Throttle body sizing, twins?

spetz · Post by **spetz** » Thu Aug 24, 2006 11:38 pm

At what size is the TB too big for a 6A12?

I am thinking of cutting the plenu, getting rid of the twin length butterflies, welding a new plenum on, with the match ported and shortened runners and using 48mm TB per side of the plenum

Thoughts?

SG · Post by SG » Fri Aug 25, 2006 2:21 pm

affects drivability heaps if you have too many throttles afaik, duno the limit though, you could get 6 pack throttles but you wouldnt have a bottom end rev range

a guy i know has had 4 pack throttles and vowed never to go back because the car was undriveable below ~3k rpm. not sure what he meant by undrivable, maybe it would stall due to low vacuum or something while on load.

spetz · Post by **spetz** » Fri Aug 25, 2006 6:21 pm

hmmm...
Though 6 pack is a bit different to just two 48mm

Does anyone have a calculator type thing that can calculate the total open area of two 48mm?
ie it is equal to single XXmm opening?

SG · Post by SG » Fri Aug 25, 2006 6:27 pm

96....

its only air going thru the measured part afaik

Post by **Bennoz** » Fri Aug 25, 2006 6:34 pm

Go postal! 1 per cylinder!

spetz · Post by **spetz** » Fri Aug 25, 2006 6:46 pm

SG wrote:96....

its only air going thru the measured part afaik

haha you know you don't just add them to get that figure?

There is a special formula!

Dras · Post by **Dras** » Tue Aug 29, 2006 9:52 am

little bit a math for yal

area of a circle = pi * r * r

for 48mm the area is 1809 mm squared
if you have 2 you get 3619 mm squared.

This is the same as a single 67.88mm throttle body.

Unless you can get this mod done real cheap I would think a 65 mm or 70 mm single throttle body to be a more economical mod.

spetz · Post by **spetz** » Wed Aug 30, 2006 3:15 am

The twin setup isn't just for the sake of tb size though

It means I also get a better flowing plenum made, faster air speed from 2 smaller throttle bodies, shortened runners and getting rid of the butterflies in the runners