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What is detonation?


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rc46

 
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What is detonation?

Fri Jul 01, 2005 7:51 am » Post: #1 » Download Post

What is detonation? okay, i hope im not being stupid but every time i read this word is always in a bad way, "oh that looks like a detonation problem" " you have a detonation / mixture problem", what gives, !!!!! detonation sounds like a good thing to me fuel goes in detonation happens power go ta da.... NO, as i keep saying im new to 2 strokes like to know whats happening when i ride my bike WHAT is this detonation term, why do we use it, come on be gentle i seriously dont know is it a mixture problem leaking heads/crankcase, exhaust what is it what causes it? TA

Thanks from STupid!!!!! Embarassed
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Andy
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Fri Jul 01, 2005 8:52 am » Post: #2 » Download Post

In the most basic of terms, detonation is an "explosion", whereas ignition is a "controlled combustion".

Detonation is usually, but not always caused by, a combination of high compression, over advanced ignition, and low octane fuel.

On a pure race bike a certain amount of detonation is acceptible (something around 4 counts per km depending on the circuit I think) as this means you will be right on the edge of the jetting. This is what a "det counter" is used for - measuring the number of times detonation occurs over a given distance.
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Wrench.

 
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Fri Jul 01, 2005 12:25 pm » Post: #3 » Download Post

Think of it this way:

In matters of milliseconds, the normal combustion process is a well-timed constant burn, creating cylinder pressures of around 3,000 psi or so.

Detonation is an erratic burn which happens much quicker. The peak pressure is reached before or at TDC and causes cylinder pressures of nearly 30,000 psi. The pressure is so great, it causes the aluminum piston crown to vaporize, leaving a sandblasted look or a hole through the piston. Detonation can be caused by too much ignition advance or by preignition (where combustion is started not by the spark plug, but by compression heat, ie: "dieseling").
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nsrmonkey

 
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Fri Jul 01, 2005 12:41 pm » Post: #4 » Download Post

Shocked Shocked Confused
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Andy
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Fri Jul 01, 2005 1:45 pm » Post: #5 » Download Post

Generally speaking Monkey, for 99.99% of us, DETONATION IS BAD! Smile
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jeff350lc
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Fri Jul 01, 2005 1:56 pm » Post: #6 » Download Post

you also get detonation with four strokes. if its bad you can hear it, its a light rattle under load. its also called PINKING!
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nsrmonkey

 
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Fri Jul 01, 2005 2:38 pm » Post: #7 » Download Post

Andy wrote:Generally speaking Monkey, for 99.99% of us, DETONATION IS BAD! Smile


thanks Andy....now where are my peanuts.
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Andy
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Fri Jul 01, 2005 2:54 pm » Post: #8 » Download Post

Laughing
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rc46

 
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Fri Jul 01, 2005 4:17 pm » Post: #9 » Download Post

Ahhhhhh, So using a high octane fuel say super unleaded and an octane booster could help? much clearer now.... Thank feck for that i can read over the other post's and understand what you lot are on about....LOL
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Andy
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Fri Jul 01, 2005 6:01 pm » Post: #10 » Download Post

rc46 wrote:...super unleaded and an octane booster could help?

Ahh, the magic word - "could"...

Yeah, it could help!
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Wrench.

 
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Sat Jul 02, 2005 1:00 am » Post: #11 » Download Post

The normal off-the-shelf octane boosters usually kill throttle response, though.

If you are using pump gas, it is best to tune the engine and CR to the lowest octane available (for best reliability/power). If you are using only race gas, tune your engine around that octane. But tuning for higher octane and trying to run avgas or octane boosters usually causes less performance and reliability than if you were just tuning for regular pump swill.
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