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I look at bicycle chain drives to picture mechanical advantage , but I can see I need a better example to illustrate the reverse of mechanical advantage, since the concept is vague to some posting here.
What astounded me was the understanding that push starting in low gears spins the engine more, yet the same person thought less mechanical advantage , parking in a high gear , would be best to augment the brake.
This is why I avoid the political pages available here.
I always park in first or reverse, knowing that reverse has the more desirable parking ratio. I've had sports car that were so puny that they would roll in third or fourth, if you were careless enough to park it that way.
I can't imagine anything would get damaged by turning the engine over backward several times, slowly. Maybe if it had VVT or fancy complicated camshafts, just maybe. But it does not, so no worries. If it turned over backward quickly it might suck something from the exhaust into the cylinder... but what something? The exhaust should be baked dry like a self-cleaning oven.
On level pavement or slight inclines, I park my C4/ZF6 in first gear (no PB) to reduce wear on the reverse light switch and PB cables. On steep downward angles, I park in first with PB applied and wheels turned. On steep upward angles, I park in reverse with PB applied and wheels turned.
Originally Posted by o2bnkc
It's actually easier to bump start a car in a higher gear than in first. Because of the ratio, there is LESS resistance. I also disagree with your theory.
Correct.
I am surprised such a simple concept can be so badly misunderstood.
Higher gear = fewer engine revolutions per distance pushed = more force to turn engine over when pushing car. In 5th or 6th, the car travels much farther for each engine revolution, so the weight of the car would likely overcome the compression resistance parked on even a moderate slope.
BUT when bump starting, TOO high a gear will not allow enough RPM for engine to light off. I would suggest bump starting in 3rd.
Lower gear = more engine revolutions per distance pushed = more resistance from engine when pushing car.
I can't imagine anything would get damaged by turning the engine over backward several times, slowly. Maybe if it had VVT or fancy complicated camshafts, just maybe. But it does not, so no worries. If it turned over backward quickly it might suck something from the exhaust into the cylinder... but what something? The exhaust should be baked dry like a self-cleaning oven.
On level pavement or slight inclines, I park my C4/ZF6 in first gear (no PB) to reduce wear on the reverse light switch and PB cables. On steep downward angles, I park in first with PB applied and wheels turned. On steep upward angles, I park in reverse with PB applied and wheels turned.
Correct.
I am surprised such a simple concept can be so badly misunderstood.
Higher gear = fewer engine revolutions per distance pushed = more force to turn engine over when pushing car. In 5th or 6th, the car travels much farther for each engine revolution, so the weight of the car would likely overcome the compression resistance parked on even a moderate slope.
BUT when bump starting, TOO high a gear will not allow enough RPM for engine to light off. I would suggest bump starting in 3rd.
Lower gear = more engine revolutions per distance pushed = more resistance from engine when pushing car.
Push starting, also known as bump starting, clutch starting, popping the clutch or crash starting is a method of starting a motor vehicle with an internal combustion engine by engaging the manual transmission whilst the vehicle is in motion.[1] The technique is most commonly employed when other starting methods (automobile self starter, kick start, jump start etc.) are unavailable.[2]
The most common way to push start a vehicle is to put the manual transmission in second gear typically, switching the ignition to on/run, depressing the clutch, and pushing the vehicle until it is at a speed of 5 to 10 mph (8 to 16 km/h) or more, then quickly releasing the clutch to make the engine rotate and fire, then quickly depressing the clutch so it does not stall. This is done by one person pushing a lightweight automobile, pulling or being pushed by another vehicle or even rolling down a hill.
Contents
1 Types
1.1 Automatic or manual gearbox
1.2 Gasoline or diesel engines
1.3 Fuel delivery systems
1.4 Ignition systems
1.5 History
1.5.1 Push starts in motor racing
2 References
Types
Push starting is most successful when the automobile is using a gasoline engine, uses a carburetor, and uses a capacitor discharge ignition (CDI) or an inductive discharge ignition system. Automobiles with other types of engine, ignition, and fuel delivery configurations may work, but may be more difficult to start. Some engines must have a battery providing some electricity since fuel injection systems must have power to operate.
Automatic or manual gearbox
A vehicle equipped with an automatic transmission (including semi automatic) is difficult to push start since selection of transmission gears is only possible when the internals of such a gearbox are rotating.
Gasoline or diesel engines
A diesel engine uses heat and high compression (compression ratios commonly 22:1 versus 9:1 for gasoline) to ignite the fuel. When normally starting a modern diesel engine, it typically uses glowplugs to preheat the cylinder(s). If a battery is completely discharged then it may not provide the necessary electrical power to 'glow' the glowplugs, making push starting a vehicle with a diesel with a dead battery almost impossible.
