Ideal rate of acceleration?

[Oval_Overload]

Sean, the ECU will come out of the dash and twist your nuts into oblivion if you try to drive at those RPMs. You would have to be going at least 70 to even get into that range, and nearly 90 mph at 3k in 4th gear. So, unless you are locked in third gear (hence the ECU butt-kicking), I doubt you'd see those revs.
You're right to keep the engine around 2k. The little fart of power at 2500 rpm before a shift is useless and puts more wear on our lemur-designed transaxles.
Do you drive in town a lot? I drive 80% country highway and get decent MPG figures from it (when the dang car works right... merf). The Taurus, with its .30 Cd, was built for the highway and can return 30 MPG. However, I've seen lawnmowers get better city mileage...

[Sean T.]

I do drive a lot in city, kindof... it's not traffic driving. Most roads I take are 55mph with streetlights, but I've done a pure highway tank and came up under 30mpg.

But I mean should I be accelerating with the RPMs at those numbers and then when I hit 45 my car always shifts down to about 1500. after that of course I would stay low RPMs.

I'm just not sure what's the best method of getting to that one major gearshift (I think it's going into 4th).

[MetroMPG]

Originally Posted by PA32R

This is a very difficult problem....

I agree with your sentiment, PA32R.

The answer to the question is a massive "IT DEPENDS" (TM). And it's why there's no tip for acceleration in the 100+ ecodriving tips list. There is no one size fits all answer.

Also, people tend to fixate on this question, when it could be demonstrated that the way you decelerate has a much larger impact on fuel economy.

[Sean T.]

Well, after a tank (+partial refill) of accelerating at 2300-2900 RPMs, I've come up with a tank MPG of 22.56, which is better than my average, but not by much.

Must... install... MPGuino... soon...

[GoodOak]

I'm really gland I found this thread.

I only recently joined Ecomodders after purchasing a gas guzzling small truck for my small business. I bought a ScanGauge and installed it this past Monday. I was surprised to see that my MPG is so low for so long when I accelerate very slowly, and when I accellerate at a more moderate pace my MPG increase much faster.

I am attributing this to the very low gearing a truck has in 1st and 2nd gear which gives you lots of power but not much efficiency. AFAICT from ~100 miles of driving, I seem to get 1-3mpg in 1st and then when it gets into second I get 6-8 mpg. Third gear brings the MPGs into the double digest. The increase in speed probably has something to do with this as well since it increase the miles in "miles per gallon".

I'm glad to see others are having similar results and that I am not crazy. My new strategy will be to accelerate more briskly to get out of 1st and 2nd quickly up to more efficient gears.

[binarycortex]

Originally Posted by MechEngVT

I have read that BMW instructs drivers to accelerate at 75% engine load and shift when the engine's mean piston speed reaches 1200-1500 feet per minute. Mean piston speed is a function of engine stroke and RPM.

Vp=RPM*S/6

Vp= mean piston speed
RPM= engine speed
S= engine stroke length, inches

I find this very interesting. I have heard that you engine is at its most efficient when it is producing the most torque. The 2.0L New Beetle's peak torque is at 2600 rpm. Using the above equation 1200-1500fpm is roughly at 2000-2600rpm. The actual numbers are 1216, and 1581fps for 2000 and 2600rpm respectively.

[skyl4rk]

i have been watching the Scangauge mpg and gph while accelerating. My theory is, at a steady gph acceleration rate, I let the rpm's increase as long as the mpg keeps increasing every second or so as the Scangauge updates. When the mpg flattens out and no longer increases, I shift to the higher gear.

On a flat road, I accelerate at about 1.5 to 1.8 gph, preferably holding at 1.5 gph if I can. The rpm range of acceleration seems to work best from about 2300 to 2900 with my 1.6l Nissan Versa.

[Scheißeglück]

Originally Posted by GoodOak

I'm really gland I found this thread.

I only recently joined Ecomodders after purchasing a gas guzzling small truck for my small business. I bought a ScanGauge and installed it this past Monday. I was surprised to see that my MPG is so low for so long when I accelerate very slowly, and when I accellerate at a more moderate pace my MPG increase much faster.

