Vacuum Guage and Digital Fuel Gauge

[krousdb]

In my intro, SVOBoy asked me to post more info on the vacuum gauge and digital fuel gauge install.



http://img357.imageshack.us/img357/6580/vacint3zx.jpg



The 2 5/8" Autometer Vacuum gauge is installed in a pod on the A pillar.



http://img468.imageshack.us/img468/5681/vacengine1ix.jpg



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.

http://img357.imageshack.us/img357/246/fuel0oy.jpg

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.

http://img483.imageshack.us/img483/323/untitled15me.jpg

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

[SVOboy]

VERY COOL!

How cheaply do you think I can get a DMM that will serve this purpose? Also, how small do they come? I'm wondering now if someone more electronically inclined could turn that display into something a bit more self contained (could be mounted on the a pillar or something)...

Very very cool. The line you tapped for the vacuum gauge actually goes from the fuel rail to intake manifold though, if I'm looking correctly.

One of the things that can be done with chipping is to use your CEL light as a shift indicator so that instead of reading the gauge you will see the flash at like 2500 and know to shift. ;)

[MetroMPG]

How cheaply do you think I can get a DMM that will serve this purpose?

if you watch for sales at your favourite parts store, you can get them cheap. i've bought a couple at $9 each over the past few years. the ones i got normally retail for $30-$40 (all figures $CDN @ .85 $US). door crasher type deals.

you could probably eBay yourself a good deal also.

ps - nice work, dan.

[SVOboy]

There are mini ones on ebay for 9 shipped, :), I'll get one soon once I finish closing down my ecu business.

[JanGeo]

Harbor Freight they go on sale once in a while and they also give them away for free on $40 orders sometimes. Usually you can get them for $2.99 - I have purchased a lot of them over the years for my scooter projects and once calibrated they hold up pretty well and do not drift much at all. Once I figure out the resistor network inside that is needed to make it function as a 20 volt meter I will be able to reduce the unit down to the display and battery size.

[krousdb]

VERY COOL!

How cheaply do you think I can get a DMM that will serve this purpose? Also, how small do they come? I'm wondering now if someone more electronically inclined could turn that display into something a bit more self contained (could be mounted on the a pillar or something)...

Very very cool. The line you tapped for the vacuum gauge actually goes from the fuel rail to intake manifold though, if I'm looking correctly.

One of the things that can be done with chipping is to use your CEL light as a shift indicator so that instead of reading the gauge you will see the flash at like 2500 and know to shift. ;)

I have 2 more just like it I bought on ebay. I would give you one but it needs a mini 12V battery, which costs more than the DMM costed, about $5 at radio shack. You are probably better off just getting the one on ebay for $9 shipped. Just a few more notes about the digital fuel gauge, you can't use the 12V from the car to power the DMM, you get bad readings. Also, you get bad readings when the ignition or accessories are on. You need to turn the ignition off completely before a repeatable reading is obtainiable. I just take a look every morning before work, because the car is usually cooled to the same temp. As you know, temp also effects resistance readings.

[krousdb]

I just thought I would track this tank on this thread to give an idea what the data looks like and how the accuracy turns out. On Monday morning, 2/6 I was at 2.8 Ohms, 6 miles. This is slightly less than a full tank as i had to drive bach home from the gas station. This morning I was at 10.9 Ohms. Now the first gallon or two is not that linear so the data is probalby off a little. Here is the MPG calculation.

10.9 is 1/3 of the way between 10.5 (1 gallon used) and 11.7 (1.25 gallons used). So I calculate 1 + (.25/3)= 1.08 gallons used. The trip odometer shows 56 miles but I need to add 3.5% for the larger tires which I calibrated over a 50 mile stretch of I -79. So 1.08 gallons used for 56*1.035=58 miles equals 53.7 MPG.

I will be back tomorrow with another update.

[krousdb]

I just thought I would track this tank on this thread to give an idea what the data looks like and how the accuracy turns out. On Monday morning, 2/6 I was at 2.8 Ohms, 6 miles. This is slightly less than a full tank as i had to drive bach home from the gas station. This morning I was at 10.9 Ohms. Now the first gallon or two is not that linear so the data is probalby off a little. Here is the MPG calculation.

