Don 95Vert
Founding Member
Merry Christmas! The SN95's and up use calculated load and RPM for spark calculations. They also use load for fueling. The MAF is used by the PCM to calculate load. When, say a 42# calibrated MAF is used, then load is essentially skewed by about 0.45. So with the stock MAF is on the motor and load is correct, then when the PCM sees max load (T4M0) at 5000 RPMs it assigns a spark value (before modifiers) of 25* assuming 10* at the crank. Same conditions, calibrated MAF, except load is 0.45 of 89% or about 40% give or take. Assigned spark at 40% load is 38* or if it's closer to 50%, it's 32*, which at 32* is not that horrible (though oversparked) on a NA motor, 38* = way oversparked, lose power, probably detonation. Do that on a blower motor, even with a base timing of 0* (which would run like crap) and you learn an expensive lesson.
Oh, and commanded fuel at 0.43-0.54 load is 0.97 Lambda - which is an A/F of 14.2 with gasoline...
A 24# calibrated MAF isn't near as bad, but it IS affected.
Lots of people do lots of things that are not best for the car and have the car 'run well' - I have seen hundreds of cars on the dyno like this, but they run REALLY well when they are done right.
This isn't really a point for opinion, it is a fact and that's the way it works. Not trying to start another argument, just trying to share some good info.
Merry Christmas!!
Don
Oh, and commanded fuel at 0.43-0.54 load is 0.97 Lambda - which is an A/F of 14.2 with gasoline...
A 24# calibrated MAF isn't near as bad, but it IS affected.
Lots of people do lots of things that are not best for the car and have the car 'run well' - I have seen hundreds of cars on the dyno like this, but they run REALLY well when they are done right.
This isn't really a point for opinion, it is a fact and that's the way it works. Not trying to start another argument, just trying to share some good info.
Merry Christmas!!
Don
