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Date:         Sun, 17 Oct 1999 16:25:15 +0200
Reply-To:     Per Lindgren <lindgre@ONLINE.NO>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Per Lindgren <lindgre@ONLINE.NO>
Subject:      Re: 1.9 heads on a 2.1 engine? Part II
Comments: To: kenneth d lewis <kdlewis@JUNO.COM>
Content-Type: text/plain; charset=us-ascii

Once again, you can see the piston differences on my web site, at http://members.tripod.com/perlindgren/wbx.html. The 1,9 and 2,1 does not have the same pistons.

PerL 87 Syncro 112i

kenneth d lewis wrote:

> I wrote: > > FWIW let's calculate stroke assuming the heads are the same. > >Bentley only mentions one piston for both engines; 9.4 cm in diameter. > >I come up with a stroke of 7.565cm for the 2.1L and 6.8475cm for the > >1.9L. > > In actuality, calculating stroke is independent of head volume. > As a matter of fact; if pistons, cylinder length and head seal thickness > are the same in both engines the head volume MUST be different. This is > assuming a 9:1 CR in both engines. Since each piston displaces 50cc more > in the 2.1L engine, then that volume must go somewhere for the CR to > remain the same. > Is volume of each head combustion chamber 50cc bigger? I do not > know, I am only theorizing. Lets assume this theory is correct and we > proceed with calculating the CR of a 2.1L engine with 1.9L heads. If the > squish volume is reduced by 50cc we have: > > CR= (525+15.625)/15.625 > > CR=34.6:1!!!!!!!!!!!!! > > This clearly is impossible so some or all of that extra 50cc must > go somewhere. A clue is given on pages 13.44 and 13.45 of the Bentley. It > shows the dish dimensions are different between the two pistons! > Unfortunately they only gives depth measurements and not volume. So our > CR calculations are at a stand still until we have some more data. Anyone > out there have some pistons laying around they can CC? > > Drive Safely & Good Luck > Ken Lewis<Kernersville,NC>86 VW crewcab;60 T-5 Coupe > > On Sat, 16 Oct 1999 00:29:13 EDT kenneth d lewis <kdlewis@JUNO.COM> > writes: > >Roger; > > This is news to me. I thought both heads were the same. The > >Bentley refers to ONE head for both engines. Anyway, here are some > >formulas so you can decide for yourself. First some definitions: > > > >Squish volume= The volume in the cylinder when the piston is at top > >dead center. > > > >Cylinder volume= the volume swept by the cylinder i.e. 2.1L=525cc; > >1.9L=475cc > > > >If memory serves me compression ratio is given by the following > >formula: > > > >C.R.= (Cylinder volume+Squish volume) / Squish volume > > > >Solving for Squish volume I come up with: > > > >Squish volume= cylinder volume/ (C.R.-1) > > > >Assuming a compression ratio of 9:1 in both engine; > > > >Squish volume for the 2.1L= 65.625cc > >Squish volume for the 1.9L= 59.375cc > > > >This supports your claim of approximately 5cc difference between > >heads. Now lets recalculate using 2.1L volume and 1.9L squish volume: > > > >C.R.=(525+59.375)/59.375 > > > >C.R.=9.84:1 > > > >There is one important piece of data we may or may not need to take > >into account; the 2.1L has a longer stoke. So how much of that change > >in squish volume is due to different heads and how much is due to > >different stroke? I will leave that question open for debate. > > > > FWIW let's calculate stroke assuming the heads are the same. > >Bentley only mentions one piston for both engines; 9.4 cm in diameter. > >I come up with a stroke of 7.565cm for the 2.1L and 6.8475cm for the > >1.9L. > > > > That's enough math for tonite, I still have to go out and > >finish installing the relays to boost the voltage to the headlights on > >my transporter. I will mull these figures over and get back with you. > > > > > >Drive Safely & Good Luck > >Ken Lewis<Kernersville,NC>86 VW crewcab;60 T-5 Coupe > > ___________________________________________________________________ > Get the Internet just the way you want it. > Free software, free e-mail, and free Internet access for a month! > Try Juno Web: http://dl.www.juno.com/dynoget/tagj.


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