10.9 is 1/3 of the way between 10.5 (1 gallon used) and 11.7 (1.25 gallons used). So I calculate 1 + (.25/3)= 1.08 gallons used. The trip odometer shows 56 miles but I need to add 3.5% for the larger tires which I calibrated over a 50 mile stretch of I -79. So 1.08 gallons used for 56*1.035=58 miles equals 53.7 MPG.

I will be back tomorrow with another update.

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG

[krousdb]

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG

Two days sick, no driving.

End of day #3, 163 actual miles, 20.6 Ohm, 3.125 gallons, 52.3 MPG

[SVOboy]

Looks like a good tank so far.

I just found a DMM in my basement, think it's my teachers but I wanna hook it up before I return it to make sure I can get the hook up working well for when I buy my own DMM (it's only 9 bucks after all).

Do you have any pictures of how it's wired into the fuel sender thing?

[krousdb]

Looks like a good tank so far.

I just found a DMM in my basement, think it's my teachers but I wanna hook it up before I return it to make sure I can get the hook up working well for when I buy my own DMM (it's only 9 bucks after all).

Do you have any pictures of how it's wired into the fuel sender thing?

No pics. I would have to take all my trip pieces out to get to it. But you don't need pics. Especially if you don't want to switch between analog and digital guage all of the time. Just locate the fuel pump and sending unit. Access should be from the inside of the car directly on top of your fuel tank. If you can't tell which is which, the fuel pump is the one that buzzes for two seconds when you turn your ignition on. You want the other one which is the sending unit. The sending unit also has smaller gauge wires than the fuel pump.

Once you find the two wires going into the sensor cut both wires, leaving yourself some room to solder them back together if you want to restore the analog gauge. Next, connect the DMM leads to the cut wires that go to the sending unit and set to 200ohm setting. You should be at 2 - 5ohm for a full tank and around 130ohms for an empty tank, according to the 92-95 civic shop manual. I have never had it higher than 110 ohms however.

You should do your own calibration since your fuel tank may be a different size or shape. I started with an empty tank, dead on the "E". I added gas in 1/4 gallon increments, taking a reading afer a few seconds of letting the reading stabilize. When you get close to 10 ohms, it only takes a small squirt to move it an ohm or two. Continue small squirts until a squirt fails to change the reading, this is what I call the full point, because I can duplicate that exact level on each fill, ensuring accurate tank MPG calcs.

Now all of this is based on the 92-95 civic. Refer to your CRX shop manual as there may be differences in locations and sensor range.

And one more thing. Readings between DMM's will vary. If your teacher's is high quality and the ebay is low quality (most likely) then you may see a few ohms difference. The ebay one will be fine, just be sure to calibrate with the ebay DMM.

[SVOboy]

Thanks, I'm pretty sure I know what it is and since I've got no interior getting to it isn't a problem.

[Matt Timion]

Just as an alternative, a digital panel meter might be better than hooking up a DMM to your car. A digital panel meter could easily be made to fit and be more permanent.

And they're rather cheap too.

http://i24.ebayimg.com/03/i/06/32/9e/82_1_b.JPG

http://search-desc.ebay.com/Digital-panel-meter_W0QQbsZSearchQQcatrefZC6QQcoactionZcompareQQ coentrypageZsearchQQcopagenumZ1QQfposZ84104QQfromZ R10QQfsooZ2QQfsopZ2QQfstypeZ1QQftrtZ1QQftrvZ1QQfts Z2QQmppfqyZQ28n600Q2cQ20an600Q2cQ20z600Q2cQ20az600 Q2cQ20Q22hondaQ20600Q22Q2cQ20Q22nQ20600Q22Q2cQ20Q2 2zQ20600Q22Q29Q20Q2dcbrQ20Q2dbluetoothQ20Q2dmotoro laQ20Q2dsonyQ20Q2dnorcoldQ20Q2dQQsadisZ200QQsargnZ Q2d1QQsaslcZ2QQsatitleZQ22DigitalQ20panelQ20meterQ 22QQsbrftogZ1QQsofocusZunknown

http://www.action-electronics.com/panelmeters.htm#Digital

I would do this in a heartbeat if someone could convert the readout to be a percentage of the tank left instead of the voltage.

[krousdb]

Just as an alternative, a digital panel meter might be better than hooking up a DMM to your car. A digital panel meter could easily be made to fit and be more permanent.

