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Old 23 Aug 2007, 01:48 pm
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Default Can you explain Honda Timing to me? Any pictures? '91 Honda Accord?

I know that you have to align the timing marks and set cylinder No 1 to TDC on the compression stroke..but actually what is that? Where can I find pictures of how to go about this action?91' Honda Accord LX
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Old 23 Aug 2007, 01:52 pm
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here is a couple links to auto zone website
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Old 23 Aug 2007, 01:54 pm
Les Les is offline
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This is really quite simple but anytime you have several simple things all done simultaneously, it becomes complex. Let's break it down into pieces and see if you can put the puzzle together...Your Accord has a 4-stroke engine, most cars do. That just means the pistons take 4 strokes within the engine to complete a combustion cycle.Stroke #1 Intake Stroke: The piston travels down and pulls a vacuum sucking in the air/fuel mixture through an open intake valve.Stroke #2 Compression Stroke: The piston comes back up compressing the air/fuel mixture.15 degrees of crankshaft rotation before the piston reaches the top extreme travel which isTop Dead Center or TDC, the spark plug fires and ignites the air/fuel mixture.Stroke #3 Power Stroke: The piston travels downward by the force of the expanding gases of combustion. This is the power stroke. That's the stroke that makes your car go!Stroke #4 Exhaust Stroke: The piston comes back up with the exhaust valve open and pushes all the spent gasses out into the exhaust pipe.Now the trick to make all this work right is to get the intake and exhaust valves to open and shut at the right times and for the spark plug to ignite the air/fuel mixture at the right time too.The valve timing is controlled by connecting the camshafts (which control the position of the valves) to the crankshaft (which controls the position of the pistons). The crankshaft and the camshafts are connected with a timing belt in your Accord and are initially set up with the timing marks on the camshafts aligned to the surface plane of the head when the crankshaft mark is at top dead center on cylinder #1. The timing belt is a toothed belt that will keep this timing proper for the life of the belt. Without the belt, this timing gets out of whack and not only will the engine not run, but you could see the valves and the pistons come into contact with eachother since (in Hondas) they share the same space but at different times.Part of the timing involves when the distributor fires the spark plug too. That is maintained by connecting the distributor rotor to the camshaft in Hondas. It is adjusted by turning the distributor housing which rotates the orientation of the plug wires so that the rotor points to the particular spark plug at a different time.Your Accord fires the spark plugs 15 degrees before the piston reaches Top Dead Center. With everything operating at breakneck speed, ok... at least 750 revolutions per minute, RPM, it takes those degrees before reaching the top to get the spark to the spark plug, ignite the compressed air/fuel mixture, and develop the right amount of force to push the piston downward on the power stroke. If that timing is too early those gases will try to push the piston down before it reaches the top and effectively try to make the engine run backward! This accounts for the rattle you hear in poorly tuned engines sometimes, also known as engine ping. It's the piston rattling in it's bore from forces it's not supposed to feel! This can occur with fuel that ignites prematurely too.If the spark comes too late, you will lose power as the piston has less and less travel left to apply power with and could end up with some backfire as the exhaust valves open when the combustion process is not complete on the power stroke.Likewise, if the spark comes very early, it could ignite the air/fuel mixture while the intake valves are still open. In cases like that, you get a backfire through the carburetor or throttle body. Those are not fun either!So, there you have it... several simple things all occuring at the same time giving the aura of complexity! I hope this helps!Any basic engine book will have this concept thoroughly explained and should include pictures.
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