[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

HELP!! Need pistons questions answered ASAP



You mentioned wanting to go turbo in the future.  Your piston selection
should reflect that.  With a 10.5 compression ratio, you're looking at a
VERY mild turbo setup - one that I would argue is not worth the expense
in terms of 'bang for buck'. 

If you're going forced induction, buy the proper stuff NOW - if not
you'll probably be kicking yourself later...  You might want to consider
dropping the compression ratio to around 9:1.  This will allow decent
(but not optimal) off boost performance, and allow you to run much more
boost (how much, I dunno, but 12-15 psi should be obtainable if you
incorporate an efficient intercooler).  Of course there are ways of
getting more boost (even with that same c/r), but I'm under the
impression that you're after a solid, fast, daily driver type engine,
not a highly stressed racing motor that's tuned to the ragged edge of
self-destruction...  Definitely do some research into what compression
ratios you can run reliably with different boost levels and try to find
that happy medium between driveability/reliability and power...

As for pistons, many people run mild to medium boost levels with good
quality cast pistons (stock VW/Audi pistons being a good example)
without issue.

Regarding forged pistons, times have changed.  There are forged pistons
out there that only need an extra half-thousandths of an inch (.0005")
clearance compared to a cast piston.  Piston slap associated with forged
pistons isn't always the issue it once was.  I'm sure not all forged
pistons are created equally though, so again, some research here will be
your best friend.  Some brands (probably the cheaper ones) will need
more clearance, and will most likely exhibit cold running piston slap.
I'm sorry I can't offer you specifics for VW/Audis as most of my engine
rebuilding experience was on domestic stuff.  Please share your findings
though, as I'll hopefully need the same information before long when I
start my forced induction engine project...

My suggestion would be to get all your options researched and out in
front of you.  Forged pistons are inherently stronger and able to handle
boost without question.  If a good quality forged set isn't out of your
price range, you might want to consider them.  You'll have more options
in the future when you get bored of the power (and you will!), and you
might not feel as guilty beating on the engine knowing you have kickass
pistons in there that will handle some abuse.  Like you said, you only
want to do this ONCE.

Decisions, decisions...  :)

Mark.
75
80 S
81 S  2.0 ABA/JH/4K







  

