Larry,

ALL WRENS turbines have the option of "onboard start" or "autostart" The difference in the two is simply what is carried onboard the plane during flight.

The "autostart" version carries all the fuel, and propane equipment as well as the glow driver onboard fulltime, so the plane is truly a fully autostart plane.

The "onboard" start version has the starter mounted on the engine, and the fuel valve stays in the plane. ALL of the propane equipment (tank, valve, plumbing) as well as the glow driver, does not.

The two engine have different ECU's, the autostart engine has a fully automated ECU, meaning, you slide your trim fully up, move your throttle stick to full then down to idle, and the engine goes through a full auto start sequence. On the onboard start, the ECU controls the fuel but the user controls the propane and glow.

If your plane will be weight or space sensitive, the onboard version is great, since you can leave off the items not needed for flight and save some weight and keep the install simple.