agree, in fact i think its the same thing im saying, but, BLMS dont instantly change, ever watch an 02 fluctuate? If it did instantly change then blms would be all over the place. There is a time element involved here where some 'filtering' or as i stated perhaps using the wrong term, as 'averaging' which is essentially filtering is occuring.. do you agree with that?
and you keep insisting that i NEEd a scan tool when so many others have programmed chips with very limited use of scan tools, successfully i might add. Why is the scan tool so important for you? It tells me nothing I cant find out through other means

 

I here what you are saying. The BLM function has a time/swithcing filter in it that will change when/how fast the BLM will move. Also, BLM move based upon Integrator movement/volatility and the Integrator being out of certain specified ranges.

You can program easily with a scan tool but it will take far less time (fewer chips) and be more accurate if you use a scan tool to isolate operating conditions (or cells of the VE or SPARK tables) and BLM at those locations... Makes for eccurate VE changes on the first try... Also, I am going to use one of those boxes that allows you to retard/advacne the spark from in the cab. I will drive at a certain RPM and MAP, then advance the spark with that box until I just see knock counts on the scan tool. Then, I will subtract one or two degrees and put the appropriate value in the SPARK table cell. I have been trying this technique and it seems to work well. No chips yet. waiting for you to call me. I also have some other table I'd like to talk to you about. I put my number in your IAC thread.