How to Accelerate?

[sickpuppy318]

pulse[when the torque converter locks in third, i give it more than enough to make it go a deep whaaaa but not enough to upshift.] glide [Before it gets too angry, (and it positively SCREEMS at 65+), i let up enough to make it sound kind of choked but not enough for the distinct partial fuel cut and engine braking.]

magical threespeed auto

[PaleMelanesian]

If the gears are still engaged, it's not a glide. If the transmission automatically "lets go" and drops the rpm to idle, that's a good glide. If the rpms stay up, you need to go to neutral for the glide. If it's staying in gear and engine braking, you'll likely get better results with steady speed.

[bbjsw10]

Originally Posted by Vince-HX

Minimize pumping losses while accelerating.

Accel - least amount of vac without going into open loop
Cruise - highest amount of vacuum @ efficient rpm

imo

I have an autometer A/F gauge in my car, open loop would be when my "rich" led's stay lit continuously, Correct? Beings it is no longer correcting itself. I noticed this at about 4in. hg. or less. Sound about right, and figured my shift point at about 2400-2500 rpms.

If this is what I am after I have been doing Greatly the opposite. High vacuum and low shifts.

[sickpuppy318]

Originally Posted by PaleMelanesian

If the gears are still engaged, it's not a glide. If the transmission automatically "lets go" and drops the rpm to idle, that's a good glide. If the rpms stay up, you need to go to neutral for the glide. If it's staying in gear and engine braking, you'll likely get better results with steady speed.

Well, my shifters all broke in the terc, so i don't want to risk throwing it into reverse. That usually sucks. My "pulse" isn't really a pulse, but its less than enough to keep a steady speed, i try to decel as if it were it in neutral, keeping load as low as possible without braking. as long as the converter is locked, i think it works

[aerohead]

Originally Posted by pumafeet10

This is something that i have posted about a few times and find my self very conflicted. I have seen the advice from Wayne to accel slowly and then once up to speed and your are ready to Fas the to pulse at higher lod to get back to your target speed. The higher lod during pulsing i don't have a problem with.

I have a 2000 Honda civic hatchback that is almost gutted on the interior i have a carbon kevlar hood so my weight is def below average civics, and its 5spd, my tires are at 70psi and lastly the car has a full lower grille block which is on the inside of the grille which im not sure is causing problems or not? Right now according to my scangauge I am doing 60.3 MPG for the tank which is awesome, but for some reason i feel like I can do better.

So how should we accelerate, what rpm,lod and Tps ? For me i try to do about 65-76 lod but that is only like 25-30 at most on Tps , thats when I pulse after fas'ing.
What about when we are coming from a stop or just getting up to your speed where you want to start fas'ing?

Not sure if I am leaving something about but I drive slowly up to speed and its working but have seen some people with different results contray to what i am doing???

so whats the concensus??? Let the Great Debate Begin

David

A very dated SAE paper dealt with acceleration/MPG.Their reference acceleration was 6- feet- per- second- per -second."jack-rabbit" acceleration of 12-ft-per-sec-per-sec showed a dramatic drop in MPG.Halving the acceleration to 3-ft-per-sec-per-sec,showed a dramatic improvement in mpg.I'll dig out the paper if you wish.These findings fly in the face of research by BMW,who advocate much more lively acceleration (presumably in one of their BMWs) explaining that the waste came within the "transient" period,so get up to speed and hold your speed,and don't fart around getting there.
I think the BMW article is in my Phil Knox aerodynamic photos album,under "good news for jack-rabbit starts".

