gear indicator indication

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Posts: 84
Joined: Fri Jun 22, 2018 2:14 am

gear indicator indication

Post by ProtoTim35 »

I'm running a Hayabusa motorcycle engine in a racecar. It has 6 sequential gears and Neutral. I was able to somewhat trick the analog input into displaying 5 of the 7 positions, using the mapping mode, but it isn't really what I want. I'm hoping someone can help me with this. I'll tell you what I did, and how I got there, and maybe someone can take it from there.

These are the measured voltages for each gear position:
N= 5.1
1 = 1.9
2 = 2.4
3 = 3.1
4 = 3.8
5 = 4.5
6 = 4.9

I took those numbers, and assigned map positions as follows:
1 = 2.4 (showing value of 2 for second gear)
2 = 3.1 (showing value of 3 for 3rd gear)
3 = 3.8 (showing value of 4 for 4th gear)
4 = 4.5 (showing value of 5 for 5th gear)
5 = 5.1 (showing value of 0 for neutral)

Unfortunately, there are only 5 map positions to fill, thus I left out 1st and 6th gears, since they are the end points and less easily confused with another gear, and I didn't feel the map would accept or display (N) for neutral.

What I'm hoping to be able to do is have each gear be able to be displayed, and have N or preferably even "Neutral" for the neutral position.

Can this be done with Lua scripting, or some other way?

If so, I would greatly appreciate it if someone wouldn't mind helping me with this either by writing the script or coaching me on how to write the script. I would love to learn more about lua scripting, but I suspect I won't be using it much once I get the MK3 set up, and I'm trying to get my car on the track, so I don't want to spend too much time trying to learn it right now.

Thanks for any and all help.

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Post by MikeD »

It's possible with lua easily, though I think you cannot display N for neutral but rather have to live with 0 (zero) which might be ok.

One question: where do you get the sensor signal for gear position and how did you measure voltages that you posted? Is this sensor connected to the engine ecu and you backprobed it with your multimeter?

Asking because the RCP MK3 can only measure 0-5V but not 5.1V, so from 6th gear to neutral there is not much room to detect correctly.
It could work depending on how clean or noisy the signal is, otherwise you may need two resistors to bring the voltage down a bit (in this case you need to know what you do, or you probably mess up the original signal to your ecu, assuming the ecu uses this signal at all?!)

You can hook up the signal to the RCP MK3 and observe it in more detail (take notes in V/mV reported by the RCP) and then let's go from there. I would also use the multimeter in parallel and observe signal voltage before/after connecting the RCP/MK3 to see if or how much the RCP would manipulate the signal. Just connect/disconnect the RCP after you have it wired and watch the values. At best it doesn't change at all when connecting the RCP, but you better have a look at it, in case the ecu uses this signal too for anything important other than displaying the data on the OEM dash.


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Joined: Fri Jun 22, 2018 2:14 am

Post by ProtoTim35 »

Hi MikeD. Thanks so much for getting back to me.

I spliced into the wire that goes directly from the sensor to the ECU. I understand that the ECU does use the signal for fuel and ignition mapping. If I need to install resistors, that could be easily done between the splice connection and the supply wire. I would just need to know what resistors to use. I only have a couple on hand, but I can get whatever I need.

I can live with the “0” for neutral. That’s not a problem.

The way I got the voltage readings will take a little bit to explain: I’m certain I did it with the MK3, but I might be remembering wrong. I hooked the wire up to MK3, and selected “gear”. I then, changed the units to volts and then Raw. Initially, I then simply went through the gears with the ignition on, but engine not running, and was getting really screwy readings, so I started the engine up, and went through the gears again, and got the readings that I posted. I had the precision set at 3, but I rounded that, since there was sufficient gap between readings that I didn’t feel anything more than precision 1 was necessary.

I can’t explain how I got readings more than 5 volts unless I am remembering wrong, and used my multi-meter, which I know I started out to do, but am certain I changed over to using the MK3. I know I used the MK3 for the readings on most of the sensors I set up.

Actually, for one of the sensors, it may or may not have been the gear sensor (I can't recall for sure), I initially selected "battery" and modified the settings (but on the channel I am currently hooked up to, not the battery channel of the MK3). I don't know if "battery" would set anything different for getting the readings or not. I don't know why it would, but I know that one of the analog channels is factory set to "battery" and it reads the battery line voltage. That might be how I got those readings.

I’ll get those readings again today, including, as you recommend with a multi-meter in parallel and by itself to be sure what I’m getting isn’t going to affect the ECU. I hadn’t been concerned about the signal affecting the ECU because someone (I think it was Brent) had said that the MK3 has such low impedance it shouldn’t affect anything. Hopefully, he’s right.

I’ll get back with you – hopefully this afternoon, possibly even this morning with updated info.

Thanks again for helping on this.

Posts: 84
Joined: Fri Jun 22, 2018 2:14 am

Post by ProtoTim35 »

Hi Mike,

Update on the Gear sensor. I ran the car while taking the readings. I re-set the gear settings as follows on Analog 4: I set the units to Volts, Prec 2, min 0 max 15 and raw. If you expand this window it might make it easier to see and compare the data below.

When reading the voltage, I got the following:
Neutral: on MK3 = variable 5.08 to 5.13. on MM with MK3: 5.07 - when disconnected from MK3: 5.07
1st gear: on MK3 = variable 1.82 to 1.92. on MM with MK3: 1.86 -- when disconnected from MK3: 1.83 - 1.84
2nd gear: on MK3 = variable 2.31 - 2.45. on MM with MK3: 2.31 -- when disconnected from MK3: 2.28
3rd gear: on MK3 = variable 3.05 - 3.23. on MM with MK3: 3.05 -- when disconnected from MK3: 3.05
4th gear: on MK3 = variable 3.78 - 3.91. on MM with MK3: 3.74 -- when disconnected from MK3: 3.73
5th gear: on MK3 = variable 4.47 - 4.61. on MM with MK3: 4.43 -- when disconnected from MK3: 4.42
6th gear: on MK3 = variable 4.79 - 4.93. on MM with MK3: 4.75 -- when disconnected from MK3: 4.75

I hope that helps. Based on that data and on your previous post, it looks like it might be a good idea to put a small resistor in the trunked off line to the MK3, to get the neutral position below 5 volts. However, with the way I mapped it as previously described, the neutral position seemed to be registering "0" just fine for the minimal testing I did with it. If so, what range would you recommend. I know I have a few 120 Ohm and something around 65K Ohm. I have a few others, but they are larger resistors and I'm not sure what they are without pulling out a chart to decipher the color coding.

I suspect though, from those readings, that having the MK3 hooked up parallel to the ECU shouldn't pose any issues with the minimal changes I see on the multi-meter readings with and without the MK3 connected. However, you have a lot more experience to my pretty much NIL experience in this, so you might want to recommend otherwise.

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