Which grounds to use for sensors ?

[TheAlien]

So as far as I understand, there are two different grounds on the DB37 on a MS2-V3. The ones to ground MS to the engine block and the ones to ground sensors.
I think 8-11 are the grounds to ground MS to the engine and 18,19 are for the sensors (IAT and CLT), right ? The problem is, I have to ground a lot more. What about the crank (hall) sensor, the cam (hall on the VR-Circuit) sensor and the TPS ? What should be done here ideally ?

I am about to make my provisional wiring permanent... So I'd like to have it right...

[fscott]

There's really only one ground, but it does matter how things are wired.

All your sensors must ground to the MegaSquirt, which is then grounded to the engine block.

You start to get problems when you ground a sensor to the engine or the frame.

You have more wires than you have pins, and that's OK. Run a single wire from pins 18 and 19. Connect all your sensor grounds to that wire. Your sensors now all ground to the MegaSquirt, so you're good.

[TheAlien]

Thank you !
So do I get this right ? I could do the following:

DB37#18 could have ONE wire go to the two hall Sensors
DB37#19 ONE wire to IAT, CLT and TPS
DB37#8-11 four wires to the engine block

I should not take one wire for each 'device' like this:
DB37#8 one wire to engine block
DB37#9 one wire to cam sensor
DB37#10 one wire to crank sensor
DB37#11 on wire to TPS
DB37#18 one wire to IAT
DB73#19 one wire to CLT
because the MS might actually grounded sufficiently with only one wire, correct ?

[TheAlien]

In the last sentence I meant to say 'insufficient' not sufficient...

[trakkies]

There's really only one ground, but it does matter how things are wired.

All your sensors must ground to the MegaSquirt, which is then grounded to the engine block.

You start to get problems when you ground a sensor to the engine or the frame.

You have more wires than you have pins, and that's OK. Run a single wire from pins 18 and 19. Connect all your sensor grounds to that wire. Your sensors now all ground to the MegaSquirt, so you're good.

I'm using the original coolant sensor as fitted to the OE injection, and that is grounded to the block. Would it make sense to change it for a two wire type - if such things exist?

[stevemgb]

On my rover v8 there is a single wire sensor for the temp gauge at the front near the alternator and a 2wire coolant sensor for the original ecu on the opposite side(large brass nut next to thermotime switch which looks exactly the same but is not!)I used this and ran its earth to the msecu.Steve.

[fscott]

I'm using the original coolant sensor as fitted to the OE injection, and that is grounded to the block. Would it make sense to change it for a two wire type - if such things exist?

Yes. The one sold by DIYAutoTune is a two wire. I had to make that change, among others, on my bike. It made a big difference. Before, I could hit the left hand turn signal and watch the air fuel meter change in time with the signal, and hear the engine's speed do the same as the fuel mix changed.

Since studying up on the grounding and doing it the way they recommend, I've had no problems.

TheAlien: You've got it right in your example.

Have a look at Bruce's video about grounding here. It makes it all very clear.
http://www.DIYAutoTune.com/tech_article ... videos.htm
It's this one. Proper Grounding and Noise Elimination - Bruce Bowling - 1:08:54

Fred

[trakkies]

On my rover v8 there is a single wire sensor for the temp gauge at the front near the alternator and a 2wire coolant sensor for the original ecu on the opposite side(large brass nut next to thermotime switch which looks exactly the same but is not!)I used this and ran its earth to the msecu.Steve.

You're right - had a brain fart. Put it down to a senior moment. ;-)

[TheAlien]

For who ever is interested to what I did:
I changed my grounds. Every sensor is grounded with a single wire to MS now and MS is grounded with the remaining wires to the engine.
Works so much better than before now. I found a sensor that I grounded provisionally directly to the engine (which I forgot about). This was probably causing all the noise that I had in my 02 signal and temp readings...
It's just plain awesomeness in comparison to before now.
Thanx guys !

[TheAlien]

Is it normal that my coolant temperature drops almost 25 Celcius degrees when I go WOT (I think that's about 45 degree fahrenheit) ? It drops from 78C (172F)down to 53C (127F)...
Shouldn't it go up, if anything at all ?
log file:
http://rapidshare.com/files/320643970/2 ... 2.msl.html
If you go into the log file there is a typical drop of the CLT reading when you jump to the maximum rpm...

[TheAlien]