[PA32R]

Originally Posted by aerohead

A very dated SAE paper dealt with acceleration/MPG.Their reference acceleration was 6- feet- per- second- per -second."jack-rabbit" acceleration of 12-ft-per-sec-per-sec showed a dramatic drop in MPG.Halving the acceleration to 3-ft-per-sec-per-sec,showed a dramatic improvement in mpg.I'll dig out the paper if you wish.These findings fly in the face of research by BMW,who advocate much more lively acceleration (presumably in one of their BMWs) explaining that the waste came within the "transient" period,so get up to speed and hold your speed,and don't fart around getting there.
I think the BMW article is in my Phil Knox aerodynamic photos album,under "good news for jack-rabbit starts".

I'd love to see both of those articles. I've posted quite a few times on this subject and brought up an issue that HAS to play into the optimization question: the adding of kinetic energy. The fuel burned (and not wasted as heat, friction, etc.) goes to two things: overcoming the total resistive force (externally, these are aerodynamic drag and rolling resistance) and adding kinetic energy (we'll ignore potential energy by assuming level ground). It's quite easy to show that to add the kinetic energy to get the vehicle mass up to, say, 55 m.p.h., all else being equal, accelerating 1/2 as fast will get you twice as far in the process of adding that kinetic energy. This argues for the slowest possible rate of acceleration. But the m.p.g. as a function of m.p.h. curve and the engine map argue for a different protocol. I haven't yet concluded how to optimize these conflicting factors.

[TestDrive]

Originally Posted by PA32R

It's quite easy to show that to add the kinetic energy to get the vehicle mass up to, say, 55 m.p.h., all else being equal, accelerating 1/2 as fast will get you twice as far in the process of adding that kinetic energy. This argues for the slowest possible rate of acceleration. But the m.p.g. as a function of m.p.h. curve and the engine map argue for a different protocol. I haven't yet concluded how to optimize these conflicting factors.

"m.p.g. as a function of m.p.h. curve"??? Was there a chart? Did I miss it?

[PA32R]

Originally Posted by TestDrive

"m.p.g. as a function of m.p.h. curve"??? Was there a chart? Did I miss it?

I developed one for my LR3, a small write up on it is at Adventures in Fuel Economy, Energy Use, Physics, and Life: The best speed for fuel economy.

Its limitations are obvious, as anyone who reads the blog entry will see, but I think it's in the ballpark.

[TestDrive]

Originally Posted by PA32R

I developed one for my LR3, a small write up on it is at Adventures in Fuel Economy, Energy Use, Physics, and Life: The best speed for fuel economy.

Its limitations are obvious, as anyone who reads the blog entry will see, but I think it's in the ballpark.

It seems worth hi-lighting the The How Stuff Works article mentioned in your blog - What speed should I drive to get maximum fuel efficiency?

Your conclusions are a bit theoretical, but seem to agree with my drive tests using a 1994 Ford Escort LX Wagon (1.9L SOC & 5sp MT) on 150.5 mile daily loop. (If you're curious about: location, distance between stops/turns, elevations and etc. click here for a google map)

This is a contract haul route for a local newspaper. I leave at 1:15 AM and complete the loop by 6:15 AM. Because this section of the country is such low population, other than wild life and the occasional escaped cow or horse, I practically own the road during these hours. On a typical night I may see five or six vehicle traveling either direction on the first leg of the route. From point B to the last turn before point K, I seldom share the road with even one other vehicle. From K to the end of the loop, I see something like 6 to 8 other vehicle depending on the day of the week.

Point B is a relay pickup point - another vehicle brings the papers to me there. When the papers arrive at Point B on time, I can drive as slow as 32 mph and still complete the route on time. When the papers arrive later, I sometimes have to drive as fast as 65 mph. If I drive the route at fairly stead 37 mph (drive with load for a few obvious hills, EOC to 13 stops, Engine Running Coast through 19 turns and use quite modest acceleration (0 to 30 mph in about 20 seconds - hitting all five gears), I average 49 mpg. If I accelerate more aggressively, my average mpg is worse. If I "ACCELERATE WITH LOAD" (Yeah, I coined the term just now), mpg can go as high as 54 mpg.

