I live in a state of trying to balance my love of driving/ racing, and getting good gas mileage. It's a dichotomy, and a challenge.
I have done extensive work to my car to make it fun to drive, and competitive in autocross/ track racing, while looking, and feeling stock, and all while getting better gas mileage than when it was new, and had a smaller engine by .9 Liters, and lower compression. My most recent addition is the "MegaSquirt and Spark" engine management system. I highly recommend it for anyone serious about saving gas! The minimum investment is about $400, but for serious tuners, about $600. With it, you can minutely tune every part of everything on your engine run by electricity (fuel, spark, solonoids, etc..). You can push the lean limits right to the point of detonation at every point of load/ RPM. Check it out at DIYautotune.com
I'm getting about 35 mpg HWY out of my (low geared) racecar, and expect about 38, when it's tuned better (and up to 45 when I get taller gears.. It's at 3500 rpm @ 60mph right now). This doesn't sound like much until you consider the following:
It's about 240HP, has full leather interior, 10 speaker stereo, and a high compression 2.5L V6.
What I love about MegaSquirt is that it is tuned on a 12X12 grid of rpm/ load, so you can set your cruising points for lean burn, and your high load racing points richer, and it sets enrichments for how fast the rpm rises, ambiant heat, etc... Mine also has 2 maps, so I'm tuning one for 87 octane cruising around, and the other for high octane racing. Even while I'm racing, I'm burning alot less gas than my competitors.
I'm poor, so I got my setup used and set up with all the sensors, software, etc.. for $300.
I'll answer any questions that I can.
240hp from 2.5 liters? Did you dyno that? That's a lot of power in an MX3!
Another user on this forum has a MegaSquirt, I think it's BEEF.
Don't forget, if you do custom gearing...you can keep a bunch of close-ratio gears for racing and have just one or two ultra-tall highway gears for FE. I don't know how feasible it is to re-gear a transmission that way. 3500rpm @ 60mph is awful, I hate 3000rpm @ 70mph enough in my car.
Glad to hear another DIY ecu tuner is here. I'd be interested to hear of any tricks you find, big or small, that can save fuel.
I have a programmable eprom ecu in my car, and luckly the entire code has been disassembled, so I've altered many things to get better mpg and better power. I've been refining the code and driving techniques for several years now. I haven't dyno'd my car, but the online HP calculators put it around 260HP. My best FE is 53mpg, although I'm averaging 43 lately.
One of the things I've enjoyed the most about this ecu is seeing where fuel is wasted, then eliminating the waste without hurting driveability. It's not always easy, sometimes the engine needs to be rich to run right.
I haven't dyno'd it yet.. The last dyno was 179 with just high compression pistons, port and polish, and a few other things. It was also done on 87 octane in Las vegas, and I'm now at sea level. I've done ALOT of work since then, and other people with very similar setups are dynoing about the same.
It is a guess, but somewhat educated
I've also had the rear hatch made out of Fiberglass, and am having the hood, and hopefully, doors done. I'm going for 2,100 lbs empty.
I can post pics of whatever you like
Left to my own discresion, I'd put up too many.
I just covered the bottom front half of the car with a plastic election sign, too.
I agree, DRW, about seeing where we can fine tune. Mine is really roughly tuned right now, until I get a wideband O2 sensor. I did discover some interesting things along the way, but don't know if they're specific to my car.
You've got great mpg for that HP! I'd like to know more about your car.
Beef, is he putting a Motorcycle engine in it?
TheHolyCow, my car will be light enough to spread the gearing out a bit. I'd thought of just putting in an MX-6 transmission, because it's the same as mine, but a slightly taller final drive, and a much taller 5th gear.
Okay, here are some that are pertinentish to gassaving
Here's my car. I made grill blockers out of a wire mesh garbage can I got at a thrift store:
I made a catch can out of a Martini shaker to filter the air coming from the PCV valve:
It has a water/ oil seperator for pneumatic lines in it, as well as copper mesh.
Here it is in use:
Here's some more aerodynamic side mirrors:
I made a ram air system out of the turn signal hole, since I put in Honda Civic projector headlights that have turn signals in them:
It is made from: Aluminum tape, an oval shaped tin that was just the perfect shape that I found at a thrift store, 6" dryer ducting, a K&N washable cone filter that I bored out to 4" inner diameter to mate to a Martini shaker that I cut to 2?" to fit in the rubber elbow that holds it all onto the throttle body. Around the filter, connected to the dryer ducting is an Aluminum Flour tin. I cut the lid to fit the back of the filter, so the body of it could fit onto it, and be removed to clean the filter.
I upgraded the coil to an MSD with an HEI module.
Here's some sideskirts I had on for a long time, but after breaking the pass. side on a curb, making another, and breaking it again, I gave up. Mileage wasn't significantly affected.
Oh, yeah.. I widened the back of the front bumper; pushed it out just in front of the wheels. modded my front windshield wiper to be out of the airflow, and took off the rear one. I also removed the rear spoiler, and put on flaired sideskirts. I made an exhaust that is just 2.25" tubeing after wrapped headers, a Flowmaster muffler, only 1 bend (mandrel), and side exit. I'm going to wrap it all the way back to keep velocity up.
Sorry I haven't posted anything. I lost my license over a year ago, and just got it back. I didn't get a moving violation, DUI, anthing like that... just unpaid tickets from 10 years ago, and it was a nightmare getting it back. I can finally tune it now, and let you know the results.
I did get the car Dyno'd in the meantime, though. They failed. It was at an RX-7 meet, and they ran my car cold, in 4th gear, and shut it down at 6600rpm. That's when it just starts getting good. It makes power up past 7,000. The power curve was the same as the last dyno, so I overlayed them, and if the line went to peak at the same rpm, it would be at about 190whp.
The dyno results were 179whp @ 6600rpm on a Mustang dyno, which are known for being up to 15% less than others. Also, I was running rich. I got a wideband O2 working in there, now.