Jetting for race/non road engine?

Hi all,

I have been reading up on a lot of threads with regards to jetting with certain combos etc of air and exhaust mods, for my project I will be running these setting:

Velocity stacks (no filter just mesh)
Open exhaust - still decided to go with seperate pipes for front and rear or a 2 into 1 like OEM

What sort of jetting should I look at? Its not the most common setting to run! There will be 0 restriction of air getting to the engine as there won't be a fuel tank above it.

[yorkie_chris]

Any airbox?

Originally Posted by yorkie_chris

Any airbox?

Nope, will just be running stacks so something like these factory pro ones, except with mesh



Something like this:

[yorkie_chris]

I guess 220

[embee]

I'd suggest you might be better off with an airbox of some sort, it generally makes it a lot easier to get it to run right under all conditions, keeps turbulence away from intakes. As big a volume as you can make it.

An intake spout which gives no more than a nominal 50m/sec at max rpm won't restrict it at all. Work out the nominal air flow simply by 100% vol efficiency at max rpm, times swept vol divided by 2 (4 stroke, one cycle = 2 revs), then work out what intake area equates to 50m/sec. Put a 10mm flare radius on the entry.

Hmm ok, I will dig into working out the airflow then, I could be tempted to run a modded stock box with maybe a forward facing intake to push air into the air box - the sort of thing you can't really do on a bike due to the tank and frame being in the way lol

[yorkie_chris]

Don't forget with ram air you need to compensate the carbs for this, like feeding the bowl breathers to your "scoop".

Also a positive pressure fuel pump. No idea how much the stock vacuum operated jobbie can deliver.

Originally Posted by yorkie_chris

Don't forget with ram air you need to compensate the carbs for this, like feeding the bowl breathers to your "scoop".

Also a positive pressure fuel pump. No idea how much the stock vacuum operated jobbie can deliver.

The engine is on a kart, so I will be using a Mikuni pulse pump to deliver the fuel, if its not up to the job I will upgrade to something better, there are 2 carbs that need fuel rather than 1.