LS1 with traditional 18436572 firing order?
04-24-2012, 02:16 AM
#41
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07-12-2012, 04:31 AM
#42
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Ready for a long comment.
1. Open the hood and look at your engine, the cylinder closest to you, to your right. That's cylinder number 1.
2. The right side counts 1357, and the left counts 2468.
3. When cylinder #1 is at TDC, and you turn the crank 90 degrees at a time, the journals at TDC on this bank will be 1-3-4-2 repeat.
4. The left bank will be fast by one. When you turn the crank, the journals at TDC are (left,right) 3,1 - 4,3 - 2,4 - 1,2 repeat for twice for four stroke cycle.
5. Pistons at TDC in this order are 6,1 - 8,5 - 4,7 - 2,3
6. There are 8 possible firing orders:
18436572(SBC, BBC, ford Cleveland, Possibly Merceds M156),
18736542 (flathead ford, non M3 BMW, coyote Ford),
18726543 (LS,351 windsor)
15436872 < nobody uses this, but I find its tonal properties to be that of a BMW M3 E92 in reverse. Upon listening to reversed M3 recordings, It sounds the same, so that's food for thought.
The other four orders fire all the cylinders on one side, then the other.
1. Open the hood and look at your engine, the cylinder closest to you, to your right. That's cylinder number 1.
2. The right side counts 1357, and the left counts 2468.
3. When cylinder #1 is at TDC, and you turn the crank 90 degrees at a time, the journals at TDC on this bank will be 1-3-4-2 repeat.
4. The left bank will be fast by one. When you turn the crank, the journals at TDC are (left,right) 3,1 - 4,3 - 2,4 - 1,2 repeat for twice for four stroke cycle.
5. Pistons at TDC in this order are 6,1 - 8,5 - 4,7 - 2,3
6. There are 8 possible firing orders:
18436572(SBC, BBC, ford Cleveland, Possibly Merceds M156),
18736542 (flathead ford, non M3 BMW, coyote Ford),
18726543 (LS,351 windsor)
15436872 < nobody uses this, but I find its tonal properties to be that of a BMW M3 E92 in reverse. Upon listening to reversed M3 recordings, It sounds the same, so that's food for thought.
The other four orders fire all the cylinders on one side, then the other.
07-12-2012, 05:03 AM
#43
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This can of worms we just opened, let's dump it on the table.. *SPLAT!*
Let's look at a firing order.
18436572
8,4 will fire within 90 degrees, wait 270 degrees, 5,7 will fire in 90, wait 270 degrees and 8,4 comes back again. What does the LS setup do, and when relative to cyl numer 1?
You get this sound, of *du-dut* wait *du-dut* repeat.
Think of what journals are firing, assuming you have exhaust manifolds bolted up. low cylinder numbers will have the deeper tone.
SBC> 14223341
LS1> 14413322
FH > 14423321
M3 > 14432231
57C> 13223441 (15436872)
Let's look at a firing order.
18436572
8,4 will fire within 90 degrees, wait 270 degrees, 5,7 will fire in 90, wait 270 degrees and 8,4 comes back again. What does the LS setup do, and when relative to cyl numer 1?
You get this sound, of *du-dut* wait *du-dut* repeat.
Think of what journals are firing, assuming you have exhaust manifolds bolted up. low cylinder numbers will have the deeper tone.
SBC> 14223341
LS1> 14413322
FH > 14423321
M3 > 14432231
57C> 13223441 (15436872)
07-12-2012, 06:08 AM
#44
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Those first comments boil down to this.
You'll need a custom cam with the new firing order.
You'll have to switch the injector wire from the old cylinder to the new one.
You'll need to change your plug wires the same way.
The computer might complain if the oxygen sensor doesn't get information at the right time, but once the engine has been idling, the CEL might go away.
This stuff would be super easy to try on an original SBC, other than the cost of the cam. A dual plane manifold will even out the playing field in terms of flow.
You'll need a custom cam with the new firing order.
You'll have to switch the injector wire from the old cylinder to the new one.
You'll need to change your plug wires the same way.
The computer might complain if the oxygen sensor doesn't get information at the right time, but once the engine has been idling, the CEL might go away.
This stuff would be super easy to try on an original SBC, other than the cost of the cam. A dual plane manifold will even out the playing field in terms of flow.
