Piston fire sequence ?
Thread Starter
Burning Brakes
Joined: Jun 2003
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Piston fire sequence ?
Hi, I've been reading a lot about V8 small blocks about performance and upgrades, rebuilts and such, but I still have one question unanswered.
How does the fire sequence of the pistons occur?
Example, do the pistons fire one after the other from 1 to 8 or something more iradic like 2,3,5,8,7,6,1,4.... or do the pistons fire 2 at a time or just 1 at a time.
I'm trying to understand exactly why a stock V8 engine would be stronger then a stock 4 cyl or 6 cyl.
Thanks for any reply or explanation
How does the fire sequence of the pistons occur?
Example, do the pistons fire one after the other from 1 to 8 or something more iradic like 2,3,5,8,7,6,1,4.... or do the pistons fire 2 at a time or just 1 at a time.
I'm trying to understand exactly why a stock V8 engine would be stronger then a stock 4 cyl or 6 cyl.
Thanks for any reply or explanation
Race Director
Joined: May 2001
Posts: 14,165
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Re: Piston fire sequence ? (TheStef)
Ok, the firing order for any SBC is 18436572
The pistons are numbered from the front of the block, counting towards the rear. The passenger side is even 2,4,6,8 the driver's side is 1,3,5,7 :cheers:
BTW, no two pistons fire at the exact time. Also when one piston is at TDC on it's compression stroke another is at TDC on it's exhaust stroke. The reason a V-8 is so smooth is it's naturally balanced design. There are 2 cylinders placed every 90 degrees around the crank. This leads to very balanced pressures and forces being applied to it.
[Modified by Nathan Plemons, 9:13 AM 9/5/2003]
The pistons are numbered from the front of the block, counting towards the rear. The passenger side is even 2,4,6,8 the driver's side is 1,3,5,7 :cheers:
BTW, no two pistons fire at the exact time. Also when one piston is at TDC on it's compression stroke another is at TDC on it's exhaust stroke. The reason a V-8 is so smooth is it's naturally balanced design. There are 2 cylinders placed every 90 degrees around the crank. This leads to very balanced pressures and forces being applied to it.
[Modified by Nathan Plemons, 9:13 AM 9/5/2003]
Team Owner
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From: Boston, MA
Re: Piston fire sequence ? (Nathan Plemons)
The reason a V-8 is so smooth is it's naturally balanced design.
Thread Starter
Burning Brakes
Joined: Jun 2003
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Re: Piston fire sequence ? (scorp508)
Cool image! thats what I wanted to see, but was expecting to imagine it in my mind :)
What does TDC meen? I've seen this term before, but can't remember what it meens? and what about BDC?
I can tell the way the V8 is moving that its really smouth, but how does the 4 stroke work exactly.. can someone explain to me the 4 steps the piston, valves, go through to create energy?
What does TDC meen? I've seen this term before, but can't remember what it meens? and what about BDC?
I can tell the way the V8 is moving that its really smouth, but how does the 4 stroke work exactly.. can someone explain to me the 4 steps the piston, valves, go through to create energy?
Race Director
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Re: Piston fire sequence ? (TheStef)
TDC - Top Dead Center - Piston is at it's highest point
BDC - Bottom Dead Center - piston is at it's lowest point
How does a four stroke cycle work... well I could explain it but this will probably be faster and it has more illustrations anyway. This is just one awesome website http://auto.howstuffworks.com/engine.htm
:cheers:
BDC - Bottom Dead Center - piston is at it's lowest point
How does a four stroke cycle work... well I could explain it but this will probably be faster and it has more illustrations anyway. This is just one awesome website http://auto.howstuffworks.com/engine.htm
:cheers:
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Re: Piston fire sequence ? (Nathan Plemons)
This is just one awesome website http://auto.howstuffworks.com/engine.htm
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Re: Piston fire sequence ? (britvette)
I think Gen III Small blocks are 1-8-7-2-6-5-4-3 (after about 1997)
Yep, started with the LS1. From Mortec.com....
The new Gen.III "LS1" motors have a different firing order than previous smallblocks. The firing order for the Gen.III smallblock and the 2001 8.1 liter (496 cubic inch) big block is 1-8-7-2-6-5-4-3. Eight individual ignition coils are computer controlled. No conventional distributor is used. The new firing order smooths out the running motor and eliminates the previous problem of the #5 and #7 cylinders firing right next to one another and causing fuel and air distribution problems. In case you were wondering, the firing order for the Gen.I, II and previous "Vortec" motors is 1-8-4-3-6-5-7-2.
