How do we go about doing this? I'm getting about 21mpg, 260miles/tank would love to bump that up to 25mpg or more....

 

The car runs really rich from the factory. By leaning out theAFR you will get an increase in MPG. Some people say they get 30MPG. I know I have been getting around 18 MPG city driving and I drive like I stole it. I am still running pretty rich too. Just make sure you have a wideband and the software to properly tune and you should see an increase in MPG.

 

I second that request for knowledge?

 

There was a guy on here claiming up to 320 to a tank on the highway with a Vishnu tune. The tune normally leans out the AF ration because its supposed to run really rich. So if you lean it out you SHOULD get better gas mileage and more power, but it doesnt always happen. Ive got a basically stock (tbe and MBC) and i average about 280 on a tank.

 

one of the ways you can increase highway mileage is increase the TPS voltage in the open loop high/low load maps. what this will do change the point at which the ecu switches to open loop from changes of the TPS voltage.

 

i thought my average 230 was good... but u guys here are running on 260 / tank

 

FWIW if I am driving to Oregon,...on the flat lands portion, at 70 MPH I get about 315-320 per tank,....at 80 MPH I get 270-280 per tank.. I prefer 80, the wallet prefers 55! My next upgrade is a cable, evoscan, and a EGT to lean the F^&% out of it at highway speeds... The mileage on this car is poor, really poor. It is truly the only thing about the car that I don't like.. Everything e;se kicks A$$!!!

 

WOW I would be very pleased with 315 miles / 12 gallons (26mpg) from a performance car....I am only getting a bit over 200 miles / tank (city driving) , but arrive to work / home everyday with a smile on my face ....

 

on my bone stock map with all highway driving between 75-80mph I was averaging 300-310 mile per tank. It all depends on how much time you spend @ WOT.

now with my modified tune and much more power I'm getting an honest 220-240 per tank while driving around town. I haven't taken a long trip recently so I don't know what the highway mileage is like now. I don't think it would be much different though because I was averaging about those miles with the stock map during around town driving, maybe a little less actually.

 

Okay.. Here's the real deal..

the ECU Operates in closed loop at idle and cruise, there is a threshold (Throttle position) of about 20% open where it crosses into open loop, and an RPM where it does it also..

In closed loop, the car will operate at 14.7:1 AFR's, whether your car is stock or modified, it tries to maintain that AFR, the more efficient the engine, the less fuel it requires to maintain that AFR, hence a modified car "Should" get slightly better mileage in closed loop operation.

Here's the catch, if you drive over 55mph, or have a heavy foot (load the car up a bit by increasing throttle in 5th gear) you cross into open loop territory where the Maps take over.

You can either increase the TPS voltage value so it requires more throttle to cross over into open loop, and then tune the maps around that new crossover area, or you can learn to drive with much less throttle input. Driving around 65mph seems to net me about 300 miles to the tank, driving at 55 is about the same, driving at 75-80 my mileage goes down to about 250..

There are quite a few things that come into play..

The faster you go, the more fuel it takes to maintain that speed at that AFR, the engine has to work a bit harder simply due to aerodynamics, the faster you go, the more power it requires to maintain that speed, the lower your mileage is..

Many of you guys add spoilers, splitters, aftermarket wheels, wheel alignment for racing, all of which will affect your mileage.. Adding downforce makes the car more stable at high speeds, however it also increases drag and therefore reduces fuel efficiency, Almost **EVERY** aftermarket front bumper hurts the aerodynamics of the car, some are functional to increase downforce, but most are just equivalent to strapping a big piece of plywood vertically to your front bumper.. Heavy aftermarket wheels and wide tires increase the power required to maintain speed too, a race wheel alignment can also affect gas mileage since your now "Dragging" the tires slightly..

All of these things add up..

So, you want the best gas mileage for driving? (These things will also help your top-end performance)

1) Remove your rear wing
2) Remove your front splitter (if you have one to increase downforce)
3) Get a proper wheel alignment for high speed driving (something that has just enough to keep the car pointing straight at high speeds, but not scrub the tires, this will also improve the live of your tires)
4) Proper air pressure in your tires will reduce friction and heat (power loss)
5) Run the lightest and narrowest wheel and tire combination you can, this doesnt help the twisties, but will help highway driving.
6) Drive at a reasonable speed, the faster you go, the more drag has an affect on fuel mileage, 60-65mph seems to be where these cars are designed to cruise at.

