question about timing retard and detonation
05-14-2004, 02:24 PM
#1
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question about timing retard and detonation
ok from my understanding retarding the timing changes the time that the spark fires.. and from my understanding detonation is when the fuel/air mixture detonates before tdc. now if your spark doesnt fire before tdc how is changing the time that the spark fires going to affect anything?
05-18-2004, 10:09 AM
#3
Re: question about timing retard and detonation (ludetech)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ludetech »</TD></TR><TR><TD CLASS="quote">ok from my understanding retarding the timing changes the time that the spark fires.. and from my understanding detonation is when the fuel/air mixture detonates before tdc. now if your spark doesnt fire before tdc how is changing the time that the spark fires going to affect anything?</TD></TR></TABLE>
But your spark always fires before TDC, about 20-40 degrees before tdc depending on where it is in the map. It takes a split second for the fuel to ignite thats why the spark has to ignite well before tdc. If your spark fired even close to tdc you egts would skyrocket and you would make no power from running way to little timing.
But your spark always fires before TDC, about 20-40 degrees before tdc depending on where it is in the map. It takes a split second for the fuel to ignite thats why the spark has to ignite well before tdc. If your spark fired even close to tdc you egts would skyrocket and you would make no power from running way to little timing.
thanks man
05-20-2004, 06:01 AM
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Re: (ludetech)
This comes up at the shop once in a while.... and maybe some of you can justify this while on topic. On the sohc or dohc hondas we have the three marks together marked red (sometimes) and then the white one noting tdc for the crank. Do most of you consider the red mark in the middle 0deg timing? And if so, would you set at around 6-8deg retarded? So when using a timing light the timing case mark shows close to half way between the red and white. I"m giving 6-8 degrees retarded as an example for around 10psi.
05-20-2004, 06:15 AM
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Re: question about timing retard and detonation (ludetech)
05-20-2004, 10:33 AM
#7
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Re: question about timing retard and detonation (ludetech)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ludetech »</TD></TR><TR><TD CLASS="quote">ok from my understanding retarding the timing changes the time that the spark fires.. and from my understanding detonation is when the fuel/air mixture detonates before tdc. now if your spark doesnt fire before tdc how is changing the time that the spark fires going to affect anything?</TD></TR></TABLE>
-Preignition is when the spark fires too early, due to overly advanced timing (or hotspots from sharp edges that cause the mixture to ignite early).
-Detonation is when the mixture "expodes" instead of the normal burn. Usually due to excessivly lean mixture, can also be brought on by extremely high intake temps.
These are two completely different, but equally destructive forces. Preigniton usually sounds like "wump wump wump wump", almost like an out of balance tire. Detonation sounds like the "ticking" or "pebble in a coffee can" that most people usually describe it as.
Preignition is usually what melts pistons and bends rods, since the piston has to force its way up agains an already burning mixture. This puts a LOT of pressure and heat into the combustion chamber. Detonation is more of an explosive force, like a firecracker. This is usually what cracks ringlands.
-Preignition is when the spark fires too early, due to overly advanced timing (or hotspots from sharp edges that cause the mixture to ignite early).
-Detonation is when the mixture "expodes" instead of the normal burn. Usually due to excessivly lean mixture, can also be brought on by extremely high intake temps.
These are two completely different, but equally destructive forces. Preigniton usually sounds like "wump wump wump wump", almost like an out of balance tire. Detonation sounds like the "ticking" or "pebble in a coffee can" that most people usually describe it as.
Preignition is usually what melts pistons and bends rods, since the piston has to force its way up agains an already burning mixture. This puts a LOT of pressure and heat into the combustion chamber. Detonation is more of an explosive force, like a firecracker. This is usually what cracks ringlands.
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