Hi Michael,
You have compared the cylinder wear on an older carbureted engine to a
more modern engine design with fuel injection, & somehow attributed the
lesser cylinder wear to the presence of fuel injection & then suggest that
manifold drains are the equivalent of fuel injection in reducing raw
fuel? Maybe two percent as efficient, I doubt if more.
I believe that there have been numerous advances in cylinder, piston, &
lubrication design & materials, as well as closer internal fit
tolerances, in the last 20 years. Particular attention has been paid to
inducing swirl to more thoroughly vaporize the fuel. These advances have
contributed greatly to engine longevity, reduced emissions & better
economy. You will note that the newer & tighter engines use much lower
viscosity oil which is needed to fit the tighter clearances & to reduce
cold oil drag on the engine parts.
Not to discount the possibility of manifold drains reducing cylinder
wear, a more reasonable & correct comparison of engine wear would be
between engines of similar design, carburetion, & age. One with drain
pipes & one without. This particular comparison has not been done, to my
knowledge.
I realize that engines which are run for long periods without cold
starts, usually have less wear for the miles on them than short run,
frequent cold start engines do. This is in part, due to more complete
fuel vaporization & less fuel washing of the cylinders which is a result
of cold starts. It is also due to the parts & oil coming up to
operating temperature, & staying there, with the resulting tighter fits
& better lubricant penetration. There is no doubt that cold starts
create most of the engine wear.
I am only questioning, in the overall picture, how effective the Healey
drain pipes are at eliminating the raw fuel that causes engine wear.
There is STILL a considerable amount of raw fuel in the cold induction
system & cylinders after the engine is started. Fuel injected engines
not excluded. The inevitable result of fuel not being fully vaporized in
a cold engine. This is the reason that a cold engine needs a richer
mixture in the first place, as you well know. This raw fuel cannot drain
out of the Healey "drains" after the engine is started in any event.
Although fuel injection does increase vaporization, reduce raw fuel &
engine wear, I don't see a valid comparison between Healey drains & fuel
injection. I doubt if the drains are anywhere near as efficient as fuel
injection in reducing cold start wear.
Did I miss the point?
Regards,
Dave Russell
BN2
Michael Salter wrote:
> Hi Dave. Although I can appreciate your thoughts on the subject of
> manifold drains I think it is worth considering just how much damage
> raw fuel does do to an engine. In my experience a carburetored engine
> is usually fairly well worn at 100,000 miles, sure people get a lot
> more but in general terms at 100K there is usually a significant
> ridge on the cylinder walls. Compare this with a modern electronic
> fuel injection engine. As far as I'm aware there have not been many
> outstanding advances in cylinder and piston materials in the last 20
> years yet we find that when the head is removed from most of these
> engines the cylinder ridge is almost undetectable at 100K miles. IMHO
> that is probably mostly attributable to the absence of raw fuel on
> the cylinder walls.
>
> Michael Salter www.precisionsportscar.com
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