Parasitic load and engine management

[eco]

Lets say that you have removed almost all the belt driven accessories from the motor leaving only the water pump and the alternator. This is theoretically going to free up a fair amount of power for the motor (88 302). But, is it going to have ANY effect on how the engine management system (EEC-IV) runs the motor? If you think about it, having less parasitic load on the belt is going to mean that the throttle does not have to open as far to get a given amount of power to the wheels with the trans in gear. Right? Also, throttle response would presumably be better. But, the TPS signal is a key factor in the computers ability to identify "part throttle", "cruise", "take off" and WOT status and then put the computer in the right strategy. So, if the throttle does not have to open as far as it did WITH all that load on the belt, will there be a problem with the TPS signal being too low at all times to get the computer to be able to identify the given driving status? Also, with almost no load on the accessory belt, could the idle speed be thrown off? With less load on the motor and the trans in neutral, the idle speed would go up...right?

 

[Fellro]

The computer reads a variety of signals: vacuum, tps, O2, rpm to make it's adjustments accordingly. If say the TPS fails, it throws a light, then ignores it, and bases the adjustments off the vacuum and the O2. As long as all of the senders are in balance, the computer will adjust the fuel accordingly. If it goes out of parameters, then it ignores that senders and evaluates according to the others that remain in parameters. So basically, if the load is light, the O2 will show it, the MAP will show it, and the TPS will agree, so the computer will adjust according to the load. The idle speed will not change because of the load either, as that is another parameter that needs to stay inside the preset range.

 

[Bob Ayers]

Absolutely not a problem! As far as the idle speed, the PCM will set it properly with the signal going to the IAC valve. The TPS, signal "static" voltage is important in the idle position, and at WOT. A
"smooth" increase in signal voltage is also important a the throttle is opened,
as the PCM uses this change in voltage to detect the throttle is being opened.

 

[eco]

I researched this a little bit further, and what I found is that the computer looks for a change of 0.04vdc from the closed throttle value to register the "part throttle" status. As long as closed throttle does not exceed 1.2vdc or drop below 0.6vdc and WOT is at least 3.2vcd and no more than the ref voltage, and any time the driver goes to accelerate the change in the TPS signal is 0.04vdc or more, all is well. The computer "zeros" out the base (closed throttle) voltage at start-up and change representing part-throttle and WOT is determined by an amount added to that base (0.04vdc), as opposed to a pre set voltage value. I doubt that minimizing load will have any effect on this. I can't see the change in voltage being less than the minimum of 0.04 volts dc regardless of how reduced the load is.

 

[Bob Ayers]

I researched this a little bit further, and what I found is that the computer looks for a change of 0.04vdc from the closed throttle value to register the "part throttle" status. As long as closed throttle does not exceed 1.2vdc or drop below 0.6vdc and WOT is at least 3.2vcd and no more than the ref voltage, and any time the driver goes to accelerate the change in the TPS signal is 0.04vdc or more, all is well. The computer "zeros" out the base (closed throttle) voltage at start-up and change representing part-throttle and WOT is determined by an amount added to that base (0.04vdc), as opposed to a pre set voltage value. I doubt that minimizing load will have any effect on this. I can't see the change in voltage being less than the minimum of 0.04 volts dc regardless of how reduced the load is.

Signal voltage can't be any higher than the "ref" voltage which is 5V. The TPS is basically a potentiometer, one end to GND, one end to 5V, and the "slider" is the signal terminal.