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Free icecream
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2,112 Posts
Discussion Starter #1
Ok, so I understand the four-stroke principal with the piston things stuck on the crank, and the 'suck, squeeze, bang, blow' stuff but how are the pistons arranged on the crank when do they fire during one revolution?

Is it two at a time firing, one, or what? Go on then, amaze me...
 

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Member No 48
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1,192 Posts
Depends on how many cylinders its got. On a standard 4 cylinder the throws are at 180 degree angles (opposite each other) and the firing order is usually 1.2.4.3. Therefore you get two power strokes per revolution of the crank.
On a straight 6 cylinder the throws are at 120 degree angles, so you get 3 power strokes per revolution....thats why a straight 6 is the smoothest engine.
I do know the gen on v6 and v8 engines but I'm having a hard time dragging the info from the depths of my poor addled brain.
Maybe some else is lucid enough to continue the education lesson?
 

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Banned
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1,743 Posts
Well don't know a huge amount about engines but when I re-built my capri V6 engine I had to find out the firing order and it was something weird like 1,4,2,5,3,6
 

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Free icecream
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2,112 Posts
Discussion Starter #4
Should have said really but it was a question about the RB engine. I'm sure i'd seen years ago a mini engine with the head off and the pistons were 2up and 2down, 180° opposed. I wondered if it was the same with the skyline if they worked in pairs or not, and so they do.

Is two the magic number then? As opposed to firing 1 or 3 at a time.

Sorry if i'm being dense but I know nothing about how a straight 6 works :)
 

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Floyd, surely with a 180 degree crank on a 4 you've got one power pulse per rev. You've got two pistons rising at any one time, but one is squeezing a fresh charge of air and fuel while the other is pushing out the exhaust gases.

Unless you're talking about a 2 stroke of course.
 

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Member No 48
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1,192 Posts
Yea your right, I told you my brain was tired.....i need my bed!
 
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