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Re: Anyone have a 2117cc 16V
I'll agree with Allyn's note that decreasing piston speed is good and try to
add a bit of explanation. I'm making this up, but it seems to me like a
good story:
So there's the decreased inertia thing, making decreased piston speed good,
but we can be a bit more specific:
We aren't really talking just about decreased piston speed - the average
speed of the piston will be one stroke per revolution, and there is no
changing that. We are actually talking about decreasing the maximum speed
the piston reaches during its travel. So decreaseing the maximum while
maintaining the average means "smoother" motion, in a sense. Less
jerkiness, less inertia change - good stuff.
Now lets talk about power instead of speed. This is the part I'm not sure
about - haven't thought it all the way through. Maybe this is the same as
saying "less side forces on the piston", maybe not.
If you draw a line through the center of the connecting rod, and extend that
line past the crank, the amount of torque transmitted to the crank (which is
the point of an engine, right?) is the force of the crank times the distance
between the line of action (the line we drew through the con-rod) and the
center of the crank. So at TDC, the line of action goes right through the
center of the crank and no torque can be created, no matter how hard you
push on the con-rod. Now, if the crank is at 90 degrees to the con-rod,
then the most torque is created for the force on the con-rod. If we had an
infinately long con-rod, then the rod could be at 90 degrees to the crank,
and at the same time 90 degrees to the face of the piston, and 100% of the
force on the piston face would be turned into the most torque possible. So
an infinately long con-rod would be nice.
I guess my point is that that sideward force on the piston is bad because it
can damage the cylinder and piston, but it also is a side-affect of the
inneficient motion of the con-ron/piston/crank assembly. That inneficiency
robs power. Nuf said.
>From: "Allyn" <amalventano1@home.com>
>To: "Randy B" <sirocco@telocity.com>, "chris jevens"
><rocco1987@hotmail.com>
>CC: <scirocco-l@scirocco.org>
>Subject: Re: Anyone have a 2117cc 16V
>Date: Wed, 31 Oct 2001 20:53:38 -0500
>
>Randy,
>Piston speed is not important, the volume is. If the storke is shorter but
>the bore is larger, it all balances out. Actually, getting piston speed
>DOWN
>is the key to high performance engines.
>Indy cars have very shallow strokes, but big bores. This enables >10k rev
>limits.
>Al
>
>Allyn Malventano, ETC(SS), USN
>87 Rieger GTO Scirocco 16v (daily driver, 170k, rocco #6) running - for now
>87 Jetta 8v Wolfsburg 2dr (daily driver, 260k, 0 rattles, original clutch,
>driveshafts, wheels :)
>
>----- Original Message -----
>From: "Randy B" <sirocco@telocity.com>
>To: "chris jevens" <rocco1987@hotmail.com>
>Cc: <scirocco-l@scirocco.org>
>Sent: Wednesday, October 31, 2001 8:37 PM
>Subject: Re: Anyone have a 2117cc 16V
>
>
> > Chris,
> > Thanks for the info :)
> >
> > Hmmm.....
> > But wouldn't the taller block create slower piston speed and therfore
>less
> > power?
> > My basic understanding is that with a smaller angle (piston further from
>the
> > centerline of crank) the speed of the piston in it's down stroke, at
>90*,
> > and it's upstroke, at 270* would be slower, pulling in less air (or
>pulling
> > it in at a slower velocity). There would also be less compression
>because
> > less air is being compressed.
> > Am I even remotely correct in these assumptions???????
> >
> > The taller block would be smoother (probably why VW went to the taller
> > setup) because of less side-load on the pistons and smaller angles for
>the
> > movement of the 'system' to overcome. Again does this make sense?????
> >
> > Also, isn't rev-ability mainly a function of airflow and/or port
>velocity?
> >
> > Thanks
> > Randy (wishing he had paid attention in physics class)
> >
> >
> >
> > > Randy I have been curious about the same type motor. I have been
>talking
> > to
> > > a couple people from Velocity sport tuning... they have been a lot of
>help
> > > to me in the past, and I have found them to have a lot of truth to
>what
> > they
> > > say. The BS is at a minimum. They recommend the use of a tall block
>from
> > the
> > > later 2.0 8v crossflow motors that seemed to have taken place of the
>16v
> > > 2.0.
> > > This would be:
> > >
> > > -95.5 crank (lightening of course, possible knife edging)
> > > -160mm connecting rods (check the EIP website they have chromoly,
> > > forged, and titanium)
> > > -pistons? I havn't gone that far, but for this application I guess
>they
> > > would custom... again Velocity has them.
> > > As far as the ratio of bore to stroke... I was told by Velocity that
>using
> > > the other older block(9A) from the later 2.0 16v motors of the early
>90's
> > > you wouldn't be able to spool all the way up to red line... how true?
>I
> > > havn't had a chance to go any further with it... though they said they
> > have
> > > done the combination 95.5/160mm rods/Bore?(didn't ask)/tall block from
>a
> > 2.0
> > > 8v, and had great success with it working ridiculously well through
>the
> > > whole power band... sounds good to me... $$$ value?? maybe it would be
> > > cheaper to go to a turbo?
> > >
> > > well I hope that helps you in your quest for power/speed...
> > > chris jevens
> > >
> > > >From: "Randy B" <sirocco@telocity.com>
> > > >To: <scirocco-l@scirocco.org>
> > > >Subject: Anyone have a 2117cc 16V
> > > >Date: Wed, 31 Oct 2001 16:45:09 -0800
> > > >
> > > >Has anyone built, or know someone who has, a 2117cc 16V (or 8V for
>that
> > > >matter).
> > > >I would like to find someone who has tried this succesfully or
> > unsucesfully
> > > >and why.
> > > >
> > > >JE (other?) 84mm forged pistons, Carillo (other?) forged rods, and
>95.5mm
> > > >TDI forged crank (knife-edged to lighten) in a 9A block (16V)
> > > >
> > > >I am considering finding a 90-92 GTI and doing a complete
> > > >motor/fuel/motronic swap.
> > > >It seems if I can:
> > > >A. B. Have the head flowed and ported as needed for the proper port
> > > >velocity.
> > > >C. Match th correct cams
> > > >D. Run ~11.2:1 compression
> > > >
> > > >I could have a monster of a motor with good streetability.
> > > >
> > > >What do you all think, need some advice here :)
> > > >
> > > >Thanks,
> > > >Randy
> > > >81 Scirocco S "Mars" - needs a bigger motor
> > > >81 Scirocco S "Cosmos" - will get the TT 1847cc 8V for daily duties
> > > >
> > > >
> > > >--
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