MPGs run, Aspire SE

[Movin]

The logic in the festy computer has only whats needed nothing more. In addition the algorithms
are small as possible to cover the fuel mixture spectrum. I have leaned the fuel mix to the point that the o2 has to work a little to richen the mixture. I can feel the difference between too lean and barely rich enough. It actually feels like I drive through "squares" of the logic. Speeding up or slowing down gets back into the sweet spot. I believe it is quite likely environmental conditions you are subjected to can influence the computer system much more on our cars than on cars with a more sophisticated computer.

[TominMO]

Eventually I want to go to a standalone computer like Megasquirt so I can tune for just rich enough, and have an alternate tune for fun.

How did you lean it out? I do notice that my tailpipe has black soot inside it, indicating I am running rich (no doubt a stock, safe tune). I have no cat to burn up the unused fuel BTW.

[mikeyjd]

In noticing that my mileage has been all over the place on the same 99.1-mile road course, 51.3 - 59.7 MPG, it occurred to me today that the more I improve aerodynamics, the more other factors come into play. When I was doing my MPG tests on my Festy, there were no aerodynamic changes made. It was all about different speeds, with basically stock aero except for the Festy rear spoiler. Now that I am playing with aero mods, other factors might be getting into the act, such as terrain; my ability (or not) to keep a constant speed; atmospheric factors like breezes, temp and barometric pressure even. Thoughts?

I'd say it's a combination of things, but I'd still lean toward fill error as the majority of the blame. I had 3 small fills of 140miles, 62 miles, 62 miles and got 55mpg, 74mpg, 83mpg on them. I'm guessing it's more likely that I got closer to 60, 70, 78 if I averaged them out just taking fill error into account on such small sample sizes. That being said, Aero-mods will tend to make the range % more sensitive. With less drag your vehicle is hard to keep at a constant speed. The fuel being used is lessened as well making the fill error % go up even more Head and tail winds will have less effect, while side winds will have slightly more effect. Day to day temps and atmospheric pressure can have a large effect on fuel economy. Also elevation changes and precipitation will change things allot.

[TominMO]

I'd say it's a combination of things, but I'd still lean toward fill error as the majority of the blame. I had 3 small fills of 140miles, 62 miles, 62 miles and got 55mpg, 74mpg, 83mpg on them. I'm guessing it's more likely that I got closer to 60, 70, 78 if I averaged them out just taking fill error into account on such small sample sizes. That being said, Aero-mods will tend to make the range % more sensitive. With less drag your vehicle is hard to keep at a constant speed. The fuel being used is lessened as well making the fill error % go up even more Head and tail winds will have less effect, while side winds will have slightly more effect. Day to day temps and atmospheric pressure can have a large effect on fuel economy. Also elevation changes and precipitation will change things allot.

Yep, all good points. Hope to make a long run on early Fri morning. My tires came in today (just ordered 'em Monday from tires-easy), so they'll go on the freshly-painted Aspire factory aluminums tmw. I'll try to not take "low" MPG results too personally.

On another note, a couple of hours ago there was a accident right in front of my house. Tweaker sideswiped the pickup right in front of my Festy, then rear-ended the sweet Mustang in front of it, pushing it into the rear of another pickup. First pickup totaled, Mustang totaled, front pickup not too bad (but possibly tranny damage?). The front two vehicles were owned by the same family. Tweaker's crapcar totaled too. Witness who had been driving behind him for awhile told the cop he was driving erratically.

[mikeyjd]

Yep, all good points. Hope to make a long run on early Fri morning. My tires came in today (just ordered 'em Monday from tires-easy), so they'll go on the freshly-painted Aspire factory aluminums tmw. I'll try to not take "low" MPG results too personally.

On another note, a couple of hours ago there was a accident right in front of my house. Tweaker sideswiped the pickup right in front of my Festy, then rear-ended the sweet Mustang in front of it, pushing it into the rear of another pickup. First pickup totaled, Mustang totaled, front pickup not too bad (but possibly tranny damage?). The front two vehicles were owned by the same family. Tweaker's crapcar totaled too. Witness who had been driving behind him for awhile told the cop he was driving erratically.

I hope everyone is alright ^

[TominMO]

I hope everyone is alright ^

Yeah, no one hurt. All cars unoccupied except the guy who did it, and he seemed fine physically.

On the road tmw. Planning on a four-hour trip, starting at 6 AM. Will report MPG results by noon.

[Movin]

Eventually I want to go to a standalone computer like Megasquirt so I can tune for just rich enough, and have an alternate tune for fun.

How did you lean it out? I do notice that my tailpipe has black soot inside it, indicating I am running rich (no doubt a stock, safe tune). I have no cat to burn up the unused fuel BTW.

