[Diy_efi] Throttle body size

[Ron Schroeder]

Hi Adrian,

TB size is based on engines needed intake airflow requirements, as you
guessed, not by the engines displacement.  a small high reving engine would
use the same TB size as a larger low reving engine assuming they were both
about the same HP.  So look for a TB from an engine of similar HP to what
you are building rather than one from the same displacement.

Just a ballpark, a 2bbl 50mm would be a good starting point.  When I EFI'd
my engine, I replaced 2 - 36mm 2bbl carbs with 2 - 32mm 2bbl TBs and still
got 10%+ more power and a LOT better throttle response.

Ron Schroeder
WD8CDH
day 631 344-4561
nite 631 286-5677


----- Original Message -----
From: "Merchant, Adnan" <Adnan.Merchant at TycoHealthcare.com>
To: <diy_efi at diy-efi.org>
Sent: Thursday, December 12, 2002 12:56 PM
Subject: [Diy_efi] Throttle body size


> Hi,
>
> This is a subject that's been covered before so my apologies in advance.
>
> How does one determine the correct size for a throttle body for an engine?
> Flow rate is the most logical parameter but the few data points I have
from
> production engines only serve to confuse.   Here's what I've found so far:
>
> Honda 2.0 non-VTEC: 55 mm
> BMW 3.5 (M30): 65 mm (nominal, since it's tapered)
> Mustang 5.0: 65 mm, 70 mm
> Mustang 4.6: 70 mm
>
> My application is a 3.0 straight six, normally aspirated, plenum style
> intake.
>
> Any suggestions on how to figure out the right size?   The original carbs
> were twin SU, 2" throats.
>
> Thanks,
> Adnan
>
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