NEW Hypermiling thread

ProfessorX5 · #1 12-27-2013, 10:33 PM

Rather than just revive one of the old threads, I thought we might start one where we don't just share our triumphs (and frustrations), but where we share strategies, tips, and even what mods we've tried in the interest of fuel economy.

I know, going for fuel economy in an expensive, high-maintenance, 4500 lb truck seems a bit counterintuitive, but I see it like a sort of game

audiophool · #2 12-27-2013, 11:24 PM

As long as you know your car burns more fuel if you put it in neutral while coasting down hills than if you just take your foot off the gas.

Helihover · #3 12-28-2013, 11:52 AM

Quote:

Originally Posted by audiophool

As long as you know your car burns more fuel if you put it in neutral while coasting down hills than if you just take your foot off the gas.

This is something I've always wondered about. So is the FIS injecting less fuel than what is needed to idle to bring down the rpms?

Also, a car going up hill in say 5th gear @ 2000 rpms @ 75% throttle. Same car going up the same hill, same speed, in 3rd gear @ 4000 rpms @ 25% throttle. Which one is getting better fuel mileage? My thoughts are if the car is FI, it would be the 5th gear and opposite for a carbureted car.

Any thoughts?

StephenVA · #4 12-28-2013, 12:12 PM

Quote:

Originally Posted by Helihover

This is something I've always wondered about. So is the FIS injecting less fuel than what is needed to idle to bring down the rpms?

Also, a car going up hill in say 5th gear @ 2000 rpms @ 75% throttle. Same car going up the same hill, same speed, in 3rd gear @ 4000 rpms @ 25% throttle. Which one is getting better fuel mileage? My thoughts are if the car is FI, it would be the 5th gear and opposite for a carbureted car.

Any thoughts?

There are so many thoughts on this issue left over from the 70's fuel crisis (for all you youngsters that was when the Gov got involved in gasoline distribution as fuel prices reached ...gasp $.50 @ us gallon).
Best practices... Use the hills to your advantage. speed up on way down and slow down on way up.
Acceleration... Burns more fuel than anything other than a cold start up. Slow, easy, allowing the trans to get in to higher gear will give you all there is to gain.
coasting.... In gear or out of gear? Out of gear allows you to speed up with out engine involvement. You are left only with rolling and air resistance. The fuel is cut off when coasting in gear but the drivetrain will slow you down REAL QUICK.
Now the real questions should be "What is the wear on an auto trans when coasting in neutral, if any?"
For those of us who do not give a rats ass other than to say "hey, it is double digits!" I say hard acceleration is why we own the V8's with fat tires.
If you want fuel economy sell it and buy a 4 cyl whatever, with skinny tires and a manual trans. I personally use my Vespa to run to the post office and the bank. Early mornings only on weekend as I do not care to become a bumper ornament on a texting idiot's Honda.

Helihover · #5 12-28-2013, 12:23 PM

Quote:

Originally Posted by StephenVA

There are so many thoughts on this issue left over from the 70's fuel crisis (for all you youngsters that was when the Gov got involved in gasoline distribution as fuel prices reached ...gasp $.50 @ us gallon).
Best practices... Use the hills to your advantage. speed up on way down and slow down on way up.
Acceleration... Burns more fuel than anything other than a cold start up. Slow, easy, allowing the trans to get in to higher gear will give you all there is to gain.
coasting.... In gear or out of gear? Out of gear allows you to speed up with out engine involvement. You are left only with rolling and air resistance. The fuel is cut off when coasting in gear but the drivetrain will slow you down REAL QUICK.
Now the real questions should be "What is the wear on an auto trans when coasting in neutral, if any?"
For those of us who do not give a rats ass other than to say "hey, it is double digits!" I say hard acceleration is why we own the V8's with fat tires.
If you want fuel economy sell it and buy a 4 cyl whatever, with skinny tires and a manual trans. I personally use my Vespa to run to the post office and the bank. Early mornings only on weekend as I do not care to become a bumper ornament on a texting idiot's Honda.

Well said. Not into gas mileage, but curious. I love mashing the pedal and being sucked back into the seat as you blow by the guy in a raced out Honda who has all ready passed you three times! (That should of went in the "Ya Baby" thread)

At the moment I believe I'm right at 13.1 mpg and that's mostly city.

audiophool · #6 12-28-2013, 06:32 PM

Quote:

Originally Posted by Helihover

This is something I've always wondered about. So is the FIS injecting less fuel than what is needed to idle to bring down the rpms?

Also, a car going up hill in say 5th gear @ 2000 rpms @ 75% throttle. Same car going up the same hill, same speed, in 3rd gear @ 4000 rpms @ 25% throttle. Which one is getting better fuel mileage? My thoughts are if the car is FI, it would be the 5th gear and opposite for a carbureted car.

Any thoughts?

If you're going down hill coasting in top gear and keeping your speed, the FI is not injecting fuel. If you put it in neutral the FI needs to provide fuel to make the engine idle, then you'll need to brake to maintain your speed. Yes, lifting in gear slows the car down. Is putting it in neutral and back in gear at speed going to cause excessive wear on the AT?

For my money, just avoid tromping the gas and unnecessary braking to get decent economy. Make sure your tires are properly inflated and get excess crap out of your car to keep the weight to a minimum.

One day I was stuck behind some turd in a Civic doing 80kph in a 110 zone and had a "Don't Honk I'm Hypermiling" sign on his trunk. I kinda wanted to punt him into the ditch...

Omerta · #7 01-16-2014, 02:56 AM

Quote:

Originally Posted by Helihover

This is something I've always wondered about. So is the FIS injecting less fuel than what is needed to idle to bring down the rpms?

Also, a car going up hill in say 5th gear @ 2000 rpms @ 75% throttle. Same car going up the same hill, same speed, in 3rd gear @ 4000 rpms @ 25% throttle. Which one is getting better fuel mileage? My thoughts are if the car is FI, it would be the 5th gear and opposite for a carbureted car.

Any thoughts?

Its a delicate balance of heat transfer, dP over the throttle plate and friction at speed. In general you would want to be between 2000 and 3000 rpm and at part load (30-60% throttle).

campy82 · #8 12-27-2013, 11:41 PM

I'm in for curiosity sake. In the past, I've used elevated tire pressure and weight savings with a "stingy" driving style for some impressive results...