Ég veit að það þjónar ekki miklum tilgangi að speculate-a um það hvað gerðist, en ég er alveg friðlaus yfir þessu. Það þarf að fara að opna mótorinn og sjá nákvæmlega hvað gerðist.
Tilgátur ráðgjafa minna í þessum efnum hafa aðallega beinst að svokölluðu Pre-ignition og svo fylgt eftir með detonatoin. Fyrir þá sem ekki vita hvað það er ætla ég að velta mér og þeim aðeins upp úr þessu.
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PRE-IGNITIONAnother condition that is sometimes confused with detonation is "preignition." This occurs when a point within the combustion chamber becomes so hot that it becomes a source of ignition and causes the fuel to ignite before the spark plug fires. This, in turn, may contribute to or cause a detonation problem.
Instead of the fuel igniting at the right instant to give the crankshaft a smooth kick in the right direction, the fuel ignites prematurely (early) causing a momentarily backlash as the piston tries to turn the crank in the wrong direction. This can be very damaging because of the stresses it creates. It can also localize heat to such an extent that it can partially melt or burn a hole through the top of a piston!
Preignition can also make itself known when a hot engine is shut off. The engine may continue to run even though the ignition has been turned off because the combustion chamber is hot enough for spontaneous ignition. The engine may continue to run-on or "diesel" and chug erratically for several minutes.
To prevent this from happening, some engines have a "fuel cutoff solenoid" on the carburetor to stop the flow of fuel to the engine once the ignition is turned off. Others use an "idle stop solenoid" that closes the throttle completely to shut of the engine's air supply. If either of these devices is misadjusted or inoperative, run-on can be a problem. Engines with electronic fuel injection don't have this problem because the injectors stop spraying fuel as soon as the ignition is turned off.
CAUSES OF PRE-IGNITIONCarbon deposits form a heat barrier and can be a contributing factor to preignition. Other causes include: An overheated spark plug (too hot a heat range for the application). Glowing carbon deposits on a hot exhaust valve (which may mean the valve is running too hot because of poor seating, a weak valve spring or insufficient valve lash).
A sharp edge in the combustion chamber or on top of a piston (rounding sharp edges with a grinder can eliminate this cause).
Sharp edges on valves that were reground improperly (not enough margin left on the edges).
A lean fuel mixture.
Low coolant level, slipping fan clutch, inoperative electric cooling fan or other cooling system problem that causes the engine to run hotter than normal.
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Detonation (also called "spark knock") is an erratic form of combustion that can cause head gasket failure as well as other engine damage. Detonation occurs when excessive heat and pressure in the combustion chamber cause the air/fuel mixture to autoignite. This produces multiple flame fronts within the combustion chamber instead of a single flame kernel. When these multiple flames collide, they do so with explosive force that produces a sudden rise in cylinder pressure accompanied by a sharp metallic pinging or knocking noise. The hammer-like shock waves created by detonation subject the head gasket, piston, rings, spark plug and rod bearings to severe overloading.
Mild or occasional detonation can occur in almost any engine and usually causes no harm. But prolonged or heavy detonation can be very damaging. So if you hear knocking or pinging when accelerating or lugging your engine, you probably have a detonation problem.
Það sem styður þetta einnig eru myndirnar af kertunum.
Dæmi um kerti hjá mér:
Sýnist kertið bera merki um sambland af tvennu. Líklega að eitt hafi fylgt öðru.
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Detonation
This form of abnormal combustion has fractured the insulator core nose of the plug.
The explosion that occurs in this situation apples extreme pressures on internal engine components.
Prime causes include ignition time advanced too far, lean air/fuel mixtures, and insufficient octane rating of the gasoline.
og svo eftir að postulínið brotnar
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Mechanical Damage
May be caused by a foreign object that has accidentally entered the combustion chamber.
When this condition is discovered, check the other cylinders to prevent a recurrence,
since it is possible for a small object to "travel" from one cylinder to another where a large degree of valve overlap exists. This condition may also be due to improper reach spark plugs that permit the piston to touch or collide with the firing end.
og jafnvel þetta
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Pre-Ignition
Usually one or a combination of several engine operating conditions are the prime causes of pre-ignition.
It may originate from glowing combustion chamber deposits, hot spots in the combustion chamber due to poor control of
engine heat, cross-firing (electrical induction between spark plug wires), or the plug heat range is too high for the engine
or its operating conditions.
Tekið af
http://www.verrill.com/moto/sellingguid ... rchart.htmStimplarnir eiga líka að geta sagt ákveðna sögu.
Hér er mynd af einum þeirra:
Eins og sést er yfirborðið orðið brunnið/hrufótt eins og það hafi í raun soðið.
Hér sést svo skemmdur stimpill vegna Pre-Ignition.
Lítur dálítið svipað út.
Tekið héðan:
http://www.theultralightplace.com/pistons.htmPre-Ignition er hljóðlaust, en það má samt sjá á tvo vegu.
1. að EGT (Exhaust Gast Tempreature) hækkar mikið og fer yfir þolmörk sem eru 600+°C (650 c.a.)
2. Bíllinn hættir að bæta við afli þrátt fyrir að snúningarnir aukist, nú eða átt er við kvekju, bensín eða boost. Þetta er vegna þess að það hættir að verða sprenging í þeim cylindrum sem eru að pre-ignite-a.
Þetta má t.d. sjá á dynokúrvum sem verða flatar áður en komið er að optimum top snúningi vélarinnar.
Þetta minnir mig í raun á það sem Gunni sagði snemma, að bíllinn vildi ekki bæta við afli fyrir ofan 5000rpm þó svo að átt væri við kveikjuna, og þá fórum við að efast um að MAFinn væri í lagi nú eða að Vanosið væri rétt tímað inn eða í raun bilað. Hugsanlega var bíllinn að pre-ignite-a strax við fyrsta tjún. Grafið er allavega mjög flatt síðustu 1500 snúningana miðað við Manthey grafið
vs
Þetta þarf þó allt að koma í ljós, vonandi fáum við niðurstöðuna fljótlega, sem er eiginlega nauðsynlegt fyrir mig og Gunna.
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