16v or 8v turbo?

[amalventano1@comcast.net (Allyn)]

okok, heres what i mean.
    by running lower c/r, you can run higher boost, meaning the engine draws in more (mass) of air
on each stroke. the lower c/r means lower multiplication of the absolute pressure coming in, so
since the lower c/r engine is multiplying by a lower factor, there is a lower peak cylinder pressure
in the lower c/r engine (with the same level of boost). the peak cylinder pressure is usually the
limiting factor.
    a (stock) 16v with ~5 lbs boost has approx the same peak pressure as an 8v with ~15 lbs boost.
this is where the ~5 lbs limit comes from for stock 16v turbos. yes the 16v may be flowing better,
but the 8v is still getting much more mass of air (and fuel) in the cylinder per stroke (due to the
much higher intake pressure).

was my rambling worse or better this time? i had just woke up when i wrote that last one.
Al

Allyn Malventano, ETC(SS), USN
87 Rieger GTO Scirocco 16v (daily driver, 180k, rocco #6)
86 Kamei Twin 16V Turbo Scirocco GTX ('it has begun', rocco #7)
86.5 Occo 16v Trailer (dotting 'i's across the country, rocco #8)
87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original clutch, driveshafts, wheels :)


----- Original Message -----
From: "Larry" <rocco16v@netzero.com>
To: "Allyn" <amalventano1@comcast.net>; "Lil B 959" <lilb959@hotmail.com>; <scirocco-l@scirocco.org>
Sent: Saturday, June 22, 2002 9:02 AM
Subject: Re: 16v or 8v turbo?


> Allyn-
>   The way you've worded your reply, it sounds like you are contradicting
> yourself:
> Less c/r ( less pressure) so you can run more boost which equals more
> pressure??
> Please expound on your position...
> ( BTW, you say less c/r lets the engine draw in more air, some listers say
> MORE c/r lets the engine draw in more air.  I say 'don't make no
> difference'.  Picture this: take a single cylinder engine of 100cc
> displacement. On the intake stroke, that engine will theoretically draw in
> 100cc of intake charge. Doesn't matter how much it compresses that charge on
> the next stroke, 2:1 or 10:1, it will only draw in 100cc. Because the
> compression stroke occures AFTER the intake, compression is dependant on
> intake, intake is NOT dependant on compression.  To say otherwise would be
> like saying the position of the throttle pedal is dependant on the engine
> output, when it's the other way around.  Follow?)
>
>  Bryson-
>   Regardless, the only way to make more power is to move more air/fuel
> through an engine. Period.
> A 16v engine will move more air/fuel (all else being equal) than an 8v,
> because it has more valve area.
> Therefore, the 16v has more POTENTIAL than the 8v. In all practicality, for
> street use the 8v would probably be the best choice when you factor in 'bang
> for the buck'.
>
> Larry
>
> ----- Original Message -----
> From: Allyn <amalventano1@comcast.net>
> To: Lil B 959 <lilb959@hotmail.com>; <scirocco-l@scirocco.org>
> Sent: Friday, June 21, 2002 7:01 PM
> Subject: Re: 16v or 8v turbo?
>
>
> > ok, heres the deal. the more air you can get in there, the better (read:
> more torque/hp). lower c/r
> > means more air (mass) can come in (i.e. more boost). the reason that more
> can come in is that the
> > lower c/r engine wont try to compress it as much, so you are keeping
> in-cylinder peak temps within
> > reasonable numbers. this lets you have more boost without doing crazy
> stuff like water
> > injection/massive intercoolers/race gas.
> > ...so that leaves the best bet being the 8v. the 16v is actually better
> suited to the task (and
> > breathes alot better), but to use it you have to drop the c/r (either by
> spacing the head or forged
> > pistons).
> >
> > p.s. dont forget the big injectors :)
> >
> > Al
> >
> > Allyn Malventano, ETC(SS), USN
> > 87 Rieger GTO Scirocco 16v (daily driver, 180k, rocco #6)
> > 86 Kamei Twin 16V Turbo Scirocco GTX ('it has begun', rocco #7)
> > 86.5 Occo 16v Trailer (dotting 'i's across the country, rocco #8)
> > 87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original clutch,
> driveshafts, wheels :)
> >
> > ----- Original Message -----
> > From: "Lil B 959" <lilb959@hotmail.com>
> > To: <scirocco-l@scirocco.org>
> > Sent: Friday, June 21, 2002 8:30 PM
> > Subject: 16v or 8v turbo?
> >
> >
> > >
> > >
> > > Hey I was wondering if I should go for a 16v or 8v turbo?  I know the 8v
> has
> > > a better compression ratio for a turbo, but if I ran less boost with the
> 16v
> > > would it be better than running more boost with the 8v?  Any information
> > > would be helpful.  Thanks,
> > > Bryson
> > >
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