Spark knock?
Post Fiend
Joined: Mar 2003
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From: Sarnia, Ontario, CANADA!
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Postmaster
Joined: Mar 2001
Posts: 4,968
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From: So Cal
Tell us more about the noise.
Spark knock comes in many different levels and may or may not be a problem.
In general terms, ping is a light knock. Knock is midway in sound level and Detonation is very bad. It is hard to describe the ligther versions of knock but when you hear them and have experience you can tell the difference.
A lot of engines, especially if they haven't had the "Carbon blown out of them" ie driven hard once in awhile, can develop a ping. Also gas that is marginal for the temperatures and load you are hauling can cause a gentle ping. Most magazine articles say occasional light ping is just an indication that the engine is running at optimum air fuel mix for economy. Normally cooler weather or a slightly better grade of gas will get rid of ping. Ping is usually not heard or occasionally audible. A gentle occasional ping is not considered bad. Ping is like a light tapping on the piston crown.
I sometimes had ping in hot weather up a long hill with my AC on, in 5th gear in an 89 SHO that had something like 10.5:1 compression, running 87 octane gas. Switching to 89 or better got rid of the ping. In winter 87 ran fine with no ping at all. Ditto my 94 F250 hauling a trailer. Hot weather, long hill, heavy load, 87 octane=ping, so I used 89 and 91 in summer while towing.
Knock is usually pronounced and fairly obvious. If you ever heard a gas engine "run on" or diesel after shutting down, that is an obvious sound of knock. Also a truck hauling a heavy load up a mountain in hot weather with low octane will have a noticable knock. Knock is damaging and eventually you will melt a piston, hammer the bearings or break something else. Knock is like hammering on the piston crown.
Detonation is very violent and sometimes sounds explosive out the tail pipe, not quite like a backfire. An engine detonating will ruin itself pretty quick.
So tell us what your noise sounds like and when does it happen? Include, engine, tranny, gears etc. Tell us the temperatures, how much load you are haulling and does it only do it in certain conditions?
Most modern engines have knock sensors and the computer usually does a good job of controlling knock. You should almost never hear knock(and only briefly) and only rarely hear ping. This assumes you are running with gas that is up to spec for your engine.
Good Luck,
Jim Henderson
Spark knock comes in many different levels and may or may not be a problem.
In general terms, ping is a light knock. Knock is midway in sound level and Detonation is very bad. It is hard to describe the ligther versions of knock but when you hear them and have experience you can tell the difference.
A lot of engines, especially if they haven't had the "Carbon blown out of them" ie driven hard once in awhile, can develop a ping. Also gas that is marginal for the temperatures and load you are hauling can cause a gentle ping. Most magazine articles say occasional light ping is just an indication that the engine is running at optimum air fuel mix for economy. Normally cooler weather or a slightly better grade of gas will get rid of ping. Ping is usually not heard or occasionally audible. A gentle occasional ping is not considered bad. Ping is like a light tapping on the piston crown.
I sometimes had ping in hot weather up a long hill with my AC on, in 5th gear in an 89 SHO that had something like 10.5:1 compression, running 87 octane gas. Switching to 89 or better got rid of the ping. In winter 87 ran fine with no ping at all. Ditto my 94 F250 hauling a trailer. Hot weather, long hill, heavy load, 87 octane=ping, so I used 89 and 91 in summer while towing.
Knock is usually pronounced and fairly obvious. If you ever heard a gas engine "run on" or diesel after shutting down, that is an obvious sound of knock. Also a truck hauling a heavy load up a mountain in hot weather with low octane will have a noticable knock. Knock is damaging and eventually you will melt a piston, hammer the bearings or break something else. Knock is like hammering on the piston crown.
Detonation is very violent and sometimes sounds explosive out the tail pipe, not quite like a backfire. An engine detonating will ruin itself pretty quick.
So tell us what your noise sounds like and when does it happen? Include, engine, tranny, gears etc. Tell us the temperatures, how much load you are haulling and does it only do it in certain conditions?
Most modern engines have knock sensors and the computer usually does a good job of controlling knock. You should almost never hear knock(and only briefly) and only rarely hear ping. This assumes you are running with gas that is up to spec for your engine.
Good Luck,
Jim Henderson
Last edited by jim henderson; Feb 7, 2006 at 06:24 PM.
