Chevy Impala SS Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
90 Posts
Discussion Starter #1
I have been looking at calibration files for the 1995 B-Body; post TSB regarding chuggle/surge or AIR pump. And have noticed that it seems like the TOW package vehicles do not use the MAF. Even before the TSB the tow package Buick does not use the Mass Airflow Sensor. I think the '95 Impala uses the MAF, but not my Roadmaster. Anyone know the thinking behind that?
 

·
Registered
Joined
·
4,532 Posts
that does not sound correct
 

·
Registered
Joined
·
567 Posts
If your car doesnt have a MAF, someone rigged it. The LT1 NEEDS a MAF.
 

·
Registered
Joined
·
90 Posts
Discussion Starter #4 (Edited)
I still haven't pulled the calibration file from my vehicle, since I am waiting on a cable.
I have been comparing bin files from fbodytech, I haven't found the latest calibration file for my vehicle anywhere else. And I certainly don't want to pay a dealership to reflash my PCM for $100 (I doubt they would flash me the 9C1 shift points either).

The latest official calibration for my 1995 Roadmaster w/ tow package is:

BULLETIN #57-65-17A
1995 5.7L 2.93 AXLE TRAILER TOW
NEW CALIBRATION NUMBER
16243171

The file, 16243171.bin, I found on fbodytech; which seems to be very legitimate.
After browsing this file using tunerpro, I noticed the MAF is disabled.
I also compared the latest files for the 9C1 and the Impala ss. It seems to me that only the Impala has the MAF enabled. They all have MAF diagnostic enabled (code 48). And I know they all have an actual MAF sensor, like all of my Roadmaster's before. But if the MAF is disabled, then the PCM uses only Speed Density mode for air/fuel metering, and the MAF sensor would be pointless to even be installed.
I am new to tuning, but I would think MAF metering would be the most accurate and preferred method if your keeping stuff relatively stock (I'm not racing this thing).
The reason for my concern is that I have the K&N intake on my car, naturally I assume this has an effect on the airflow into my engine. If the MAF sensor is used I assume the PCM would sense this change in airflow characteristics and adjust accordingly. If the MAF is not used then the PCM refers to the Volumetric Efficiency Table and uses the MAP sensor. Now I am sure the MAP readings would also notice and reflect the changes caused by the new air cleaner. But I still have one question, does that mean the VE table should be adjusted? Basically what I want to know, after assuming the only change done to an engine is a higher flowing air intake, then does this effect the volumetric efficiency of the engine? I assume it's an easy "Yes!" to that question, but in the case of my K&N filter on my Roadmaster with stock engine, would it even make enough of a difference for me to be concerned with the VE table?
And if I am correct about the factory disabling the MAF sensor, then what would be their thinking behind such a thing? They must think their VE table is on point.
I also installed a cat-back exhaust with stock manifolds and converters. I'm sure the exhaust effects the VE of an engine as well.
 

·
Registered
Joined
·
976 Posts
I also noticed that a later calibration for my '94 the MAF was indeed disabled as well.
Did not understand the reasoning behind this change either.

One size fits all VE tables should always be re-tuned IMHO.
Even the MAF tables may need some tweaking with the K&N/exhaust mods.
Every engine is a little different, and they all benefit from tuning.
I personally would re-enable MAF if you update the calibration.
 

·
Registered
Joined
·
90 Posts
Discussion Starter #6
I also noticed that a later calibration for my '94 the MAF was indeed disabled as well.
Did not understand the reasoning behind this change either.

One size fits all VE tables should always be re-tuned IMHO.
Even the MAF tables may need some tweaking with the K&N/exhaust mods.
Every engine is a little different, and they all benefit from tuning.
I personally would re-enable MAF if you update the calibration.

Thank you sir. I am glad I am not the only one to notice this. And I definitely agree with you on the tuning. I just want the best mileage out of my fuel, I'm curious to see what difference the MAF would make.
 

·
Registered
Joined
·
1,422 Posts
Can you attach your definition file? All the versions I have do not have such a parameter. Does it show up under scalars or flags?
 

·
Registered
Joined
·
1,422 Posts
You might want to hit up Steveo on gearhead and pose the question. It may not be a thoroughly flushed out definition.

Or run the disabled bin and mod some of the MAF curve values and see if any thing changes.

If I recall right, that latest bin and a some others looked like they had their MAF curves polished a bit. Wouldn't make sense to do that then disable it.
 
1 - 11 of 11 Posts
Top