ULTM8Z

So I'm curious how the ECM does this. I know for 8D that it looks at the baseline voltage initially at engine startup and then uses that for delta-TPS calcs on the AE.

But I'm looking at Tunerpro and seeing some constants that I'm curious how they play into this... also since the factory setting for the TPS voltage is .54V. I can see in TP that my ECM is seeing .57V from the TPS.

AIR FUEL Param, TPS Factor for Low Voltage => If after lag filtering, TPS voltage is lower than a calculated threshold (0x0099-see AIR FUEL Param, TPS Initialization Voltage), this factor is used to increase TPS voltage to an acceptable level before computing TPS%.
Factory Default = 0.41

AIR FUEL Param, TPS Initialization Voltage => Initial TPS voltage at key-on or if engine not running. Becomes the threshold (0x0099) against which TPS voltage is measured after being lag filtered. Factory Default = 0.94 Volts

AIR FUEL Param, TPS Initialization Voltage Filter Coefficient => Used to gradually reduce lag filtered TPS Initialization Voltage. Factory Default = 0.39%

ULTM8Z

So thinking about this a little more....

Is there some significance to the .41 and .94 voltages in these parameters? .94 - .41 = .53S versus the factory setting of the TPS voltage supposed to be .54V?

The ECM checks the TPS voltage after lag filtering and if it's less than .94V, it adds .41V to it for the final voltage?

So if someone has the TPS voltage set to say, .60V (which is less than .94V), the ECM will then add .41 to it which will make the default .101V?

I'm not sure what difference this makes, but I'm just curious how it works...

RBob

iTrader: (1)

Unwritten rule, need the PROM location of the parameters. The names aren't always easy to match up with an XDF and hac.

As for the above, it is the auto-zero parameters for the TPS. The '90 - '92 TPI/MPFI/TBI don't have a 'set' factory value for the TPS base. The sensor isn't adjustable, it is what the voltage is.

Simplest explanation is that the ECM keeps track of the lowest seen TPS voltage. And uses it for the 0% TPS base line. This lowest seen voltage gets filtered into the init TPS voltage to bring the base idle TPS 0% voltage into line (hopefully that statement didn't confuse things).

The base idle 0% TPS at key-on, engine-off is the TPS Initialization Voltage. This is where it starts for 0% TPS. Then once the engine is running the ECM adjusts this value according to what the TPS reports for the lowest seen voltage.

This base idle 0% TPS voltage is what is used to calculate the actual TPS percentage (%).

Not sure about the low TPS voltage factor, maybe an assist for a malfunctioning TPS? To keep things from going totally off the wall.

Recall that the TPS is nothing more then a rheostat, like the old TV & radio volume controls. And we all know how noisy they get.

RBob.

ULTM8Z

Thanks RBob...

0x3E4 AIR FUEL Param, TPS Factor for Low Voltage => If after lag filtering, TPS voltage is lower than a calculated threshold (0x0099-see AIR FUEL Param, TPS Initialization Voltage), this factor is used to increase TPS voltage to an acceptable level before computing TPS%.
Factory Default = 0.41

0x3E5 AIR FUEL Param, TPS Initialization Voltage => Initial TPS voltage at key-on or if engine not running. Becomes the threshold (0x0099) against which TPS voltage is measured after being lag filtered. Factory Default = 0.94 Volts

0x3E6 AIR FUEL Param, TPS Initialization Voltage Filter Coefficient => Used to gradually reduce lag filtered TPS Initialization Voltage. Factory Default = 0.39%

ULTM8Z

While I have your attention..

There are a couple of other parameters too...

0x3E7 AIR FUEL Param, Coolant lag filter coefficient - There's no description on this at all. Factory default is 6.27. What happens if I increase or decrease it?

0x4A0 Loop Closed Param, SLOW o2 Coolant Temp Factor, again no description. Factory default is 60%. Again, what happens if I increase or decrease?