And they're rather cheap too.

http://i24.ebayimg.com/03/i/06/32/9e/82_1_b.JPG

http://search-desc.ebay.com/Digital-panel-meter_W0QQbsZSearchQQcatrefZC6QQcoactionZcompareQQ coentrypageZsearchQQcopagenumZ1QQfposZ84104QQfromZ R10QQfsooZ2QQfsopZ2QQfstypeZ1QQftrtZ1QQftrvZ1QQfts Z2QQmppfqyZQ28n600Q2cQ20an600Q2cQ20z600Q2cQ20az600 Q2cQ20Q22hondaQ20600Q22Q2cQ20Q22nQ20600Q22Q2cQ20Q2 2zQ20600Q22Q29Q20Q2dcbrQ20Q2dbluetoothQ20Q2dmotoro laQ20Q2dsonyQ20Q2dnorcoldQ20Q2dQQsadisZ200QQsargnZ Q2d1QQsaslcZ2QQsatitleZQ22DigitalQ20panelQ20meterQ 22QQsbrftogZ1QQsofocusZunknown

http://www.action-electronics.com/panelmeters.htm#Digital

I would do this in a heartbeat if someone could convert the readout to be a percentage of the tank left instead of the voltage.

Problem is that the sensor output is not linear. Yiu would need to set up a lookup table. If that could be done, sign me up for one.

[Matt Timion]

Problem is that the sensor output is not linear. Yiu would need to set up a lookup table. If that could be done, sign me up for one.


Ah, I was under the impression that the output was linear. If it was then the conversion equation would be REALLY easy to do. Assuming 2.6Volts was "full" and 0 volts is "empty, the percentage would just be "(x/2.6)*100," or just "38.46x," where "x" is the voltage.

If it's not linear, however, I have no idea. Perhaps some of the electronics guys on this site want to make a LITTLE extra money and whip something up for us? Huh? Anyone?

[krousdb]

Problem is that the sensor output is not linear. Yiu would need to set up a lookup table. If that could be done, sign me up for one.


Ah, I was under the impression that the output was linear. If it was then the conversion equation would be REALLY easy to do. Assuming 2.6Volts was "full" and 0 volts is "empty, the percentage would just be "(x/2.6)*100," or just "38.46x," where "x" is the voltage.

If it's not linear, however, I have no idea. Perhaps some of the electronics guys on this site want to make a LITTLE extra money and whip something up for us? Huh? Anyone?


Take a look at the chart that was included in the first post. The sensor is quite linear from the full to half tank mark at about 4.8 ohms/gallon. But after that you can see a more of curve. You probably notice this on your analog gauge also.

Lets just keep our fingers crossed that the SuperMID will work with non-toyotas. If so, in addition to showing tank, trip and lifetime MPG, it shows fuel used in the lower right hand corner, and is extremely accurate, as is the ODO after calibration. It takes awhile to get used to the metric display. But just remember to multiply km/L by 2.35 to get MPG. So 50 mpg would be 21 - 22 km/L. The fairly commom 11.9 gal fuel tank is 45L. The 15.9 tank is 60L. Didn't you ever wonder why the odd tank size, well it's not so odd if you convert to liters.

[JanGeo]

The meter should have a calibration but it may be automatic - however all you need to do is go through a pot to adjust the voltage range so full tank reads 100 on the meter. Hell calibrate it to gallons!!

[krousdb]

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG
End of day #3, 163 actual miles, 20.6 Ohm, 3.125 gallons, 52.3 MPG
End of day #4, 182 actual miles, 23.2 Ohm, 3.675 gallons, 49.4 MPG

OUCH! Running errands sucks. Lots of short trips, but only one cold start. So calculating backwards, my MPG for day 4 was around 38. I hope the WAI didn't cause any of that.

[krousdb]

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG
End of day #3, 163 actual miles, 20.6 Ohms, 3.125 gallons, 52.3 MPG
End of day #4, 182 actual miles, 23.2 Ohms, 3.675 gallons, 49.4 MPG
End of day #5, 235 actual miles, 27.6 Ohms, 4.563 gallons, 51.6 MPG

Whew! Back over 50. Day 4 reading could have been a fluke.

