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Old 04-28-2008, 11:29 PM   #1 (permalink)
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Long time modder, 1st time poster :)

Hello everyone. I'm a 23 year old computer programmer and I enjoy squeezing MPGs out of my Cavalier. I also own a Porsche, but that car is strictly for fun and wasting money on.

I'm quite good with electronics and have been programming AVR microcontrollers since 07. I made a simple controller board for my Cavalier's IAC motor to try and lower the idle, but I was unsuccessful. The board worked just fine, but the ECU switching from lean to rich made the reduced idle wander. The next microcontroller project I want to tackle is a board that will take over the fuel injection tasks of the ECU. Once I can take full control of fuel delivery, I'll be able to get a few more city MPGs out of the car.

Recently, I've installed a Bosch wideband O2 sensor in the vehicle, mated to a breadboarded circuit that allows me to maintain a 17.5:1 AFR. From a 50 mile round trip, I averaged 42.8 MPG on E10 87 octane gasoline. I could probably do better on pure gasoline, but I can't find any around these parts. I'll build the circuit into the car this week.

I do have a Scangauge II, but I find it to be unreliable since it cannot read injector pulse widths. It's only accurate for a single AFR, and my car can be anywhere from 12.5:1 all the way up to fuel-cutoff. During FCO, the SG reads 0.8GPH, when the engine is burning no fuel. This makes it impossible for the scangauge to reinforce good driving behavior.

A project I want to start is a true MPG meter, one that connects to the #1 injector and to the VSS lines of the car. That way I will have a very accurate MPG rating regardless of air/fuel ratio or fuel cutoff.

I hope to pick up some good MPG tips from you guys

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Old 04-28-2008, 11:43 PM   #2 (permalink)
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Welcome to the site, I would check out the instrumentation/mpguino subforum, you'll find some stuff right up your alley there.

Great to have you aboard!
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Old 04-29-2008, 12:20 AM   #3 (permalink)
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Wannabe - '05 Honda Civic LX
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Welcome JG!

The Cavalier is a great car to mod. My son is looking forward to working on his once school is out. You should add your car to the EM Garage.
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Old 04-29-2008, 03:26 AM   #4 (permalink)
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Hey, JG, here's a fuel log of one of our member's Cavalier. It should give you some inspiration.

http://ecomodder.com/forum/em-fuel-l...?vehicleid=155


http://ecomodder.com/forum/emgarage....&vehicleid=155
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Old 04-29-2008, 09:59 AM   #5 (permalink)
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Wow, phleas is putting down some great numbers!

Our vehicles are just a little different. Mine was the last year of the 2200 motor, which is a 2.2L 8 valve pushrod. He has the 2.2L 16v DOHC Ecotec. Both are rated 33mpg highway by 2007 ratings.

Unfortunately, I'm not going to be able to put down all highway tanks like he does. My work commute is 3.2mi of city driving on a cold engine.

I'd be interested to know which mods got him that huge increase. I'm considering fiberglassing a belly pan as well.
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Old 04-29-2008, 10:30 AM   #6 (permalink)
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Welcome to the site.

His biggest mod would be to his right foot (aka driving technique). It'll net you more mpg and cost less than any modification. The best article is actually here on driving technique.

I hate to sound like a broken record (I've mentioned this to others recently), but you do know by leaning out your fuel mixture you are going to increase NOx emissions which cause some pretty ugly damage to the environment, right?
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Old 04-29-2008, 10:47 AM   #7 (permalink)
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Quote:
Originally Posted by JohnnyGrey View Post
My work commute is 3.2mi of city driving on a cold engine.
Not if you use a block heater.

Also, with that commute length, sounds like you're a good candidate for the "bicycle" mod , at least in good weather.

Anyway, welcome to the forum! As Ben noted, maybe you'll be able to sink your chops into the open source fuel economy computer project.
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Old 04-29-2008, 10:47 AM   #8 (permalink)
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Quote:
I hate to sound like a broken record (I've mentioned this to others recently), but you do know by leaning out your fuel mixture you are going to increase NOx emissions which cause some pretty ugly damage to the environment, right?
Absolutely. However, if you look at what happens in a typical engine, you'll find the increase isn't as dramatic as what some people make it out to be. More on the order of 20%, so I figure my 2.2L's NOX emissions are similar to that of a stock 2.7L. Our environmental standards limit PPM, not total NOX output. If that were the case, you wouldn't see any SUVs on the road. I like to look at the glass half full, so think of it as a 2.7L motor with the fuel consumption of a 1.8L



Actually, if you compare the NOX output between the stock 14.7:1 ratio and the 17.4:1 ratio I'm running at, my NOX emissions might be a little less than stock, not to mention HC emissions!
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Old 04-29-2008, 07:38 PM   #9 (permalink)
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Quote:
Originally Posted by JohnnyGrey View Post
Wow, phleas is putting down some great numbers!

Our vehicles are just a little different. Mine was the last year of the 2200 motor, which is a 2.2L 8 valve pushrod. He has the 2.2L 16v DOHC Ecotec. Both are rated 33mpg highway by 2007 ratings.

Unfortunately, I'm not going to be able to put down all highway tanks like he does. My work commute is 3.2mi of city driving on a cold engine.

I'd be interested to know which mods got him that huge increase. I'm considering fiberglassing a belly pan as well.
Don't dispair. I usually go 50% highway, but today I took a more rural route with a few stops. Although I had to stop 4 or 5 extra times, I was able to go a little slower and take advantage of more coasting opportunities that would have been useless at a higher speed. The difference was a 5 mpg increase! I will continue to test this route for the next few days. Never give up!

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