07-12-2012, 09:26 AM
#46
Ready for a long comment.
1. Open the hood and look at your engine, the cylinder closest to you, to your right. That's cylinder number 1.
2. The right side counts 1357, and the left counts 2468.
3. When cylinder #1 is at TDC, and you turn the crank 90 degrees at a time, the journals at TDC on this bank will be 1-3-4-2 repeat.
4. The left bank will be fast by one. When you turn the crank, the journals at TDC are (left,right) 3,1 - 4,3 - 2,4 - 1,2 repeat for twice for four stroke cycle.
5. Pistons at TDC in this order are 6,1 - 8,5 - 4,7 - 2,3
6. There are 8 possible firing orders:
18436572(SBC, BBC, ford Cleveland, Possibly Merceds M156),
18736542 (flathead ford, non M3 BMW, coyote Ford),
18726543 (LS,351 windsor)
15436872 < nobody uses this, but I find its tonal properties to be that of a BMW M3 E92 in reverse. Upon listening to reversed M3 recordings, It sounds the same, so that's food for thought.
The other four orders fire all the cylinders on one side, then the other.
1. Open the hood and look at your engine, the cylinder closest to you, to your right. That's cylinder number 1.
2. The right side counts 1357, and the left counts 2468.
3. When cylinder #1 is at TDC, and you turn the crank 90 degrees at a time, the journals at TDC on this bank will be 1-3-4-2 repeat.
4. The left bank will be fast by one. When you turn the crank, the journals at TDC are (left,right) 3,1 - 4,3 - 2,4 - 1,2 repeat for twice for four stroke cycle.
5. Pistons at TDC in this order are 6,1 - 8,5 - 4,7 - 2,3
6. There are 8 possible firing orders:
18436572(SBC, BBC, ford Cleveland, Possibly Merceds M156),
18736542 (flathead ford, non M3 BMW, coyote Ford),
18726543 (LS,351 windsor)
15436872 < nobody uses this, but I find its tonal properties to be that of a BMW M3 E92 in reverse. Upon listening to reversed M3 recordings, It sounds the same, so that's food for thought.
The other four orders fire all the cylinders on one side, then the other.
07-13-2012, 01:46 AM
#47
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Ford:gm
1:2
2:4
3:6
4:8
5:1
6:3
7:5
8:7
54813726 -> 18726453
Just as a note, BMW and Audi number their cylinders like ford. GM and Ferrari number them, their way.
07-13-2012, 02:13 AM
#49
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Check out the cleveland.
15426378> .. 21843657 18436572.
How about the Ford Flathead, or any non m3 bmw v8
15486372>.. 21873654 18736542, which is a 4-7 swap on an SBC.
I've done the same numbering deal for the v8 from the BMW m3, and the same firing order requires a 1243 crankshaft. But if the sound were to be had backwards, from a clockwise engine, you get a 15436872 firing order. By the looks of it, it would be horrible for a front throttle body LS setup, but it should run fine on a dual plane intake.
07-13-2012, 09:34 PM
#51
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Well, since we know the order, and the fact that it improves engine output, perhaps we should try to understand why it's good.
the rignt bank on an LS engine is more to the front of the car, as a note.
18726543
1 - close to the throttle body
8-7 both breathe at the back, and 7 is closer to the throttle body by a little bit, so the engine doesn't struggle to breathe.
2 - really close to the throttle body again
6-5-4-3, each of those cylinders breathes closer to the throttle body than the last one, thus less air movement is required to feed the cylinder.
18436572
1 - close to tb
8-4, these breathe closer to the T.B.
3-6, one breathes close to the T.B., the other one craves air from deeper within the manifold.
57, same situation of breathing wanting manifold air.
2, close to the T.B. again.
On a dual plane manifold, this would go do the long runners first, then the short ones, not staggered from front to back, so it might vibrate.
18736542 4-7 swap on sbc, stock 5.0 mustang, ford flathead, BMW v8.
same as LS out to step seven
36, craves deep manifold air
54 - still wants deep manifold air, but not as bad.
2, back to the tb again.
This order would love a single plane sbc though
outer four cylinders, inner four cylinders, in a staggerd fashion.
Who wants to think about how the crank gets stressed?
