The best all round velocity stacks for the 20V BT are the ones that came with
the engine from the factory. Toyota will have spent thousands of hours perfecting
the shape and size to be the best compromise between packaging, performance
and acceptable sound level for a general market car. I have not yet seen a report
on an aftermarket stack that can give better all round performance.
Yes... in some cases shorter stacks will give a bit more top end at the expense
of losing a bit of bottom end performance. Long stacks may produce a little more
torque low down only to lose power at high rpm. So why do we use aftermarket
velocity stacks ?? Is it because...
1. They look cool without filters.
2. They promote road safety because people can hear you approaching.
3. They make a cool noise (skank whistle ?).
4. It is easier to use open stacks than build a proper cold air box.
5. You live in a dust free area.
6. They make your car
sound fast.
7. They improve performance.
I have read some detailed analysis of intake/stack design written by people who
get right into the maths and numbers. They can show that for a certain intake
length, rpm, valve timing, exhaust design, etc a certain length of stack will show
some improvement at X rpm and lose a bit at Y rpm. By fiddling with the variables
you can move these plus and minus zones up or down the engine speed range.
And no two engines are exactly alike,
so results will vary. This is why no-one will
come out with a velocity stack design that is guaranteed to improve performance.
Of course, some people will get lucky and buy a stack that actually does something
in the rpm range they use. Others will gain nothing or lose some... luck of the draw.
The nice thing is that you can justify your purchase with one of the other reasons
for putting aftermarket stacks on your car
Cheers... jondee86
