Hp Tuners user defined pid’s
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Joined: Sep 2007
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From: hattiesburg, Ms
Hp Tuners user defined pid’s Been trying to get different information from the speed sensor in hp tuners. My end goal is to try and calculate how much clutch slip I have. I can hand calculate all this with mph and engine rpm but I would rather know what the driveshaft speed is or the input shaft speed.
If I can use the user defined pids part in vcm scanner to do this then that would be great but I’m having trouble trying to figure out how to do that if it’s possible.
If I can use the user defined pids part in vcm scanner to do this then that would be great but I’m having trouble trying to figure out how to do that if it’s possible.
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If you can create a math parameter for RPM/MPH, you'll get a ratio that will normally have one of 5 or 6 ratios (depending on how many gears your trans has) with some random values while you're starting and shifting. If you log a short run through all gears, just spending a few seconds in each gear, you'll see what the ratios normally are.
Then when you log some interesting driving (a drag pass, for example), and plot that ratio over time, you should see a few straight lines with some short squiggles at each shift. If your clutch slips I suspect you'll see a shift squiggle followed by a bent line. And I'm guessing that bend will stand out enough to give you the insight you are looking for.
Then when you log some interesting driving (a drag pass, for example), and plot that ratio over time, you should see a few straight lines with some short squiggles at each shift. If your clutch slips I suspect you'll see a shift squiggle followed by a bent line. And I'm guessing that bend will stand out enough to give you the insight you are looking for.
Thread Starter
TECH Fanatic
Joined: Sep 2007
Posts: 1,244
Likes: 7
From: hattiesburg, Ms
If you can create a math parameter for RPM/MPH, you'll get a ratio that will normally have one of 5 or 6 ratios (depending on how many gears your trans has) with some random values while you're starting and shifting. If you log a short run through all gears, just spending a few seconds in each gear, you'll see what the ratios normally are.
Then when you log some interesting driving (a drag pass, for example), and plot that ratio over time, you should see a few straight lines with some short squiggles at each shift. If your clutch slips I suspect you'll see a shift squiggle followed by a bent line. And I'm guessing that bend will stand out enough to give you the insight you are looking for.
Then when you log some interesting driving (a drag pass, for example), and plot that ratio over time, you should see a few straight lines with some short squiggles at each shift. If your clutch slips I suspect you'll see a shift squiggle followed by a bent line. And I'm guessing that bend will stand out enough to give you the insight you are looking for.
I will post the formula later on tonight.
honestly my biggest issue with the vcm scanner is that I cannot put at least a single decimal place on the mph so when I calculate the amount of clutch slip, it would be really accurate.
Last edited by nmass399; Feb 18, 2021 at 03:23 PM.
Thread Starter
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Joined: Sep 2007
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From: hattiesburg, Ms
((Gear ratio*336)*mph)/tire diameter in inches)=driveshaft rpm
driveshaft rpm*current trans gear ratio=inputshaft speed
For 4th gear in the trans with the converter locked ((1085.28*[sense.20.Imp])/24.91)*.688
It never would equal the pid (trans input shaft rpm) for some reason but it was only around 50 rpm away at most.
Also it would not equal the engine rpm most of the time but at one point it calculated the input shaft rpm that I setup to be more than the actual engine rpm. I guess it’s about as good as it’s gonna get here.
My camaro is a t56 car and won’t measure input shaft rpm in the pid’s, not sure why exactly other than it doesn’t know what gear it’s in.
driveshaft rpm*current trans gear ratio=inputshaft speed
For 4th gear in the trans with the converter locked ((1085.28*[sense.20.Imp])/24.91)*.688
It never would equal the pid (trans input shaft rpm) for some reason but it was only around 50 rpm away at most.
Also it would not equal the engine rpm most of the time but at one point it calculated the input shaft rpm that I setup to be more than the actual engine rpm. I guess it’s about as good as it’s gonna get here.
My camaro is a t56 car and won’t measure input shaft rpm in the pid’s, not sure why exactly other than it doesn’t know what gear it’s in.
