2.3L NG conversion in my 84 4KQ

[Larry C Leung]

Compression can come from the head or the pistons, depends upon the
engine designer. It's easier to get it from the pistons, however.
Displacement comer from the from the bore of each piston x the stroke of
the crank (i.e. piston swept area x bore), the compression ratio is based
upon the total combustion chamber volume  @  BDC - total combustion
chamber volume  TDC - the displacement of the engine. Any change in the
head or top of the piston to modify (reduce) the combustion chamber
volume will change (increase) the combustion. Different head shapes
(wedge, hollow dome (hemispherical), flat) do different things to the
intake charge, different piston top shapes, (same as above and raised
dome, which increases compression by removing combustion chamber volume)
also are done to change the path of intake charge under compression, or
change the overall compression. As a point of fact, the turbo I-5 10V
engines use a hemispherical (hollow dome) piston top to reduce
compression. Too bad that, in order to maintain combustion chamber
volume, intake charge flow characteristics, and heat and combustion force
characteristics, they ended up raising the edges of the piston, making
the engine have interference with the valves should the timing belt
break. Without the raised edges (and dished piston tops) on the N/A
engines, they (10V) are non-interference, even in the higher (10:1)
compression versions. Lucky you!

LL - NY 

On Wed, 18 Jul 2001 11:08:38 -0400 "Swann, Benjamin R.  (BSWANN)"
<BSWANN at arinc.com> writes:
>Javad and all ye experienced engine swappers,
>
>I may be wrong, but I coulda swore that the higher compression came 
>from the
>head, but don't have the info. in front of me right now, and of course 
>may
>have been given incorrect information previously.  
>
>Can anyone else verify what Javad is saying.  
>
>I'm not trying to refute, or prove anyone wrong on any of this.  Only 
>that
>this would be new information for me, and would to possibly change 
>some of
>my engine swap strategies, both now, and in the future.
>
>Question again is:  In the NG/NF engine setup, does the higher 
>compression
>come from the Block and Pistons, or from the Head, or is it a 
>combination of
>the two?
>
>Again, I'm not trying to prove anyone wrong, and I admit have given 
>some
>bogus information on this list before, and always like to set the 
>record
>straight.  This is a great way to learn, and sometimes is hard to 
>swallow if
>you give or go on incorrect information, so I'd appreciate to get 
>some
>confirmation on the answer to this question.
>
>Thanks,
>
>Ben
>p.s. sorry to keep all of the prior posts with this reply, but I think 
>it is
>important to understand what we have been discussing..
>-----Original Message-----
>From: JShadzi at aol.com [mailto:JShadzi at aol.com]
>Sent: Wednesday, July 18, 2001 10:56 AM
>To: BSWANN at arinc.com; mdg3369 at altavista.com
>Cc: quattro at audifans.com; ReD4000QuATTRo at aol.com
>Subject: Re: 2.3L NG conversion in my 84 4KQ
>
>Ben, you are mistaken, the combustion chambers are identical (29cc), 
>the 
>compression bump comes from the pistons ONLY.
>
>Audi engineers had a lot of reasons for going to the CIS-3 setup, but 
>
>increased hp really had nothing to do with it.  The HP increase came 
>with
>the 
>NG bottom end, the CIS-3 is a more advanced version of CIS offering 
>knock 
>sensing, maps for the timing curves, diagnostic output tests, higher
>capacity 
>fuel meter with higher system pressure, transistorized ignition coil, 
>etc.  
>These are mostly saftey measures to make the newer cars more "idiot 
>proof" 
>because of the high compression and possibilities for knocking and
>detonation.
>
>Peymon's car is worth a few grand at the most, he will now run 92 
>octane,
>and 
>for less than $1k he now has a basically brand new engine compartment. 
> This
>
>all after spending maybe 20hrs prepping and building the motor, and 
>one 
>weekend to swap it in, the result -I would estimate 140hp and a 0-60 
>of
>about 
>7.5 sec, not bad.
>
>HTH Ben, good luck with your projects.
>
>Javad
>
>In a message dated 7/18/2001 6:15:25 AM Pacific Daylight Time, 
>BSWANN at arinc.com writes:
>
><< Javad,
> 
> I understood that the higher compression comes from the Head on the 
>NG
> setup, not the Block.  The high compression is largely what buys the
> additional Torque and HP across the RPM spectrum.  Someone correct me 
>if
>I'm
> wrong.  I seriously doubt that the VW/AUDI engineers went through all 
>the
> trouble to modify the 4 and 5 cyl. setups with these changes for such 
>a
> limited return.
> 
> Data Point:  this is similar to two 4 cyl swaps I did on Type 1 
>Scirocco:
> 1) used 1.8l '85 Scirocco/GTI setup with lower compression and CIS 
>with oxy
> and no knock sensor.
> 2) used 1.8l '88 Jetta GLI engine with Motronic setup(I broke out 
>portions
> of the systems to support CIS with oxy) and included the knock
> sensor/ignition portion from the '88 Jetta setup.
> 
> The '85 1.8 8:1 was good.  The '88 1.8 10:1 and knock sensor blew the 
>'85
> setup away.  A 268 cam and Gillette exhaust and header was later 
>installed
> to sweeten it up even more.  
> 
> I had considered putting in a turbo engine and did not for a few 
>reasons:
> 1) The NG motor was available for low cost, and I could have just 
>plopped
> the thing in.
> 2) The Turbo setup requires more retrofitting than just a wiring 
>harness
> swap, including fitting of the Intercooler, and turbo oiling and 
>cooling
> lines, etc.  It was just beyond the scope of what I wanted to do for 
>a
> street car and my very limited time and budget.
> 
> Maybe someday, if my wife doesn't kill me, I'll take on a turbo swap, 
>but
>it
> will probably be in a newer car.
> 
> Anyway, this is just to clarify and verify my sanity that what I am 
>doing
>is
> in order, and that certainly the 2.3 swap you guys did was also.
> 
> Happy Quattroing!
> 
> Ben
>  >>