ENGINE BASICS

On Fri, 12 Jun 2009 06:05:01 -0700 (PDT), cmyr
wrote:

On Jun 11, 8:06?pm, wrote:
On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr

wrote:
? Going back to some hot rodding roots,I believe V.E. was increased
in the late '60's-70's thru the use of a specially designed double
cone affair placed in the collector pipe of a tuned exhaust
system,which created a stronger vacuum effect , creating stronger
scavenging of exhaust, and to some extent , helping draw more fuel/air
mix into the cylinder.

The anti reversion cone was a dirty fix for a crappy header design.
Better than a manifold, but not as good as a proper "tuned" header.

As I recall, this system was on the cover of Hot Rod magazine, on a
high end test vehicle,and was "scientifically" researched. In this
instance the reference to a crappy header design would be wrong.


I stand by my appraisal. It made a crappy header design work (sorta).
Just because it was on the cover of hot rod doesn't make it good. It
was a lot better than the standard "shortie" header without the cones
- but still nowhere near a properly tuned long header.

On Fri, 12 Jun 2009 13:12:48 -0500, "Tom Wait"
wrote:


"cmyr" wrote in message
...
On Jun 11, 8:06?pm, wrote:
On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr

wrote:
? Going back to some hot rodding roots,I believe V.E. was increased
in the late '60's-70's thru the use of a specially designed double
cone affair placed in the collector pipe of a tuned exhaust
system,which created a stronger vacuum effect , creating stronger
scavenging of exhaust, and to some extent , helping draw more fuel/air
mix into the cylinder.

The anti reversion cone was a dirty fix for a crappy header design.
Better than a manifold, but not as good as a proper "tuned" header.

As I recall, this system was on the cover of Hot Rod magazine, on a
high end test vehicle,and was "scientifically" researched. In this
instance the reference to a crappy header design would be wrong.

All the previous 6 or7 posters have come up with methods of increasing VE
w/o superchargers. I want to add 4 or more valves per cylinder which would
probably increase the mass of the valve train. Certainly the complexity. I
don't see how a massive rocker arm or longer fatter pushrod could decrease
VE. Certainly a larger valve head would increase mass but would also
increase VE. A thicker valve stem would increase mass and decrease VE but I
think only marginally. I think the only way more mass would decrease VE
would be if the push rods were rubber.
Tom

Heavy valve trains only affect VE at high RPM - when the valves start
to float. Light valve-trains are better at high RPM, but are not
terribly effective in improving the power of a low speed "tractor
engine"

"Morgans" wrote in message
...

"Charles Vincent" wrote in message
news
Torn Lawence wrote:
The British made some WWII engines with rotating cylinder sleeves that
had in and out ports cut into them - rotary valves! No poppets. Good
performance, but burned oil and left conspicuous smoke trails, not a
good thing for a warbird to do.

That's what I remember from an engine class, unless I'm hallucinating
again.

That was a sleeve valve engine, Harry Ricardo's magnum opus. The Bristol
Hercules and Centaurus. Wear was an issue they never did tackle.

When engines were changed as often as shirts, and as easily as shoes, that
isn't a big issue either, IMHO.

You have always got spares sitting around wherever you stop frequently,
and in an hour or so, you put in a new engine and are on your way.
--
Jim in NC
While I would have phrased it a little differently, I am certainly on the
same page.

During the war, a little more horsepower was a far greater asset than longer
TBO,
and enemy fire was at least as great a threat as wear.

Peter

wrote in message
...
On Fri, 12 Jun 2009 06:05:01 -0700 (PDT), cmyr
wrote:

On Jun 11, 8:06?pm, wrote:
On Thu, 11 Jun 2009 07:40:10 -0700 (PDT), cmyr

wrote:
? Going back to some hot rodding roots,I believe V.E. was increased
in the late '60's-70's thru the use of a specially designed double
cone affair placed in the collector pipe of a tuned exhaust
system,which created a stronger vacuum effect , creating stronger
scavenging of exhaust, and to some extent , helping draw more fuel/air
mix into the cylinder.

The anti reversion cone was a dirty fix for a crappy header design.
Better than a manifold, but not as good as a proper "tuned" header.

As I recall, this system was on the cover of Hot Rod magazine, on a
high end test vehicle,and was "scientifically" researched. In this
instance the reference to a crappy header design would be wrong.


I stand by my appraisal. It made a crappy header design work (sorta).
Just because it was on the cover of hot rod doesn't make it good. It
was a lot better than the standard "shortie" header without the cones
- but still nowhere near a properly tuned long header.

