AEM 30-4900 Failsafe UEGO, spikes on RPM signal. RESOLVED.

[Nigep]

I`ve swapped from my old AEM UEGO AFR gauge to a new AEM 30-4900 Failsafe UEGO.

It has a great feature than will cut boost (or whatever I choose) when it sees AFR outside of preset values when in boost. It also doubles as a combined AFR AND Boost gauge, so I`m killing 2 birds with one stone.

Unfortunately, when I use the inbuilt datalogging of the gauge (Yeah, it logs Boost, AFR & RPM too), I`m seeing spikes on the RPM signal.

I`ve taken the RPM signal from the Coilpack trigger on my ECU. (Megasquirt 1, V3).

Unfortunately, as you can see on the screenshot below, the RPM (RED trace on the bottom graph) is picking up noise somewhere.



I`m guessing I need to add some sort of small circuit to remove whatever is causing the spikes, or pick up the RPM signal from elsewhere, but I`ve no idea where to start !.

For info, this is the AEM Log that`s picking up noise. Megasquirt / Tunerstudio is working perfectly, no spikes, it`s just the AEM that`s seeing noise from somewhere.

Any ideas please ?

[slow_hemi6]

Use the basic tacho out. http://www.msextra.com/doc/ms1extra/MS_ ... m#tachoout

[Nigep]

Thanks for the link.

A bit of feedback which may help other in the future.

Circuit added, used JS0 as the Tacho Output Pin. Circuit Tacho output via SPR3 to get to the outside, then from Pin #5 to the AEM.

I had to change the resistor from 1K to 470 Ohms as shown on the circuit below.


1K was too big, 470 seems fine. A nice smooth RPM signal. (Bottom trace, RED)

[slow_hemi6]

It's not uncommon to have to adjust the pull up to suit the needs of your load. All loads will have a certain input impedance that needs to be overcome. You do however have to ensure you don't overload the transistor so a safe figure like 1K is generally shown. With 470 ohm the 2n22222a is switching about 30mA which is still well under its maximum switching current of about 0.5 to 0.8A

[Nigep]

It's not uncommon to have to adjust the pull up to suit the needs of your load.

I didn`t know that ! Not having to do much modification to the ECU in the past, it isn`t something I`ve ever come across before.

All loads will have a certain input impedance that needs to be overcome. You do however have to ensure you don't overload the transistor so a safe figure like 1K is generally shown. With 470 ohm the 2n22222a is switching about 30mA which is still well under its maximum switching current of about 0.5 to 0.8A

Thanks for the clarification that what I`ve done is still `safe`