Datalogging RPM Signal

[JedIEG]

I have an LM-2 data-logger that I am trying to use to tune my car. I have one wideband O2, TPS, MAP, and a Narrow Band O2, but it is all kind of meaningless because my RPM is not working. I have talked to Innovate about it and they have not suggested much beyond adding the potentiometer (which I did from day one). I have even sent the logger back to Innovate and gotten a replacement, but that didn't change anything. Has anyone else had this problem?

 

[DereII]

Dug up this old question, hoping OP solved the issue.

I wound up having to be very careful to isolate the tach signal from my car's MSD-6AL box all the way to the potentiometer. I was routing all of the accessory wires through one grommet in the firewall, when I segregated the tach wire and wrapped it with aluminum foil where it ran with others I got a good read on it. This year it will have a new route to clean things up.

 

[JedIEG]

Thanks for the follow up. I do have the LM2 working fairly consistently now. My tach wire is twisted with a ground wire similar to a CAN wire and run separately to the rest of the harness, similar to what it sounds like you are doing.
The biggest thing that has helped me with both the O2 and tach signal reliability is very odd- I moved the O2 control circuit board to the #2 position. For whatever reason, everything works way better that way.

 

[DereII]

Good deal. I've got no LM2, went piecemeal with a PL-1 Pocket Logger recording from an SSI-4 Plus that's got an MTX-L Plus, tach feed and MAP sensor feeding it. Thinking of adding a TPS, sometimes I'll get a run that's a little faster or slower than expected when the car doesn't follow air changes like the other cars I race with. 60' is normal, but mph and e.t. falls off or picks up. Just bugs me a little thinking it could be a throttle issue and I'm missing it. Plus, could correlate throttle position with my guesses as to when the carbs are transitioning from idle circuit to mains. And who doesn't appreciate more wires into and out of the interior?

 

[JedIEG]

I like the concept of the LM2 because it basically has the capacity for all those other devices in one unit. Reliability is only ok though.

And who doesn't appreciate more wires into and out of the interior?

LOL for sure. What's another wire? I have all the 5v wiring routed in their own harness with the hope of one day removing it... or I think the only sensors I'm missing for EFI is crank and cam pos. So that's always in the back of my head if I get too irritated with carb tuning.

Thinking of adding a TPS,

Yeah it's worth it in my opinion. I have my TPS rigged up to a bracket that let's it actuate off of the kickdown bell crank instead of directly to the primary throttle shaft. It was way cheaper than the setup that Holley sells and I think just as clean. My big debate is on adding a second TPS to the secondaries to see when they are opening. I have also thought about running a cheap USB bore scope into the air cleaner and recording the primary venturi to confirm when the boosters are starting to flow. Something to think about...

 

[DereII]

I run either a Thermoquad or a Mighty Demon, have considered trying to link up to the throttle cable so the carb doesn't matter, or get the Innovate that is supposed to work with Demon carbs and just use it with that one---although mine has vac fittings where that one connects to the primary throttle shaft. No kickdown linkage as the transmission has a manual valve body.

With most driving around town being an idle circuit deal I'd also like to know when the main circuit starts up and shuts off at those low RPM's. Same with the TQ's secondary fuel system. Curiosity, mostly.