> -----Original Message-----
> From: scirocco-l-bounces@scirocco.org [mailto:scirocco-l-
> bounces@scirocco.org] On Behalf Of stetson
> Sent: April 16, 2004 3:53 PM
> To: David Utley
> Cc: scirocco list
> Subject: Re: HELP!! Need pistons questions answered ASAP
> 
> Yes that's true.....sorta.
> 
> I want to do this once, the 3A swap is this seasons planned upgrade
and I
> want to do it right. I want to be able to jump up and down
(figuratively
> and literally) on this engine and have it grin back @ me saying, "Is
that
> all you've got?"
> 
> Next season might be (Depending on finances, availablity, the weather,
> etc.) TURBO time (even if just for the 5PSI I can get away w/. Perhaps
I
> should be looking @ a lower compression piston as well).
> 
> But this being the case, bottom line is that I need a 83mm dia. piston
> that has compression between 10.5:1 and 8.5:1 for a 144mm rod (I'm
sure
> there are other considerations that I'm just too thick to appreciate @
the
> moment that have direct and serious implications.) w/ rings and maybe
> wrist pins and circlips.
> 
> I would prefer hyper-whatzis ones but will gladly acccept forged.
> 
> Explaining thing w/ the depth and understanding that spawns phrases
like,
> "The mud was like wet dirt",
> 
> Tim
> 
> <LIM> mmmm, multitextured donuts....
> <knghtbrd> LIM: with fruit filling?
> <LIM> knghtbrd: chocolate cream...
> 
> On Fri, 16 Apr 2004, David Utley wrote:
> 
> > I might be able to offer some ideas, and although I cringe at the
> thought of
> > another debate, -BUT-, why do you want to go forged?  If you are
> planning on
> > doing something extreme in the future (IE, turbo+nitrous), then I
might
> could
> > understand.  If I have my facts straight, forged pistons tend to be
hard
> on
> > rings even after they are fully warm.  If you were racing, this
would
> not
> > matter, but I am under the impression this was for a quick DD?
> >
> > Cheers,
> >   David Utley
> >
> > Quoting stetson <tim@unrealexpectations.ath.cx>:
> >
> > > K then,
> > >
> > > A rather demanding topic I know...but I'm under the gun here.
> > >
> > > So....as you know, the 3A is in the shop where it was granted a
clean
> bill
> > > of health for just about everything EXCEPT the cylinder bore.
> > >
> > > That needs to be milled .50mm over stock.
> > >
> > > This means I need new pistons (the shop will not bore w/o them in
> hand). I
> > > would like to get some nice hypereutetic <sp?> or forged and the
only
> > > place I'm finding for them is Autotech for........
> > >
> > > $750 !!!!!!!!!!!
> > >
> > > YEA GODS AND LITTLE FISHES!!!!!!!!!
> > >
> > > Right now for block cleaning, tolerence checking, magnafluxing,
and
> boring
> > > it's costing me $260 +tax. This means if I can find a cheaper
piston
> set I
> > > could perhaps get it blueprinted and balanced.
> > >
> > > I want to do this to this engine ONCE, no more. The engine may not
> stay w/
> > > this Roc but I want to have a known, proven, hardened engine @ the
end
> of
> > > this fiscal blood letting that I KNOW is good.
> > >
> > > I have Dave @ Adirondack checking into pistons for me right now
> (Potter
> > > can't get 'em) but will appreciate any and all info or
recommendations!
> > >
> > > Are there any pistons from a ABA or 2.0 16v that could be used in
it's
> > > place? Weisco's site has them listed that seem to have the same
> diameter I
> > > need (83mm) and the right rod length I need (144mm) and the right
> > > compression (10.4-10.5).
> > >
> > > Any thoughts Uber-Dubbers?
> > >
> > > Burning up my mail accounts quotas,
> > >
> > > Tim
> > >
> > >
> > > New York is a jungle, they tell you.  You could go further, and
say
> that
> > > New York is a jungle.  New York *is a jungle.*  Beneath the
columns of
> > > the old rain forest, made of melting macadam, the mean Limpopo of
> swamped
> > > Ninth Avenue bears an angry argosy of crocs and dragons, tiger
fish,
> noise
> > > machines, sweating rainmakers.  On the corners stand witchdoctors
and
> > > headhunters, babbling voodoo-men -- the natives, the jungle-smart
> natives.
> > > And at night, under the equatorial overgrowth and heat-holding
cloud
> > > cover, you hear the ragged parrot-hoot and monkeysqueak of the
sirens,
> > > and then fires flower to ward off monsters.  Careful: the streets
are
> > > sprung with pits and nets and traps.  Hire a guide.  Pack your
> snakebite
> > > gook and your blowdart serum.  Take it seriously.  You have to get
a
> > > bit jungle-wise.
> > > -- Martin Amis, _Money_
> > >
> > >
> > >
> > > _______________________________________________
> > > Scirocco-l mailing list
> > > Scirocco-l@scirocco.org
> > > http://neubayern.net/mailman/listinfo/scirocco-l
> > >
> >
> >
> >
> > David Utley
> > -----------
> > Cable Volkswagen
> > 405-470-3129
> > 1-800-522-6793
> >
> 
> 
> _______________________________________________
> Scirocco-l mailing list
> Scirocco-l@scirocco.org
> http://neubayern.net/mailman/listinfo/scirocco-l
> 
> ---
> Incoming mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.655 / Virus Database: 420 - Release Date: 08/04/2004
> 

---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.655 / Virus Database: 420 - Release Date: 08/04/2004