It Howls with small throttle bodies

[Jeremy Pronk]

On Wed, 30 Oct 1996, tom cloud wrote:

> Now I'm confused....  With my limited knowledge and cranial ability,
> I thought that throttle size had little effect on FI.  I can see that
> a larger TB gives less velocity and therefore less momentum and
> mixture of the fuel/air, but can anyone 'splain to this ole boy
> how to determine a TB size (talking normally aspirated).

Ok, to my understanding a "stock" type car has throttle bodies optimized
for nice city driving (ie good power down low). Now if you increase this
size heaps, the velocity of air in the throttle bodies is very low at low
rpm because of the venturi? effect. But at high rpm's the car should have
an advantage (along with other mods) of being able to suck in more
air/fuel because of the greater tb size (thats what I was saying). I didnt
put the 45mm's on, but I want to choke them down a bit to increase low rpm
velocity and there fore low speed drivablity. Please correct my if I am
wrong. If there is a formula to calculate the size, please say so (the car
used to run carbies).

(sorry if this is to far off topic)


regards,

Jeremy, Sydney AUSTRALIA 
http://www.st.nepean.uws.edu.au/~jpronk/
'83 AlfaSud Ti (Haltech E6 efi)