A while back I bought a Gear Vendor Overdrive. I've had a love/hate relationship with the thing but I think I have at last made peace with it.
The thing is like having a genius kid that won't do his homework. The MPG
improvement seems to be there but I'm had trouble keeping it working long enough to find out.
Mechanically, the GV is bulletproof. Electrically, it's cheap-charlie. It has a control box that automatically downshifts when your road speed gets too low for the hydraulic pump in the gearbox to hold the clutch in - somewhere around 20 MPH. When there is any electrical disruption it defaults you into a disengaged mode.
At first it was the cheesy electrical connections. I'd hit a rough spot in the road and it would drop out. Good quality avionics-grade connections helped but then the brainbox got a wild case of temperature sensitivity. When the outside air temp got below 30 F or above 90 F the darned thing just wouldn't stay engaged.
Apparently this is not a new issue and I should have it worked out. If it stays in OK I'll do some winter MPG
My truck gets about 24 MPG
winter in my mixed driving test loop without the GV. One-third state roads (60 MPH), one third Interstate (70 MPH) and one third urban/suburban (moving along with traffic. I like to got about 1500-1600 miles (four fill-ups) so inconsistencies in my filling procedure averages out. In summer I get 26 MPG
I'm (from earlier partial tests) expecting an additional 1.25-1.5 MPG
winter and a full 2 MPG
From what I've found out about BMEP curves you want to operate in a high load/low RPM mode. Right at the ragged edge of a lug. for me my drivetrain delivers. 1325 RPM and 600 degrees TIT at 70 MPH. 1125 RPM and 550 degrees at 60 MPH.
My aerodynamics for this winter are OK but sub-optimal. I run a flat hard tonneau and a conveyor belt air dam (very rugged). If I had a good aero-lid I'd expect and additional 1.5 MPG
. If all goes well, I'll address the aero aspects in the spring.
Let's get a good season of GV operation first.