P3 speed discrepancy

If it still chuffs exactly 4 times per revolution (but scaled by the speed error - so 2 chuffs/rev for double speed) over a range of speeds then my guess is you have an issue with the striped flywheel - dirty stripes, not-positioned the correct distance to tach sensor, etc.   Can be a bother to remove the shell on the engine but that's my suggestion.

If it chuffs exactly four chuffs/rev, I don't think it's the tach or sensor as missing stripes would logically drop the chuffs/rev to less than what is programmed.

I'm going to open it up and see what's up.Thanks.

I cleaned the flywheel.Sensor appears to be spaced properly vis a vis the flywheel.But definitely getting more than one revolution per 4 chuffs. At 22 scale miles per hour it is actually traveling at 30 scale mph. Any thoughts would be appreciated.

First off, make sure the sensor is really about 1mm (thickness of a dime) from the flywheel.  If it's off that by much, that can cause it to miss stripes.  Next, you may want to consider replacing the flywheel tape if it's at all stained, and finally, you'll probably want to consider a new tach sensor.

Those would be the things I'd be checking.

What do you mean by "cleaned the flywheel"?  Are the stripes painted on or is this strip of "paper" taped on to the flywheel?  The idea is to get distinct white and black transitions to reflect or not-reflect an optical beam coming from the sensor board.  Another possibility is some kind of gunk (that's a technical term!) on the tiny sensor component.  I don't know if there's a prescribed cleaning method but the idea is to clean off anything stuck to the two windows facing the striped flywheel.  Apparently the sensor is "missing" about half of the stripes since you're going ~30 vs. ~22 sMPH.

Thanks for the input John and Stan. I cleaned the flywheel tape.It was little dirty. The sensor seems to be closer than 1mm. And I'm going to attempt to clean the sensor board. I'll let you know how it turns out

If it miss counts stripe it thinks it is going slower than ordered so the processor will send more voltage/current to motor so it runs faster than ordered.  Of course the faster it goes the chance it misses more stripe is feasible.  G

Too close is bad as well as too far on the tach sensor.

The sensor seems to be closer than 1mm. And I'm going to attempt to clean the sensor board. I'll let you know how it turns out

This may not be the way the repair guys do it but I would jury rig the reader holder  somehow to avoid soldering spacers. Ex .. A small plastic wire tie  to pull up  ,  sliver of wood, anything to get the proper spacing.

If it's a small difference, a spacer to push it out a bit should work fine.