Who's Winding Back The Odometers?
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Yeah, they look good. I should try to fit them on mine. But being a GTSt, the guard shape probably doesn't suit properly. -
Nah, it's not a simple voltage divider. I'm not enough of an electronics guru to know how they make these circuits work. If I had a better idea of how the ECU's temperature measuring is done, I could then actually do as you want, which is turn that resistance chart into a voltage chart. But my approach has not worked. What I did was interpolate the sensor ohms values for the temperatures you listed, as you did not have any of them on a temperature ending in zero or 5. These are: °C ECU V sensor ohms (interpolated) 58 2.68 11.85 57 2.7 11.89 56 2.74 11.93 54 2.8 12.01 49 3.06 12.208 47 3.18 12.284 43 3.37 12.42 I then assumed 5V supply to the resister and calculated the voltage drop across the sensor for each of those, which is just 5 - the above voltages, and then calculated the current that must be flowing through the sensor. So you get: Values in sensor °C ECU V sensor ohms (interpolated) Supply volts Volt drop Current 58 2.68 11.85 5 2.32 0.195781 57 2.7 11.89 5 2.3 0.19344 56 2.74 11.93 5 2.26 0.189438 54 2.8 12.01 5 2.2 0.183181 49 3.06 12.208 5 1.94 0.158912 47 3.18 12.284 5 1.82 0.14816 43 3.37 12.42 5 1.63 0.13124 And then use that current and the ECU's sensed voltage (which must be the voltage drop across the in ECU resister is there is one) to calculate the resistance of that in ECU resistor. You get: Values in sensor Other resistor °C ECU V sensor ohms (interpolated) Supply volts Volt drop Current Volt Drop Resistance 58 2.68 11.85 5 2.32 0.195781 2.68 13.68879 57 2.7 11.89 5 2.3 0.19344 2.7 13.95783 56 2.74 11.93 5 2.26 0.189438 2.74 14.46381 54 2.8 12.01 5 2.2 0.183181 2.8 15.28545 49 3.06 12.208 5 1.94 0.158912 3.06 19.25592 47 3.18 12.284 5 1.82 0.14816 3.18 21.46325 43 3.37 12.42 5 1.63 0.13124 3.37 25.67816 And that's where it falls apart, because the resulting resistance would need to be the same for all of those temperatures, and it is not. So clearly the physical model is not correct. Anyway, you or someone else can use that information to go forward if someone has a better physical model. I can also show you how to interpolate for temperatures between those in the resistance chart. It's not fun because you've got to either do it like I did it for every 5°C range separately, or check to see if the slope remains constant over a wide range, then you can just work up a single formula. I'm just showing how to do it for a single 5° span. For the 58°C temperature, resistance = 11.77+2*(11.97-11.77)/5 The calc is a little arse backwards because the resistance is NTC (negative temperature coefficient), so the slope is negative, but I'm lazy, so I just treated 58 as if it was 2 degrees away from 60, not 3 degrees away from 55, and so on.
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Um.... This is not easy. I will have a fiddle with it, but make no promises. I think, given the explicit resistances vs temperature, and your ECU measured voltages, it should be possible to match them up. I will do that by assuming a 5V supply from ECU to sensor, find out how much current would have to flow to produce that voltage, then use that current as a .... nah f**k. That won't work. The supply voltage is fixed, but there's nothing to say that the ECU regulates the current too. Um... I dunno. I guess there's a voltage divider setup in the ECU. As in, there's another resistance between the ECU's sense terminal and ground. That way, as the sensor resistance changes, that's how they get a floating voltage that varies with the temperature, without having to control the current. Give me a minute or 3.
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*that* is a question for chatgpt (or someone that understands maths....but I'd try chatty). Drop them the table and ask for the formula -
Alright. Exhaust has been looked at, and booked in 'soon'. I'm not 100% convinced it's going to be as good as possible but I'm going to go with it anyway. If I get a reasonable thing that works for 10 years I mean that's twice as long as I've lived with the current one. I have a more pressing issue. I have fixed my MPVI3 (by buying a new one). Excellently, one can wire in analog 0-5v inputs to the ECU itself. I had wideband already via Serial so I also wired it in via the direct input. The idea being I can use the standalone logging without a laptop and have Wideband data in it. The other wire I thought I'd use oil temp. This is where I've gone crazy. HPTuners requires you to implement a formula so you know how much volts = how much temp. This seems relatively simple to me. However I cannot find the scale for this anywhere on the internet, nor decipher how to figure it out without removing the sensor from the car. All I know is that voltage actually goes up as temperature goes down. I am using the actual gauge, so I can see what the temp is. The signal wire has been branched off into the MPVI3. EXAMPLE: 2.68v = 58C 2.7 = 57C 2.74v = 56C 2.8V = 54C 3.06V = 49C 3.18V = 47C 3.37V = 43C I think the gauge is 50-150C. It may be more. It may be less, because I can't find it for the love of f**k. It appears all the information about the gauges I have has been scoured from the internet, but the sender is VDO 320.021 I believe the resistance chart is this How the f**k do I convert this to a voltage? Once I have a voltage... I then have to perform this transform of said voltage to show it in the scanner: https://www.hptuners.com/help/VCM-Scanner/Content/vcm_scanner/defining_a_transform.htm @GTSBoy you're probably my only hope here TEST YOUR MIGHT
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