[krousdb]

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG
End of day #3, 163 actual miles, 20.6 Ohms, 3.125 gallons, 52.3 MPG
End of day #4, 182 actual miles, 23.2 Ohms, 3.675 gallons, 49.4 MPG
End of day #5, 235 actual miles, 27.6 Ohms, 4.563 gallons, 51.6 MPG
End of day #6, 286 actual miles, 33.8 Ohms, 5.583 gallons, 51.2 MPG
End of day #7, 339 actual miles, 39.1 Ohms, 6.313 gallons, 53.7 MPG

Nice and warm today, 44F in the AM and 55F in the PM

[MetroMPG]

glide question, krousdb...

i'm sure you've calc'd this already, but i'm curious to know: how much of your normal daily commute happens with the engine shut off?

[krousdb]

glide question, krousdb...

i'm sure you've calc'd this already, but i'm curious to know: how much of your normal daily commute happens with the engine shut off?

Actually after the discussion on the other thread about coasting with engine off, I began to think about what benefit I was getting and I made a few changes to my routine. First, I decided that I would only shut down if I could bump start by using momentum. So now the only time I use the starter leaving from home and leaving from work. I also identified several steeper slopes that I could just use engine braking (injectors off above 1100) and not lose any distance. The result is about 1/2 as many Ignition on/offs per day. What I am down to is 6 engine shut downs each way averaging 1 mile each. So of my 50 mile daily commute, I estimate 12 miles coasting with the engine off. Another 13 miles is light throttle, high vacuum (15-20 in hg)cruising. Another 12 miles is mild hill climbing, intermediate vacuum 11-15 in hg. The remaining 13 miles is serious hill climbing, low vacuum (7-10 in hg).

Many think that hills are bad. But as long as you keep your speeds moderate, below 50 when aero drag really kicks in, hills are quite good. This is because your engine is more efficient when working hard climbing hills as opposed to cruising. Even though I burn more fuel going up the hill, I also gain potential energy which is released free of charge while coasting downhill with engine off or engine braking with injectors off. In the end I believe the hilly route will be better than the flat route unless you have a D15Z1 which will give you lean burn under cruising conditions.

With the help of SVOboy I will be trying to simulate lean burn in my D15B7. For the 1/2 of my commute that the engine is on and vaccuum between 10 and 20 in hg, lean burn could reduce consumption by 10-20%, or 5-10% for the entire 50 mile trip.

[krousdb]

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG
End of day #3, 163 actual miles, 20.6 Ohms, 3.125 gallons, 52.3 MPG
End of day #4, 182 actual miles, 23.2 Ohms, 3.675 gallons, 49.4 MPG
End of day #5, 235 actual miles, 27.6 Ohms, 4.563 gallons, 51.6 MPG
End of day #6, 286 actual miles, 33.8 Ohms, 5.583 gallons, 51.2 MPG
End of day #7, 339 actual miles, 39.1 Ohms, 6.313 gallons, 53.7 MPG
End of day #8, 390 actual miles, 50.9 Ohms, 7.667 gallons, 50.9 MPG

Obviously a non-linearity in the 6 to 7 gallon region.

[krousdb]

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG
End of day #3, 163 actual miles, 20.6 Ohms, 3.125 gallons, 52.3 MPG
End of day #4, 182 actual miles, 23.2 Ohms, 3.675 gallons, 49.4 MPG
End of day #5, 235 actual miles, 27.6 Ohms, 4.563 gallons, 51.6 MPG
End of day #6, 286 actual miles, 33.8 Ohms, 5.583 gallons, 51.2 MPG
End of day #7, 339 actual miles, 39.1 Ohms, 6.313 gallons, 53.7 MPG
End of day #8, 390 actual miles, 50.9 Ohms, 7.667 gallons, 50.9 MPG
End of day #9, 445 actual miles, 63.1 Ohms, 8.563 gallons, 52.0 MPG
End of day #10, 477 actual miles, 75.2 Ohms, 9.190 gallons, 51.9 MPG

[SVOboy]

Looks like you're doing pretty well this tank. :p

I just bought my new thermostat. I'll send you my old one and you can compare and hopefully learn they're the same and can therefore get mine for 7 bucks, :p

I hope the lady put the 195 in the box and not the 170, ;)

[krousdb]

Looks like you're doing pretty well this tank. :p

I just bought my new thermostat. I'll send you my old one and you can compare and hopefully learn they're the same and can therefore get mine for 7 bucks, :p

I hope the lady put the 195 in the box and not the 170, ;)

I just stopped by Autozone and ordered the 192F thermostat for $17. It should be in on Tuesday. Stopped by the Honda dealership and ordered the engine block heater for $42. Should be in by Friday.

