Ford IAC questions etc.

[panel]

Thanks Lance once again. I'll try those % increases in the morning.

Quote from Matt(not my post he responded to but reference only)

Re: PWM IAC

Postby Matt Cramer on Thu Jun 03, 2010 4:56 am
That is backwards from how the 5.0 IAC valves we've tested work. But I see that under Tables -> Idle PWM Duty Cycle, you've got the table set to 100% - fully open - the whole time. Normally it should taper down to much less when the engine is warmed up. The Mustang we were tuning yesterday seemed to idle well at around 30%.

So it looks like what your saying is the valve can be at lets say a certain % like 30% or 85% when fully warmed up. I was under the impression that the valve HAD to have the 0% or the 100% in the last bin (which I'm trying to figure out)

Lance-->

Then your PWM Idle PWM curve should start at 85%, and end at 0% when fully warmed up (and note that you set your fully warmed up rpm with the physical throttle stop, not the idle PWM% software setting.)

Mine could end up with 85% then at fully warmed up if the valve actually starts(cold) at a low %?

I'll try this tomorrow morning at report back

[Matt Cramer]

The Warm Up Enrichment is the curve that has to be at 100% in the last bin.

The IAC duty cycle can be at whatever value in the last bin gives you the idle speed you want.

[Bernard Fife]

Marc,

Yes, if you found that a small PWM percentage gave higher engine speeds at a given temperature (i.e. the valve is open), and high percentages gave lower speeds (the valve is closed), then your PWM% would rise going to the right, as shown in your illustration.

There are good reasons for the valve to be either way. If 0% is closed, then most of the time (when the engine is warmed up) the valve draws no current (and creates less electrical noise, etc.). On the other hand, if 100% PWM (or some non-zero value) means the valve is closed, then if the the wiring fails the valve opens and the engine won't stall on a cold start (but will have a fast warm idle). So it depends what the designers thought was more important.

I don't agree with Matt that, "The IAC duty cycle can be at whatever value in the last bin gives you the idle speed you want". I feel you should *always* use the throttle stop to set the warm idle speed. The last PWM% value should be set to completely close the idle valve. Otherwise the current in the idle vale varies with under hood temperature and supply voltage, and this can leads to a wandering or non-constant idle speed.

Lance.

[panel]

OK......got a log and MSQ + a pic for you guys. As you can see in the pic the lower the % the more open the valve gets and thus a higher RPM.

[panel]

Is there also a way to change the CLT gauge in this pic to read RPM instead? You can read the bars on the left to know what the temps are and you can also see the 'dot' move up the graph for the temp readings.

And is there a way in 'Megatune' to 'Inc' or 'Dec' the % values similar to that in the 'Warmup Wizard' ? Would be a neat function rather than always manually changing the values. ...Just an idea.

[Bernard Fife]

Marc,

To change the gauge, look for this section in the INI:

Code: Select all

   curve = ipwBins, "PWM Idle Duty Cycle"
      topicHelp   = "http://www.megamanual.com/mt28.htm#ep"
      columnLabel = "Coolant", "Idle PWM"
    #if EXPANDED_CLT_TEMP 
      xAxis       = -40, 600, 9
    #else 
      xAxis       = -40, 250, 9
    #endif
      yAxis       =   0, 100, 6
      xBins       = tempTable, coolant
      yBins       = ipwmTable
      gauge       = cltGauge

Change the last line to:

Code: Select all

      gauge       =tachometer

Lance.