Article 41673 of rec.autos.makers.vw.watercooled:
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  From: apotter@elk.uvm.edu (Alexandra S)
  Newsgroups: rec.autos.makers.vw.watercooled
  Subject: Re: Turbodiesel intercooler
  Date: 10 Nov 1996 03:20:16 GMT
  Organization: EMBA Computer Facility, The University of Vermont
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  Jake Russell (jaker@u.washington.edu) wrote:
  
  : But there are still some problems: * Will it be necessary to modify /
  : replace wastegate to increase boost pressure to compensate for intercooler
  : pressure loss?  
  
  There is no pressure loss introduced with an intercooler,  a (very) 
  slight lag from the extra piping perhaps, but no pressure loss.  
  
  * Will the fuel enrichment device on the fuel pump still
  * : work satisfactorily or require modification / new part?
  
  Since it works from boost PSI which will stay the as it's tied to the
  wastegate, this should not require modification. 
  
  : I have heard that the difference in hp goes from 68 w/o intercooler (us) to
  : 80 w/intercooler (euro)  This spec is also with no airflow through the
  : intercooler - hp is higher with increased air velocity due to increased
  : charge cooling, so you looking at a nice hp increase!
  
  The hp increase is due to the calibration of the injection pump.  Hp does
  not increase with airflow across the intercooler unless the engine has an
  electronic control system that can discern when the engine is receiving
  more air (not boost) and signal the injection pump to provide
  proportionally more fuel.  All increasing air flow alone into a diesel
  (like by adding *only* an intercooler) will do is lower exhaust emissions
  and maybe raise your mpg a tiny bit... 
  
  - Mac
  
  
  
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  From: "Jake Russell" 
  Newsgroups: rec.autos.makers.vw.watercooled
  Subject: Re: Turbodiesel intercooler
  Date: 12 Nov 1996 05:49:29 GMT
  Organization: Microsoft
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  Alexandra S  wrote in article
  <563hlg$76s@swen.emba.uvm.edu>...
  > Jake Russell (jaker@u.washington.edu) wrote:
  > 
  > : But there are still some problems: * Will it be necessary to modify /
  > : replace wastegate to increase boost pressure to compensate for
  intercooler
  > : pressure loss?  
  > 
  > There is no pressure loss introduced with an intercooler,  a (very) 
  > slight lag from the extra piping perhaps, but no pressure loss.  
  
  Actually an intercooler will drop pressure.  Same with each piece of tubing
  and each bend the air charge has to flow through.  The stock VW
  turbodiesel's wastegate gets it's pressure right from the turbo, so it will
  deliver the same about of pressure @ the turbo.  Downstream of the
  intercooler the pressure will be a little lower.  (I've heard that a
  well-designed intercooler system shouldn't drop more than 2 psi)  You have
  an analogy with airflow to electricity, where you increase resistance and
  voltage drops.
  
  > * Will the fuel enrichment device on the fuel pump still
  > * : work satisfactorily or require modification / new part?
  > 
  > Since it works from boost PSI which will stay the as it's tied to the
  > wastegate, this should not require modification. 
  
  Have you verified this by comparing parts?  Or just guessing?  I wouldn't
  be surprised if there's more to it than just adding on the intercooler... 
  The injectors might be higher capacity or have a different breakpoint to
  inject more fuel...  The wastegate could be different (or maybe the same
  wastegate just plumbed differently)  I wouldn't even rule out a different
  injection pump to supply more fuel, or a different turbo enrichment device.
   The turbo enrichment device could be plumbed before the intercooler, or
  could be of different design that would sense post-intercooler charge air
  temperature...
  Ok maybe the charge air temperature sensor is a bit far-fetched, with the
  vw diesel being as mechanical as it is.
  
  > : I have heard that the difference in hp goes from 68 w/o intercooler
  (us) to
  > : 80 w/intercooler (euro)  This spec is also with no airflow through the
  > : intercooler - hp is higher with increased air velocity due to increased
  > : charge cooling, so you looking at a nice hp increase!
  > 
  > The hp increase is due to the calibration of the injection pump.  Hp does
  > not increase with airflow across the intercooler unless the engine has an
  > electronic control system that can discern when the engine is receiving
  > more air (not boost) and signal the injection pump to provide
  > proportionally more fuel.  All increasing air flow alone into a diesel
  > (like by adding *only* an intercooler) will do is lower exhaust emissions
  > and maybe raise your mpg a tiny bit... 
  
  Yes but I would not make the assumption that VW simply added on only an
  intercooler...
  
