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Old 03-05-2008, 12:19 PM   #1
fgummett
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Question Is Bump starting an AWD bad..?

This is my first AWD so I'd like to be sure if bump starting is safe.

Towing an AWD vehicle, with say the front wheels in the air, will mean a 100% speed difference between the axles. Say goodbye to your center diff.

Bump start: Pushing the car, setting the key to on, and slowly releasing the clutch in second gear will start the engine. All axles and drivetrain are at the same speed.
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Old 03-05-2008, 03:01 PM   #2
GFimpreza
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I don't see why there would be any problem, although I've never been able to bump start my impreza. Even going ~15 mph and using 2nd gear, it won't start.
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Old 03-05-2008, 03:29 PM   #3
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if all wheels are rolling then your fine.

but ouch that hurts doing that.
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Old 03-05-2008, 06:43 PM   #4
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why 2nd gear? wont the lowest gear (1st) give the most engine rotation per wheel rotation? i.e - lower wheel speed required and more mechanical advantage to spin the crank.
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Old 03-05-2008, 08:01 PM   #5
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1st is too rough on the drivetrain. I would generally try it rolling downhill with the electric power on, clutch pedal down and 2nd selected.. when going fast enough for 2nd let the clutch up quickly... be ready to give it gas and if needed you can also drop the clutch again again as soon as it fires.
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Old 03-05-2008, 08:27 PM   #6
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Quote:
Originally Posted by RaceFaceXC View Post
why 2nd gear? wont the lowest gear (1st) give the most engine rotation per wheel rotation? i.e - lower wheel speed required and more mechanical advantage to spin the crank.
cause it hurts when the car lurches and you hit your head on the steering wheel
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Old 03-05-2008, 08:45 PM   #7
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Quote:
Originally Posted by RaceFaceXC View Post
why 2nd gear? wont the lowest gear (1st) give the most engine rotation per wheel rotation? i.e - lower wheel speed required and more mechanical advantage to spin the crank.
I once had a tiny car with a bad starter solenoid. Before I fixed it, the easiest way to start it was, sitting in the drivers seat, put it in reverse, depress clutch with right foot, put left foot on the ground to push the car back a little, then pop the clutch. The last time I ever did that, it started fine, but just sat there with the engine running, in gear and not moving: Busted axle.
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Old 03-05-2008, 08:49 PM   #8
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I bump start mine daily, cause it dies coming out of gear. haha. but yeah, I will sometimes bump start mine 10 times a day. I don't like it though, its just a fact of highly modified life.
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Old 03-05-2008, 10:05 PM   #9
GrundleJuice
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i have never heard of highly modified cars not running out of gear. what mods do you have?
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Old 03-05-2008, 10:15 PM   #10
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It dies when I take it out of gear (sometimes) and then coast. Like to a stop.
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Old 03-05-2008, 10:25 PM   #11
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I had a old 95 nissian altima, the starter went, didnt want to spend the money to fix it because i was get rid of it soon. anyways i had no issues with bump starting it, minus the pain in the ass if i had to go somewhere and it was all flat. but lucky me, my driveway is a hill. parked it at the top every night, next morning bumb started it down the hill. and drove to work, park in on the hill (far from my job, but it made it easy to get it going when i left) did it every day for a month had no issues.
It was fun when i had anyone with me, "why do you park up here?" oh... you'll see!!!!
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Old 03-05-2008, 11:31 PM   #12
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The easiest way to do that is to use 3rd gear. You have to selcet a gear that gives the engine more leverage over the car's weight. Think of it from the engine's point of view, would it be easier to use 3rd or 4th gear(fewer engine rpm's in relation to the axles rpm's) Or using a gear where the engine has to turn many rpm's to turn the axle few rpm's.


~Josh~
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Old 03-06-2008, 01:26 AM   #13
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Quote:
Originally Posted by RaceFaceXC View Post
i have never heard of highly modified cars not running out of gear. what mods do you have?
SC/Turbo twincharging something or other...I stopped trying to remember all the permutations reddevil's tried
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Old 03-06-2008, 08:46 PM   #14
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Quote:
Originally Posted by ballitch View Post
The easiest way to do that is to use 3rd gear. You have to selcet a gear that gives the engine more leverage over the car's weight. Think of it from the engine's point of view, would it be easier to use 3rd or 4th gear(fewer engine rpm's in relation to the axles rpm's) Or using a gear where the engine has to turn many rpm's to turn the axle few rpm's.


~Josh~
But thats argument makes sense in the opposite way you intend. A low vehicle speed having a high engine speed means the vehicle has more "leverage" or mechanical advantage over the engine. the more quickly you can turn the engine the easier it will start. 3rd gear @ 5 mph would be something like 50rpms. 4th gear would be even worse. Anyway, i understand why 1st gear is tough on the car and maybe the driver if they meet the steering wheel.
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Old 03-06-2008, 11:23 PM   #15
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When you turn your car on the starter doesnt exactly spin the motor at a very high rpm either. It's probably about or under 100 rpms. I guess I didnt type it the way I was thinking it. I should have said you have to select a gear that uses the car's weight to an advantage. You can try using 2nd gear, but I have found it easier to use 3rd.


~Josh~
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Old 03-07-2008, 12:48 AM   #16
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Quote:
Originally Posted by RaceFaceXC View Post
But thats argument makes sense in the opposite way you intend. A low vehicle speed having a high engine speed means the vehicle has more "leverage" or mechanical advantage over the engine. the more quickly you can turn the engine the easier it will start. 3rd gear @ 5 mph would be something like 50rpms. 4th gear would be even worse. Anyway, i understand why 1st gear is tough on the car and maybe the driver if they meet the steering wheel.
Perhaps the point is using first gear will wind the engine up so quickly (at the cost of rapidly reducing vehicle speed to the point of stop) that the duration of starting time (time car is pushing engine) is reduced vs using a taller gear (less engine speed - longer duration). As posted below the engine doesn't have to achieve high RPM to start. It's easier to push a car in a higher gear because of less engine speed, maybe thats what he mean't by leverage? I think I just confused myself...
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Old 03-07-2008, 01:05 AM   #17
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I'm under the impression it is bad for cats.
Correct me if I'm wrong.
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Old 03-07-2008, 01:35 AM   #18
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Quote:
Originally Posted by LTracer View Post
It's easier to push a car in a higher gear because of less engine speed, maybe thats what he mean't by leverage? I think I just confused myself...
Normally you don't push the car in gear. You get the car moving and let out the clutch.
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Old 05-27-2016, 10:15 AM   #19
downsouthman1
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Quote:
Originally Posted by davidji View Post
Normally you don't push the car in gear. You get the car moving and let out the clutch.
If you're doing it alone, you would push it in gear with your foot on the clutch & then pop the clutch to start the car.
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Old 05-27-2016, 03:34 PM   #20
Patrick Olsen
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Quote:
Originally Posted by downsouthman1 View Post
If you're doing it alone, you would push it in gear with your foot on the clutch & then pop the clutch to start the car.
Thank God you bumped this thread 8 years later to clarify that!!

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Old 05-29-2016, 01:10 AM   #21
CosmoTheCat
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lol

I always use 5th gear, it gets the engine spinning plenty fast and there isn't much shock.
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