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Old 05-27-2008, 12:51 AM
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compression ignition vs common rail injection 101

400 psi static compression ratio will ignite Diesel fuel in a 617 prechamber without glowing. Common rail systems handle Diesel fuel at tens of thousands of psi. Why doesn't Diesel fuel ignite in a CDI fuel delivery system?

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Old 05-27-2008, 12:55 AM
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No oxygen in the fuel delivery system -- only fuel. No oxygen, no combustion.
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Old 05-27-2008, 12:56 AM
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Man, I'm glad someone here is thinking

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Old 05-27-2008, 03:32 AM
ForcedInduction
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The 617's 400psi is compressed air, the CDI is compressing fuel.
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Old 05-27-2008, 08:25 AM
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ehh sometimes i think air bubbles can get into the system... but CDI injection systems don't get hot enough to ignite the fuel.
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Old 05-27-2008, 08:31 AM
Craig
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Quote:
Originally Posted by 79300sdtd View Post
ehh sometimes i think air bubbles can get into the system... but CDI injection systems don't get hot enough to ignite the fuel.
Correct, the combustion is caused by the high temperature (resulting from the compression of the air), not from the pressure itself. You will not get combustion by pressurizing liquid fuel, which actually does not require very much energy and does not add much energy (heat) to the liquid fuel.
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Old 05-27-2008, 10:37 AM
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Quote:
Originally Posted by Craig View Post
Correct, the combustion is caused by the high temperature (resulting from the compression of the air), not from the pressure itself. You will not get combustion by pressurizing liquid fuel, which actually does not require very much energy and does not add much energy (heat) to the liquid fuel.
Yes, what he said...that's why bicycle pumps and air compressors get so darn hot, it is the energy of compressing the air which makes it hot enough to burn the fuel, not the act of compression per-se. Technically liquids are considered incompressible too (though they do compress ever so slightly) which is why it takes so little energy to spike the pressure in a liquid filled space (like your brake system) but so much more to compress a gas like air.

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