The system works by reading the rpm of both engines and comparing them. It then changes the servo signal to the salve to match the master. If it loses the master rpm signal it drops out and sends the receiver signal to the slave, giving you direct control of the slave rpm. This will cover failure of the master speed sensor, in which case you are flying as though the sync unit were not there. If it loses the slave signal with both engines running you have a problem. The slave will go to full throttle, giving you control of the master engine only. I've not had either problem, but it needs to be considered.

The instructions say to start the slave engine, tune it, then shut it down and start the master. When the master is set restart the slave. BUT. this makes the slave start at full throttle, then the sync unit will close the throttle on the slave to match its rpm to the master. I do not like starting at full throttle.

Several ways to get around this. Start the slave, and without shutting it down start the master. This is the easiest way. Or you can set the throttles to starting point, and turn the airplane's radio off. Start both engines and turn the radio back on. I've used both ways, they work, and are better than starting the slave at full throttle.

The unit works, and works well. I didn't like the response time on quick throttling, the slave always has a little delay following the rpm of the master. The instructions mention the possible need of more than two magnets for precise operation on slow turning engines, so I went to four magnets on each engine. Now the delay is so short as to be no problem, so long as the engines will spool up as quickly as you give the higher throttle signal. With two magnets the airplane would yaw a little, took about 3/4 second to match speed. There is still a delay with four, but almost imperceptible.

Summary:

The sync unit at $90, the specially cut Tru-Turn spinners and adapter nuts for another $90, and roughly $20 for the additional wire and connectors added $200 to the cost of the plane.

Is it worth the cost? I might well have gotten the spinners, but the original Du-Bro plastic spinners were less than $20 the pair, much less cost than the Tru-Turn, but the metal spinners are a lot prettier, and actually weigh less than the Du-Bro. The weight savings was lost with the other added parts though.

I guess my opinion of the worth is best illustrated by my not bought a second one.

Nice, yes. Needed? No.

Bill.