4 cylinder firing order options?

[joeschmo_57]

Hey dudes,
I was thinking, 4 cylinders fire on the 1-4, 2-3 sequence. What is the science/logic behind this? Is it possible to have them set with a different pattern? Surely it is whet it goes 1 3 2 4 or would it lose out on torque.
Or is this an old thing and newer engines are set different? If so what are the pros and cons.
Then there's tuning. Is it harder to be tuning something with a different striking order?

Or am I just a noob

[maxhag]

I am not even sure where to begin..... :0

Firing order for 4age's is 1-3-4-2

Are you suggesting to custom make a crankshaft?

[Skylar]

Say you start with 1, the next cylinder to fire is 3 because it's not next to 1 (for better heat distribution, would be stupid to fire 1,2,3,4). Then whichever cylinder you fire next will have to be 2 or 4. Either one of these are next to 3 so it's inevitable that you're firing two adjacent cylinders. If you fired two next, making twin scroll manifolds would become as easy making an equal length ram-horn mani. Sweet! The problem with this is your crank is, um... not out of balance but the balancing cylinders are further apart... if that makes sense? A normal 4 cyl crank has 1 and 2 in opposition, and same with 3 and 4. If firing order was 1-3-2-4 then 1 would counterbalance 4 while 2 would for 3.

I have no idea honestly. Made that up after thinking it through. I know the heat distribution part is correct but the rest seems logical?

[lolwat]

believe boxers have a different firing order

[sundee]

Agreed.

Boxers fire 1,4,2,3 - this is more a balance thing I believe.

[sundee]

Here is a flat motor, it is an aircraft engine, but you get the idea.

[ill-minded]

My understanding is that it's more of a by-product of the way the cranks are arranged. This all boils down to balancing issues. For the crank to be balanced easily, it needs to effectively be "symmetrical" between the front two and rear two cylinders (excluding the snout on the front for the crank pulley and the rear for the flywheel). This is why when 1 is at TDC, 2 and 3 are BDC and 4 is also TDC. Same thing applies to inline sixes. I forget the maths behind it, but someone who's gone through a mechanical engineering degree recently can probably understand what I'm on about. Firing in the order of 1-3-4-2 (or 1-2-4-3, which is the same, but in reverse) is the only way you can get a single ignition event on each cylinder on a full 720° cycle. I'd say someone probably decided on 1-3-4-2 and everyone just followed suit. Boxer motors vary because the of the opposing cylinders, meaning different pistons being at TDC compared to an inline 4.

Firing in the order of, say, 1-2-3-4 (or 1-3-2-4, or either in reverse order) would mean that you would have an odd-firing engine, where you would effectively have 1 and 4 firing simultaneously, the crank rotates 180 (out of 720°) then 2 and 3 simultaneously, then there is 540° where there are no ignition events. This would be bad for numerous reasons, including it sounding like a Harley and making the power delivery somewhat jerky, compared to an even-firing engine.

No idea if that makes sense to anyone else. I could make a diagram, but I am incredibly lazy.

[joeschmo_57]

That answered all my questions. So when 1-4 are TDC, 2-4 are BDC, but 1 still fires before 4?

So how the ef does the 5 cylinder Audi and Volvo engines fire?

[joeschmo_57]

That answered all my questions. So when 1-4 are TDC, 2-4 are BDC, but 1 still fires before 4?

So how the ef does the 5 cylinder Audi and Volvo engines fire?

[4A-GE Power]

When 1 and 4 are at top dead 2 and 3 are at bottom dead on 4AGEs and probably a lot of other 4 cyls because all are on a 180 degree plane crank. The Yamaha R1 for example has a cross plane crank meaning instead of firing 180-180-180-180 the R1 engine fires 180-90-180-270, kinda like half a V8 engine. 5 cyls would be something like 1-2-4-5-3.