Finite element analysis is hard to do mathematically, but more intuitive if you physically look at what you're dealing with.
the rignt bank on an LS engine is more to the front of the car, as a note.
18726543
1 - close to the throttle body
8-7 both breathe at the back, and 7 is closer to the throttle body by a little bit, so the engine doesn't struggle to breathe.
2 - really close to the throttle body again
6-5-4-3, each of those cylinders breathes closer to the throttle body than the last one, thus less air movement is required to feed the cylinder.
18436572
1 - close to tb
8-4, these breathe closer to the T.B.
3-6, one breathes close to the T.B., the other one craves air from deeper within the manifold.
57, same situation of breathing wanting manifold air.
2, close to the T.B. again.
On a dual plane manifold, this would go do the long runners first, then the short ones, not staggered from front to back, so it might vibrate.
18736542 4-7 swap on sbc, stock 5.0 mustang, ford flathead, BMW v8.
same as LS out to step seven
36, craves deep manifold air
54 - still wants deep manifold air, but not as bad.
2, back to the tb again.
This order would love a single plane sbc though
outer four cylinders, inner four cylinders, in a staggerd fashion.
Who wants to think about how the crank gets stressed?
Finite element analysis is hard to do mathematically, but more intuitive if you physically look at what you're dealing with.
01-31-2013, 04:16 AM
#52
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So, it's been like a long time, and I got through more of my engineering school.
Here's the whole deal.
LS 18726543 Every time it fires left to right, it does it on the same journal, and close to the flywheel. It's easier to twist some angle out of a long piece of metal than a short piece.
SBC 18436572 Total opposite. Runs with more harshness.
You can do it.
1: You'll need A one-of-a-kind cam
2: Switch the plug and injector wires for cylinders 4&7, 2&3.
3: Beware of Knock sensor. It may expect stronger signals and not get them.
You'll only notice a sound difference if you're using exhaust manifolds or shorty headers.
It'll sound like a Dodge/boat anchor.
I'm being paid to swap an LM7 into a 2002 4.8 Sierra SC/SB. Owner wants a custom cam, so I'll order one with the Gen 1 grind. JBA shorties, H-pipe where the crossover pipe used to go. No cats, Borlas, dumped right at the bed gap.
I think it'll sound like this.
.3.0.35i39l2j0l4j0i3j0l3.373.1207.0.3339.5.4.0.0.0.0.280.617.1j2j1.4.0...0.0...1ac.1.hXWYMtcHSiE
Here's the whole deal.
LS 18726543 Every time it fires left to right, it does it on the same journal, and close to the flywheel. It's easier to twist some angle out of a long piece of metal than a short piece.
SBC 18436572 Total opposite. Runs with more harshness.
You can do it.
1: You'll need A one-of-a-kind cam
2: Switch the plug and injector wires for cylinders 4&7, 2&3.
3: Beware of Knock sensor. It may expect stronger signals and not get them.
You'll only notice a sound difference if you're using exhaust manifolds or shorty headers.
It'll sound like a Dodge/boat anchor.
I'm being paid to swap an LM7 into a 2002 4.8 Sierra SC/SB. Owner wants a custom cam, so I'll order one with the Gen 1 grind. JBA shorties, H-pipe where the crossover pipe used to go. No cats, Borlas, dumped right at the bed gap.
I think it'll sound like this.
02-06-2013, 06:59 PM
#54
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Eh, it'll be fine. The shear limit for solid 2.558" journals on 60KSI cast iron is 62500 foot pounds. On 25ksi cast iron, half the cross sectional area, and load limited to half shear, and divided by 2 for the heck of it is 6538 foot pounds, plus downward shear from combustion. That might break it, but I don't think 5.3 cranks are made of white cast iron. My guess is a 60+ ksi ductile cast iron.
02-06-2013, 10:58 PM
#57
Gm didn't change it! The ls series has its firing order because it works the best for this engine. Where do people come up with stupid **** such as they copied ford etc...wth>????? what other stupid wild **** do you dream up?
02-07-2013, 11:33 AM
#60
This was brought to my attention by Joseph, & by an engineer on the Corvette design team.
It doesn't make any difference on the overall firing order, but it does begin with #6, if we're agreeing that all of these listed firing orders begin dot-to-dot.