Recently my car has been getting poor gas mileage so I logged a cruise around town and found that my BLM's were at 108 basically all the time, obviously running rich = bad mpg. So I unplugged the MAF and now the BLM's are approx 128.

After that simple test I though the MAF was bad or maybe not calibrated right (I have the ZO6 MAF conversion from ls1speed.com, it is supposed to be calibrated for an lt1). So I took some logged data and calculated the air flow as the PCM would in speed density mode:

[(RPM/2)*(Engine displacment)*(Pressure)*(Volumetric Efficiency)] / [(gas law constant)*(temperature)]

I then compared that to the MAF readings, to my surprise, the approx the same ±2-3% (±0.5 g/s crusing at 45 mph)

So can we not make that comparison? When the MAF is disconnected is some other sensor ignored (it would have to be one that is not recorded by datamaster)?

 

I just discovered today my car did pull 14* knock retard and I am brousing the posts but I decided to stop at yours for a second.

When you disconected your MAF the computer reverts to Speed density and if your calculations came up that close to the new MAF I would say you need to keep an eye on the O2s output.


Is it safe to assume your computer is looking up a table (as in 128 BLms) and just sending the equivalent Injector Pulse rate untill the BLMs adjust to the oxygen sensors output?


Remember it takes time for the BLMs to adjust so if you just unplugged your MAF isnt it safe to say that the Computer is just using a default look up table until enough time has passed to adjust the BLMs to match the O2s output?

what are your Integrators returning?? 128 too? somehow I think they are way off the scale right now. They should be if your car has a fuel delivery problem.


Go check them (Integrators = short term fuel trims).


Marvin

 

Was your SES light on with the MAF unpluged? Have you changed fuel pres or injector size? Both of those can throw off the computer if the changes are larger enough. Another thing to remember is that, for some reason, LT1 motors do not respond well to MAFs other then the stock peice.

 

StockZ thats the formula I've been looking for. What is the gas law constant? and what "Units" of measurement are used for this formula?

Like *pressure* is that in HG? and how about Temp is that in farenheit? Celcius? what about VE? is the LT1 85%? 90%? Stock that is, just like mine.

can you help?