[krousdb]

End of Day #1, 58 actual miles, 11.7 Ohms, 1.08 gallons, 53.7 MPG
End of Day #2, 110 actual miles, 15.9 Ohms, 2.125 gallons, 51.6 MPG
End of day #3, 163 actual miles, 20.6 Ohms, 3.125 gallons, 52.3 MPG
End of day #4, 182 actual miles, 23.2 Ohms, 3.675 gallons, 49.4 MPG
End of day #5, 235 actual miles, 27.6 Ohms, 4.563 gallons, 51.6 MPG
End of day #6, 286 actual miles, 33.8 Ohms, 5.583 gallons, 51.2 MPG
End of day #7, 339 actual miles, 39.1 Ohms, 6.313 gallons, 53.7 MPG
End of day #8, 390 actual miles, 50.9 Ohms, 7.667 gallons, 50.9 MPG
End of day #9, 445 actual miles, 63.1 Ohms, 8.563 gallons, 52.0 MPG
End of day #10, 477 actual miles, 75.2 Ohms, 9.190 gallons, 51.9 MPG
End of day #11, 501.5 actual miles, 90.8 Ohms, 9.680 gallons, 51.8 MPG

Filled 9.68 gallons. Starting new tank.

[SVOboy]

Oh schnizzle that was some on target jive.

[krousdb]

Oh schnizzle that was some on target jive.

Yes, at the end of the tank it is very accurate due to the faster rate of change of the reading. But you can see in the middle of the tank the numbers bounced around a bit. Still, much better than trying to eyeball a analog gauge.

After I install the SuperMID I won't need the digital fuel gauge. I will reconnect the analog gauge and you can have my DMM if you want it. Another knick knack for free. A small token for all of your help. ;-)

[SVOboy]

That'd be fly! I need to give my teacher back his DMM, and his huge battery, and his power drill...

He'd be mad if he knew I had it all.

[kickflipjr]

Hey krousdb, I have to give you props on your mpg numbers. Do you have any tips?

[krousdb]

Hey krousdb, I have to give you props on your mpg numbers. Do you have any tips?

Thanks for the props!
I wish I had a magic bullet, but it is just a combination of all of the standard mileage tips plus a route to and from work that is optimized to take advantage of hills, have few stops and little or no traffic. No short trips and garage kept car help to mitigate the cold start penalty. Manual transmission is a must, as is low weight.

Good Luck!

[MetroMPG]

i'm really impressed by the consistency and "height" of your mpg too. nice job! it almost makes me wish i had to commute, so i'd have more time behind the wheel to fine tune my driving.

maybe you could illuminate some of the specifics of your commute? you've indicated the car sees little stop & go driving in a tank of gas - is it pretty much a dedicated commuter?

- what % of your tank is non-"city" driving?
- what kind of speeds do you see in your commute?
- do you use strategic drafting?

your numbers inspired me to split my garage/gaslog records for my 2 fireflies. i was treating the cars as "equals" since they were the same year & specs - so i had combined the total fuel consumption data into a "composite" of the two. but when i split the data between cars, it showed me i'm continuing to improve: the "new" car's lifetime MPG is already slightly higher than the last one.

[krousdb]

i'm really impressed by the consistency and "height" of your mpg too. nice job! it almost makes me wish i had to commute, so i'd have more time behind the wheel to fine tune my driving.

maybe you could illuminate some of the specifics of your commute? you've indicated the car sees little stop & go driving in a tank of gas - is it pretty much a dedicated commuter?

- what % of your tank is non-"city" driving?
- what kind of speeds do you see in your commute?
- do you use strategic drafting?

Let me answer your specific questions first. Since it is a two seater, it is dedicated to commuting plus any errands I do on the weekend that don't require me to drag the family along with me. Typically I drive 50 miles per day during the week and 25-50 miles over the weekend.

I don't know how to define non-city driving. 25%, 6-7 miles each way is on I-79. But that particular stretch is very curvy/hilly and there is a truck speed limit of 45 MPH for half of it, the other half is 55. I average 50mph. Most cars go about 65-70 on that stretch so it's not that bad. The rest of the drive , 75%, has speed limits of 25-45 mph. I don't not use any form of drafting because that would require that other vehicles are around and that they are obeying the speed limit. That combination almost never exists and there is not much benefit to drafting at such low speeds anyway.

