Re: Importance of float level

Rocco Taco /
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> Graham Motzing Wrote:

> -------------------------------------------------------

> EX:

>

> just after posting i remembered a really good example of this. Due to

> manifold constraints and packaging i went from a VM22 on a moped build

> to a VM18. Despite being similar design and layout, these two carbs are

> (obviously) different castings and always end up running really

> different tuning parts.

>

> I had a 165 jet in the VM22, when i put the VM18 i was running a 75 jet.

> since mikuni jets are sized based on fuel flow, its easy math to see

> that dropping the jet size resulted in a (1-(75/165))= 65% decrease in

> flow rate through the jet.

>

> now, the speed of the moped didn't decrease much, and it was properly

> tuned in both scenarios, which means we can assume that mass air flow

> rate stayed relatively constant and fuel flow rate stayed relatively

> constant.

>

> so, because mikuni did the hard work for us and linearized the mass fuel

> flow rate of the jets, the math is really easy to say that (give or

> take) there was a 65% increase in differential pressure across the main

> jet to accomplish the same mass fuel flow rate with a smaller jet.

>

> so the differential pressure of having a different float level setting

> as a percentage change in mass fuel flow rate decreased by a factor of

> whatever that pressure drop is. if you wanted to just make up some

> numbers as an example you could say that the main jet delta p on the

> VM22 was, lets say, 10 cm. So then the 65% increase on the VM18 needs

> the pressure to to be (10/.45)= 22.2 cm differential to make the same

> mass flow rate. Now if you are .2 cm off on your float level, on the

> VM22 that will be a (.2/10) =2 % change in mass flow rate, whereas if

> you are .2 cm off on the VM18 it will be a (.2/22.2)= 0.9% change in

> mass flow rate.

>

> I think that math is right but i'm not super sure that you can use the

> mikuni jet size flow rates in a linear fashion like that, either way it

> shows a pretty good example of how the original poster is way the fuck

> wrong.

I’m definitely wrong too!

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Subject Written By Posted
  Importance of float levelTopic by: Michael Forrest Michael Forrest 08/28/19 11:16AM
  Re: Importance of float levelRe: live ɘvil live ɘvil 08/28/19 11:44AM
  Re: Importance of float levelRe: Michael Forrest Michael Forrest 08/28/19 11:46AM
  Re: Importance of float levelRe: jayson sumpter jayson sumpter 08/28/19 12:00PM
  Re: Importance of float levelRe: live ɘvil live ɘvil 08/28/19 11:52AM
  Re: Importance of float levelRe: Michael Forrest Michael Forrest 08/28/19 11:58AM
  Re: Importance of float levelRe: Rocco Taco Rocco Taco 08/28/19 12:15PM
  Re: Importance of float levelRe: Michael Forrest Michael Forrest 08/28/19 12:26PM
  Re: Importance of float levelRe: live ɘvil live ɘvil 08/28/19 12:34PM
  Re: Importance of float levelRe: Michael Forrest Michael Forrest 08/28/19 12:42PM
  Re: Importance of float levelRe: live ɘvil live ɘvil 08/28/19 01:37PM
  Re: Importance of float levelRe: Michael Forrest Michael Forrest 08/28/19 03:05PM
  Re: Importance of float levelRe: live ɘvil live ɘvil 08/28/19 03:34PM
  Re: Importance of float levelRe: Michael Forrest Michael Forrest 08/28/19 04:06PM
  Re: Importance of float levelRe: live ɘvil live ɘvil 08/28/19 04:12PM
  Re: Importance of float levelRe: Rocco Taco Rocco Taco 08/28/19 01:59PM
  Re: Importance of float levelRe: Michael Forrest Michael Forrest 08/28/19 03:15PM
  Re: Importance of float levelRe: live ɘvil live ɘvil 08/28/19 04:07PM
  Re: Importance of float levelRe: Braedan Cvetkovich Braedan Cvetkovich 08/28/19 04:50PM
  Re: Importance of float levelRe: ken gilbert ken gilbert 08/28/19 04:55PM
  Re: Importance of float levelRe: Rocco Taco Rocco Taco 08/28/19 05:13PM
  Re: Importance of float levelRe: live ɘvil live ɘvil 08/28/19 07:02PM
  Re: Importance of float levelRe: Michael Forrest Michael Forrest 08/28/19 09:15PM
  Re: Importance of float levelRe: live ɘvil live ɘvil 08/28/19 09:36PM
  Re: Importance of float levelRe: Rocco Taco Rocco Taco 08/28/19 09:51PM
  Re: Importance of float levelRe: K Olena K Olena 08/30/19 11:25AM
  Re: Importance of float levelRe: Michael Forrest Michael Forrest 08/30/19 11:38AM
  Re: Importance of float levelRe: Rocco Taco Rocco Taco 08/30/19 11:56AM
  Re: Importance of float levelRe: Rocco Taco Rocco Taco 08/30/19 11:57AM
  Re: Importance of float levelRe: Graham Motzing Graham Motzing 08/30/19 11:58AM
  Re: Importance of float levelRe: Graham Motzing Graham Motzing 08/30/19 12:27PM
  Re: Importance of float levelRe: Rocco Taco Rocco Taco 08/30/19 12:59PM
  Re: Importance of float levelRe: live ɘvil live ɘvil 08/30/19 01:53PM
  Re: Importance of float levelRe: Rebel Moby Rebel Moby 08/30/19 05:33PM
  Re: Importance of float levelRe: Overpriced Parts Overpriced Parts 08/30/19 07:28PM
  Re: Importance of float levelRe: baird co baird co 09/01/19 01:17PM
  Re: Importance of float levelRe: Norris Hall Norris Hall 09/02/19 10:25AM
  Re: Importance of float levelRe: Rebel Moby Rebel Moby 09/02/19 05:38PM
  Re: Importance of float levelRe: Rocco Taco Rocco Taco 09/02/19 08:03PM
  Re: Importance of float levelRe: Rebel Moby Rebel Moby 09/03/19 06:04PM
  Re: Importance of float levelRe: Norris Hall Norris Hall 09/02/19 06:57PM
  Re: Importance of float levelRe: Rebel Moby Rebel Moby 09/03/19 06:03PM
  Re: Importance of float levelRe: Norris Hall Norris Hall 09/02/19 06:59PM
  Re: Importance of float levelRe: Norris Hall Norris Hall 09/04/19 12:42AM
  Re: Importance of float levelRe: Rebel Moby Rebel Moby 09/04/19 06:05PM

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