losing RPM signal sometimes

sirandrewbutler
Posts: 4
Joined: Thu Apr 08, 2021 1:42 pm

losing RPM signal sometimes

Postby sirandrewbutler » Thu Apr 08, 2021 2:08 pm

Over winter I replaced an old Pi Systems data logger and dash in my car with a DL1 Club & Dash4. I picked up all the sensor inputs from the Pi loom including REVs which I have connected to the the high level input on the DL1 because I don't have a wiring diagram and am unsure of the origin of the signal.

It all seems to work and I've got the analogue sensors scaled correctly but during shake down yesterday I was getting drops in the rev signal, the dash would show a totally unrealistic and unchanging value and sure enough, the logs show the same thing.

It could be just a simple bad connection but the problem seemed to be strongly correlated to my battery going flat (no functioning alternator at the time). At the start of the day the drops were infrequent and at the end of the day it was a persistent issue. After a recharge, the problem seems to have disappeared again.

Is it conceivable the RPM input levels were dropping below the required input threshold for the high level input?

Thanks,

Andrew

Support
Posts: 383
Joined: Mon Nov 21, 2005 4:09 pm

Re: losing RPM signal sometimes

Postby Support » Fri Apr 09, 2021 3:39 pm

Hi Andrew - Yes very conceivable, is the vehicle fuel injected? You could connect the switched negative side of a fuel injector to the RPM low level input (RL) and retest. Be aware the DL1 CLUB will need to be configured for the low level input. Open the DL1 CLUB configuration utility > go to the RPM inputs section and enable the low level input with 1 pulse per revolution for your initial test.

Important: Don't forget to read the current settings back from the data logger before making any changes.
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Posted by Race Technology Support

sirandrewbutler
Posts: 4
Joined: Thu Apr 08, 2021 1:42 pm

Re: losing RPM signal sometimes

Postby sirandrewbutler » Mon Apr 12, 2021 3:25 pm

Hi Yes, the vehicle is fuel injected but Id rather not mess about with the loom as its quite nicely built. I'll trace the rpm feed and if it comes from a low source which will be free of transients I'll connect to the Low RPM input and see if that improves things.

I've tested some more since my first posting and even with a decent battery voltage the RPM signal drops so I think it must be right on the minimum threshold for the high input on the DL1. Can you tell me what the min input voltage would be on that input please?

Andrew

sirandrewbutler
Posts: 4
Joined: Thu Apr 08, 2021 1:42 pm

Re: losing RPM signal sometimes

Postby sirandrewbutler » Mon Apr 12, 2021 8:41 pm

Ok...

The tacho wire i used from the old Pi systems loom comes directly from the tachometer out pin in the Omex 600 ecu.

I would have thought this would drive the DL1 low input but I tried that and got 0 RPM on the dash with the engine running.

I’m thinking a pull up may be required.

Any help much appreciated.

Andrew

sirandrewbutler
Posts: 4
Joined: Thu Apr 08, 2021 1:42 pm

Re: losing RPM signal sometimes

Postby sirandrewbutler » Wed Apr 14, 2021 9:03 pm

I’ve put a scope on the tacho output from the OMEX. It’s a 0v-battery voltage square wave 50% duty cycle with two pulses per revolution.

This sounds ideal to drive the low RPM input on the DL1 but that doesn’t seem to work.

Does the RPM earth need to be removed from the DL1 when going from the high input to the low one?

Also does anyone know the minimum swing to trigger the high RPM input?


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