How difficult is it to crank a modern engine manually?

[halik]

take the spark plugs off and you can turn it with a 1/2" drive wrench.

 

[JulesMaximus]

It's pretty easy if you have the engine out of the car and no cylinder heads mounted...then it's fairly easy to turn it over by rotating the flywheel.

In the car with full compression? That would be much more difficult. Honestly, I don't understand why you'd want to do this. Starters are fairly cheap and reliable as are modern car batteries.

 

[Zenmervolt]

Originally posted by: goku
How difficult is it to crank a modern engine by hand? I heard that in the old days that people would break their arms trying to crank an engine, why is that? How difficult would it be to crank the engine with your legs? How much torque does it require to crank an engine? Something like 100lbs or 200lbs of torque, right?

The reason people broke their arms cranking old engines is because there is a chance, on those old engines, of the engine "kicking back", which would whip the crank handle back into the person's arm and snap it. They didn't break their arms by pushing hard on the crank handle.

Also, it definitely does not take 100-200 pounds to turn over an engine. It's actually not too difficult.

ZV

 

[Zenmervolt]

Originally posted by: Zolty
If you actually want to test this lift your manual transmission car off the ground to a comfortable level, remove one of the drive tires. Now you will want to fashion a lever or crank on to that drive tire and crank away, if you think it is easy then you haven't put the car into first, you need to do that.

Actually, you'll never get the same ratio by cranking at the wheels. A crank on the crankshaft is a 1:1 gear ratio. Even in overdrive (typically a 0.7:1 transmission ratio) the final driver ratio (typically between 3:1 and 4:1) makes the overall ratio well above 1:1.

ZV

 

[IGBT]

..tough. ya may as well walk if that's your only option.

 

[spidey07]

Guess you're too young to know how to start a tractor.

There was a large metal "flywheel" that you would crank to turn over the motor through a couple strokes (maybe about 6 full cycles...24 strokes) and achieve combustion. The weight and size of this wheel allowed you to crank the motor by hand.

Now just turning a car motor over by hand isn't that big of a deal. Turning it over with enough momentum to carry a full 4 strokes a few times to actually start it IS.

 

[Kelvrick]

Sport bikes, at least the lighter ones are often started this way when it dies.

Hop off, start running like a maniac (with it in second gear), start to release clutch, give it some gas and hope you don't drop it.

 

[BooGiMaN]

you must have a huge ass.......you seem to have an endless supply of off the wall threads threads you keep pulling out of it...

 

[BillyBatson]

Originally posted by: XJustMeX21
lock in 5...4...

why would this be locked?

i know you can roll certain cars to a start, did you ever watch Little miss sunshine?

other than that i dunno

 

[spidey07]

Originally posted by: BillyBatson

Originally posted by: XJustMeX21
lock in 5...4...

why would this be locked?

i know you can roll certain cars to a start, did you ever watch Little miss sunshine?

other than that i dunno

You can "pop-start" any motor. What do you think your starter motor does? Magically start the motor?

Pop-starting a vehicle is very easy. It's got weight. Use that to turn the motor. Best if you're in 2nd or 3rd gear if you do so.

Now trying to start a modern car engine by hand? I'd probably break an arm as well from the kick back - I'd need something like the flywheel on a tractor, something with weight/inertia to prevent a lack of force to push the pistons past TDC and having them slam a wrench into my face.

Ever seen the starters they use on indy cars? Those things could probably rotate a small house if they needed to.

 

[JulesMaximus]

Originally posted by: spidey07

Originally posted by: BillyBatson

Originally posted by: XJustMeX21
lock in 5...4...

why would this be locked?

i know you can roll certain cars to a start, did you ever watch Little miss sunshine?

other than that i dunno

You can "pop-start" any motor. What do you think your starter motor does? Magically start the motor?

Pop-starting a vehicle is very easy. It's got weight. Use that to turn the motor. Best if you're in 2nd or 3rd gear if you do so.

Now trying to start a modern car engine by hand? I'd probably break an arm as well from the kick back - I'd need something like the flywheel on a tractor, something with weight/inertia to prevent a lack of force to push the pistons past TDC and having them slam a wrench into my face.

Ever seen the starters they use on indy cars? Those things could probably rotate a small house if they needed to.

Has to be a manual transmission though. I'd like to see you pop start an automatic...:laugh:

 

[Zenmervolt]

Originally posted by: JulesMaximus
Has to be a manual transmission though. I'd like to see you pop start an automatic...:laugh:

Actually, some old automatics had a provision for push-starting. It's the modern ones that aren't built to do that.

ZV

 

[spidey07]

Originally posted by: JulesMaximus
Has to be a manual transmission though. I'd like to see you pop start an automatic...:laugh:

meh, we could rig something. Say drain the tranny fluid from said auto transmission?

