I am going to be taking a road trip soon and I am wondering how much I can lean out the 93 octane map to get better mpg safely.


I dont have the smart setup yet so I would have to be going off any datalogging I can do & my egt gauge.

 

It doesn't matter. At cruise, load is low and the stock ECU will trim fuel to stoichiometric.

donour

 

If I am correct doesnt the stock ecu use the readings of the narrow band 02 sensor to determine when to add and subtract fuel at part throttle. If this is the case no matter how much fuel you take out at part throttle the ecu will keep adding more to make up for it so that the car maintains about ~14.7 AFR.

 

Just put **** loads of pressure in your tires and get an alignment!

If you have a pocket logger you and read your long term fuel trims. Problem is the only way to adjust them is with an ECU flash. This is normally adjusted by changing injector dead time and global fuel. Doesn't look like you have many options for tweaking other than what I mentioned above.

 

If you are running a SMART system (with functional C-Reader), you can also add 4-5 degrees of timing during cruising loads (under vacuum, NOT boost). This, in itself, will improve fuel economy by 2-4mpg.

shiv

 

could you turn off 02 feedback with the xede and run leaner than stoich during cruise, like 14.9-15.5 A/F. this would not be good for emissions, but i think it could help fuel economy greatly

 

You could turn off o2 feedback by simply unplugging the front 02 sensor (the plug is right near your spark plug cover) and dialing in a leaner cruise AFR. The only problem is that it will/may feel like a dog at times since there is no way you can get cruise fueling dialed in well enough (for max mpg, that is) without some sort of closed loop fuel control.

shiv

 

just another thought, could you use the smart system (with the stock o2 unplugged)to do closed loop at this AF?
it will probably feel bad driving because its so lean and there is no power, but if you want the best mileage....

 

So i'd need an active smart timing system for this to work? Having a c-reader and adding in the timing myself wouldn't work and/or would be dangerous?

 

with SMART can you set the AF ratio to 15.5:1 at cruise and vacumn without the ECU trying to correct it to 14.7 to 1? If so, which MAP do you adjust?
Thanks, Gary

 

Sorry to sound ignorant, but would I then correctly assume that vacuum loads are achieved in rpm ranges where the turbo is not spooling up yet? i.e. less than 3000 rpms, or are you referring to loads under, say, 20% at any rpm, or a combination of the two?

l8r)

 

Not sure what he is talking about. I thought he was talking about any RPM that is under vacumn but that would create a MAP with spikes or a biphasic MAP with a timing peak in vacumn and another under boost.

 

bump it up

 

What are you guys getting for mileage. I seem to get 26MPG at 75. I'm not a very aggressive driver though so I'm not in boost very much.

 

I'm getting 22 MPG at 80 mph. I drive 100 miles to work so I'm hoping I can do better.