free Jetting for Weather Calculator

Michael Forrest /

is my video on how to use the Jetting for Weather Calculator and where to download it from. Just in time for seasonal changes.

Re: free Jetting for Weather Calculator

Thank You. Oh you have a great looking site that I'm sure I'll reading.

Re: free Jetting for Weather Calculator

That's neat. I havent looked, do you consider relative humidity also? that can make a pretty big change too.

I assume you're looking at just an ideal gas law density change, which going from 75F to 32F is maybe a 10% (guessing) change in air density, but also 90% relative humidity at 75 is 2 volume % higher than 90% RH at 32. So there's that additional effect too, water vapor displacing oxygen/air

Re: free Jetting for Weather Calculator

Michael Forrest /

yes it takes humidity into its calculations

Re: free Jetting for Weather Calculator

Why should I change the only jet I've run for the last 10 years , in all 4 seasons ; from the gulf coast to the mountains and desert to flooding roads ? Because the weather is a bit different ?

I guess I must have missed something .

Re: free Jetting for Weather Calculator

Michael Forrest /

If you live where the climate is very stable, or you only ride during nice weather, then you wouldn't need this calculator. Some carbs are jetted right in the middle of where they should be for the minor weather changes the rider experiences.

But racers and people who experience big weather changes would benefit with a jetting change for weather/altitude changes.

Re: free Jetting for Weather Calculator

I'm not a racer , but , I do run my bike at full throttle very often for long periods at 30+ mph . The bike is stock but for a bit of piston crown 'channeling' and less one ring .

I've been traveling the continental USA for that last 9+ years , full time , in all seasons . That , from sea shores to mountains ;100% humidity to as low as 7 % humidity and temps from 30s to over 100° in full sun shine to driving / drenching rain and even both at the same time on occasion , all the while running the same jets .

In those 9 years and conditions , other than mud daubers or my pinching an oil line , the bike has not skipped a beat . Usually starts first kick and runs quiet enough to sneak up on just about anyone .

But , maybe I'm missing something .

Re: free Jetting for Weather Calculator

Nice indeed

Excellent it works in OpenOffice as well

Re: free Jetting for Weather Calculator

Pretty cool.

While reading about moped racing in France I came across multiple bloggers who mention having to adjust multiple times throughout the day because of changing weather conditions.

Some even bring weather monitoring equipment and keep detailed notes for their records.

It's probably most useful for highly tuned engines.

Re: free Jetting for Weather Calculator

Michael Forrest /

With high performance engines that depend on every little bit of power of course the racer would notice the difference in power with weather/altitude change but not so much a street rider on a low performance ride.

Re: free Jetting for Weather Calculator

Some of us are hardy enough to ride year long in CanadaLand, that would cover the range of -15°c to +35°c, with humidex values into the +45°c range. A lot of us have put some tuning into their cycles so they are not the average 1,5hp 50km/h off the shelf engines. Weather, humidity, temperature and altitude count often, specially going up a good grade.

> Michael Forrest Wrote:

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

> With high performance engines that depend on every little bit of power

> of course the racer would notice the difference in power with

> weather/altitude change but not so much a street rider on a low

> performance ride.

Re: free Jetting for Weather Calculator

the change in air density between 0 and 100F can be as much as a 10% change in available oxygen in the same volume of air

Re: free Jetting for Weather Calculator

> Born to be WillD Wrote:

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

> the change in air density between 0 and 100F can be as much as a 10%

> change in available oxygen in the same volume of air

AFAIK , it's always been a given that most any motor runs better in cold weather , due to the higher oxygen content per cubic foot .

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