HapHazard
Well-Known Member
Hi All,
Still looking into different engines for my future project.
Was intrigued to look at Jabiru's figures for their engines. They are running relatively short strokes on big bores, yet claiming and getting direct drive RPM'S of the mid 2000's. I know you cant beat sheer capacity through big bores, but the combo goes against conventional thinking of longer strokes producing better low-down torque. On paper, the engine should be developing its power/torque much higher up the RPM scale.
A friend who flies behind a Jabiru claims he can get his engine sitting quite happily in the cruise back at around 2,200 rpm!
Obviously cam and head/inlet design contribute towards achieving such low usable RPM's, so my two questions are, how do they achieve such a low RPM with torque and if they can do it, why cant a VW be made to develop more low-down power? Are those VW heads that limiting???
Hap onder:
Jabiru 2200
Bore- 97.5mm
Stroke- 74mm
(Bore/stroke ratio of: 1.317)
As a comparison...
0-200
Bore- 103.1mm
Stroke- 98.6mm
(Bore/stroke ratio of: 1.046)
Revmaster R 2300
Bore- 94mm
Stroke- 84mm
(Bore/stroke ratio of: 1.119)
Still looking into different engines for my future project.
Was intrigued to look at Jabiru's figures for their engines. They are running relatively short strokes on big bores, yet claiming and getting direct drive RPM'S of the mid 2000's. I know you cant beat sheer capacity through big bores, but the combo goes against conventional thinking of longer strokes producing better low-down torque. On paper, the engine should be developing its power/torque much higher up the RPM scale.
A friend who flies behind a Jabiru claims he can get his engine sitting quite happily in the cruise back at around 2,200 rpm!
Obviously cam and head/inlet design contribute towards achieving such low usable RPM's, so my two questions are, how do they achieve such a low RPM with torque and if they can do it, why cant a VW be made to develop more low-down power? Are those VW heads that limiting???
Hap onder:
Jabiru 2200
Bore- 97.5mm
Stroke- 74mm
(Bore/stroke ratio of: 1.317)
As a comparison...
0-200
Bore- 103.1mm
Stroke- 98.6mm
(Bore/stroke ratio of: 1.046)
Revmaster R 2300
Bore- 94mm
Stroke- 84mm
(Bore/stroke ratio of: 1.119)