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Dr. Z06 = KABOOM


Dr. Pomade

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Renner, when you type, I read. Your explainations are detailed so that you don't have to live under the hood to understand them. Thank you. BTW this is Bimmerjoe, minus the Bimmer.

 

Thanks Joe, I had heard you got a rolling time bomb. ;):D

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In a running engine, aluminum does not “burn”, it melts or fractures. The boiling point for pure aluminum is 2200C (4000F), for a cast aluminum alloy it is several hundred degrees higher.

 

Wouldn't that be (drastically?) different due to the pressures at the time it would have been melting?

 

Also to a lesser extent with the atmosphere that it's in?

 

Just wondering, I'm defintely sure you know more about this stuff than I do so I'm wondering. I tried to search google and I couldn't find any phase change graphs (for temp versus pressure) for any type of aluminium or an alloy.

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Here again, if you had read the post, I said guess, how would I have known he ran it al all ofter it blew. But I am sort of curious, since the motor is mutliport EFI, and to O2 sensor would have been seeing some level of almost raw fuel, and would have tried to pull fuel from it to get it back in tune, why would it have still been rich.

The 02 dosent see the fuel, only the oxygen. If a cylinder isnt firing, all that unspent oxygen is going to be detected and the computer will dump extra fuel to compensate trying to use the extra oxygen.

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The 02 dosent see the fuel, only the oxygen. If a cylinder isnt firing, all that unspent oxygen is going to be detected and the computer will dump extra fuel to compensate trying to use the extra oxygen.

 

It sees the ratio of air to fuel, that is why cat's do not effect measurement. If it sees the O2 is staying constantly rich(er) then normal, it will begin to compensate with the short trims, then it'll soon roll over to the long trims, slowly taking away fuel based on the long term trims.

 

Chip a piston and drive it for 200 miles, you learn alot of data logging. It should hover around stoic, rich to lean, yadda yadda, but when you pop a piston, you can cleary see the uncombusted mixture (the output is not your typical sine wave pattern)

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Usually the o2 is before the cat, so it gets the amount of unburnt o2 coming from the cylinders. Some cars run dual (or 4 in the case of f bodies) 1 before and one after the cat.

It is an o2, all it masures is the amount of unburnt o2. thats it. Dosent care how much unburnt fuel there is, just sees the o2.

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Usually the o2 is before the cat, so it gets the amount of unburnt o2 coming from the cylinders. Some cars run dual (or 4 in the case of f bodies) 1 before and one after the cat.

It is an o2, all it masures is the amount of unburnt o2. thats it. Dosent care how much unburnt fuel there is, just sees the o2.

 

Pre cat O2s are bank x sensor 1 on GMs, they determine fueling changes in closed loop and can apply a bias to open loop (supposedly). Post cat O2s are just there to make sure the catalyst is working

 

Maybe I worded it wrong, but incomplete combustion = unburnt fuel = unburnt oxygen, the charge is saturated. I guess the name says it all though.

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I think you are confusing the word burn with melt.

 

In a running engine, aluminum does not “burn”, it melts or fractures. The boiling point for pure aluminum is 2200C (4000F), for a cast aluminum alloy it is several hundred degrees higher. And this is just the point where aluminum becomes a stable liquid that can undergo a phase change, this is not the temp where aluminum actually ignites and combusts. The combustion (or burning) temp is of course much higher.

 

Just because you have seen a beer can melt in a camp fire with a cool green flame doesn’t mean that it somehow applies to what happened to John’s piston. :p

 

 

 

Um, I already did.

 

If it got hot enough for the aluminum piston to "melt" would the block and heads melted along with it?

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If it got hot enough for the aluminum piston to "melt" would the block and heads melted along with it?

 

No, and the reason is that the thinnest part of anything in the combustion chamber is the dome of the piston. The cylinder walls are NOT aluminium either, aluminium blocks are sleeved with cast iron typically. Reason this is done is aluminium sucks for thermal expansion, and if aluminium slides against another piece of aluminium it will typiccally wear quickly, or seize together.

 

So that only leaves the head, and that because aluminium will transfer heat very well, and the heads are full of coolant, getting the heads hot enough to melt would be so great the oil in the motor would fail and the motor would seize long before you would have any real melting occur. But if you lift a head, and loose the seal between two cylinders, it can melt a groove in the head between the cylinders.

 

You also need to realize that when a motor goes into a hard detonation, not only do cylinder pressures spike to 10 to 20 times what a normal burn would be, but with the pressure spike, there are localized areas of very extreem heat because of the detonation of the fuel and air as well as the extreem pressures that are involved.

 

Ask a submairner about what happens to the people on a sub that crushes because it goes too deep, the actually are incenerated, not drown or crushed as one might think. Reason is that the interior of the sub goes from 20 or so psi to 7000 to 10000 psi in microseconds. anytime you get that sort of pressure change you will get an extreem increase in heat.

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Ask a submairner about what happens to the people on a sub that crushes because it goes too deep, the actually are incenerated, not drown or crushed as one might think. Reason is that the interior of the sub goes from 20 or so psi to 7000 to 10000 psi in microseconds. anytime you get that sort of pressure change you will get an extreem increase in heat.

 

No one wants to ask a submairner anything. What kind of dumb thing to say is that? Ask a submariner? Honestly sometimes you just don't seem to get what is obvious to everyone else.

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I hear whitenoises ...

 

sorry about your engine Doctor, well mostly not really sorry, but it sucks to see/hear of it happening to such a renowned car. Sorry was just my way of trying to relate to your situation ... but I really have no idea.

 

Regardless, I'm sure it'll continue to hold one of the 'baddess Z06 in Columbus' titles. Just build it so you can beat Crash, that should be number one priority :). Then you'll have no worries with anyone else.

 

just my opinion, don't wanna sound like a suckass.

 

Have fun with whatever you decide though.

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Dear desperado,

 

Please use your vast knowledge of thermodynamics to post exactly how much the internal energy of the combustion chamber contents increased as it was compressed, and how that created such a temperature as to melt a cylinder. Until such time revert back to your practical knowledge and stop speculating on shit using submarines.

 

Thanks,

Your resident engineering corps

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