MS3X & MS3Pro - Tacho calibration

[dap930]

For people using MS3/MS3X and MS3Pro for EFI, you can calibrate your tachometer to read what Tuner Studio shows for your actual engine RPM's. I my case, my tachometer was reading a little high, so I adjusted it using the Tacho drop down menu:




Note that you will need to do a power reset once you select "variable". Then you can select a percentage that bring your tachometer in line with what TS is reporting for engine speed. I noted tachometer readings at various engine speeds rechecked the car tachometer after adjusting the tacho %.

[boosted79]

Does that mean your tach was reading 14% high? So when it was saying 6000 rpm, the actual was 5263?? 5263 x 1.14 = 6000. If so, that's huge, or is the 86% just hypothetical?

[Tippy]

I need to adjust mine too

[dap930]

My tachometer was rebuilt several years ago when it quit working. Ever since, it seemed that read a little high and it seemed a little over damped. Since converting to EFI, I have always noticed that it read higher than what Tuner Studio reported. I just recently saw a post in the Megasquirt forums where someone said that the tacho output could be used to adjust the car tachometer output. I had not been aware of this. In my case the car tachometer would read close to 1200 RPM's when TS indicated 950-1000 RPM's. I did check at 2K, 3K, 4K and 5K and the tach did track closely with RPM's TS showed. As far as the tach being 14% off, it did not seem to respond in linear manner with 1% changes in TS. I guess I could look at the tacho signal with an o-scope to see the difference between 100% and 86% settings.

[db9146]

Dennis,
What output on the MS3 are you using? Pin 25 (IAC1A) or something else?

Dee

[jpnovak]

Yes, all my factory tachs read higher than actual measured rpms.

[billjam]

I have noticed the same issue with my tach. It reads significantly higher than what I see in TunerStudio, however I don't understand how an adjustment in TS will render my tach reading correct once TS is disconnected. Am I missing something here?
Dennis, I can't find that Tacho Output window anywhere in TS (v3.0.28).

PS, my car is running great now.

[GJF]

The signal is sent from the ECU not Tuner Studio. Once the value is edited to the ECU using Tuner Studio, it doesn’t matter if the Laptop is connected the edited value in the ECU is what your tach will display.

[Tippy]

My tach is opposite. It lags TS.

For some reason, once it hits about 5K, it slows down and never actually reaches peak RPM that TS shows.

Never minded it much, honestly.

[billjam]

Originally Posted by GJF

The signal is sent from the ECU not Tuner Studio. Once the value is edited to the ECU using Tuner Studio, it doesn’t matter if the Laptop is connected the edited value in the ECU is what your tach will display.

Ah yes, that makes sense. Still can't find that Tach Output window though.

[billjam]

Found it ... but it doesn't have the same options in my TS.

[Tippy]

You have the latest TS?

[dap930]

Bill,

I have V3.0.28 for TS. Do you have the paid version? It should auto update.

[billjam]

Dennis, I have V3.0.28 and it is the paid version which auto updates.
I just looked at the Help menu in TS and there is an item called "Upgrade for even more features" to a version called MS Ultra.
This may be what you have, so the extra MS Ultra functions might include the tach adjustment. It is a $40 upgrade.

[dos531]

Originally Posted by billjam

Dennis, I have V3.0.28 and it is the paid version which auto updates.
I just looked at the Help menu in TS and there is an item called "Upgrade for even more features" to a version called MS Ultra.
This may be what you have, so the extra MS Ultra functions might include the tach adjustment. It is a $40 upgrade.

It's not the version of tunerstudio, it's probably the firmware on your megasquirt. Have you updated that recently?

[dap930]

Bill,

dos531 is right, the Tacho adjustment feature was available on V1.4.1 firmware because that was the version I had when I made adjustments to my tach. Of course V1.5.1 is now the latest, but it implements engine states which requires a little work to fill in the engine state parameters.