Got a tune from PCMforless now on my (recently repaired) '95 PCM and I'm seeing that one of the many things Bryan changed was the injector flow rate...bumped up slightly. How does this benefit performance and what effect does it have on daily commuting? I understand the PCM is going to try to find a 14.7:1 AFR but does this calculation tend to make it run more on the rich side?

 

Immediately speaking, it would lean you out across the band, but the BLMs will compensate for it.

 

why did he change the injector flow rate?

 

So then changing injector flow rate is sort of useless?
I changed it from 24.91, stock, up to 25.61 on my car and the blm's seem to have gone from being in the mid to upper 11X's to mid to upper 12X's...which is what I was trying to do. Part throttle seems crisper now.
It seems that the closer the blm's are to 128 the better the car runs. Worked the exact same way on a friends 93 w/ a 396. Exremely noticable on that car.
In my limited knowledge on this, it seems that getting the blm's closer to 128 by changing injector size works pretty well.
What is the difference between this and changing the MAF sensor calibration file?

 

Yes, upping the constant works if you're already off from the 128 ideal BLM value.

The difference between it and MAFS tables is that they are split into four sections, which cover different airflow areas, whereas the injector constant affects the entire RPM/MAP band the same way.

I.e., if your BLMs are only off at certain cells, use the MAFS tables, otherwise if they're off the same everywhere, try the injector constant.

This is kind of a hack, though.

 

OK.
Only thing I'm not sure of now is how the frequency in the MAF tables relates to rpm?
Any help there?

 

It doesn't specifically relate to only RPM. It's basically a function of load and air temperature.

The best way to use it would be to log your driving, and see what the airflow readings are in the areas where your BLMs are off. Then raise or lower that cell area accordingly.

I've never done it before, but that's how I would use it.

Solomon

 

Sort of useless, but in your case if you were almost always 11x BLM area nd it brought you to the 12x area then obviously in your case it did the trick. When your under 128 your car is pulling fuel, when your over 128 your car is adding fuel, so by increasing the injector rate you lie to the computer by saying you have larger injectors than you really do. What this does is, the car calculates your fuel needs and the injector rate plays into that, so since it thinks you have bigger injectors than you really do, it calculates more fuel than will actually ever make it into your cylinder.

You can do the same thing with the MAF by lying about air flow, to lean or enrichen...