| Author | Message | ||
     Bryn1203 |
a very knowledgeable engineer has suggested that changing a XB12 to XB9 primary drive stresses the g/box - which is then more likely to fail. Does using the lower gearing stress the g/box more ? Can anyone attribute g/box failure to primary drive change ? | ||
| Reepicheep |
I have a hard time imagining it would be a problem... Think about it, the power curve on an XB9 and an XB12 motors are fairly similar, the 12 just goes maybe 10% higher if you have really wound the motor out to 7200 RPM (or whatever you poor disadvantaged 12 owners are limited too these days  ). So up until you are almost at redline, an XB12 with the 9 gearing isn't seeing any more stress then an XB9 transmission would see on a daily basis. I suspect the XB gearbox was "designed" for a 120 HP XB9 turbo. You won't be anywhere near those kind of stresses no matter what you do with gearing. I think the only downsides to the switch are that fuel economy drops a little (higher revs at X mph), your "smoothness sweet spot" for your uniplaner suspension moves a little, and your motor top end life drops a little (more piston strokes per mile, and the long stroke XB12 is already pushing the edge of the envelope for an air cooled twin). All minor though. If I had a twelve, I would seriously consider it. I saved the trouble and just bought a 9. |