Fuel delivery systems
Fuel injection is most common for modern gasoline and diesel engines. Fuel injection needs electrical power to open and close the fuel injectors. If a battery is of a sufficiently discharged state that it cannot provide the power to turn an automobile self starter then it may also not be possible to activate the injectors. The most common method to start such a vehicle engine is to jump start it.
A fuel pump is used for fuel injection. It can be mechanically driven or is electrically driven. If electrical then the same problem may arise which the battery cannot turn the pump because it is heavily discharged. A carburettor only needs suction from the internal combustion engine to work best when push starting. Once the engine is running, a fuel pump (mechanical or electrical) will continue to supply fuel to the carburettor.
Ignition systems
A modern gasoline engine contains an electronic ignition system which precisely times the electrical pulse to the spark plug. The advantage of such a device is that it can deliver a full power electrical pulse to the spark plugs even when the alternator is turning very slowly (as in push starting a motor). The out-dated method of a mechanically timed ignition system is that is cannot deliver a full electrical pulse at very low engine revolutions per minute (RPM). This may affect the ease of push starting an engine to life.
History
In the early 20th century, many motorcycles could only be push started; the 1908 Scott was distinguished by introducing a kick starter feature.[3] Excelsior Motor Company's Welbike, intended to be carried by paratroopers in World War II, was designed to be started only by push starting.[3]
Push starts in motor racing
Motorcycle road races required push starts by the riders. This involved all riders starting from normal positions on the starting grid, with stopped engines. This practice was banned in the mid to late-1980s.
References
All of the above come to mind when reading some of the posts.
Some of the responders should just trust in the manual, do as it sayes and dont try to think, it could hurt you
You can push start a fuel injected Corvette, my starter went out not long after I bought it. My buddy pushed me and I popped the clutch in second, started right up.
Honestly these cars can be bump started in any gear. Car fires right up in reverse backing down my driveway. Anytime I pull in and know I'm going to be leaving soon I do it. Yes, reverse gear is the best to hold your car, but the inertia of a 3000 pound car going 3 miles an hour overcomes it.
The best option would be to have had GM put a decent handbrake on the car to begin with. With my old celica, once that brake was applied, those tires wouldn't turn a single degree if you dragged it with a duramax.
Fuel injection has nothing to do with push starting a vehicle, the pump stops when system reaches proper pressure. When there is pressure the injectors will still fire. Only difference between FI and carburetor is that later utilizes air flow over a venture to atomize liquid fuel. None of this has any bearing on engine compression or it's ability to stop a car from roiling away when in gear. FI engines are easier to start weather through an electric motor or push start but that's another totally different topic.
I know it's pretty much impossible with a motorcycle. (fuel injected)
Probably varies by model, but back in the day had a 1985 BMW k100rs -- fuel injected. A common failure of these 1st generation k-bikes was the starter sprag slipping. Bumped started many times, usually in 2nd or 3rd.
Originally Posted by DRAFT1
If one were traveling at the speed of light and turned his head lights on......what would happen?
Speed of light is constant, so the photons leaving the headlights would be speed of light. I think to a bystanding stationary observer, the car would appear compressed and shifted blue.
If one were traveling at the speed of light and turned his head lights on......what would happen?
LOL - If it was really dark and the only source if light were the car's headlights, the driver wouldn't be able to see ahead of him... The road for him would be dark!
Sent from my DROID TURBO XT1254 using IB AutoGroup
According to physicists, since 1887, the speed of light is constant for all observers, no matter the observers' speed. So, for the driver in the car, his headlamps look normal. A guy standing on the sidewalk would see the car as shortened and blue (ultraviolet-shifted).
If one were traveling at the speed of light and turned his head lights on......what would happen?
If he were in a C5 the DIC would light up at light speed as well with these codes
B0844 BCM Temporarily Inhibit ABS
C1780 Loss of Steering Position Signal
U1016 Loss of Communications with PCM
U1040 Loss of Communication with TCS
U1056 Loss of Communications with RTD
U1064 Lose of Communications with DCM
U1128 Loss of Communications with radio
U1153 Loss of Communications with HVAC
U1160 Loss of Communications with LDCM
U1161 Loss of Communications with DCM
U1166 Loss of Communications with SCM
U1176 Loss of Communications with RFA
C2120 TPM System malfunction (No Sensors Received -TPM
You guys crack me up on how a simple question on parking goes to 3 pages of physics lessons. Sorta like the one few months ago on whether or not air leaks out of tires through the rubber. That one was hilarious.
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.
:beatdeadh orse:
: rofl:
If one were traveling at the speed of light and turned his head lights on......what would happen?
