Rotax Technical specs

[RodK]

Just bought a chaparral VR 223 and importing it to France.. for registration i need to know the bore and stroke of the Rotax 150hp engine. Unable to find it anywhere on the web. Any leads would be gratefully received !

 

[swatski]

@veedubtek

 

[veedubtek]

100mm bore. 63.4mm stroke.

Which strikes me as kinda odd.

 

[RodK]

thats great.. many thanks !

 

[smashedheadcat]

100mm bore. 63.4mm stroke.

Which strikes me as kinda odd.

Can I ask why you think it's odd? I am just curious.

 

[RodK]

I guess veedbubtek should answer but my understanding of his comment was that typically you would expect the bore to be longer than the stroke, not the other way round

 

[smashedheadcat]

There are advantages to running an "over-square" engine and also an "under-square".

I don't really find it odd, but I can certainly understand going with a longer stroke vs bore as smaller bores are typically less prone to detonation. Something that forced induction engines are certainly prone to. On the other hand, when you run a larger bore, you can fit larger valves. The shorter stroke will keep pistons speeds down (compared to a longer stroke) as rpms increase.

I have to guess that BRP found the large bore/short stroke formula to be most advantageous when compared to the under-square design. Like I said, it definitely has its disadvantages. Noise (high rpms), lack of low rpm torque, etc.

 

[RodK]

Possibly this arises from Rotax's aero engine heritage .. higher revs and lower package space may be an advantage there.. The lower package space seems also to be an advantage in the Chap.. but of i agree the higher revs are a disadvantage

 

[veedubtek]

Nothing crazy, just screams high revving hp and no torque to me on paper. And, it kinda is. 143hp, 103lb/ft ish. It just doesn't perform like that. My holeshot feels like I have a pair of torque monsters back there. I honestly expected it to be closer to square. Looking through all the specs of all the different Rotax engines, they make them in all kinds of flavors it seems, including undersquare.