MitsuStyle - View Single Post - Egt Temps, Knock Sum, Timing, Datalogging,

LightningGSX · 03-31-2004

Knock-Knock is bad.Knock can mean 1 of 2 things, pre-ignition knock (which comes from mixture igniting before you want it to), or post-ignition knock (which comes from the mixture burning to quick).Either results in peak combustion chamber pressures before the engine is meant to deal with them.Do a google for NACA, they were the WWI-II equivalent of NASA, they have the best papers on Knock and other topics.Including pictures of actual knock, from an engine with a quartz window in the combustion chambers

Timing-Timing can refer to 1 of 2 things also, cam timing or ignition timing.The latter is what is usually meant when people speak of timing.Basically it is how many degrees before TDC the spark plug ignites the mixture.In non-knocking combustion, after your plug ignites the mixture, it takes a certain amount of time for peak chamber pressure.You generally want the peak pressure to be at or just after TDC, otherwise the combustion energy is fighting the crankshaft rotational energy.As RPM increases, since burn time stays relatively the same, the ECU advances ignition timing to keep the peak pressures where they are suppose to be.Not enough timing advance and you're wasting your combustion energy, too much timing advance and you're not only wasting energy, but you're putting severe stress on mechanical parts.

Air/fuel ratio-Most production vehicles aim for a ~14.7:1 mixture, any leaner or richer and emissions increase rapidly.Best power is usually obtained at about 12 or 13:1.

EGT temps-In my opinion EGT temps are nearly worthless, other than giving you warning of impending engine damage.

03-31-2004	#5
LightningGSX Hellbound Join Date: Nov 2003 Location: St Paul Posts: 1,390	Knock-Knock is bad.Knock can mean 1 of 2 things, pre-ignition knock (which comes from mixture igniting before you want it to), or post-ignition knock (which comes from the mixture burning to quick).Either results in peak combustion chamber pressures before the engine is meant to deal with them.Do a google for NACA, they were the WWI-II equivalent of NASA, they have the best papers on Knock and other topics.Including pictures of actual knock, from an engine with a quartz window in the combustion chambers Timing-Timing can refer to 1 of 2 things also, cam timing or ignition timing.The latter is what is usually meant when people speak of timing.Basically it is how many degrees before TDC the spark plug ignites the mixture.In non-knocking combustion, after your plug ignites the mixture, it takes a certain amount of time for peak chamber pressure.You generally want the peak pressure to be at or just after TDC, otherwise the combustion energy is fighting the crankshaft rotational energy.As RPM increases, since burn time stays relatively the same, the ECU advances ignition timing to keep the peak pressures where they are suppose to be.Not enough timing advance and you're wasting your combustion energy, too much timing advance and you're not only wasting energy, but you're putting severe stress on mechanical parts. Air/fuel ratio-Most production vehicles aim for a ~14.7:1 mixture, any leaner or richer and emissions increase rapidly.Best power is usually obtained at about 12 or 13:1. EGT temps-In my opinion EGT temps are nearly worthless, other than giving you warning of impending engine damage. __________________ -Nulli Secundus-