JAY, HERE YA GO!
Detonation Insights
By Rod Machado
The cylinder's fuel-air charge expands as it's ignited by the sparkplugs.
Properly done, this isn't an explosion so much as it is a smooth,
progressive burning of the combustible gases within the cylinder. As these
gases expand, they increase pressure, pushing the piston downward during its
power stroke.
Detonation occurs when the fuel-air charge explodes, burning in a short,
fierce burst of energy rather than a controlled, even burn. Such an
explosion can be very damaging and sometimes fatal to the engine. Detonation
occurs after the sparkplug fires, when the unburned portion of the fuel-air
charge, ahead of the burning charge, suddenly explodes. High engine and
cylinder head temperatures increase the likelihood of detonation. They may
aid in the abnormal exploding vs. the normal burning of the ignitable gases
within the cylinder.
With the exploding of the cylinder's fuel-air charge, combustion takes place
earlier. This suddenly and dramatically releases the heat from the
combustion process to the cylinder, piston and valves (too much heat at one
time-that's the problem). The exhaust gases that are released have already
expended their heat.
The following are several known causes of detonation:
1. Using a lower grade of fuel than what is recommended by the manufacturer.
Higher octane fuels have additives which help prevent detonation.
2. Over-leaning. Excessive leaning can raise cylinder head temperatures,
increasing the likelihood of fuel exploding instead of burning within the
cylinders.
3.Overheating an engine by climbing too steeply on hot days.
4. An abrupt opening of the throttle.
MATT
-----Original Message-----
From: Mooberry, J [mailto:j.mooberry@lmco.com]
Sent: Thursday, August 19, 1999 2:13 PM
To: 'dakota-truck@buffnet.net'
Subject: RE: DML: RE: Turning over 5500 rpm's, unbelievable
<<on that note could somebody tell me exactly what detonation is? thx.
-jay<<
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