Re: Vespa engine cases

Graham Motzing /
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yeah, good advice, i dont have a kit to look at, but i looked at some pictures for ideas. this is supposed to be a street bike, so I kept things conservative. I could have gone a few mm deeper, and even a mm or so wider on each side, but i didn't want to risk snagging a ring, and due to the re-shaping of the transfers, i dont plan on using the boost for a primary flow path, just for a slight improvement in scavenging.

while you do get more port area out of a squared-off port, the flow through the port doesn't improve significantly because flow through a 'corner' is severely restricted by the two sides being in close proximity, and you cant go as wide without snagging a ring. the domed exhaust port maintains better torque than the same sized squared off port, because the exhaust gasses that start flowing out of the center of the bore can leave while maintaining more pressure to keep the edges of the cylinder burning at high rpms. Jennings alludes to this, and so does Bell, but niether of them really get into the chemistry and fluidic implications that show the real potential for modifying ports like this. I can assure you, a port shaped like this with the same time-area as a square port will produce a much more useable powerband, and higher max power. I could go to a much more agressive time-area target with this and still maintain more torque with more power, but like i said, this is a daily driver for my girlfriend.

I also dont have any intentions of running a variator on this bike, in which case i would have been comfortable sacrificing a bit more bottom end.

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Subject Written By Posted
  Vespa engine casesTopic by: Graham Motzing Graham Motzing 12/09/09 12:11PM
  Re: Vespa engine casesRe: Sunset Paul Sunset Paul 12/09/09 12:21PM
  Re: Vespa engine casesRe: Sam Blk Sam Blk 12/09/09 12:30PM
  Re: Vespa engine casesRe: Organ Robbin' Organ Robbin' 12/09/09 12:48PM
  Re: Vespa engine casesRe: maciek maciek 12/09/09 07:33PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/09/09 09:15PM
  Re: Vespa engine casesRe: Maitland Of the Loin Maitland Of the Loin 12/10/09 03:15AM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/10/09 01:06PM
  Re: Vespa engine casesRe: Organ Robbin' Organ Robbin' 12/10/09 01:09PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/10/09 03:00PM
  Re: Vespa engine casesRe: Sunset Paul Sunset Paul 12/10/09 03:18PM
  Re: Vespa engine casesRe: Organ Robbin' Organ Robbin' 12/10/09 03:27PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/10/09 04:39PM
  Re: Vespa engine casesRe: Organ Robbin' Organ Robbin' 12/10/09 04:40PM
  Re: Vespa engine casesRe: Josh G Josh G 12/10/09 08:49PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/11/09 12:19PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/14/09 08:17PM
  Re: Vespa engine casesRe: Sunset Paul Sunset Paul 12/14/09 08:50PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/15/09 12:09PM
  Re: Vespa engine casesRe: Sunset Paul Sunset Paul 12/15/09 03:56PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/15/09 06:32PM
  Re: Vespa engine casesRe: jason w jason w 12/15/09 08:30PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/15/09 09:24PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/15/09 11:20PM
  Re: Vespa engine casesRe: Jason W Jason W 12/16/09 01:55AM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/18/09 10:57AM
  Re: Vespa engine casesRe: Jason W Jason W 12/18/09 12:59PM
  Re: Vespa engine casesRe: Sunset Paul Sunset Paul 12/18/09 04:53PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/23/09 10:36AM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/26/09 01:35PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 12/28/09 02:52PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 01/04/10 11:19PM
  Re: Vespa engine casesRe: James G James G 01/05/10 12:42AM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 01/05/10 03:43PM
  Re: Vespa engine casesRe: Organ Robbin' Organ Robbin' 01/05/10 03:54PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 01/05/10 04:29PM
  Re: Vespa engine casesRe: Organ Robbin' Organ Robbin' 01/05/10 04:38PM
  Re: Vespa engine casesRe: jens jens 01/05/10 04:48PM
  Re: Vespa engine casesRe: jens jens 01/05/10 05:00PM
  Re: Vespa engine casesRe: Graham Motzing Graham Motzing 01/05/10 05:13PM

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