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Old 02-08-2011, 10:49 AM   #6 (permalink)
Crazyrabbit
EcoModding Lurker
 
Join Date: Dec 2009
Location: Sunny Arizona
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Quote:
Originally Posted by Ryland View Post
You can cut the fuel on a diesel rabbit by turning the key off, the mechanical fuel pump has a solenoid valve, a single wire going to the valve, that is the only thing that keeps the engine running is the fuel getting to the pump.
As for the alternator, a smaller alternator isn't going to make much of a change other then the stock alternator an electrical load is an electrical load, spinning the two alternators without a load should be about the same drag, so spinning them with the same amount of load should be about the same.
Ryland you are right about cutting the fuel with the key, but that sometimes confuses the glowplug controls and the seatbelt interlock, so I have a switch to do that. I don't use it anymore though because it is not 100% reliable. I tried a normally closed momentary switch for a dome light, but that switch was all over the place and would have anywhere from .3 to 1.2 ohms resistance, that worked about 75% of the time. I replaced it with a Volvo rocker switch that is much more consistent at around .2 ohms, but it is still not perfect. At 2 amps the solenoid coil can't stand much additional resistance in series and still produce enough force to lift the core. A manual control would go around that completely and draw no current.

If I got rid of the solenoid coil the average current drain on the car would drop so much I could probably put the 15 Watts of PV panels I have on it and just toss the alternator. Since I put in Bosch 80010 4 second glow plugs the starting performance is simply spectacular. Even on a cold day (for Arizona) the starter only has to crank for a second or two.

Thinking about this made me curious enough to calculate:

Glow plugs are on a 50 amp fuse so 0.00066 kWh per start.

Starter assuming its 2 hp, 0.0008 kWh per start.

Fuel Solenoid 0.024 kWh per hour use.

Headlamps 65W each, 0.13 kWh per hour use.

15 W PV panels 6 hour average insolation per day 0.09 kWh

So, I conclude I could easily add the PV panels and given my normal commuting duty cycle easily toss the alternator. If I can slack it off and wire the belt out of the way, I could easily reconnect any time I need it. And, if I got a manual control on the fuel flow, I might never need it again.
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