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Old 06-29-2000, 09:25 PM   #1
Scooby Newbie
Member#: 1772
Join Date: Jun 2000
Location: Nepean
Post What is detonation?

Hey all,

I'm trying to learn about turbos/superchargers and everything. I hear the term detonation associated with them. Is this something you hear? What is it from? What does it sound like? Is it bad for the car?

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Old 06-29-2000, 10:30 PM   #2
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Member#: 1710
Join Date: Jun 2000
Chapter/Region: E. Canada
Location: ON, Canada
1998 2.5RS/2002 WRX


when the fuel explodes before the piston reaches TDS (top dead centre) and creates a rough sound in the engine...If you have it, I suggest you take you're car in before the engine blows (cylinders will overheat)
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Old 06-29-2000, 10:33 PM   #3
Scooby Newbie
Member#: 1506
Join Date: May 2000
Location: Charlotte, NC
1993 RX-7
Competition Yellow Mica


detonation: lean mixture caused by too much air and not enough fuel mixed in the combustion chamber. The air/fuel mixture becomes very hot when combusted, the piston swells from the heat and rubs against the cylinder walls possibly scoring or scratching it. Sometimes makes a high pitched whining noise, or pings.
*edit for spelling*

[This message has been edited by RotrPwr (edited June 29, 2000).]
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Old 06-29-2000, 11:45 PM   #4
Scooby Specialist
Member#: 607
Join Date: Dec 1999
Location: SF Bay Area, CA

Detonation is another term for pre-ignition or ping or knock. It's occurs when the air/fuel mixture ignites before you want it to (i.e. while the piston is on the way up). The effects of serious detonation can be quite unsightly. Instead of a clean, smooth burn (normal combustion), detonation is an uncontrolled explosion. Cylinder temps and pressures rise to high heaven almost intantaneously, taking out pistons, valves, rings, and even rods! Detonation can be caused by a lean air fuel mixture (lean mixtures burn faster and are easier to ignite than rich mixture) or an overy agressive ignition advance.

Minor detonation sounds like little marbles ticking around under your hood. More serious detonation sounds like big marbles banging around under your hood. With the windowns down and radio up, detonation is hard to hear. Windows up and radio off. Listen carefully for it during the tuning process. If you hear it, get your foot off the gas and figure out what is wrong. Hope that helps...

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