TBI tuning question

[ThatDude-98]

Hello everyone, I have began getting my feet wet with tuning..theoretically, to save time instead of following the procedure to tune the ¨right¨ way (add aftermarket parts, get vehicle to idle, datalog, emulator, or burn chips, rinse, repeat, etc) could a guy just advance timing until spark knock- then back off a few degrees until no more knock, follow the procedure to reset the IAC and then turn the idle screw in or out to get the vehicle to idle...then make the fuel pressure regulator adjustable to adjust afr (lean or rich), read spark plugs (white = lean, chocolate = about right) and continue to adjust idle screw and FPR, then read the plugs again and again until you get ¨close¨with your target RPM and spark plug color, exh smell, etc? I get this isnt the correct way of dialing the vehicle in after headers, heads, cam, intake, etc. This is just an idea I thought of. I am anxious to hear others opinions. Also If someone were to adjust the timing, fuel by the FPR and idle as described, would injector BPW or other scalars need edited to compensate? I hope this thread can create a good discussion, as I always like to learn and hear others ideas, theories. PS, I am not dead set on this ¨method¨ just curious is all, Thanks - AJ.

[dave w]

Hello everyone, I have began getting my feet wet with tuning..theoretically, to save time instead of following the procedure to tune the ¨right¨ way (add aftermarket parts, get vehicle to idle, datalog, emulator, or burn chips, rinse, repeat, etc) could a guy just advance timing until spark knock- then back off a few degrees until no more knock, follow the procedure to reset the IAC and then turn the idle screw in or out to get the vehicle to idle...then make the fuel pressure regulator adjustable to adjust afr (lean or rich), read spark plugs (white = lean, chocolate = about right) and continue to adjust idle screw and FPR, then read the plugs again and again until you get ¨close¨with your target RPM and spark plug color, exh smell, etc? I get this isnt the correct way of dialing the vehicle in after headers, heads, cam, intake, etc. This is just an idea I thought of. I am anxious to hear others opinions. Also If someone were to adjust the timing, fuel by the FPR and idle as described, would injector BPW or other scalars need edited to compensate? I hope this thread can create a good discussion, as I always like to learn and hear others ideas, theories. PS, I am not dead set on this ¨method¨ just curious is all, Thanks - AJ.

Been there, Done That . . . Now I have a Laptop.

dave w

[ThatDude-98]

hey hey Dave good to hear from ya man. Would BPW need tuned, or, leave it be?

[1project2many]

I get this isnt the correct way of dialing the vehicle in after headers, heads, cam, intake, etc. This is just an idea I thought of. I am anxious to hear others opinions.

Well, this was the way before we had access to the bits inside the computer. Many sharp folks spent many, many hours playing with different MAP sensors, injectors, rising rate fuel pressure regulators, MAP line length and diameter, ESC controllers, TPS resistor networks, swapping factory calibrations and ecm's, putting resistors on O2 sensor signal wires. In short, we lied to the ecm in as many ways and as many times as we could in order to trick it into doing what we wanted. In some cases folks actually bragged about how badly their engine idled or how much it over fueled simply because the current state was much improved over a previous state. Thank goodness for all the folks who have helped make computer tuning a reality.

I may be able to hook you up with the old DIY-EFI and GMECM archives if you'd like to learn about some of these old tricks.

Injector BPW values represent the relationship between the amount of fuel delivered by the injector and the displacement of the engine. For mild changes such as headers and a small cam it's not usually necessary to change the BPW constant. If you have substantially raised fuel pressure along with other changes then you may need to adjust the BPW to reflect the change.

[ThatDude-98]

sounds good 1project2many send archives on over

[1project2many]

Here ya go:

GMECM
http://web.archive.org/web/200503010...gmecm/archive/

DIY-EFI
http://web.archive.org/web/200503050...y_efi/archive/

[trlrider]

[QUOTE=ThatDude-98;92098]Hello everyone, I have began getting my feet wet with tuning..theoretically, to save time instead of following the procedure to tune the ¨right¨ way (add aftermarket parts, get vehicle to idle, datalog, emulator, or burn chips, rinse, repeat, etc) could a guy just advance timing until spark knock- then back off a few degrees until no more knock, follow the procedure to reset the IAC and then turn the idle screw in or out to get the vehicle to idle...then make the fuel pressure regulator adjustable to adjust afr (lean or rich), read spark plugs (white = lean, chocolate = about right) and continue to adjust idle screw and FPR, then read the plugs again and again until you get ¨close¨with your target RPM and spark plug color, exh smell, etc? I get this isnt the correct way of dialing the vehicle in after headers, heads, cam, intake, etc. This is just an idea I thought of. I am anxious to hear others opinions. Also If someone were to adjust the timing, fuel by the FPR and idle as described, would injector BPW or other scalars need edited to compensate? I hope this thread can create a good discussion, as I always like to learn and hear others ideas, theories. PS, I am not dead set on this ¨method¨ just curious is all, Thanks - AJ.[/QUOTE

[ralmo94]

If you don't know what the computer is doing, you have no idea what you are telling it to do.
For example, I had a truck that had something wrong with the O2 circuit. I had no idea what exactly was going
on before I was able to datalog. I even had a Wideband in it. It would crank the mixture all over the place, until it would
decide the O2 was bad, set the code, then run open loop. I was trying to adjust FPR to tune, but.....
Another truck I had, had the wrong injector settings. You would never know if I didn't have a wide band.
Fuel trims were within reason. but going down the road AFRs where erratic between 12-18.

The one with the faulty circuit, the computer could make way more adjustments than i could by changin FPR.

I'm in no way an expert, but these are some of the problems I have ran into.

[telecasterfool]

Hello everyone, I have began getting my feet wet with tuning..theoretically, to save time instead of following the procedure to tune the ¨right¨ way (add aftermarket parts, get vehicle to idle, datalog, emulator, or burn chips, rinse, repeat, etc) could a guy just advance timing until spark knock- then back off a few degrees until no more knock, follow the procedure to reset the IAC and then turn the idle screw in or out to get the vehicle to idle...then make the fuel pressure regulator adjustable to adjust afr (lean or rich), read spark plugs (white = lean, chocolate = about right) and continue to adjust idle screw and FPR, then read the plugs again and again until you get ¨close¨with your target RPM and spark plug color, exh smell, etc? I get this isnt the correct way of dialing the vehicle in after headers, heads, cam, intake, etc. This is just an idea I thought of. I am anxious to hear others opinions. Also If someone were to adjust the timing, fuel by the FPR and idle as described, would injector BPW or other scalars need edited to compensate? I hope this thread can create a good discussion, as I always like to learn and hear others ideas, theories. PS, I am not dead set on this ¨method¨ just curious is all, Thanks - AJ.

All the stuff you're saying is not tuning using the computer, it's tuning without the ECM and a laptop. That's fine if that's what you want to do. The best way forward if that's your thing is a carburetor, and HEI ignition. Then you won't be fighting the computer, and you will know what your motor is doing. ANY motor will benefit from a wideband O2 sensor - they are cheap now. I use the computer, and datalog, but I have a wideband with a gauge, too. I can see if the AFR is good. Good luck