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Re: Piston fire sequence ? (scorp508)
I also heard that you could essentially get a cam set uyp for the LS1 firing order for use int he Gen1 and Gen 2 blocks, but I don't know how true that is or if it will work
Drifting
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Re: Piston fire sequence ? (scorp508)
I suppose if you had a cam ground, and swapped the plug wires round, our motors could be 18726543. Wonder if there is a real advantage. It was OK the old way for about 150 years, or however long the Chev V8 has been alive, on the other hand they thought it was worth doing for the LS1..... :confused:
Sorry Jeff we were posting at the same time! :)
[Modified by britvette, 11:06 PM 9/5/2003]
Sorry Jeff we were posting at the same time! :)
[Modified by britvette, 11:06 PM 9/5/2003]
Race Director
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Re: Piston fire sequence ? (britvette)
Thing is if you actually draw it on paper it doesn't look like a huge deal.
In the original you have 2 cylinders fire on the same bank twice. Once when you go 5/7 and once when it goes 8/4. In the new design this only happens once, on the 2/6.
So it seems to me that this would actually be more unbalanced. As it sits with the original design you have a two cylinders that fire right after each other on each bank. In the new design only one bank does this. The only thing it really does is keeps two cylinders from firing directly next to each other but how much of a problem is that really?
In the original you have 2 cylinders fire on the same bank twice. Once when you go 5/7 and once when it goes 8/4. In the new design this only happens once, on the 2/6.
So it seems to me that this would actually be more unbalanced. As it sits with the original design you have a two cylinders that fire right after each other on each bank. In the new design only one bank does this. The only thing it really does is keeps two cylinders from firing directly next to each other but how much of a problem is that really?
Drifting
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Re: Piston fire sequence ? (Nathan Plemons)
Thing is if you actually draw it on paper it doesn't look like a huge deal.
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From: SCMR Rat Pack'r Charter Member..Great Bend KS
Re: Piston fire sequence ? (TheStef)
Stef,
To address your second question: a V8 is stronger (if by stronger you mean more powerful), because a V8 is USUALLY larger (more displacement) than a four or a six.
Even if you had two engines with the same displacement, say a six and an eight, the engine with more cylinders would be capable of making more power because it will have more valve area. Valve area is very important in flow and flow is very important in making power.
That's why no Corvette in the last 45 or so years has had anything but a V8.
:)
Larry
code5coupe
:seeya
To address your second question: a V8 is stronger (if by stronger you mean more powerful), because a V8 is USUALLY larger (more displacement) than a four or a six.
Even if you had two engines with the same displacement, say a six and an eight, the engine with more cylinders would be capable of making more power because it will have more valve area. Valve area is very important in flow and flow is very important in making power.
That's why no Corvette in the last 45 or so years has had anything but a V8.
:)
Larry
code5coupe
:seeya
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: Piston fire sequence ? (Nathan Plemons)
5 & 7 being next to each other is a problem for several reasons. A few off the top of my head, is trying to feed them with a single intake duct can't be done effectively, since 5 will steal air from 7. On a TPI car, this affects the "tuning effect" also. And I'm sure there's issues with heating that corner of the engine up too much.
The newer order avoids this by firing two cylinders that are further apart.
Oh, and prior to that, as far as I know, ALL 90 degree V-8s had the SAME FIRING ORDER. They just numbered the cylinders differently.
My Ford 5.0 HO is special though. It's cam is backwards basically, so it's firing order is a mirrored image of that.
The newer order avoids this by firing two cylinders that are further apart.
Oh, and prior to that, as far as I know, ALL 90 degree V-8s had the SAME FIRING ORDER. They just numbered the cylinders differently.
My Ford 5.0 HO is special though. It's cam is backwards basically, so it's firing order is a mirrored image of that.
Pro
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From: memphis tn
Re: Piston fire sequence ? (oldace84)
nascar has been using several different firing orders on their chevy engines for years... there are several different ones , although i dont know them off the top of my head. supposedly , a gain of as much as 10 horsepower can be found by doing this. although i dont believe the cost of a custom ground cam would justify doing it to a street car.
ok, just looked it up. b.t.w. its in the october issue of super chevy. there are 7 others that have been used. supposedly , reher-morrison has found the 1-8-7-3-6-5-4-2 gives the actual 10hp gain & also stated that reliability is increased.
[Modified by neverendingproject, 2:39 AM 9/9/2003]
[Modified by neverendingproject, 2:41 AM 9/9/2003]
ok, just looked it up. b.t.w. its in the october issue of super chevy. there are 7 others that have been used. supposedly , reher-morrison has found the 1-8-7-3-6-5-4-2 gives the actual 10hp gain & also stated that reliability is increased.
[Modified by neverendingproject, 2:39 AM 9/9/2003]
[Modified by neverendingproject, 2:41 AM 9/9/2003]
