random spike on the rev counter

[westysprinter]

Hi
I have fitted a DL1 previous and now a Dash 2 into my Westfield. (not the Westfield bulk buy item) the problem I have is that the rev counter suddenly spikes to max with all the shift lights coming on whilst driving.
The rev counter is output from an Omex600 ECU, which never gave problems with my old analogue rev counter. aso the engine doesnt cough as I would expect from a spike in the ECU.
Some fellow Westfield people are having the same problem from various wiring ECU and engine combinations.
Is there a fix?

[osborni]

What sort of shielding are you using on your signal wires? Engines are really good EMI generators.

You should use either twisted pair - where the paired wire is grounded to the chassis to absorb the high frequency spikes - or shielded wire, again with the shield grounded to the chassis. You should only ground the shield or the paired wire at one end of the cable.

You can also play with the rate of change to prevent spurious spikes from showing up.

[westysprinter]

Its a singal wire from the ecu which sits on the tunnel to the dash which is just above it. It's all of 200mm long. There are now 7 people who all have the same problem regardless of there engine, ecu or configuration, this must be a race technology problem

[osborni]

Have you tried to use a Hz filter in the analysis software? Cut it off 10% higher frequency then max RPM pulse should be.

Length of the wire is not as relevant as its orientation to frequency generators around it. (ever hear of the "right hand rule" for electromagnetic fields?) Longer wires just have more opportunity exposure. Really should use twisted pair or shielded wires. Poor grounds or ground loops can do it too. Make sure you ground on only one end of the electrical circuit, not two.

The simplest way is to just wrap a wire of the same gauge around the signal wire at about 1 full wrap per 1/2 inch to inch. Then ground one end of the wire. The wire acts as sort of a capacitive sink to high frequency spikes.

Cars are really noisy environments. Frequency spikes should be expected.

I have a BMW M Coupe (e36 M3 US motor and electronics). Fully shielded signal wires but no frequency filters in software and no issues with spikes.

[westysprinter]

Cheers, its a simple thing to try, but due to the various instalations im aware of with the same problem in suprised it will work.
Not sure about the hz filter, where do i find that in the set up
Cheers WS

[osborni]

Data > Variable Manager

Open up the External Inputs > RPM channel > Advance Options > Filtering.

A Low pass filter will cut out the high frequency junk. You need to set the Hz to something appropriate that will let your main RPM signal come in without an issue, just reject the garbage.

You can also change the "rate of change" to something more appropriate to your throttle response.