XS11 cylinder firing order?

[TajMan]

How are the power strokes of this 4 cylinder 4 stroke engine, is it one(different) of the pistons power strokes during each of the 4 engine cycles? Does that make sense?
Is it uneven like 2 pistons, then nothing, then 2 pistons, then nothing?

Just wondering, for the use of a small turbo close to the engine, equal lengths of manifold piping or not.

And I'm sure engine compression is pretty high stock, 11:1? Are double headgaskets possible and grinding work in the head to lower CR a little?

[oseaghdha]

If I had to guess, I'd say 1-3-4-2.

[Silent]

From the coils, wouldn't it be more like 1-2-3-4, or 1-4-3-2? Both 1 & 3 plugs fire at the same time with a wasted spark. 2 & 4 fire at the same time as well with a wasted spark.

[Yahman]

It's paired 1 - 4 and 2 - 3 on the coils. For example 1 is firing on the power stroke and 4 is firing on the exhaust stroke. The firing order is 1 - 2 - 4 - 3.

Larry

[TajMan]

thats fine thats fine on specific order, so long as they are evenly spaced out (1 piston fire for each of the 4 engine strokes of the other pistons)

I guess its just V-twin motorcycle engines that I know of which have unusual power stroke firing orders..

[DiverRay]

I guess its just V-twin motorcycle engines that I know of which have unusual power stroke firing orders..

That is ONE of the reasons we like the XS so much. The inline four, air cooled, SMOOTH engine.
When you put together the pipes for a turbo, keep the fire order in mind! put them in a circle, 1-2-4-3, and then into a collector about 4" long BEFORE the turbo. That should give you the best power at low RPM, and keep the pulses down at higher RPM. The '80 and up "big valve" head WILL lower the compression ratio about 1/2 point. The bikes start at 9.2:1, so it would get you into a sweet spot with 8 to 10PSI boost.
As my engine starts to get back together I'll have some pictures to post.

[Jerry]

Yahman has the right of it, 1-2-4-3. However, these bikes use what is known as a 'wasted spark' architecture. When #1 fires on the power stroke, #4 also fires - it is tied to the same coil that fires #1 - but since #4 is at the bottom of its exhast cycle (?) at the time there is no power generated.

Anytime you see spark plug wires run directly to coils (no distributor) and fewer coils than the number of cylinders, i.e. 2 coils and 4 cylinders, the engine is running a 'wasted spark' ignition system.

[TajMan]

Thats an excellent compression ratio for boost already, at least closer than most other non-turbo engines!

If I use an '80 or later "big valve head", it will bolt right up to my '79 Special motor and lower the CR a little for me?

From engine, 4" out and into a collector, then into turbo? Sounds pretty good..

I'm a 3000GT twin turbo guy, 1 small stock 9B turbo I think is perfect for a beginning turbo setup on an XS11 engine. (I bet its good for 165-185hp, 6-10psi)

[mike_y]

is the motor a 180 degree crank?
and what is the pick up coil gap????

[bikerphil]

Firing order is 1-3-4-2
PU coil gap is 0.7MM (.027")
180º crank

[TajMan]

Flashback 2009
got me a '80 with a recent head rebuild I was told,
actually in search of parts for that turbo kit now