  Moving the turbo enrichment device to a different place (close to turbo's
  output) might be something to consider.  Assuming charge temperature there
  will be unchanged from the addition of the intercooler.
  
  I have no axe to grind or anything, but I really would like to know all the
  parts which are different on vw's stock intercooled turbo-diesel, compared
  to the stock turbo-diesel.  I think vw might have done more than just added
  on an intercooler.  They sure did change a lot with the addition of the
  turbo!
  
  Jake
  - Turbo-diesel engine swap in progress into '81 Rabbit - replacing normally
  aspirated diesel
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  Jake Russell (jaker@u.washington.edu) wrote:
  : Alexandra S  wrote in article
  : <563hlg$76s@swen.emba.uvm.edu>...
  : > Jake Russell (jaker@u.washington.edu) wrote:
  : > 
  : Actually an intercooler will drop pressure.  Same with each piece of tubing
  : and each bend the air charge has to flow through.  The stock VW
  : turbodiesel's wastegate gets it's pressure right from the turbo, so it will
  : deliver the same about of pressure @ the turbo.  Downstream of the
  
  Yes, but on a system that small it's doubtful that it's anything you'd want 
  to up the wastegate opening pressure for.
  
  : > Since it works from boost PSI which will stay the as it's tied to the
  : > wastegate, this should not require modification. 
  
  : Have you verified this by comparing parts?  Or just guessing?  
  
  Guessing.  All the turbo enrichment device does is limit full fuel until 
  there is sufficient boost to avoid alot of smoke, so it makes sense to me 
  that it's not something that would have to be changed.  The actual 
  calibration of the injection pump is almost certainly different, but it's 
  still probably the same basic bosch VE pump - even the TDI has it.
  
  : I have no axe to grind or anything, but I really would like to know all the
  : parts which are different on vw's stock intercooled turbo-diesel, compared
  : to the stock turbo-diesel.  I think vw might have done more than just added
  : on an intercooler.  They sure did change a lot with the addition of the
  : turbo!
  
  They had to make those changes to keep the turbo from burning it up. There
  are only so many things VW could have done when they added an intercooler
  that would have made a *noticable* difference.  I don't beleive they did
  many of them - it just wouldn't have been worth the effort.  
  
  - Mac
  
  Article 42305 of rec.autos.makers.vw.watercooled:
  Newsgroups: rec.autos.makers.vw.watercooled
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  From: bernie@metapro.com.au (Bernd Felsche)
  Subject: Re: Turbodiesel intercooler
  Message-ID: 
  Organization: MetaPro Systems, Perth, Western Australia
  References: <55v7fu$foi@news.nstn.ca> 
  Date: Wed, 13 Nov 1996 16:23:41 GMT
  Lines: 39
  
  In 
     David Pipes  writes:
  
  >In article <55v7fu$foi@news.nstn.ca>, D C  writes
  >>I understand that a GTD model of the Jetta was made for Europe with an 
  >>intercooler on the turbodiesel engine.
  >>Does it have any effect on engine life?
  >>Does it make much difference?
  >>Can it be added to a '96 Jetta?
  
  Really only worth it on a turbo'd engine.
  
  >I imagine you're talking A2 Jetta. In the UK we had an intercooled A2
  >Golf (the GTD), got one myself. The intercooler should have no bad
  >effect on engine life, lubrication failure of some sort is the diesel
  >engine's biggest nightmare (I know, I bought my 1990 car March/April,
  >drove less than 4K miles and had to have the engine rebuilt - a previous
  >owner had been somewhat careless with servicing, oil changes etc.)
  
  OOPS!
  
  >The intercooler boosts performance of the 1588cc diesel engine to 80hp,
  >up from 70hp, makes a difference but not that much - which is why my
  >engine (now in bits) is having various work done which should see output
  >up around 105-110hp when it's finished, hopefully in the next two weeks.
  
  While it's in bits, see if you can get some advice from Papmahl in
  Germany, if you haven't already. They have more tricks to do on diesel
  VWs than sleeves! 110hp doesn't sound unfeasible. Still not a GTI,
  though it'll probably leave one behind for the first 30 metres of a dash.
  
