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DETONATION: When it can happen and how to tell if you have it. Plug Color Reading Too


We get many emails and see on many forums about people thinking that they have detonation and how to determine if they do or do not.

It seems common to have people think that they are hearing detonation at idle.

HERE is a link to an article that directly speaks to the definition of DETONATION..LINK--> DETONATION

Let's clear that up right now... It is near impossible to have detonation at idle. Can it happen? MAYBE... are you experiencing detonation during idling? Very unlikely. That is not to say that there are not odd noises occurring at idle . BUT detonation is probably not one of them. IF you are hearing pinging at idle.. you prob have some other issues that need addressing

Detonation, almost always, requires engine load in order to exist. There is little to no load on the engine during idling.

Having said that, the higher the rpm the least likely it is for detonation to occur. 

Lean main jet settings and WOT, loaded high rpm running will be a great recipe for the onset of detonation. You have to load the engine for a good amount of time in order to find out if your main jet is too lean.

It is also common for people to check their spark plugs to see how it is running.

This plug reading tuning was very prominent in the 60's,70's and 80's when we had,GOOD, leaded fuel ,very similar oils (also not so many of them),simple ignition systems, mainly air cooled engines, and more primitive spark plug technology. 

Given these factors, you could get SOME indication of how much heat was in the head and piston via plug color. Since most everybody was using the same fuel and an oil that was derived from the same base stock, you could come up with some indicators across the board that helped you tune.
Those days have long passed! With all the different oils, fuels, additives, liquid cooled engines, high volume cooling etc etc etc..... the color of your plug tells you very little as to the state of tune of your engine. 

I know this will be controversial with many of you, but looking for a brown plug and tuning until you achieve one, may likely lead you to a tune that is not ideal. 

The chemical make up of the oil has a lot to do with the color of your plug. Also, modern plugs have improved in how effective they are at removing heat from an engine. (Yes, Plugs remove heat)

In short, times have changed and plug color reading is not nearly as valid for determining how well your engine is tuned. 
That is not to say that you can not get valid information from plug inspections, you can... But the color is down on the list in terms of importance.

Hope this helps out some?

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