
09092008, 09:42 PM

#1

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More Acceleration enrichments
I had a question about the AE's and MT doesn't appear to have a help topic on them...
I pretty much understand the basics about the TPSBased system, it see's how fast the TP voltage changes, and opens the injectors X milliseconds according to the table.
But my question is... Since I have a 2001, and this is from a 9495 PnP, are these rates the same? Is the fastest I could hit the pedal make the voltage change 8.0V ? Is there any way to figure this one out?
Also, what is the TPSdot Threshold and how to I obtain it?
I figure understanding these would help me tune the AE's much better.



09092008, 09:45 PM

#2

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Just thinking... If I measured the volts of the TP with it all the way open, is that what the max voltage per second could be?



09092008, 10:32 PM

#3

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Quote:
Originally Posted by compy
But my question is... Since I have a 2001, and this is from a 9495 PnP, are these rates the same? Is the fastest I could hit the pedal make the voltage change 8.0V ? Is there any way to figure this one out?

Should be. Both devices are potentiometer voltage dividers, fed with 5v.
Quote:
Also, what is the TPSdot Threshold and how to I obtain it?

" The TPS/MAPdot threshold setting determines the rate at which acceleration enrichment begins. If you set it too high, no accel enrichments will be applied, and the engine may respond poorly, backfiring or coughing under sudden throttle movements. If you set it too low, however, you may have inadvertent enrichment triggered by noise on the TPS signal."
source: http://www.msextra.com/manuals/MS_Ex...nual.htm#accel
Quote:
Originally Posted by compy
Just thinking... If I measured the volts of the TP with it all the way open, is that what the max voltage per second could be?

Nope. Let's say the minimum voltage is 0.5v, and the max voltage is 4.5v (which is pretty close to what it will in fact be). If you depress the pedal fully from closed over 1/2 second, then the rate is 8 v/sec. If you mash it open in 1/4 sec, then it's 16 v/sec. Etc...
For some reason, reality seems to differ from the software settings slightly.



09092008, 11:07 PM

#4

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Quote:
Originally Posted by Joe Perez
Nope. Let's say the minimum voltage is 0.5v, and the max voltage is 4.5v (which is pretty close to what it will in fact be). If you depress the pedal fully from closed over 1/2 second, then the rate is 8 v/sec. If you mash it open in 1/4 sec, then it's 16 v/sec. Etc...

I guess I don't understand this. I measured it and it was about .6 at 0% and 3.78 at 100%. So how could you produce more than 3.78 volts per second no matter how hard you hit the pedal?
I guess I'm missing something since I think that 3 volts/sec would be max acceleration, 1.5 volts/sec would be half acceleration, and so forth.
So my question is, how could it be more voltage per second than what the TPS provides? Without hitting the pedal more than once in a second.



09092008, 11:21 PM

#5

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Forget the actual maximum value, we're talking rate of change, which is relative.
First off, your delta is only going to be ~3.2v, since your minimum is 0.6 and your max is 3.78 (which I'll round to 3.8).
If you go from mix to max, and it takes four seconds, that's 0.8 v/sec. If you take two seconds, then that's 1.6 v/sec. If you do it in one second, that's 3.2 v/sec. With me so far?
Ok, so given that, what do you call it when you do it in 1/2 sec? IOW, 3.2v/halfsecond.
Maybe we step back to elementary school math for a second, and express these as fractions. We all agree that 2 / 4 is the same as 1 / 2, right? And that 1 / 2 is the same as 0.5 / 1, yes? So that's the same as 0.25 / 0.5. It doesn't matter how far we break this down, so long as both the numerator and the denominator are scaled by the same factor.
Ok, so we'll now do it with your numbers. 3.2 / 0.5 is what happens if you mash the throttle from closed to open in a half second. But MS needs us to enter data in volts per second, not volts per halfsecond. So we just scale the fraction up so that the denominator becomes one, which gives us 6.4 / 1.



09092008, 11:23 PM

#6

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Didn't I just explain this to you last week?



09092008, 11:34 PM

#7

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Gotcha now. And No Paul.
Thanks for clearing that up.



09102008, 08:53 AM

#8

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Must've been Artie. Which means I'll probably have to explain it a few more times.



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