"Accelerate With Load" means - Shifting to the next higher gear as soon as it is at all possible to accelerate without engine knock.

Consider for a moment the upshifting recommendations in the 1996 Ford Escort Owners Manual (Don't have a manual for my 1994. 1996 is the oldest manual available at https://www.fleet.ford.com/maintenan...ls/default.asp)

Upshifting
For normal acceleration, you should upshift at the following speeds:

.......... 1.8 Liter Engine ..... 1.9 Liter Engine

1 to 2 ........ 11 mph ............... 12 mph
.............. (18 km/h) ............ (19 km/h)

2 to 3 ........ 24 mph ............... 22 mph
.............. (39 km/h) ............ (35 km/h)

3 to 4 ........ 34 mph ............... 31 mph
.............. (55 km/h) ............ (50 km/h)

4 to 5 ........ 43 mph ............... 42 mph
.............. (69 km/h) ............ (68 km/h)


For cruising, you should upshift at the following speeds:
.......... 1.8 Liter Engine ..... 1.9 Liter Engine

1 to 2 ........ 10 mph ............... 11 mph
.............. (16 km/h) ............ (18 km/h)

2 to 3 ........ 17 mph ............... 17 mph
.............. (27 km/h) ............ (27 km/h)

3 to 4 ........ 29 mph ............... 25 mph
.............. (47 km/h) ............ (40 km/h)

4 to 5 ........ 39 mph ............... 35 mph
.............. (63 km/h) ............ (56 km/h)

If you use the second - cruise -shift table and accelerate aggressively, the engine knocks. If you're on level ground and accelerate lightly/moderately, the upshift indicator light more or less matches the second shift table. If you accelerate extremely lightly - as if there were a raw egg between the sole of your shoe and the accelerator pedal and you'll lose a $100 bet if the egg cracks - the upshift light indicates an upshift somewhat sooner than the table. If I up shift at the points denoted by the indicator light when using such minimal acceleration, I can still accelerate in that next higher gear - with out producing engine knock at a rates of acceleration slightly more aggressive than dictated by the raw egg parameter. Actually, it's possible to shift well before the indicator light designates and continue accelerating (as if raw egg under foot) in the next higher gear without engine knock. eg.

• Shift from 1 to 2 at 9 mph
• Shift from 2 to 3 at 13 mph
• Shift from 3 to 4 at 17 mph
• Shift from 4 to 5 at 23 mph

That's what it takes to go from 49 mph to 54 mph with all other parameter the same as indicated above.

A couple of notes of caution for anyone contemplating attempting this technique.

• Turn your radio off! Engine to knock can cause serious damage. You need to be able to hear what's going on.
• You need a deserted or very lightly traveled stretch of road. Otherwise, rest assured some idiot will rear end you. Not to mention, it would be pretty discourteous to drive this way in the midst of traffic.
• If it's not illegal in your state, drive in stocking feet - no shoes - when you first attempt this.

FWIW My 94 Escort is essentially unmodified. Tires are the next taller profile than stock (odometer reads under by 6.5%). The only areo modes are a crack in the front bumper (kamakazi jackrabbit = increased drag) and missing plastic grill (kamakazi pheasant = increased drag). Tire pressures are as indicated on door post. Run of the mill TropArtic 5w30 oil. Generic ATF in the tranny.

[greenitup]

i have found so far with my truck that it gets better fe the easier you are on the pedal, it is hard to accelerate because takes alot of gas to move. So far p+g has hurt me but i am planning on trying different ways to include it.

I would think that theoretically it would depend on your engine size (50% power output from a big v8 is different than one from a v6) aerodynamics (the more aerodynamic the easier to accelerate the move acceleration from same power) weight (the heavier the vehicle the more power it takes to accelerate, and if that is paired with a smaller engine the better efficiency is to accelerate slow and not p/g; but if you have a big engine compared to the weight of car then you are better off accelerating average and p/g)

so it is all based on the car.