  >The intercooler, brackets, pipework etc. is available from UK
  >dealerships. You have a '96 model, an A3 presumably - wouldn't the
  >intercooler from the TDI fit?
  -- 
  Bernd Felsche {speaking for himself}
  MetaPro Systems Pty Ltd, 130 Fauntleroy Avenue,
  Redcliffe, Western Australia 6104
  Phone: +61 9 479 3722    Fax: +61 9 479 3720
  
  --------------
  
  Article 55576 of rec.autos.makers.vw.watercooled:
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  From: "Dave Oh" 
  Newsgroups: rec.autos.makers.vw.watercooled
  Subject: Re: Theory: Intercooler = Longer Life (for VW Diesel)
  Date: 11 Feb 1997 21:50:18 GMT
  Organization: The University of Western Ontario, London, Ont. Canada
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  Jake Russell  wrote in article
  <01bc133d$d7239f20$0fef5f80@AJaker.u.washington.edu>...
  > The theory: Intercooling a turbo-diesel extends engine life.
  > 	"The cooler air temperature lowers the cylinder firing pressures which
  in
  > turn reduce the thermal and mechanical loads on the engine. The increased
  > air density resulting from cooler intake manifold air temperature
  increases
  > power 10% and fuel economy approximately 5%. Engine life is extended over
  > that obtained with a non-intercooled turbocharged engine."
  
  The primary function of the intercooler is to reduce the charge air
  temperature and thereby increasing the density of the intake air.  It does
  nothing to reduce combustion pressures or temperature.  Reducing the intake
  air temp from say 80 Celcius to 50 is meaningless when combustion
  temperatures are upwards of 1000 deg.  The quote is somewhat contrary, when
  it says "The cooler air temperature lowers the cylinder firing pressures
  ... [and] the increased air density resulting from cooler intake manifold
  air temperature increases power 10%"
  
  The work done in the cylinder is a function of cylinder pressure alone
  (brake mean effective pressure) and horsepower is a function of torque
  (torque@rpm/5250).  So, what's torque?  It is the force acting through a
  distance, in this instance, distance refers to the stroke.  Force is the
  pressure resulting from expansion of gases in the combustion chamber
  divided by area (cylinder bore).
  
  This bit of thermodynamic theory my mean little to you, but what it says is
  that the company is contradicting itself when it claims that adding an
  intercooler will simultaneously lower cylinder pressure and yet yield more
  power.
  
  As I said in the beginning, where the intercooler does have an advantage is
  that it allows a denser air charge into the cylinders of your TD, and if
  nothing else is done to compensate (ie. increasing the fuel delivery rate),
  it will yield slightly less smoke emissions because the motor is now
  effectively running at a slightly greater excess of air.
  
  Because of the operational differences between the Diesel and Spark
  ignition engines, they react differently to intercooling.  Modern gas
  engines must run at or near stoichiometric mixture ratios in its operation
  for optimum performance-economy ratio, and thus any effective increase in
  the amount of intake air going in will result in an approximately equal
  increase in fuel consumption.  But the result is more power!  I say
  approximately because there are other effects and factors that fundamental
  thermodynamic theory doesn't immediately address:
  
  In contrast, a diesel runs unthrottled and mixture ratios can range from
  about 18:1 at full load to upwards of 100:1 when idling.  Intercooling in a
  diesel, when accompanied with adjustments to fuel delivery rate, will
  increase HP, but it is used primarily for emissions reasons.
  
  To come to a simple conclusion, intercooling, whether in a gas engine or
  diesel, has the potential to increase power, lower fuel consumption, or
  reduce emissions but never all three at once at levels that would be
  meaningful. It certainly does not mean that your TD will last appreciably
  longer with one than without.  Were that so, I trust VW would have done it
  long ago with its first TDs as it does with the current TDI.
  
  > Now it seems to me that the weakest link in the VW TD is the piston
  rings. 
  > If you increase the boost, the piston rings will take the wear.  An
  > intercooler would lower the temp during high boost, which would keep
  engine
  > more "thermally stable," meaning less temperature change as boost
  pressure
  > rises or falls.  This lower, more stable temperature would result is less
  > expanding/contracting of the pistons+rings, and result in less friction +
  > rubbing between the rings and the cylinder walls.  This would extend
  engine
  > life, whereas without intercooler and under high boost coindition, the
  > rings wear more, making them lose their seal quicker, shortening engine
  > life, making blow-by when engine is cold, and making cold-startup less
  and
  > less possible (where engine is cold and max. compression is required.)
  
  Actually, the fact that many VW TDs go for hundreds of thousands of miles
  with the original rings points to me that the factory rings are just fine. 
  I will go as far as to say that there are NO aftermarket solutions yet that
  outlasts the factory part.
  
  Where I've heard of problems is in the TD's head gasket, which is prone to
  blowing (still rare, but more reports of it than other problems).
  
  
  Dave Oh
  Mechanical Engineering II
  University of Western Ontario
  London, Canada