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Old 06-24-2012, 11:29 PM   #1 (permalink)
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how to drive a stick?

okay so i've always wondered about this, and i figured this would be the best place to ask, so i finally joined.
My question is, how do you guys drive stick shifts? What i've been doing is pretty much shifting as soon as i can to get into as high of a gear as possible for best economy. but i can't figure out if i'm maybe straining the engine more by doing it that way, and in straining the engine, maybe i'm actually losing mpg?
another thing is that i think by shifting earlier i have to be a little bit heavier on the throttle to achieve the same amount of acceleration that i would've in a lower gear, so those two might just cancel each other out...
i don't have my own car, so i haven't done any calculations...
what do you guys think?
edit: by the way, this is essentially based on the idea that in order to get better gas mileage, rather than creep up to speed, you should use medium acceleration to get up to coasting gear faster. my theory is, why not drive a stick and just put it in coasting gear, even if you're only going 35, not 50?


Last edited by Banana Jack; 06-25-2012 at 12:45 AM..
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Old 06-25-2012, 12:30 AM   #2 (permalink)
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I tend to accelerate briskly, 15-20% throttle and shift @about 2500rpms, frequently skip 4th gear
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Old 06-25-2012, 01:11 AM   #3 (permalink)
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i used to get in top gear as soon as possible with very light throttle loads , however im told thats wrong.

the advice was accelerate briskly [about 80% power] fully utilizing the peak torque segments of YOUR engines power curve in all gears then at cruise around about peak torque for your engine .i go into top gear [4] at about 40MPH and thats some pretty fast stick whipping at 80% for sure
not to say you should red line the thing in the low gears. but run it up until you can fall into the next gear at a good torque #
a power curve chart [fuel-power] is helpful in deciding the best engine speed shift points
notice on the attached chart for my engine that the lowest fuel consumption mirrors the highest torque..
based on this chart i up shift about 3200- 3500 RPM , never run below 2000 RPM and cruise in the big cog at 2800-4500 RPMs. thats between 50 & 80 in top gear

all engines are different.. with *experience* you will develop a feel for it based on subtle sounds and vibrations ..well at least with the machines i run you can ,vibrations and even the sound the carb makes as the throttle plate opens
i do use a manifold vacuum gauge , which is helpful in judging ,i accelerate at 5-10 INHG and like to pull hills at 10. cruise at 15-18 INHG.

all engines are different and have different power-fuel charts. i think they should put them in the operators manual.
maybe this makes sense to you maybe not , maybe its the *right* way maybe not.
just my thoughts based on a lot of miles in many different types of equipment

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Old 06-25-2012, 03:21 AM   #4 (permalink)
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Quote:
Originally Posted by MGB=MPG View Post
i used to get in top gear as soon as possible with very light throttle loads , however im told thats wrong.

the advice was accelerate briskly [about 80% power] fully utilizing the peak torque segments of YOUR engines power curve in all gears then at cruise around about peak torque for your engine .i go into top gear [4] at about 40MPH and thats some pretty fast stick whipping at 80% for sure
not to say you should red line the thing in the low gears. but run it up until you can fall into the next gear at a good torque #
a power curve chart [fuel-power] is helpful in deciding the best engine speed shift points
Mind you I only know the theory of driving stick, and can't actually do it, but peak torque doesn't really mean peak efficiency, since torque has more to do with the volumetric efficiency provided by your intake and exhaust acoustic resonance and cams.

Light throttle acceleration is definitely bad, but what engine speed do you use? It's hard to find BSFC charts but out of all the ones I've ever managed to dig up BSFC is in a "very good" range between 2000-3000 on most engines. That's not to say going outside that range is necessarily going to make a noticable impact, but using somewhere between 2-3krpm to accelerate would appear to be ideal for most cars. I imagine as you go up in displacement per cylinder that number goes down since the cooling losses are comparatively smaller with a large combustion chamber.

Also the higher you rev, the more energy the rotating assembly, flywheel, and input shaft soak up, which may or may not be significant, I never bothered to figure out the order of magnitude of those losses.

