ITB air filters

[Jhonno]

38mm is pretty small!! Considering the Vaux XE engine (similar 500cc/cyl) runs 42-48mm tbs

throttle response should be awesome!! will have a nice mid range also, and help hide any lumpy cam you might have

[Jhonno]

should work out ok actually.. 2v flow vs. 4v flow etc etc

[oakey]

38mm is small but more than big enough for plenty of power potential. What size is the standard TB? Anyone know how to work out the inside area of a circle? lol

[oakey]

should work out ok actually.. 2v flow vs. 4v flow etc etc

Runner length and tb size has all been calculated for the hp I want and the rev limit

[Jhonno]

Pie*r^2

LOOOOOADS more area than the standard tb anyways

[maxfield]

I've got 263mm² for the area of the ITB's

[oakey]

I've got 263mm² for the area of the ITB's

Whats the for?

[maxfield]

Because I don't know how correct it is...

[oakey]

Well considering 38mm squared is 1444mm I think you might be

[maxfield]

R = Radius.

And the radius is 14mm

[oakey]

If I measure a square inside the tbs of 25mmX25mm I get a surface area of 625mm yes? Times that by 6 and you get 3750mm so surely your'e doing something wrong. Or my brain is completely fekked

[maxfield]

3750mm is 3.75m...

And to me that sounds a lot of surface area for TB's!

[oakey]

Im doing something badly wrong here with my calculations arent I?

[oakey]

You were right all along maxfield! That will teach me not to smoke in the daytime

Does the area of the tb's sound too small?

[maxfield]

I'm not sure what a good area for ITB's is TBH.

But seen as it's only a 2v per cyl engine I would of thought 38mm is about right.

[maxfield]

Oh shit done it completely wrong!

Radius is 19mm

[oakey]

Oh shit done it completely wrong!

Radius is 19mm

Lol! We must seem like proper numpties! My excuse is I havent been tought maths for 7 years! What yours?

[Jhonno]

How many zoner's does it take to work out the radius of Oakey's tbs?!

[maxfield]

I've slept since then

I only learned it a couple of years a go..

Does 68.046cm sound about right?

[oakey]

How many zoner's does it take to work out the radius of Oakey's tbs?!

More than 3 it appears

Besides its area were trying to figure out

[agreen]

i cant rember what size my itb's are 48mm i think

so for more low down torque long trumpets ? correct ? ? ?

[lance1a]

^^^^as a general rule, yes, but you might have to play with the lengths to get the torque where you want it.
With carbs, and filters straight onto them (no stacks) I was getting into 6500rpm as quick as hell, but no bottom end. In fact, when I took the 120mm trumpets off to fit the filters straight on, I though something had come loose, so much difference it made! Though the trumets I was using were too large in diameter (58mm vs 40mm venturi) so the airspeed was too low. Now with the smaller stacks the torque is almost right. I want to make up 90 dergree bends in alloy tubing of 40mm diameter, as I read that a 90 degree bend will cause a vortex to occur, and further increase airspeed.

[Turbo-Brown]

as I read that a 90 degree bend will cause a vortex to occur, and further increase airspeed.

Not sure that vortices in your inlet system are a good thing, pretty sure they won't increase air speed either.