I agree with you about placement on the cover of Hot Rod, and the same
applies to most other publications: the ability of a writer to meet regular
and repeated deadlines is a far more important qualification than
outstanding knowledge of a subject.

Notwithstanding that cones were also tried as part of a "shortie" header
system, and may have been a little more or less usefull than "stepped"
pipes, there might be few modern applications aside from professional drag
racing and tractor pulls. Of course, you could argue that the exhaust on
the Merlin and Griffin, and also the Allison V12 of which I can not recall
the name, acted as untapered cones.

OTOH, most of the what I can recall from those days is related to OEM
advertising, mainly by Ford, to the light and medium truck market and
friends told me at the time that the use of anit reversion cones on truck
engines was far more widespread than I supposed and certainly not limited to
a single brand. However, I never personally had nearly new engines apart
and I don't know whether the cones may have appeared on the scene at the
same time that head castings became much more accurate. Recall that the
iron heads from the fifties and early sixties had very irregular ports and
the resulting outlets were smaller than the gaskets and headers--effectively
giving them a marginally predictable anti reverson property along with their
poor efficiency at higher speeds.

In other words, they are part of a compromise that may be usefull or may
not, depending on the application and the space available to mount the
engine along with its accessories and its exhaust and cooling systems.

the ability of a writer to meet regular
and repeated deadlines is a far more important qualification than
outstanding knowledge of a subject.


Snurf , sniffle, ... {:-(

Jim
Monthly Columnist
Kitplanes

Peter Dohm wrote:
snip

I agree with you about placement on the cover of Hot Rod, and the same
applies to most other publications: the ability of a writer to meet regular
and repeated deadlines is a far more important qualification than
outstanding knowledge of a subject.


I guess that depends on the publication in question not expecting
both. For example, Weir knows what he's talking about and makes a
monthly deadline every time.

Dan, U.S. Air Force, retired

A couple of workshop manuals were part of my childhood - the trove of
my Fleet Arm Arm artificer brother - but I finally tossed them...

Brian W

Gerry van Dyk wrote:
Ah yes the "sleeve valve" engine

Bristol's Hercules in the radial engined Halifax and Lancaster
bombers, and Centaurus in the Sea Fury and several transports. Also
the Napier Sabre in the Hawker Typhoon and early Tempest.

The Centaurus turned into a real workhorse, but the Sabre died out
quickly. The Brits seem to keep the Bristols in service in warbirds
but American's tend to replace them with R-3350s, presumably for
spares availability this side of the pond.

Gerry
......
The British made some WWII engines with rotating cylinder sleeves that
had in and out ports cut into them - rotary valves! No poppets. Good
performance, but burned oil and left conspicuous smoke trails, not a
good thing for a warbird to do.

That's what I remember from an engine class, unless I'm hallucinating again.- Hide quoted text -

Charles Vincent wrote:
Torn Lawence wrote:
The British made some WWII engines with rotating cylinder sleeves that
had in and out ports cut into them - rotary valves! No poppets. Good
performance, but burned oil and left conspicuous smoke trails, not a
good thing for a warbird to do.

That's what I remember from an engine class, unless I'm hallucinating
again.

That was a sleeve valve engine, Harry Ricardo's magnum opus. The
Bristol Hercules and Centaurus. Wear was an issue they never did tackle.

Charles

Ricardo! Reminds me of those current amusing INTEL commercials with the
theme;
"Our pop-stars are not like your pop-stars..."

Brian W

"RST Engineering - JIm" wrote in message
...
the ability of a writer to meet regular
and repeated deadlines is a far more important qualification than
outstanding knowledge of a subject.


Snurf , sniffle, ... {:-(

Jim
Monthly Columnist
Kitplanes

Oh c'mon!

You are far more of a doer than a writer.

Peter

"Dan" wrote in message
...
Peter Dohm wrote:
snip

I agree with you about placement on the cover of Hot Rod, and the same
applies to most other publications: the ability of a writer to meet
regular and repeated deadlines is a far more important qualification than
outstanding knowledge of a subject.


I guess that depends on the publication in question not expecting both.
For example, Weir knows what he's talking about and makes a monthly
deadline every time.

Dan, U.S. Air Force, retired

True, and I frequently wish that I could do so as well.

Regrettably, it is not universally true, even in the specialized media and
it seems to be much worse in the popular "mainstream"!

Peter