[Vwdiesel] EGT temps and max temp for a TDI

LBaird119 at aol.com LBaird119 at aol.com
Mon Sep 9 01:35:43 EDT 2002

> My guess is that overall operating temps on the tdi are lower than the idi
>  engines.  What with lower compression ratio and all.  The problem is I
>  know!  Somebody must have a tech paper on the tdi that spells this out.

  I'd sure think there'd be an SAE paper on them but I've sure never heard
anybody pipe up about finding one.  Maybe someone knows where to look
for them?
>  >
>  > Dude!  Go 3 inch!  At LEAST do 2 1/2 inch.  I've always said 2 1/2 for
>  > 1.6 TD and Jake scoffed at the idea.  He had a 2 inch Techtonics system.
>  > He finally did change it and could feel the difference.  He now agrees on
>  > the 2 1/2 inch size.
>  The problem with the A3 is the path of the pipe over the rear axle.  It is
>  real pinch point.  It is also alot more difficult for the local muffler
>  to make some of the funky bends of the system.  The aftermarket people have
>  computer controlled machines that do the bending.

  I guess I'm spoiled.  Our local muffler shop never complains about
intricate bends.  They just consider them a place to show off their
skill!  :)  How about using 3 inch as far as you can and choking to
as large as you can get away with over the axle?  I personally think
something on the order of a 2 cycle expansion chamber arrangement
is what would work best.  Something big to dump into but it really doesn't
need to be as big by the rear of the car.  It's usually just simpler to stay
one size, unless space constraints don't permit it.
>  >
>  > These might help underhood temperature but will do nothing for the EGT
>  > unless you're sucking underhood air, which you shouldn't be.  If you were
>  > then expect a 1:1 drop for intake to exhaust temperature.
>  The fan I installed pulls cool air from the front of the compartment and
>  channels it using some flexible duct work over the exhaust manifold and
>  turbo.  I have actually considered taking some copper tubing and wrapping
>  the exhaust manifold and running coolant through it to help keep temps

  Just be sure you're pulling fresh air into the intake. Other than underhood
temps there is no benefit to cooling the exhaust system other than letting
the turbo cool down before shutting it off.  You'll only end up adding heat
load to the radiator, which in turn will raise under hood temps.
>  > My uncle always used water spray on his van.  You'll see a 1:1 drop in
>  > temp from one.  Of course you want a fine nozzle or a BIG water supply.
> )
>  > Checking your intercooler efficiency would be helpful here.  Compare
>  > your ambient, pre intercooler and post intercooler temperatures.  If your
>  > exit temp is still well above ambient, more intercooler would be the most
>  > efficient step.  without VNT I'd guess 20psi would see CHT around 400
>  > degrees or more!  Jake was seeing well into the 200's F with almost 10
>  > best as I can remember.  That was with mid 50 F ambient as I recall.
>  Does your uncle inject the water into the intake stream or is he just
>  spraying the intercooler.  What I had in mind was to rig a fine mist
>  in front of the intercooler and using in only during heavy load.  Would
>  probably mix in some alcohol to help drop the temps even more.

  He used it on the exterior.  Had 3 or 4 nozzles that sprayed across the
radiator for when he was pulling his trailer.  He was sometimes nearly
paranoid fanatical about things.  Of course he drove truck since he was
in his early teens.  Too bad he's gone now.  :(
>  Thanks for the ideas.  I will probably try them all.  hayden
  Keep us updates on how it all pans out.  Dad's wanting more oomph for
his Passat.  It's nice on an empty road but with a car full and cars to
pass with hills, it's not quite as jumpy as would be nice.  He's thinking
Wetteraur (sp) I presume it's the hands down favorite?  Better mileage
would be a nice plus also.  He's only getting a fairly consistent 48 mpg
now.  ;-)

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