csmeance

But thats while accelerating, you are right, but this is the way that works

By remaning at lower RPM's for a longer time to accelerate, you are using more gas, example of this is this

Excelerate to 60 from 40
option 1
Keep under 2K the entire time, which results in 30 second climb time.

option 2
Keep under 3.5K, one gear lower, which results in 15 second climb time.

In this case, option 2 would save more gas, it uses about 15-20% less gas.

But if you are cruising at a constant speed, and not accelerating, it's best that you keep your RPM as low as possible.

tweeder82o

While the topis was on highway speeds, my concern is regarding accelerating at lower speeds

I used to own a 99 pontiac grand prix gt, in which, i was able to get a smooth yet zippy acceleration.

However, I recently switched over to a 04 acura TL, and as many of you may have already noticed it lacks low end torque till about 2000rpm, then there's more torque than you know what to do with.

This, thus, results in a jerky acceleration coming out of a stop sign or red light. Where the car hardly moves then at 2000rpm launches giving every one a whiplash.

I can avoid the whiplash if I pull out slow and steady like a grandma. So I'd like to know how has everyone dealt with this, while still able to zip out of a stop and accelerate smoothly at an above-average pace (not drag racing or anything).

Sonnick

True...BUT that's only if you use constant, hard pressure on the throttle. If you are using the throttle with the same pressure you would in 5th when you are in 6th, you will use less gas. However, if you are driving up a moderate hill and are in 6th at 35mph, pushing more on the throttle to keep up speed would use more gas than being in 4th without using much pressure at all.

Didn't realize this thread was a couple months old. But hey, always good to have extra info

adrian_04tl

i might have been worried when gas was $5.05/galon but, now its only $2.79 time for us gentlemen with 6mt to have some fun (shift at around 4k rpm).

btw, ive noticed that crusing at around 75mph (2600 rpm, 6th gear) seems to give me the best gas milage, 28mpg. not bad at all.

YeuEmMaiMai

pulsating the speed is bad for gas milage and causes more wear and tear on the car

I usually keep the tach around 2.5K when accellerating and cruize around 70 or so depending upon traffic

YeuEmMaiMai

you are correct, you mpg is maximised when your engine's max efficiency = effort to move the car forward. lugging a car in a higher gear = efficiency lost and same for higher revs in a lower gear

ahrajani

The key here is to not think of it in terms of pressing the gas repeatedly. but instead thinking about it as letting your car decelerate repeatedly. Here's a useful analogy:

Convinced that it was a waste of energy to keep our apartment's thermostat at a steady 68 degrees, my college roommate insisted on cranking the thermostat to 90 degrees, waiting until it got really hot and then shut the heat completely off. 45 mintues later, when the apartment was freezing cold, he cranked it back up. Apart from the serious heat rash I developed at the time, my roommate was greeted with an energy bill (which he paid) that was about 35% higher.

Just like my roommate wasted much more fuel by shutting the thermostat off, you are taking your foot off the gas. The effect is that your car loses its momentum, which you can only get back by accelerating.

And most importantly, you drive like my mom -- and that's not cool.

jmkiang

iTrader: (5)

Sorry to bump this old thread but I have a quick question.

Say I want to attain a cruising speed of 50mph. Would it be better to get to 50mph (~4.5K RPM) quickly and then maintain it(~1.5K RPm)? Or would it be better to slowly get up to 50mph, keeping the rpm's low (constant 2K RPM)?

Sorry if this has been covered.

chairguru22

Not sure about saving gas but flooring it to 50 is more fun. Also fun to look at everyone you left in the dust in your rearview.

I hate cars

Your best mpg is going to be at a steady state cruise obviously. The quicker you get there, the better within reason. The difference between normal and light acceleration up to freeway speed just isn't large enough to cover the extra time spent accelerating.

With an auto, it's best to get up to the speed you want to go in a normal manner. The less throttle and rpm you have, the more energy is lost through the torque convertor.

With a manual, usually low rpms and slightly higher throttle openings are the best.

Theoretically, the best mpg would be a gear so tall you had to have the pedal to the floor to maintain speed.

jmkiang

iTrader: (5)

Haha
Ok so since I drive a 5AT, its better/more efficient to get up to speed (as long as I'm not redlining) and then maintain.

OK cool thanks. Was wondering this on my way to work. I know some people that accelerate like grandmas to conserve gas... wondered if they are actually getting better MPGs. I know going too slow can lower your MPGs too.

SpecialFX

[QUOTE=

Theoretically, the best mpg would be a gear so tall you had to have the pedal to the floor to maintain speed.[/QUOTE]

Um... What?

superNoid

Constant speed.

dracer219

Steady foot pressure FTW it doesnt make any sence to rev then release your not making your motor happy there sir

knavinusa

IIRC, this is because the valves would be fully open, allowing air to move easily into the combustion chamber which results in a complete, efficient burn.