View Full Version : Jetting for race/non road engine?
m1tch_1987
27-04-12, 01:30 PM
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
27-04-12, 04:24 PM
Any airbox?
m1tch_1987
27-04-12, 04:58 PM
Any airbox?
Nope, will just be running stacks so something like these factory pro ones, except with mesh
http://hareemil.info/img.php?fl=o5n4q4i413443416562614k4s5h5l574a4w506s 234x5f4s2i4m494f4e40654p3u2u2w2q2w2a484r224d4m494
Something like this:
http://www.alfabb.com/bb/forums/attachments/alfa-romeo-parts-sale-wanted/195763d1292351956-weber-45-velocity-stack-filter-64-mm-2-50-bfv8pfqbmk-kgrhqiokkyery-hqcyrbl-2m8-w-_3.jpg
yorkie_chris
27-04-12, 05:06 PM
I guess 220
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.
m1tch_1987
27-04-12, 08:54 PM
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
27-04-12, 09:03 PM
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.
m1tch_1987
27-04-12, 09:59 PM
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.
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