[Vwdiesel] EGT temps and max temp for a TDI

[dieseltdi at earthlink.net]

>
> I'd heard 100 F drop across the turbine.  It seems it'd be closer to nada
> than 100 but better safe.  It stands to reason there should be a temperature
> drop across the turbine.  Laws of conservation of energy would dictate it.
> I've just never looked up the formulas and done the math to see how many
> degrees it would actually be.  The higher the boost the larger the drop,
> would make sense.  So maybe it's ~100F max?
Actually there is a formula that indicates that once the exhaust and turbo
reach operating temp, it takes alot more heat to cause them to heat up more.
The idea is that when you are cruising at highway speed, then temp preturbo
and postturbo are almost identical.  I don't beleive that it really makes
any difference on the boost except that from my experience watching the egt
there is an instantaneous response under heavy load and acceleration.  So we
can't be moving much across the turbo.  I can go with 100degrees F but that
is probably high.
>
> Our 1.5 and 1.6 engines are listed at 1300 or 1350 as I recall so that's
> good for almost 1200F downstream.  I'd expect the TDI to come in at the
> same specs or slightly higher but not enough higher to count.  The only
> reason I'd see it being lower is different metallurgy (doubtful it would be
> of lower temperature tolerance) or if an IDI burns cooler in the cylinder
> than a DI diesel.  I'd actually expect an IDI to have higher internal
> temps than a DI.
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 don't
know!  Somebody must have a tech paper on the tdi that spells this out.
>
> Dude!  Go 3 inch!  At LEAST do 2 1/2 inch.  I've always said 2 1/2 for the
> 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 a
real pinch point.  It is also alot more difficult for the local muffler shop
to make some of the funky bends of the system.  The aftermarket people have
computer comtroled machines that do the bending.

>
> 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 down.


> 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 psi
> 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 sprayer
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.

Thanks for the ideas.  I will probably try them all.  hayden

-- Visit my homepage at http://home.earthlink.net/~dieseltdi
    2002 Jetta Wagon GLS TDI
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