fuel flow at high rpms but no throttle in a car

[imasaluki]

Some driving tips I use to help increase mpg are... 1) timing traffic lights to keep my speed up to avoid having to re-accelerate, 2) drive the speed limit or the "sweet spot speed" for your engine/rear-end gear combination, 3) shift, shift, shift...get to final gear, 4) park in spots where I can "pull through" to eliminate the need to back out of a spot and reverse course, 5) use the minimal amount of steering needed to make my turns... the friction of turning causes deceleration and the need to re-accelerate, 6) pretend there's an egg underneath your accelerator pedal when you accelerate... squeeze it... don't mash it, 7) don't idle... just don't do it.

I don't have much input on the injector duty cycles of an Evo, but coasting is never really a good idea even if it did save you .2 mpg. That's my thoughts at least.

 

[PGT]

your car uses VERY little gas when idling

 

[SoCalAprch]

Granted Im not a mechanic or even smart by any means but I have always been taught that it saves gas when you keep it in gear. If the car is idling/coasting while not in gear the engine needs fuel to keep the engine running, spinning, idling at its 1200 RPM or whatever. If you are slowing down while in gear the engine is turning not by fuel but by the wheels. Not very technical terms but thats how I always visualized what was being said. And either way its probably only a .1 or .2 MPG difference.

 

[Blip16]

your car uses VERY little gas when idling

it may use very little gas, but in the winter my ecomony goes from 20ish to 14ish in town because of all the idling/warm up time

 

[imasaluki]

your car uses VERY little gas when idling

You're kind of correct in assuming a small amount of gas is used when idling, but you will absolutely kill your fuel economy by idling. Every second the engine is running while your car is stationary will destroy your mpg. Think about it... if you do a ten minute trip in a 20 mpg car, but you idled your car at 0 mpg for 3 minutes before you even began the trip... it's very clear you're taking a few steps back by idling.

BuickCFI, I don't do the stationary warmup in the winter anymore... I just go light on the throttle until I get a good rise on the coolant temp gauge.

 

[imasaluki]

Granted Im not a mechanic or even smart by any means but I have always been taught that it saves gas when you keep it in gear. If the car is idling/coasting while not in gear the engine needs fuel to keep the engine running, spinning, idling at its 1200 RPM or whatever. If you are slowing down while in gear the engine is turning not by fuel but by the wheels. Not very technical terms but thats how I always visualized what was being said. And either way its probably only a .1 or .2 MPG difference.

Fairly good explanation if you ask me.

 

[PGT]

Honestly, I don't care about MPG as much as I care about protecting my engine.
For one, keeping the engine idling saves wear and tear on starting system plus the most amount of engine damage is done at startup. In the winter, I like to warm up my car before I go into it so I'm not freezing cold, it if requires 5 min of idling to warm up then so be it. And finally engines do not like to be operated when cold. I know the Mitsubishi Evo says not to drive it until the temp gauge has moved off the C mark.

Try shifting a manual transmission car when it's freezing cold and you haven't warmed it up, the gear box oil feels like sludge...that can't be good on the transmission internals.

 

[imasaluki]

Honestly, I don't care about MPG as much as I care about protecting my engine.
For one, keeping the engine idling saves wear and tear on starting system plus the most amount of engine damage is done at startup. In the winter, I like to warm up my car before I go into it so I'm not freezing cold, it if requires 5 min of idling to warm up then so be it. And finally engines do not like to be operated when cold. I know the Mitsubishi Evo says not to drive it until the temp gauge has moved off the C mark.

Try shifting a manual transmission car when it's freezing cold and you haven't warmed it up, the gear box oil feels like sludge...that can't be good on the transmission internals.

That's fine, but the thread was started with the intent to address the matter of saving gas. We obviously know you can do whatever you want to do with your car whenever you want to do it. Furthermore, your comments are nothing more than speculation.... I'm sure Mitsubishi engineers never thought of shifting their manual transmissions with cold gear oil. And if you increase your fuel mileage a few mpg and don't recoup AT LEAST the cost of a new starter in 10 years... I'll buy one for you.

 

[Blip16]

You're kind of correct in assuming a small amount of gas is used when idling, but you will absolutely kill your fuel economy by idling. Every second the engine is running while your car is stationary will destroy your mpg. Think about it... if you do a ten minute trip in a 20 mpg car, but you idled your car at 0 mpg for 3 minutes before you even began the trip... it's very clear you're taking a few steps back by idling.

BuickCFI, I don't do the stationary warmup in the winter anymore... I just go light on the throttle until I get a good rise on the coolant temp gauge.

that works ok when it is 20F outside, not -20F

 

[roundout]

Stationary warmup won't work in a diesel. Hell, when it's 10 or 20 out it takes me driving 10 minutes at highway speeds to start getting hot air out of the heater. God bless heated seats.

 

[Matt13C]

I personally dont see the use in sitting in the driveway idling for 10 mins. I start my car, get the ipod set up, pick an album and maybe scrape a window then drive away. When warm the car idles at 900rpm, when cold it idles around 1600. Shifting is no problem, dont know if it is the synthetic oil or what, but it does not feel much different than when warm. I simply dont go over 2k rpms and I drive down my street or through the work parking lot, if after work, at around 2k rpms. Car warms up much faster.

My thought on it is you save wear and tear heating the engine up quicker than if it were to sit in the driveway running cold longer. As long as you give it a min or two to get the oil flowing and all the parts properly lubricated I dont think you will see any real difference in wear and you will save time and fuel.

 

[Blip16]

i don't know if you really save fuel because a cold engine is a lot less efficient. but it does warm up a bit quicker when under load. but when it gets below 0 you need to let it warm up for a few mins before driving or you risk some pretty severe damage

 

[Matt13C]

i don't know if you really save fuel because a cold engine is a lot less efficient. but it does warm up a bit quicker when under load. but when it gets below 0 you need to let it warm up for a few mins before driving or you risk some pretty severe damage

If it gets below zero that is a different story. I am not going to sit in a car that cold, I will run out start it and be back inside. It rarely gets that cold here though, especially the last few years.

 

[PGT]

That's fine, but the thread was started with the intent to address the matter of saving gas. We obviously know you can do whatever you want to do with your car whenever you want to do it. Furthermore, your comments are nothing more than speculation.... I'm sure Mitsubishi engineers never thought of shifting their manual transmissions with cold gear oil. And if you increase your fuel mileage a few mpg and don't recoup AT LEAST the cost of a new starter in 10 years... I'll buy one for you.

Yea but everything that has been said on here will improve gas mileage by .5, maybe 1-3mpg but that's about it. Sorry that's not worth it to me, I'd rather have a warm car to get into and warm engine while getting 25mpg than freeze my butt off and have 28mpg.

 

[imasaluki]

That's cool... I'll stick to saving money.