I am attributing this to the very low gearing a truck has in 1st and 2nd gear which gives you lots of power but not much efficiency. AFAICT from ~100 miles of driving, I seem to get 1-3mpg in 1st and then when it gets into second I get 6-8 mpg. Third gear brings the MPGs into the double digest. The increase in speed probably has something to do with this as well since it increase the miles in "miles per gallon".

I'm glad to see others are having similar results and that I am not crazy. My new strategy will be to accelerate more briskly to get out of 1st and 2nd quickly up to more efficient gears.

I have noticed this as well with my jeep. Even though it is an automatic, how far I push the accelerator can vary the RPM's before it shifts. When I accelerate slowly, it will shift anywhere between 2000-2250 RPM. I find that this usually gives me a worse MPG in the long run because the longer the time it takes for the transmission to build up the RPMs, resulting in a long and drawn out rate of consumption of fuel. If I accelerate at a brisk pace, the RPM's will hit between 2500-3000 RPM, which gets me a better MPG in the long term because the time it takes to get up to those speeds is shorter, thus reducing the rate of consumption of fuel.

And that's always the thing about big trucks and SUV's, having terrible consumption in low gear. By having the smaller/shorter gearing, the torque is amazing, but it takes so much energy to get it up to speed. Something that helps though in those low gears is having a 4 WD truck with a limited slip or some type of actuating locker. By having power go to all 4 wheels when accelerating, the energy needed to get the transmission going in low gears is reduced, making accelerations quicker, much cleaner, and helps reduce the fuel consumption from a dead-stop acceleration.

Since I need to replace the front differential on my jeep (thank you lil' sis for engaging the true-locker and taking a turn and blowing the whole thing out), I have been researching a couple replacement options. The two I find best for on-road, and off road if that's your forte, are Auburn Gear brand lockers and Powertrax "no-slip traction system." What's nice about the Auburn Gear ones are they are electronically acuated. When in an off position, the locker acts like a limited slip, but when on acts as a full locker turning both wheels on your axle at the same rate. The Powertrax one is a cheaper alternative that I personally think is brilliant. Inspead of acting like a limited slip, whihc cuts power to the wheel that has grip to the one that has least amount of traction, it will cut power to the wheel with less traction and give it to the wheel that has more traction, thus keeping you moving forward. Rear differentials will end up giving your axle the feel and control like a posi-traction rear end, and the front end diffs will have the same effect.

Links if anybody wants to check these out are:
StylinTrucks.com
Lockers and Other Jeep Parts and Jeep Accessories by 4 Wheel Drive Hardware

The Powertrax locker is made by Richmond Gear. What's cool about this one is they manufacture them for any type of accepting axle for cars, trucks, tractors, and UTV's.

[JacobAziza]

Originally Posted by rmay635703

my Dodge crew cab is abysmal but generally I need to get out of 1st asap

Originally Posted by GoodOak

I am attributing this to the very low gearing a truck has in 1st and 2nd gear which gives you lots of power but not much efficiency.

Some trucks (mine for example) are meant to be started in 2nd, except when going up very steep hills or towing/hauling very heavy loads. 1st is really more like "extra low", and 2nd is really 1st.

[KJSatz]

I'm going to start shifting at 2100rpm now. Their range gave me 2100-2600 (previously shifted normally at 2400-2900).

PS - Sean, I assume you got 2300rpm for 1200fpm and 2900rpm for 1500fpm? The BWM recommendation is to upshift when you reach 1200-1500rpm, and we'd probably work on the low side, so you would probably upshift at 2300rpm.

Another factor is how far apart your gears are. BWM likely has internal consistency, but other makes are probably quite different; this would cause a different upshift recommendation (what, exactly, I don't know).

Edit: To me it felt like I was lugging the engine excessively shifting at 2100rpm keeping LOD at 75-ish. I'm going to try to keep it lower than I have before though, perhaps 2400rpm.