[s-cars] RE: Good read on cylinder pressure, engine balance, mep bmep etc..

[Richard Tanimura]

Trevor,

When you find interesting articles, can you try and select ones with lots of
brightly colored pictures. I like those the best. I also noticed that the
dotted lines in some of the diagrams, e.g. the 4 cycle combustion pictures,
were not numbered making it very hard to know how to connect them together.
I really had to guess but I think I succeeded.

Rich
  -----Original Message-----
  From: Trevor Frank [mailto:tfrank at symyx.com]
  Sent: den 11 mars 2004 19:08
  To: Audi20V_Kruemmer at yahoogroups.com; s-car-list at audifans.com;
CaptMagu at aol.com; richard at tanimuras.com
  Subject: Good read on cylinder pressure, engine balance, mep bmep etc..



http://www.ceconet.com/actt/actt_main/downloads/Engine%20Balance%20-%20The%2
0Thinking%20Has%20Changed.pdf



  Ok this is a really good read on the subject and more to the point that I
was looking at, cylinder pressures, mep timing etc and how they relate.





  -----Original Message-----
  From: MLP [mailto:mlped at qwest.net]
  Sent: Thursday, March 11, 2004 7:50 AM
  To: s-car-list at audifans.com; CaptMagu at aol.com; richard at tanimuras.com;
Audi20V_Kruemmer at yahoogroups.com
  Subject: [Audi20V_Kruemmer] FW: [s-cars] I don't understand lowering CR
for boost



  Well, Ok, this ought to expose my ignorance in trying to work
ass-backwards
  to justify the faith / conventional wisdom for arguing on should consider
  dropping stock CR's slightly for added boosted engine performance.  What
do
  you think of this approach:

                  CR                MaxBoost           Effective CR (the
java
  applets say)
  Stock        9.3 to 1          20.0  psi   ~~~>  @ 21.95 to 1

  I know everyone is/wants to run more, in fact a lot more than a paltry
  20psi, but just for arguments sake, lets suppose the above represented the
  practically knock/no-knock limits of your fuel/motor.  Can one then assume
  that, to get to the same CR limit if you started off with, oh for example,
  an

                 8.0 to 1          20.0 psi   ~~~>   @ 18.88 to 1
                 8.0   "            25.6 psi   ~~~>    @ 21.93 to 1

  So, with an 8.0 CR, and an assumed VE of say @ 85% "fill" and ignoring for
  the moment (lets say you just have an awesomely powerfully efficient FMIC)
  any significant temperature differences at the intake manifold in the
  arriving 20psi in the 9.3 CR motor vs. temperature of the arriving 25.6
psi
  for the 8 to 1 CR motor, then

  in Case #1, for the 9.3 to 1 engine, you get to jam some 378 cc's (being @
  85% of a swept cylinder volume of 445 cc's) of 20 psi charge vs. Case #2's
  378 cc's of 25.6 psi air/fuel in the 8 to 1 motor.  Somewhere there's got
to
  be a conversion for psi of air to mass or lbs/air, and assuming the
  temperatures are roughly equivalent, there's got to be a lot more
  combustible O2 in the 26psi air charge vs. the 20psi charge on a cc for cc
  basis.

  Alternatively, one could play with and compare the Ray Hall boost applet
  results at http://www.turbofast.com.au/TFcompB.html  which suggests that
to
  run 20 psi of boost in a motor with a standard CR of 9.3 to one (81mm
bore,
  86.4mm stroke & a VE of 85%) the applet suggests one should be using 118.4
  octane gas.  With a standard CR of 8 to one, at 20 psi the octane
  recommendation drops to 110 gas.  One has to push the boost up to 26+ psi
in
  the 8 to 1 Cr motor to get the anti detonation gas requirement back up to
  the 9.3 to 1 @ 20 psi's 118 recommendation.   Isn't 110 octane vs. 118
  another way of looking at ignition advance?   So again, with the 8 to 1 CR
  one gets to run an additional 6psi of boost vs. the stock 9.3 to 1 CR
motor.

  So, assuming you get your chip map(s) adjusted to your revised base CR,
you
  get to run a lot more boost, with perhaps a bit more advance to make up
for
  power lost in off boost, naturally aspirated mode by dropping the
  compression ratio?  My guess is the major re-mapping must be in the
ignition
  timing area of the ECU's triumvirate, boost v. timing v fuel at rpm/load?

  Minhea?
  Bob P.?
  QShipQ?
  Anyone else got an opinion?

  mlp


  -----Original Message-----
  From: CaptMagu at aol.com [mailto:CaptMagu at aol.com]
  Sent: Tuesday, March 09, 2004 8:11 PM
  To: mlped at qwest.net; richard at tanimuras.com; s-car-list at audifans.com
  Subject: Re: [s-cars] I don't understand



  Mike

  I want the reeeeaaaallllyyyy long answer.

  Hap, dreamin in Evahboost, Maguire



  [Non-text portions of this message have been removed]





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