I used a few approaches to leaning. I suscribed to the idea that the exhaust stream going down the pipe has the heavier gases near the edge of the pipe and lighter gases including oxygen near the center of the flow. Using this reasoning the stock location of the o2 sensor in the center of the flow will be reporting lean and causing a desired somewhat rich mixture for proper cat action. I used "sparkplug savers" for early fords with the large sparkplugs that oil foul all the time. I drilled it slightly bigger and installed it in the pipe then screwed my o2 back in. This places the o2 at the edge where most of the hydrocarbons are and the same o2 now reports a richer mixture causing the computer to lean the mixture somewhat. The stock ignition timing with lean mixes is a little doggy feeling. Bumping the timing a little allows complete combustion of leaner mixtures. New spark plugs with the gap set wider, around .050 , also makes it more likely that the spark will intersect a few fuel molecules in all that air.

To complement this leaner thinking , especially for short trips during open loop I marked the location of the vane air flow meter adjustment under the plastic cover and leaned it 3 notches. All meters are different, I did it to where I was feeling the barely lean feeling. This forces the o2 to richen slightly which to me means the fuel mix will be lean a little more of the time than it is rich.

I also bought a cheap adjustable resistor from radio shack and wired it in place of the air temp sensor. There are charts for diagnosing these sensors that show the temperature for for each resistance. I can fine tune the mixture with this and avoid check engine lights by lying to the computer about the current temperature.

One reason I use the festy, or festy and trailer is that in my forays into all day trips on dirt and or sandy roads is that I can go days without finding a town for fuel. I had lifted the car and carry a lot of weight at times . Towing I get 35mpg or better and I needed to keep these figures with the better off road ability. Currently the car alone gets better economy 35 plus off road than my Honda Rincon 650 which gets about 25 mpg.

[TominMO]

^^ Ingenious! I will look into doing some of these myself.

Well, as promised I went on a long test this morning. STL to Effingham, IL 243 miles round trip. Things I did to the car:
installed 155/80x13 tires on light Aspire alum. rims, to lower rolling resistance and rotating mass
front air dam, side skirts, rear wheel skirts, covered hole in bumper
filled gap between body and rear fender (duct tape)
filled gap between rear window and SE spoiler (styrofoam/duct tape)
removed wipers and mirrors
kept it as close to 60 MPH as possible

Soooooo......243 miles. 4.5 gallons of gas. 54 MPG. REALLY looking for 60+ here!
My conclusion is that the only definite mod that helped is the front air dam and covering the bumper opening, the first thing I did. Everything else seems to have been of little to no help; meaning, I guess, that the Aspire SE is pretty slippery as designed. Gonna take everything off except the air dam and bumper opening cover. Any meaningful gains at this point would require a boattail, which I don't want to do.

[mikeyjd]

I think 0w20 mobile in the tranny was worth a couple mpg. I also think a well designed partial kammback would be really helpful on an aspire. Between those 2 mods I think you'd be at 60 The rear window tapers to quickly for good attached airflow. If you brought it to 12% you'd be in much better shape.

[zoom zoom]

54 mpg is kinda crazy, I'm thinking somebody's filling up to the click jotting down numbers and topping off from there ^.^

[Movin]

Its awesome as I think this still just testing the car, no hyper mileage techniques?
Get some plastidip and paint the car anywhere air makes a sharp corner. The extreme orange peel look works like a golf ball pulling the size of the hole in the air close to the car. You can peel it off when done.

[TominMO]

Gonna try a kammback next. John can help me with plastics acquisition. That will probably be my last test on this car. BTW thanx for the 12 degrees figure mikey.

Correct Movin, just doing aero testing. Hypermiling would confuse the results.

I was noticing today how flat the front of a Prius is. Excellent flow over the hood and windshield. but the rear angle is the part I need to focus on

[mikeyjd]

Kamm-back

Gonna try a kammback next. John can help me with plastics acquisition. That will probably be my last test on this car. BTW thanx for the 12 degrees figure mikey.

Correct Movin, just doing aero testing. Hypermiling would confuse the results.

I was noticing today how flat the front of a Prius is. Excellent flow over the hood and windshield. but the rear angle is the part I need to focus on

This is a popular template used on EM to help get your car streamlined. To use use it, take a side pic of your car and overlay the template lines starting by putting the bottom straight line at road level.



To use use it, take a side pic of your car and overlay the template lines starting by putting the bottom straight line at road level.

Like thus

[mikeyjd]

Here is an example of an aspire kammback





It would be better with rounded instead of sharp corners, but that limits visibility more ^

[Movin]

Skirts make sense but the rest of that rear is not what I have seen from wind tunnels, course that is aged tech, are there any windtunnel tests to verify this shape around the tail? It seems that increasing the sizefor vacuum to act on would be the opposite of desired.