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16v or 8v turbo?

Subject: 16v or 8v turbo?
From: amalventano1@comcast.net (Allyn)
Date: Sat, 22 Jun 2002 21:15:05 -0400
References: <F442ROONwIidWZe2BS700003162@hotmail.com>
cause im dropping the c/r to that of an 8v. that way i get the better VE of the 16v with the higher
boost allowed with the lower c/r.
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: "Michael Abatzis" <abatzis2@hotmail.com>
To: <scirocco-l@scirocco.org>
Sent: Saturday, June 22, 2002 8:34 PM
Subject: Re: 16v or 8v turbo?


> then why are ya using 16v's for the twin?
>
> >From: Allyn <amalventano1@comcast.net>
>
> >ok, now that requires a slightly different explanation.
> >     BMEP is the MEAN pressure, i.e. the average pressure. for this you
> >have to picture whats going
> >on during the combustion process. you cant simply consider the peak
> >pressure, you must consider the
> >pressure maintained during the combustion stroke. after all, the peak
> >pressure at tdc is doing
> >effectively no work at all (picture bicycle pedal at tdc). as the piston
> >moves downward, the effect
> >is a pressure drop (naturally). combustion continues well beyond tdc, so
> >combustion keeps the
> >pressure up, acting against the pressure drop. this results in a large
> >pressure being maintained 90
> >(crank) degrees beyond tdc (pedal parallel to ground). it is that pressure
> >that is doing the work
> >for you, ultimately resulting in high BMEP numbers.
> >     now lets go back to the 8v vs 16v stuff. keep in mind i am talking
> >stock engines (with added
> >turbos) in both cases. previously we established that we had to limit peak
> >pressure (at tdc) by
> >using lower boost on the 16v. another aspect of the peak pressure to
> >consider is that spark occurs
> >before tdc, so your calculated peak pressure is actually lower than the
> >actual peak that the engine
> >sees. what this peak is actually accomplishing is detonation, since the
> >air/fuel has had so much
> >energy (pressure) added to it that it all detonates at once. this results
> >in extreme pressure spikes
> >(~1500 psi), causing ring lands to go poof and pieces of pistons to go
> >byebye.
> >     oops, started getting off track there. ok. here, i'll make it simple.
> >
> >- 16v: higher c/r, therefore lower boost, therefore lower mass of air in
> >cylinder.
> >- 8v: lower c/r => higher boost => more mass of air in cylinder => more
> >fuel to burn => more
> >combustion => higher pressures maintained at/through the 90 degree mark =>
> >higher BMEP numbers =>
> >more torque => more hp.
> >
> >hope that straightens some more stuff out for ya :)
> >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 5:47 PM
> >Subject: Re: 16v or 8v turbo?
> >
> >
> > > Al-
> > >   Either you were more awake, or I was, since your second explanation
> >was
> > > much clearer to me.
> > >
> > > However, since Brake Mean Effective Pressure (BMEP, or the 'peak
> >pressure' I
> > > believe you're speaking of) is the true indicator of power (torque,
> > > actually, put for simplicity's sake we'll call it just 'power'), it
> >sounds
> > > like the 16v would be the engine of choice, since it will (with 5 lbs
> >boost)
> > > produce the "the same peak pressure as an 8v with 15 lbs of boost."
> > > Aaarrrgghh, I'm getting more conFUSED!!
> > >
> > > Larry
> > >
> > >
> > >
> > > > 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
> > > > > > >
> > > > > > >
> >_________________________________________________________________
> > > > > > > MSN Photos is the easiest way to share and print your photos:
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References:
- 16v or 8v turbo?
  - From: abatzis2@hotmail.com (Michael Abatzis)
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