Re: OEM 16v throttle body?

[Brett Van Sprewenburg <brett@netacc.net>]

> I have a 50mm throttle body on the Scirocco I just bought.  I 
>thought ya'll said they all had ~42mm bodies, and that the only 50mm 
>ones are Audi 5000 stuff.  So did someone replace the throttle body 
>for me, or do all 16v's have 50mm and only the 8v's have 40 or 42mm? 
>If the 16v's have 50mm's, then why do people use Audi 5000 throttle 
>bodies instead of 16v thorttle bodies when upgrading to 50mm?
>
>Querilously yours;
>
>Brian Haygood
>

It's not the throttle body that people are talking about when they talk
about '50mm'.  It's the intake manifold diameter, as in the 16v only
intake tubes that run over the cam cover and turn down into the front
of the cylinder head.  The stock USA scirocco 16v ones have a 40mm cross
section, many 2L's (Passats especially I guess) have a 42mm unit, and
the Europeon specification 16v's of that era had a 50mm diameter set up.
Many people switch to the 50mm units to increase airflow, and I encourage
as many people as possible to do it because it means I'll be able to spank
their ass all the way to what-ever speed that matters with my 40mm intake. :)
Ah, the reason would be that the 50mm manifold reduces intake velocity at
lower rpms, and engine volumetric efficiency accordingly.  Nothing beats
the 50mm intake for racing though, but for zooming from light to light,
and sub 5700rpm driving, the 40mm has got it all over.  Get someone that's
got a tuned 2L 16v with a 50mm and ask them how soft the engine response
is in 'normal' driving, and try to get them to answer honestly.  Don't
even bother talking to the poor people with a 50mm manifold on a 1.8L
16v, they're in a sad place already IMO... :-)

==Brett

 \/  '84 Scirocco (ITB racer 2B) | "Hot VW's, take two home. They're small"
\/\/ '88 Scirocco 16v (Show), '92 Passat 16v (Winter+) | - brett@netacc.net

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