 

[thedarkwolf]

Originally posted by: Zenmervolt

Originally posted by: JulesMaximus
Has to be a manual transmission though. I'd like to see you pop start an automatic...:laugh:

Actually, some old automatics had a provision for push-starting. It's the modern ones that aren't built to do that.

ZV

Yep. My old 67 galaxie with a FMX automatic trans could be push started. Think it has to do with the pump in the trans being ran off the driveshaft rather than the torque converter like most. If I remember right you had to get it up to 20mph to do it so good luck unless you were on a hill . I never tried to do it.

 

[Brainonska511]

I was about to say, "Oh crap, he's back," but it looks like someone just responded to a month old thread.

 

[Mrfrog840]

Send me a pic of that. I would laugh!!!!

 

[Rastus]

It probably would be possible if the engine had a generator instead of an alternator. With an alternator, you need voltage to energize the field coils or you get nothing out of it. With a generator, just turning it will generate enough juice to create spark to fire it up.

That's not taking into consideration the compression ratio of modern engines, or the fact that modern ignition systems might need a lot of power to ignite.

 

[Safeway]

Okay, think about it think way. It requires a very, very high speed DC motor (your starter) to give your engine the kick it needs to start. It then must continually use the force of contains explosions to continually propel the pistons, and thus, cycle the engine.

Your legs != contained explosions.

 

[LordMorpheus]

Haha, I thought he meant crank the engine as in rotate the crank through partial motions using a breaker bar/torque wrench when working on the engine (valve job, or something like that).

 

[Zenmervolt]

Originally posted by: Rastus
It probably would be possible if the engine had a generator instead of an alternator. With an alternator, you need voltage to energize the field coils or you get nothing out of it. With a generator, just turning it will generate enough juice to create spark to fire it up.

Bull. You can push start a car just fine if it has an alternator, there's no need for it to have a generator instead.

ZV

 

[Colt45]

Originally posted by: Zenmervolt

Originally posted by: Rastus
It probably would be possible if the engine had a generator instead of an alternator. With an alternator, you need voltage to energize the field coils or you get nothing out of it. With a generator, just turning it will generate enough juice to create spark to fire it up.

Bull. You can push start a car just fine if it has an alternator, there's no need for it to have a generator instead.

ZV

Yeah, but this is because a "dead" battery still has enough juice for the exciter, but not enough to crank the engine. If the battery was completely flat, it wouldn't work.

 

[MmmSkyscraper]

Originally posted by: Brainonska511
I was about to say, "Oh crap, he's back," but it looks like someone just responded to a month old thread.

LOL, me too.

 

[DivideBYZero]

Originally posted by: Zolty
If you actually want to test this lift your manual transmission car off the ground to a comfortable level, remove one of the drive tires. Now you will want to fashion a lever or crank on to that drive tire and crank away, if you think it is easy then you haven't put the car into first, you need to do that.

Differential > j00

 

[funboy6942]

Originally posted by: EarthwormJim
I doubt it would be any harder to crank a modern compared to an older one, if there was a hand crank implemented. In fact when on a lift and my car is in 1st I can crank the engine with as little as 50 ft-lbs.

Modern engines are much lighter and have lighter rotating components.

People broke their arms in the past from kick back. If you don't remove your hand fast enough when rotating the crank, it'll hit you very hard once the engine starts.

Well your right on all point and even got kick back WORD right but not right about how you broke your arm.

Its called kick back because it would actually at times kick the engine backwards while trying to start, motorcycles (older ones that had kick starts) do the same thing and if not careful would kick the pedal back up shattering your ankle, foot, or knee, I have come close to having to happen to me on the many older bikes I have owned.

But anyway the engine would fire before the piston would make it past Top Dead Center on the power stroke side. It would still be on the up stroke of the compression side when the fuel would ignite causing the engine to spin backward. Your arm is going one way and when the engine fires your force is the weaker of the two and snap crackle pop goes your arm when the bar your turning decides to go the opposite way without much or no warning.

Hence the term Kick Back.

 

[Turin39789]

I've done this before, the problem is when the engine catches, whatever you are using to turn it starts to spin really fast and will hit you, that's how the arm gets broken.

Mine was on my 72 beetle, so not exactly modern, but I was able to put a socket wrench onto the generator, which is tied by a belt to the crank pulley. I can't for the life of me remember why I was doing that with the key in the ignition, but I was. I honestly didn't expect that it would catch, I was probably goofing with the carburetor. Anyway, it caught and thankfully I got my hand out of the way in time, the socket wrench popped off the socket and managed to fall out of the engine bay, and I ran up and shut the engine off.

Had a beer and went back to work.