Injection Timing
Postmaster
Joined: Sep 2007
Posts: 4,195
Likes: 6
From: Medford Oregon
I would think somewhere near TDC, depending on oil temperature. In reality there are probably only a hand full of people that really know as that is embedded in the PCM code. Since detonation can't occur until fuel delivery there is no "just before", unless you use some chemical injected into the air intake system for hard/no starts conditions, a very bad idea on our diesels.
Lead Driver
Joined: Aug 2006
Posts: 5,259
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From: Gambrills
Mountain Pass
Joined: Dec 2005
Posts: 137
Likes: 0
ok quick lesson on 4 stroke diesels. In the most basic sense, here is how it works
1) intake: piston travels down, intake valve is open and exhaust valve is closed
2) compression: intake valve closes and piston is traveling upward compressing the air making it very hot
3) power: all valves closed, fuel injection begins as the piston is nearing top dead center on the compression stroke and continues for x number of degrees of crankshaft rotation, explosion pushes piston downwards
4) exhaust: exhaust valve opens as piston moves upward letting exhaust gases escape
1) intake: piston travels down, intake valve is open and exhaust valve is closed
2) compression: intake valve closes and piston is traveling upward compressing the air making it very hot
3) power: all valves closed, fuel injection begins as the piston is nearing top dead center on the compression stroke and continues for x number of degrees of crankshaft rotation, explosion pushes piston downwards
4) exhaust: exhaust valve opens as piston moves upward letting exhaust gases escape
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Tuned
Joined: Jul 2007
Posts: 291
Likes: 0
From: Cookeville, TN
As I thought, and this explains the high injection pressure required.
