Everybody is always discussing where the most power is made, but I'm wondering just the opposite. When you're driving in town or what have you, where on the tach are you most fuel efficient? I try to keep it under 4k when cruising, and shift before 6 k. But truly, I have no idea.
Anybody know the answer?

 

Best fuel mileage is achieved when you're in the lowest gear for you desired speed without lugging the engine. I'd say shifting around 3000 would give it to you.

 

thats crazy talk! it should be illegal to shift when the tach is in the white area on the tachometer. shifts should only be done while at redline!

 

i used to think this was true, but i am not so sure. i just had my best mpg ever (city driving) and i was not keeping the rpms as low as possible.

i think it had to do with which rpms is the engine most effecient. on a GSR, i think accelerating through the sweet spot of the lower cam profile (4-6000 rpm) gets the most bang per drop of fuel. but this is light acceleration, not floored.

if you really want to stretch your fuel dollar, get a vacuum gauge and try to keep the engine between 20" and 10" of vacuum. Its a real challenge to do this and keep up with traffic, and you will notice you're shifting higher and pressing on the gas less. thats why they call it the gas pedal! just because the engine is spinning faster doesnt mean you're sucking more fuel... you'll notice you push the pedal much less if you let the engine wind up to 5-6k in normal driving.

i have to admit its been very hard for me to get used to doing this. it seems like you're wearing the motor out revving it like that just for normal driving, but trust me, the GSR is meant to be revved, just dont bounce off the rev limiter!


Joe



[Modified by falconGSR, 4:55 PM 12/18/2001]

 

That is exactly what I try and do. Since doing this I noticed that my MPG went up 3-4 mpg over what it was when I used to shift at 4k all the time. You have to give it more gas at the lower rpms than at the slightly ones.

 

Huh... Interesting!
I wonder if a baseline dyne would show you exactly what the most efficient range is?
I guess it's obvious the more you lay on the gas, the more is being used. Especially during the second VTEC stage.
Revving highher makes sense though. You're producing more torgue higher up the tach, right? Torque overcomes inertia. At lower revs (ie slogging it), you have to pump more gas into the chamber to produce the power to go.
I suppose that makes perfect sense! That's why on the interstate, even though I'm turning over 4k (in fifth), I still get about 30-32 mpg.
I guess it's just a matter of overcoming the feeling you need to shift when it starts to scream while driving in town.
I'l try it.

 

when cruising if you can keep it right bellow the vtec switch, that is the best I have found, right at about 80-85 mph. unfortunately cops don't care if you are trying to be fuel efficeint or environmentally consious..

I agree that slow revving is the way to go on efficiency though..

 

When i had my turbo in, i would drive off of the vac gauge, keeping it at -10 i could hit 37mpg.

Tom

 

i try to shift before 3K to get some good mileage. this is when cruising. I remember during one summer where I got almost 320 mile to the tank. it works for me. now when autoxing, redline all the way. normal acceleration is the key, I think. just my $.02

Ron

 

yeah my car is wierd too, when I was driving to canada at an average speed of 100 miles an hour at 5000-6000 rpm I got around 36mpg everyone tells me its impossible, but tell me how I made it back and forth from washignton to canada on 10 or so gallons with enough to spare for a few days.

 

How about this fact...
Our torque peak is at 6200 rpm. Assuming your oil pressure isn't high enough to engage VTEC, the fuel mixture should be pretty lean, and the engine is at maximum efficiency, or somewhere around it.
Is this the answer? Cause it sounds good to me.

 

Why does it seem that cars with automatic transmissions tend to usually get lower mpg than cars with manual transmissions?
Does this have anything to do with what has been talked about so far, or is it something else different entirely?

So from what I understand so far about maximum mpg would be:
1. Accelerate slowly
2. Reach highest gear possible without lugging the engine
3. Achieve peak torque for that gear? (maintain speed of 100 on the freeway )


[Modified by 2001 Integra GSR, 1:12 PM 12/18/2001]

 

it really all depends on the driver. I guess shifting at the sweet spot is important so you're not stuck in a low gear and godly low rpms while trying to floor it to make it faster. Automatics are nice because you just leave your foot on it and you can keep the acceleration somewhat linear. oh yeah, automatic cars are heavier!

 

And automatic transmission saps power going to your wheel. You need to press that much more gas on an auto to equal a manual.

 

There is only 1 stage of VTEC. Its at 4400 RPMS on a GSR. The secondary intake manifold runners open up at 5700. This is what makes it get loud around 6k. Just clarifying. One more thing, when i got an ITR tranny, my gas mileage improved noticeably. Im at 4.4-5k RPM@ 80 mph now, where as with the GSR tranny, i would be right @ 4 k. Kinda strange.

 

I read an tech article back in the day about shifting for gas mileage and they basically concluded that best mpg was achieved when driving at 1/2 to 3/4 throttle and making relatively quick shifts at slightly higher rpm than you would think (i.e. 5K rpm on their Bimmer test car). Also, get better mpg by keeping your speed as constant as possible w/o abrupt deccelerations or accelerations


[Modified by kent, clark, 8:28 PM 12/18/2001]

 

yup. autos have a torque convertor which allows them to be in a gear while stopped and still transmit power when you get on it. Unfortunately, this also means you're losing energy since the engine is not directly connected to the wheels.

Over the last few decades, torque convertors have improved dramatically, and many auto trannies "lock up" the torque convertors when in top gear (on the highway), so there is much less difference between autos and manual trannies nowadays when it comes to mileage.

Joe

 

It makes sense.

It's just that when I went to look at cars, there was always a difference between the autos and manuals. For example, the manual tranny would get 30 mpg while the auto tranny would get about 27 or mpg (highway drving).

Your explanation makes sense. Thanks.

 

Huh! I've always heard of people who swapped for ITR trannies replacing the 5th gear with the taller GSR cog.
I suppose just cause you're making more racket doesn't necessarily mean you're sucking more gas. Still, at 80 (and yes, at 80 I'm at eaxctly 4k in my GSR) and turning around 5k, you're closer to that torque peak, so it makes sense you'd get better mileage.
It's funny, cause the idea of revving the engine to the heavens to get better mileage is contradictory to what you learned all those years ago. But heay, whatever works!