I guess there's also the issue of "throttle %". You'd have to know how your engine requested torque vs. pedal position is calibrated if it's drive by wire throttle, but I think if you just press halfway down you'll get something like 50-70% torque which is pretty good. With a cable throttle it's harder, and it'd be good to have a manifold vacuum gauge or something, and aim for 0.7 bar absolute pressure or somewhere around there.
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Old 06-25-2012, 05:01 AM   #5 (permalink)
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Brake "specific fuel consumption - Wikipedia, the free encyclopedia
Any engine will have different BSFC values at different speeds and loads. For example, a reciprocating engine achieves maximum efficiency when the intake air is unthrottled and the engine is running near its torque peak."

of course thats wiki and a consensus position ,
some charts for the curious
Brake Specific Fuel Consumption (BSFC) Maps - EcoModder
http://gm-volt.com/forum/attachment....8&d=1323735475
http://www.turbodieselregister.com/t...1_FEimage1.gif

start ups with a manual transmission is only the beginning of the process , how will you manage cruise
my best FE speed ON THE FLAT is about 40 MPH @ 2200 RPM , however its rolling hills around here and the first grade i came to i would have to downshift, therefore i burn hills up and down .try to hold 10 INHG or better on the upgrade no less than 5. then when i top grade and start descent, maintain 15-18 INHG .which is a pretty light throttle setting . machine will be accelerating ill run it out pretty fast if the downgrade is long enough and john law is not around, then on the next up grade hold 15 INHG >10>5 , at 2200 RPM look for a lower gear.

i worry about FE to keep my tank range up. i only logged 3 K miles last year , but in a misspent youth logged about 20000 hours *throttle time*

as i learned through time i tended to use the EGT more along with the exhaust note and engine vibrations , not to mention the tachometer
2 sticks and 15 forward gears
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Old 06-25-2012, 07:54 AM   #6 (permalink)
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Quote:
Originally Posted by Banana Jack View Post
edit: by the way, this is essentially based on the idea that in order to get better gas mileage, rather than creep up to speed, you should use medium acceleration to get up to coasting gear faster.
When accelerating, you need horsepower.
An engine will produce that HP most efficiently al rather high loading (say around 80% engine load or so) and low rpm.
So you'd need to use a fair bit of throttle, but shift early - say 2500 rpm on a small(ish) displacement petrol engine.

But you don't really need to look at the current gear / rpm setting to decide when to shift ; you should look instead at what the engine will do when you get into the next gear.
You need to shift at the point where the engine no longer starts to lug once it gets into the low rpm in the higher gear.

The bigger the engine, the sooner you should be able to shift up.


Quote:
my theory is, why not drive a stick and just put it in coasting gear, even if you're only going 35, not 50?
The engine needs to be able to pull that off.
Some cars can do it , others simply can't.
If it can't, the ECU will throw on extra fuel just to keep the engine running, giving miserable fuel economy.
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Old 06-25-2012, 08:51 PM   #7 (permalink)
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I am no way an expert, but here is what I do. I try to find the max torque curve of the engine and not exceed that rpms. I use that as the upper rev limit rather an automatic or stick. Many cases with a stick Ill use a lower gear to maintain speed in slow areas like 25-35 mph. Outside of those I use the highest gear possible unless I need to suddenly accelerate. In those case I go down 2 gears and floor it.

If you got a torquely motor in many cases you dont need all the gears. In my sidekick with the 16 valve engine and 5 degree cam advance I frequently do 1,3,5 for highway driving, 1,2,4 for city.
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Old 06-26-2012, 09:44 AM   #8 (permalink)
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I think it depends on terrain and the particular vehicle.

With my ranger, I usually go 1,2,3,5. Short shifting, moderate throttle. Up hills, I won't skip gears.

In my daughters saturn wagon, I find that 1,3,5 is easier and smoother. I find with that vehicle, the 1,2 shift is kind of jerky. I think this is because the gears are very close, so it's almost like going from 1 to 1 again.

So, what it comes down to is experiment a little. Listen to you engine. To me, my ear tells me more than the tach does. If you are lugging, you will know.
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Old 06-26-2012, 10:20 AM   #9 (permalink)
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i havnt had my new truck long enough to tell which is best but im currently accelerating with about 50% throttle and changing up around 3000rpm (no tach so guessing a bit) my gears are really short though so i start in 2nd then go 3rd around 20kmh and 4th around 40kmh

this is in a '77 F100 with 351
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Old 06-26-2012, 10:29 AM   #10 (permalink)
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Pretty brisk until 3000 because then I'm getting close to the tubrbo, and coasting in neutral when I'm not actually accelerating.

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Transmission type Efficiency
Manual neutral engine off.100% @MPG <----- Fun Fact.
Manual 1:1 gear ratio .......98%
CVT belt ............................88%
Automatic .........................86%

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