Let me get this straight. Only half of car's cylinders are

jtvang125

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Nov 10, 2004
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A simple example would be an inline four engine. During combustion the energy released will push down on the 2 of the pistons. This action causes the crankshaft to turn 1/2 way and force the 2 pistons that were down to go up. These 2 pistons were not generating any power at that moment. Combustion of these two pistions will then turn the crankshaft the remaining 1/2 and complete a full revolution. Does that sound about right?
 

Heisenberg

Lifer
Dec 21, 2001
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Modern engines are four stroke - intake, compression, combustion, exhaust. You only produce power on the combustion stroke.

Edit: Typo
 

jtvang125

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Nov 10, 2004
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Originally posted by: Heisenberg
Modern engines are four stroke - intake, compression, combustion, exhaust. You only produce power on the compression stroke.

Yes I know about the 4 strokes but what I'm saying is that only half of the cylinders are actually making that power during the power stroke.
 

Toastedlightly

Diamond Member
Aug 7, 2004
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Originally posted by: jtvang125
Originally posted by: Heisenberg
Modern engines are four stroke - intake, compression, combustion, exhaust. You only produce power on the compression stroke.

Yes I know about the 4 strokes but what I'm saying is that only half of the cylinders are actually making that power during the power stroke.

more likely only 1 is actually making power at that given time (headed down on the compression stroke)

I was thinking V8
 

Viper GTS

Lifer
Oct 13, 1999
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Originally posted by: jtvang125
Originally posted by: Heisenberg
Modern engines are four stroke - intake, compression, combustion, exhaust. You only produce power on the compression stroke.

Yes I know about the 4 strokes but what I'm saying is that only half of the cylinders are actually making that power during the power stroke.

No, with four cylinders and four strokes how could 2 possibly be firing at the same time?

Viper GTS
 

Hyperlite

Diamond Member
May 25, 2004
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if there is only one cylinder firing at any given instant, then yes, only one cylinder is applying power....i know the firing order on older LS1 engines was 18273645
 

rivan

Diamond Member
Jul 8, 2003
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The timing for each cylinder's power stroke is staggered. I think you've got the idea, but it's actually only one cylinder firing at a time in most engines. Even classic v8s are that way - look online for how a distributor cap works for a basic mechanical explanation for it.

Newer cars (anything with 'electronic ignition') no longer uses a distributor, accomplishing the same function by electronically timed pulses instead of a mechanically timed pulses to the spark plugs.
 

Beattie

Golden Member
Sep 6, 2001
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Originally posted by: jtvang125
A simple example would be an inline four engine. During combustion the energy released will push down on the 2 of the pistons. This action causes the crankshaft to turn 1/2 way and force the 2 pistons that were down to go up. These 2 pistons were not generating any power at that moment. Combustion of these two pistions will then turn the crankshaft the remaining 1/2 and complete a full revolution. Does that sound about right?


4 stroke = 2 revolutions of the shaft per cycle.
 

spidey07

No Lifer
Aug 4, 2000
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Originally posted by: jtvang125
A simple example would be an inline four engine. During combustion the energy released will push down on the 2 of the pistons. This action causes the crankshaft to turn 1/2 way and force the 2 pistons that were down to go up. These 2 pistons were not generating any power at that moment. Combustion of these two pistions will then turn the crankshaft the remaining 1/2 and complete a full revolution. Does that sound about right?

You're way off.

each cylinder fires at a different time in the full two revolutions in a four cycle motor.

In a 4 cyclinder picture this.....

1 - ignition
3 - compression
4 - exhaust
2 - intake

and then repeat. bam - bam - bam - bam. That's the sound of each cylinder firing for a full cycle and turning the crankshaft two revolutions.
 

LeadMagnet

Platinum Member
Mar 26, 2003
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most cars have a 4 stroke engine (Suck / Squeeze / Bang / Blow) only the cylender in the BANG cycle is delivering power - all the others are consuming power.

So it you have a V8 engin only 2 cylinders would bein the BANG cycle at a time - the other 6 would be robbing you of power.
 

rivan

Diamond Member
Jul 8, 2003
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Hyperlite's got classic GM firing correct, with the cylinders numbered:

1 5
2 6
3 7
4 8
 

rivan

Diamond Member
Jul 8, 2003
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Originally posted by: LeadMagnet
most cars have a 4 stroke engine (Suck / Squeeze / Bang / Blow) only the cylender in the BANG cycle is delivering power - all the others are consuming power.

So it you have a V8 engin only 2 cylinders would bein the BANG cycle at a time - the other 6 would be robbing you of power.

The firing in classic V8s is staggered as well - there's no dual firing.

disclaimer: this may not include *all* engine designs; I'm referring to classic american car V8s
 

rivan

Diamond Member
Jul 8, 2003
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6s fire the same way, as do 3s and 4s. Hell, for that matter, so do rotary engines ala the RX-7.

While I'm not an engine designer, I'd expect firing more than one cylinder at once (which I've never seen) would produce less... uhm... even torque in low RPM applications, making the engine easier to stall. It would also require firing two spark plugs at once, and there might be some power related drawbacks to that.

Edit: If newParadigm's question meant firing order, that can vary from engine to engine and make to make. Again, I'd conjecture the firing order - at least in the GM V8 I mentioned above - to be staggered as it is to produce better/less vibration while running. As you see, on that V8, the firing order jumps from side to side and runs in opposite directions. It's likely tailored to each motor for best power, torque and vibration control.
 

Armitage

Banned
Feb 23, 2001
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4 stroke takes 2 revs of the crankshaft
Rev1, downstroke - Intake
Rev1, upstoke - Compression
*ignition*
Rev 2, downstroke - Power
Rev 2, upstroke - Exhaust

So any given cylinder is only making power half of every other stroke, so 1/4th of the time.