2 Stroke versus 4 Stroke

4 stroke good points:-
slower revving
lower fuel consumption
clean flexible power
lower emissions
has more torque at lower speeds

2 stroke good points:-
light weight
high power
uncomplicated (only three moving parts)
can be used in any position

4 stroke bad points:-
complicated (lots of moving parts
can only be used in a fixed position
lower power (depending on engine size)

2 stroke bad points:-
smokey (dirty)
higher emissions
not very fuel efficient
narrow power band (not flexible)

What would be an ideal power unit for a chainsaw, brushcutter, hedge trimmer, blower:-

First it must be light (as you've got to pick it up).
It must be able to function in any position.
All these machines run at one speed (full power) within a set power band, therefore you don't need a lot of flexibility.
Small in size (won't get in the way).
High power to weight ratio.

It sounds like 2 strokes would be ideal to me.

Wouldn't it be better if a 2 stroke could be as economical (fuel efficient) as a four stroke?

Wouldn't it be better if a 2 stroke could be as clean as a four stroke (fewer emissions)?

Wouldn't it be better if a 2 stroke had the pulling power and flexibility of a four stroke?


'X' torq is a 2 stroke engine concept which gives you a 20% improvement in fuel consumptions, plus a 60% reduction in exhaust emissions.

And, most dramatically, as engine speed of the 'X' torq motor slows, unlike traditional 2 strokes, it just keeps on pulling - this is torque…...

Engine power can be measured in two ways. Brake horse power (B.H.P.). This is measured at the engines highest speed. Torq is measured at the engines speed where it has the greatest push.

Putting it simply, horse power is a 'punch' and torque is a 'push'.

Now to give a basic explanation of 'X'torq.
A disadvantage of 2 strokes is that the incoming fuel air mixture gets mixed up with the outgoing exhaust gasses. Fuel air mix can end up in the exhaust and wasted exhaust gasses can also be forced back into the engine cylinder, diluting the fuel air mix (caused by the exhaust pulse).

4 strokes don't have this problem as they waste (half) an engine revolution just to push out the exhaust gasses.

'X' torq engines have a porting system that during every engine revolution a shot of clean, cold oxygen rich air is introduced to the cylinder. This acts as a buffer between the incoming fuel air mixture and the outgoing exhaust gasses.

This separates the inlet gasses from the exhaust gasses. This with the 'super scavenging' front positioned ports gives probably the most efficient small 2 stroke so far made.

At full speed B.H.P. is the same. At lower speed the X torq motor out pulls a conventional 2 stroke.

The X torq concept has been used successfully for a few years now on certain Husqvarna machines, such as the 455 and 576XP.

The 576XP is a machine that in use can perform along with some 90cc saws. As the saw is reasonably compact and can be used for heavy, limbing with a short bar, then because of it's high torque motor is used also for felling with a long bar.

One saw for 2 jobs. A 30% saving in fuel consumption, a lot less to carry into the forest.

The now tried and tested X torq engines have now been introduced across a range of Husqvarna saws, including the 435, 440, 450 and 576XP..

The future is 2 stroke
The future is 'X' torq
The future is HUSQVARNA