In my intro, SVOBoy asked me to post more info on the vacuum gauge and digital fuel gauge install.
The 2 5/8" Autometer Vacuum gauge is installed in a pod on the A pillar.
I tapped into the vacuum line that runs between the throttle body and the valve on the fuel rail.
When fully warmed up, the car idles at about 650 rpm, 22-23 in/hg. When driving, I try not to drop below 10 in/hg during acceleration and I upshift at 15 in/hg. When going downhill with foot off of the accelerator, the gauge shows 25 in/hg. According to the shop manual, the ecu shuts off the fuel injectors when the throttle is fully closed and the engine rpm is above 870. I try to take advantage of that as much as possible.
Again, during accel I shoot for 10 and upshift at 15 in/hg. In Pittsburgh, it is quite hilly so I find myself approaching uphill climbs in 4th gear at 10 in/hg, then downshifting to third and holding 10 in/hg. Some hills require 5 in/hg to hold speed but I have never had to drop to 2nd gear.
On long downhill stretches I typically shut off the engine completely and coast for 1 to 2 miles. On my drive to work, I have three occasions when I can coast for about 2 miles so this contributes to the 50 MPG tanks. The trip back only has one 2 mile coast. I have spent lots of time optimizing my commute to maximize fuel efficiency. My route is slightly different for the del Sol than for the Prius because, well it would take lots of typing to explain. Suffice it to say that much of my fuel efficiency can be attributed to staying off of the interstate and using the service roads that run along side it. The speed limits on these side roads range from 25 to 45 mph. I do spend about 6 miles of the 25 mile commute on the interstate where the speed limit is 55. This alternate route takes an additional 5-10 each way, but the distance is actually shorter by a fraction of a mile.
Here is a picture of my digital fuel gauge. It is a DMM set to ohms which lives in the center console. In del Sols, you have to remove the rear storage compartments to get access to the fuel pump/sensor. In civics, just remove the back seat. There are two sets of wires, one to the fuel pump and one set to the fuel sensor. I just cut the fuel sensor wires and extended (by splicing more wire) them into the center console, basically adding 2 ft of length. In the middle of the wire extension I cut them and reconnected them using a connector. I also installed a matching connector on the DMM. So I can use the analog gauge in the dash by connecting the two connectors on the extended wires. Or I can use the digital gauge by connecting the DMM to the connector that goes to the fuel sensor.
As you can see from the picture, the resistance is at 2.7 ohms, which is nearly full. At 2.0 ohms, the sensor is maxxed out. I always fill to 2.5 ohms to get the most accurate tank MPG calculation. This is much more accurate than guessing or topping off.
Here is the fuel sensor map that I have developed by filling my tank in 1/4 gallon increments on three separate occasions. I take a reading before leaving work every morning to get an idea of how my tank mileage is progressing. My garage floor is perfectly level so I get a good reading every time. I also use the same pump to fill the tank and the ground is level there also.
So far I am able to use this method to determin e tank MPG and can get within 1 MPG. It ain't perfect, but it helps.
Does anyone have an OZTrip Computer? That would make the Vacuum Gauge and Digital Fuel Gauge unnecessary.
Dan
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