ENGINE BASICS

"cmyr" wrote in message
...
On Jun 11, 11:32?am, George wrote:
I believe that Ballenger Headers had the "pickle" located in the
collector of 4 tube equal length headers and there was also the
"coanda" effect which is specifically what I think you were speaking of.
? It was used experimentally in a truly weird exhaust setup in the early
days by of one of the major racing teams back in the mid 60s, but my
memory is a bit foggy for specifics that far back, such as who or on
what car, sorry.



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.- Hide quoted text -

- Show quoted text -

You remembered the word I couldn't put my finger on........coanda

---------------------------------------------------------------------------------------------------------

Back in the 70s or so, there was a three cylinder two stroke radial, with
all three cylinders in a common crank case - that used the exhaust system
exclusively for scavenging the engine. There was no intake draft without it.

It was featured on an ultralight one year at OSH.

"cmyr" wrote in message
...
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.

There have been a number of things that improved VE: Generally, higher
compression ratios help especially at higher RPM, roller tappets seem to
withstand much faster ramp angles and can stay open further during the open
part of the valve cycles, and anti-reversion cones in the exhaust are said
to work very well in the mid-range of RPM for any given four cycle engine.
In addition, intake and exhaust port shapes play a major role; as do other
aspects of head ad piston crown design.

In a nut-shell, there has been a lot of progress over the past three
quarters of a century, and the only place that I can think of in which
aircraft engines have led the way has been in the area that we used to call
"blue printing" in which the ports are more carefully caste, machined, and
finished to closely match the design drawings for the engine. Today, every
late model engine that I have seen is done that way at the factory; but
forty years ago, automotive engines were really crude.

Peter

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.

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.

"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

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

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.

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

On Jun 12, 3:55*pm, Torn Lawence wrote:
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

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 -

- Show quoted text -

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

On Jun 12, 4:27*pm, 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

On Jun 12, 3:55*pm, Torn Lawence wrote:

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

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 -

- Show quoted text -

If you ignore oil consumption, (No one succeeded in fixing that
problem.) Bristol sleeve valve radials had a lot to recommend
them. Maybe today with modern metallurgy and high temperature
elastomers someone could.

However, without poppet valves and rocker towers in the heads, the
engine diameter was much smaller. Without a hot exhaust valve in the
combustion chamber, the compression ratio could be a point or two
higher with the same octane fuel and the same detonation margins - and
the engine tended to last longer. At the time, and maybe still,
poppet exhaust valves were the weak point.

They have Sir Harry Ricardo to thank for the sleeve valve design.

"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