Trail Tech Tachometer Setting By dannicus (Read 5,603 times)

[dannicus]

I just installed a new TrailTech TTO Tach/Hourmeter on my Znen Milan. Had one on my BMW that worked great.

Only problem is, I'm confused about the pulses per rotation (PPR). The tach picks up an inductive pulse off of the spark plug wire. I figured that the the ignition setup on these 150s is a "wasted spark," or one spark per rotation rather than every other; on the compression stroke. When set to 1 pulse per rotation, the tach obviously reads half of actual RPMs, so I ended up setting the thing to 0.5 PPR.

Anyone else come up with the same findings?

[Bashan]

You are absolutely right, we waste a spark. They fire every revolution so you must set your tach accordingly. I'm not familiar with that tach so I wouldn't know what to tell you. I use a Tiny Tach and the set up on it is a breeze, it lets you pick from different degrees of firing depending on the number of cylinders. So for my GY6 I toggled to 360 and waited 30 seconds....done. It's really easy to see in the daylight too, I wish I could say the same about my Tom Tom. But I can't get to critical of my GPS, it fell off of its suction mount at 60+ MPH and still works. Rich

[dannicus]

The TTO gives the option of 0.5, 1, 2 pulses per revolution. I'm only assuming that it's reading half of actual based on my rpms @ 60mph coming up as around 3800. There's no way.

Anyways, it works fine set to 0.5PPR. Strange, tho. I did get a recommendation from Trail Tech via email to try running the sensor wire longitudinally along the spark plug cable rather than wrapping it around as per the instructions.

<UPDATE>

Got another email back from Trail Tech. They tell me that having to set the Tach for 0.5PPR is typical for alot of scooters despite the single spark per rotation ignintion.

[Cruiser]

1 PPR setting should be accurate. The ignition gives one spark pulse per revolution. There is only one power stroke every other revolution so one spark pulse is wasted. You want to measure the revolutions of the engine not the amount of power strokes (like a 2 stroke) so the 1 PPR setting is accurate.

[dannicus]

Oct 12, 2010 21:21:05 GMT -6 Cruiser said:

1 PPR setting should be accurate. The ignition gives one spark pulse per revolution. There is only one power stroke every other revolution so one spark pulse is wasted. You want to measure the revolutions of the engine not the amount of power strokes (like a 2 stroke) so the 1 PPR setting is accurate.

Not in this case.

[Cruiser]

Possible that the spark on some scoots is weak enough where you have to compensate by using the .5 PPR setting. I wonder if this would change with a high output coil.

[dannicus]

Oct 12, 2010 22:49:31 GMT -6 Cruiser said:

Possible that the spark on some scoots is weak enough where you have to compensate by using the .5 PPR setting. I wonder if this would change with a high output coil.

Could be. Can't imagine why it would consistantly miss out on every other spark, tho.

Wonder if things will change if I run the sensor wire longitudinally.

Anybody have a CDI schematic? there might be some answers in there.