 

I think David Buschur had a thread where he picked up power due to a wheel alignment, and another one where he went with lighter brake discs..

The power itself is lost doing work, either scrubbing the tire, or trying to rotate additional mass, this stuff actually shows up on the dyno as lower/higher power readings.. Tires aligned for drag racing, are perfectly parallel, for road race, there may be toe-out and toe-in on front/rear helping you dive into turns.

A drag alignment is bad for high speed daily driving since the driver has to think about maintaining a straight line more and makes the car a "Hand full" at high speeds, and a SCCA short track alignment is bad for tire life at high speeds... etc... A proper street alignment has just enough adjustment to make the car track straight, and handle the turns well, these are OEM Factory specs (and most cars purchased new are not aligned as precisely as you would expect, and if have miles on your car, a few speed bumps, etc, can throw your alignment off)

 

Okay, looking in my ecu cal, I see that the Open Loop Throttle High Load and Low Load maps are set exactly the same. Here's the data:

RPM Voltage
500 3.00781
1000 3.00781
1500 3.00781
2000 3.00781
2500 3.00781
3000 3.00781
3500 3.00781
4000 2.5
4500 1.79688
5000 1.81641
5500 1.81641
6000 1.77734
6500 1.73828
7000 1.73828
7500 1.69922

So, if you're cruising on the expressway at 70-80mph, you'll be around 3000-4000rpm. So, you'd bump those voltages up a tad, keeping you in closed loop longer. Right? Has anyone actually tried this? How much did you bump them? After changing them, how do you verify that you haven't caused a problem? Since the stock cal has 3V as the highest TPS value, I'd be afraid to raise above that. Maybe just tweak the 4000-4500 value up towards 3V? elhalisf, if you've made changes, please post your cals.

I'm considering two risk scenarios:

1.) As you press down the throttle, the time it takes to go open loop is delayed. This means you might be running leaner at WOT for a short time before the ECU 'catches up'. As it is, I've seen logs where I'm in the mid 13's at 3000 rpm for this reason.

2.) If you have an MBC, you know you can run nearly full boost at partial throttle (quite easily if on a hill and in 5th gear). If you also keep in closed loop, wouldn't you risk running too lean.. if not knocking, then very high EGT's?

I love this idea, but I don't want to experiment on my car w/out fully understanding it.

 

I thought this was a great thread, why did it all stop??

 

A very good post, but I'm not sure I follow this point. Stoichiometric is a specific air fuel mixture, so it would seem like some mods, like more air, would make the car inherently use more fuel, not less.

Actually, the whole 14.7 thing is worth a look when talking about fuel economy. The car does not run here for either power or fuel economy. It runs here for emissions. This is where the cat is most efficient. If you don't have a cat, then you could save fuel by running at 1.05 lambda (about 15.4:1) instead of 1.0 lambda closed loop. As long as fuel distribution is even (the engine does not run rough), this is much closer to the engine's "Best Economy", than stoich. The engine will also run cooler.

I have experimented a bit with this myself, though not on an Evo. I simulated the output of a narrow band sensor with a wideband, but shifted the stoich point from 1.0 to 1.05. If the ECU uses learning code, you probably will have to tweak your open loop map(s) as well, but the fuel savings can be significant.

IMPORTANT: Don't do this with a cat installed! Running at 1.05 lambda could make for a very hot cat.

-jjf

 

Just to throw some values out there:

Cruising around town in 4th gear at about 2300 or so is load of 30ish
Highway on flat ground at 50 and 60 it stays about 60ish with TPS at 25%

I leaned my fuel maps out (this might be a IX thing I dont know) from 30-60 and even when I am showing 20% TPS its running in the new numbers. I am cruising 15.4-15.8 and the engine has no tip in issues as it transitions to boost. Even adjusting the map in the idle portion of the map seens to have made a difference.

JB