Starting from my home, the first 2.4 miles is residential, pretty flat 35 then 25 MPH with two stop signs and then a stop light that is always red but turns green quickly. Then turn onto main road, accel to 25 and kill the ICE. COast downhill for a mile or so then bump start at a stop sign. Turn right, up hill to another stop sign. then down hill then up hill then long downhill with ICE off, timing the light at bottom, bump start. Then killer uphill (about mid point my temp gauge reaches normal operating temp) then short cruise then 3 lights in a row. It is critical to time these properly. At this point I am at 6 miles.

Next turn on to a road alongside I-79, 45 MPH speed limit, hold steady throttle, max 55 at bottom, min 35 at tops, down, up, down, up , down, up, stop sign. Then 25MPH thru residential area then kill ICE for 1/2 mile steep downhill, bump start at bottom then steep uphill at 25 MPH, kill ICE at peak, then down long stretch about 1.5 miles,50 mph max, bump start, cruise at 35. Stop sign then right across I-79 to another road that runs along side it. Kill the ICE and coast for 1.5 miles, bump start, criuse 1/2 mile, Kill ICE, coast 1/2 mile then bump start and accelerate onto I-79 south at the ohio river bridge. Cruise at 45-55 up 6 mile incline, vacuum at 11-13 in hg. Exit rt 60 which is 35 MPH and 8 stop lights, exit rt 22/30 (55 MPH) kill the ICE, long 2 mile downhill, exit and come to stop light before bump start. One more stop light then uphill climb at 30MPH in 3rd gear, no stop right turn and cruise 1 mile into work parking lot. Whew! 25 miles.

I guess I really didnt realize how many lights there were but I time 95% of them successfully. The key while timing lights is to downshift and use engine braking instead if brakes. During engine braking, fuel is cut off.

The drive back is identical for the first 75% then I have 2 routes for the remaining 25%, depending on the color of one particular light as I approach it.

This route is exactly the same as when I drove the Prius. I optimized the technique on the Prius and it seems to work pretty well on the Del Sol. The supermid is on the way. Soon I will be able to optimize accel rates, which gear to use while climbing hills, verify that the fuel is really cut off during engine braking etc....

If the optimization goes well, and when the normal benefits of warmer weather take hold, I have my fingers crossed for 60MPG. I should also get 1 MPG from losing the winter blended fuel.

[MetroMPG]

thanks for the insight into your methods. you've refined your commute to an art form (or a science - take your pick).

I don't know how to define non-city driving.

when we get to this level of discussion, "hwy" and "city" distinctions aren't enough. we almost need a more comprehensive set of driving conditions to use as shorthand, e.g...

- city (lots of stop & go, congested, some idling, speeds under 30 mph)
- suburban (less stop & go, not congested, less idling, speeds under 40 mph)
- ex-urban (a little stop, more go, no idling, speeds 35-45 mph)
- highway (both uncontrolled & controlled access, infrequent stops/lights, limits 45-55 mph)
- freeway (controlled access, speed limit 55 mph+)

i've found my peak mileage comes in what i'd call "ex-urban" driving, on roads with speed limits around 35-40 mph, with widely spaced traffic stops/lights (that permit lots of coasting while timing the lights).

I don't not use any form of drafting because that would require that other vehicles are around and that they are obeying the speed limit.

on my last freeway trip, for several killer long uphills, i timed it so i sped up after being passed by a larger vehicle (usually a transport), and drafted up the incline. the increased speed didn't cost as much as it would have without the draft.

I have 2 routes for the remaining 25%, depending on the color of one particular light as I approach it.

that's cool. alternate route to avoid a stop.

[SVOboy]

Where did you run the gauge tube through the firewall? I just got a gauge (for free) and need to mount it up. I'll step by step DIY the process, including the damn mounting, for fun and such.

[krousdb]

On the del sol, there are two identical holes in the firewall. One for the throttle cable and one for the cruise actuator cable. Since mine doesnt have cruise, I popped out the rubber grommet and ran all of my stuff thru there. Covered up the mess with duct tape to keep air out of the cabin.

[SVOboy]

I guess I'll just squeeze it through somewhere, no biggles.