Another gas mileage (mpg) thread. But with a COOL twist.

[shootmymime]

Your 4Runner won't run rich or lean based on altitude. If all the pertinent sensors and the ECU are working properly.



The ECU will gather the data from the pertinent sensors, and adjust the amount of fuel injected in real-time, so the air/fuel ratio stays as close as possible to the pre-programmed value, at any elevation.

Rich or lean no. So you are correct. But what they are saying is with less air you use less fuel in order to keep the afr in check. Thus better mileage.

 

[02SE]

Rich or lean no. So you are correct. But what they are saying is with less air you use less fuel in order to keep the afr in check. Thus better mileage.

Believe me, I'm well aware of that.


I was only correcting his incorrect lean/rich statement.

 

[farmerjon]

Your 4Runner won't run rich or lean based on altitude. If all the pertinent sensors and the ECU are working properly.

The ECU will gather the data from the pertinent sensors, and adjust the amount of fuel injected in real-time, so the air/fuel ratio stays as close as possible to the pre-programmed value, at any elevation.

Rich or lean no. So you are correct. But what they are saying is with less air you use less fuel in order to keep the afr in check. Thus better mileage.

[MENTION=2541]02SE[/MENTION] Thanks for clarifying, I appreciate it. I meant richer/leaner only slightly because yes, the engine would tune it, but I didn't think to explain it that far. [MENTION=14772]shootmymime[/MENTION] said closer to what I was trying to say, that with the leaner air, you can use less fuel... It is a slight clarification that I needed, otherwise I almost had the whole idea. Thanks for taking the time, guys! editing my post...

 

[JayRolla]

I say its voodoo magic. You guys think about this to hard. LOL. I have seen anywhere from 12-18mpg city, highway, mixed. So many many variables. Nothing has changed, just the variables.

 

[shootmymime]

#engineers

 

[Johnnie]

I just got my 99 auto, with 245K on it, pretty much gets 19-21 city/hiway, although the other day on a trip I hit 23

 

[TheDurk]

Rich or lean no. So you are correct. But what they are saying is with less air you use less fuel in order to keep the afr in check. Thus better mileage.

I don't think that's right. You lose power, but no effect on fuel economy at the engine. You lose about 3% of your vehicle's horsepower for every 1000 foot in elevation. Each detonation with a lower content of both fuel and air generates less torque, so you need more of them, cancelling out the reduced use of fuel per detonation. What does happen is the reduced air drag due to lower atmospheric pressure causes an increase in fuel economy, but that has nothing to do with the engine.

 

[diponyou]

I have literally heard this exact story multiple times on multiple forums.

Back in the day a fellow at work bought a new VW bug and constantly bragged about his great gas mileage. A few of us got together and would top his car off from a can of gas a couple of times a week. After a few weeks he happily reported that his already great mileage was getting to unbelievable levels as the car got broke in. Then we stopped adding fuel.