Hi there, I was wondering what all the ECM on my 89 firebird TBI V8 controls? I know that it adjusts fuel to air ratio, but not sure if/how it controls fuel pressure and things like that.

 

Injector pulsewidth is controlled by the ECM, while fuel pressure is generally handled by a mechanical regulator connected to your intake manifold vacuum.

 

What is injector pulsewidth? Is it when/how long the injector fires? The reason I am asking these questions is that I have swapped a 350TBI L05 for the 305TBI L03. I used the injector pod and regulator from the 350 TBI, and I was lead to believe that the 350 has 55lb injectors as opposed to the 40lb injectors from the 305. Is my ECM only pulsing (?) enough for the 40lb'ers or does that even make a difference after the regulator is involved?

 

Injector pulsewidth is the length of time the injector is open and spraying fuel. Yes, the 350 TBI engines do use a larger injector. There are at least two different sizes for the 350's, a 61#/hr and a 68#/hr.

Swapping to the 350 injector pod helped a lot. If the engine is basically stock then finding a PROM to match may make it run better.

The regulated fuel pressure is the same between the 305 and the 350.

How does it run now? Have you been able to data log it.

RBob.

 

Thanks for all your input.
The engine seems to running fine at this point. I had to change to the 350 ESC module, but since i've done that it runs pretty smooth.
I have no idea what data logging is, or how to accomplish that. Is that something I can do with a Snap-on scantool?
I have changed the air cleaner to that triangular Edelbrock one. I had to bore out one of the ports in the bottom to accept my IAT sensor, and I also just pushed the stud through the top of it and then just bolted the wing nut on top of it. LOL It doesn't look that bad
The engine is a L05 from and 87 Suburban. 210hp-300#tq
8.25:1 compression, and baby-sized valve springs that I will need to change before I do a can swap.
I was thinking about going for the LT1 aluminum heads from a 4th gen, but I don't think those heads have any coolant passages in the intake side.
I was also contemplating getting the 4th gen exhaust manifolds.
Any thoughts on any of this?

 

Data logging is the next step up from just scanning. Some scan tools will allow a limited amount of data logging. Data logging is the action of saving the scan tool information (from the ALDL line) to a disk file on a real time basis.

The file is known as a data log and contains all of the information the ECM sent out during that period of time. Once back at home base this data log is analysed for various information. Most of the time it is used to help in tuning the engine.

For your engine/vehicle there is WinALDL. This is free software that runs on a PC (disktop or laptop), and data logs along with providing a real time display.

RBob.

 

I went remember seeing something baout datalogging when I was over a tbichips.com, I think it was instructions on how to make the link cable.
My question is, since I don't have a laptop PC, then I guess I am not going to be able to accomplish this at all, huh?
I would guess that the engine is running pretty well, because I just passed MD's treadmill emissions test a little over a week ago.
That was before I switched to the 350 ESC module, and the new air cleaner. I know the engine feels stronger with the new air cleaner assy.
So as far as the pulsewidth goes, I guess the computer is only letting the injectors spray as long as is required for the 40lb injectors on the 305? I do notice that at stoplights, it seems to have a verrry slight stumble. It never stalls, just drops the rpms down about 500, it seems to happen every cycle of the engine, but at cruising speeds, or WOT, it acts just fine.
Since I installed the 180º thermostat, it stays around 160º when cruising.
Which fan switch should I purchase? The one that turns on at 180º and off at 160º, or the one that turns on at 200º and off at 185º? I would think that the 200-185 would be better suited to my thermostat.
I am also in the process of replacing the origninal radiator with a new 3 core style to help with the cooling. It likes to heat up in traffic. Nothing new, the last 3rd gen I had did the same thing until i put a clutch fan, 3 core rad, new aluminum water pump, and 180º thermo. Then I could sit in traffic w/ the AC on, and it would never get over 180º.
The trans is going to be going soon too, i think it was Vader that said, either my clutches and/or overrun(?) sprag is going. Either way, it won't catch the RPM's up when I manually downshift. It is a 700r4 that the previuos owner had not taken care of at all.
You should have seen what the internals of the 305 looked like when I pulled the valve cover off. (Pukes) Guy must have never changed the oil. I mean, there was build up all the way to the nuts on the rockers!
Sorry this letter is so long, I just get started, and sometimes I can't stop. LOL.
So what do you think of the 4th gen heads and/or exhaust manifolds deal? You have an input on these? I know that I can get the manifolds fairly cheap. (At least alot cheaper than 50 State headers). But I think that the heads don't have water passages in them, so I don't think they will work with a 3rd gen.

 

If you think you'll be into this for a while, consider getting hardware to burn chips, etc. An Ebay search came up with this:

http://cgi.ebay.com/ebaymotors/ws/eB...tem=2471137735

And even comes with a laptop, chip burner, cable, etc...