- Apr 8, 2009
If I really wanted to accurately determine how much difference any particular change made, I would make upgrades immediately after filling the tank, and then do only change at a time, going the entire tank and calculating mileage before doing another.
I don't have that kind of patience.
When I wrote last about it (the post with the pictures) I had begun those mods several days into a new tank of gas.
I looked up what was typical for the same model and year of truck online (there are no EPA estimates for it) and found people reporting anywhere from 10mpg to 18mpg.
Myself, loading it to it's max for work, but being a generally gentle driver, before I had ever heard of hypermileing I was getting between 15 and 17mpg.
By changing just my driving habits, driving slow, accelerating gently, coasting when coming to a stop, I raised it to 19.7mpg.
After the first stage of changes to the truck (the tank I was on when I wrote about them March 21) I ended up getting 21.75 miles with a gallon of gas.
Once again, I filled up, and then several trips into the new tank, got around to starting my next series of upgrades.
I still have yet to go to the salvage yard to try to find a manual steering gear and electric vacuum pump (so the brakes work when the engine is off). I was planning to go today, but the rain had me change my mind.
I did make it down to Al Lasher's last week for some switches.
Nobody makes a wiring diagram for this year for the diesel engine.
I spent many hours over several days upside down under the steering wheel, trying to trace and test various wires.
-If you happen to own a 7th generation (80s) Diesel F-250, and you want to wire in a kill switch or remote starter: The thick red wire with a green stripe goes to the injector pump (for a kill). The thin red wire with a blue stripe goes to the ignition relay (for a start).
The switches are dual purpose: wire them one way and they are momentary open, wire them the other and they are momentary closed. I used one each way, so that one stops fuel to the engine, the other triggers the starter. I mounted them side-by-side in a block of scrap wood, attached to the gear shift with a strip cut out of a steel can lid (mandarin oranges, of course).
As I had hoped, they definitely make the pulse and glide (coasting, etc) much faster, simpler, more precise, and safer, then using the key each time (especially since the ignition on this truck has been very finicky as long as I have had it) which encourages me to do it a lot more often.
-The orange wire running from the external voltage regulator to the alternator controls whether the alternator is charging or idle. If you open the circuit the alternator stops charging. Even though it is still being turned, there is no resistance, it just freewheels.
If anyone is inspired to do a similar project (with any vehicle), DO NOT just disconnect the alternator from the battery w/o disconnecting the smaller wires. It will continue to produce current, but since that charge has nowhere to go, the alternator will self-destruct.
At first I just disconnected the wire, but now I have it on a switch so that if the battery ever does run too low, I can charge it with the engine just by flipping the switch.
-Another point of note: diesel trucks tend to have very large batteries. Mine has two. This gives me a lot of reserve power to tap into without draining them too much. With an ordinary car battery you will damage it by cycling it too deeply. Once it finally dies, replace it with a deep-cycle (RV or marine) type battery and you'll be fine.
These have been my only changes. They facilitate they way I have already been driving, but do not, in them selves, reduce engine load or increase aerodynamics at all.
This most recent tank included jobs such as moving a full truck bed of bikes, bike parts, and tools across the windy Dumbarton Bridge
and hauling over a ton of concrete blocks, scrap wood, and plant debris on the freeway to the transfer station
As of my last fill up, my average mileage is 23.75mpg
Higher than the national average for all passenger cars on the road.
Higher than the average for model-year-2008 light trucks.
Next stop, eclipsing the average for all new passenger vehicles.