[Vwdiesel] More Power From Insulation (Science Again)
mark at shepher.fsnet.co.uk
Sun Feb 13 20:30:37 EST 2005
Ok it's not the weekend (for me now) but this science thread
is not entirely OT
A few weeks ago I queried whether we could 'insulate' the
piston face and ignition chamber to reduce some of the 30%
energy losses to the coolant.
Loren kindly pointed me to a site that provides coatings for
But quite frankly I was disappointed with what their site
was showing in terms of enhances in performance. The % gains
(if any) were minimal. I found the graphs very superficial
and didn't show thickness of coating etc and was only done
for one engine. The graph on the retail is different to the
one in 'bulk' and has silly errors.
I surmise that if the chamber area is 'insulated'
sufficiently then one could arguably start the diesel
without glowplugs as the temp rise without losses by
compression is of the order of 1000 deg F.
I aim to show that chamber heat losses can be reduced to a
significantly with a thin barrier film.
The following is some mathematics that I have run through to
see the predicted effects:
Aluminium has a thermal conductivity of 230ish W/mC (The
units are a little confusing because its W/(m x m) @1m
thickness. Different books write it differently [not to
mention BTU's CHU's Calories etc]. Oops )
Now most ceramics are of the order of 0.5W/mC
Thus using 'ball park' estimates.
Losses through piston face might be 230/0.01m is 23,000W per
1sq m of piston face and 1 deg C temp gradient.
If we were to coat the face to 1mm thickness with a ceramic.
0.5/0.001 or 500W.
Adding inverses (which is equivalent to adding capacitances
in series) we get 489W/mC
This shows that heat losses can be reduced 46 fold through a
10 mm ally wall.
If we settle for a 1/ 20 and we know that the bulk of the 30
% energy loss of an engine, into the coolant is via the head
and piston face; (hence the bountiful water cooling in the
head and the oil squirters aiming at the pistons).
The power gains (or fuel economy increase) ought to be
Of the 30% or so heat losses down the exhaust how much do we
claw back via the turbo?
These figures tumbling round my head makes me wonder why the
improvements shown by the industrial coatings company are
somewhat pathetic. Was it Mark Shirley who mentioned SAE
papers not showing much gain.Can we have more info?
More information about the Vwdiesel