<VV> Kamm Back and Exhaust Fumes

[james rice]

All:  We can discuss historical nomenclature about Kamm Back and why most
Corvairs have the exhaust coming out the side vs. out the back and the
effects thereof until we are blue in the face from carbon monoxide
poisoning.

Never the less, these points: 1. Any ground vehicular which moves with any
speed has a low pressure area behind it.  2. Why did GM change the air
intake location between the EM & LM?  Styling, not aerodynamics.  The EM is
actually better if you are going seriously fast, which is why Stingers have
the doors in the engine lid.  3. Suffice it to say hundreds of us have
driven tens of thousand of miles with rear facing exhaust pipes with no
perceived ill affects.  Exhaust fumes cannot craw up and over the engine lid
into the gills in ether EM or LM locations.

Therefore, the over riding point is this:  If you smell exhaust fumes or get
a headache while driving your Corvair, you are getting exhaust into your
passenger compartment.  This is not good.  Find out where or how the fumes
are getting there, and FIX IT.  Failure to do so will make you senile,
sterile and/or dead.  Mostly dead.

Until you get it fixed, you should probably drive with the foot well vents
at least partly open and the back windows cracked so the resulting airflow
carries the fumes out of the car.

Previous posting suggest the fumes are coming from the exhaust packings
between the engine and exhaust manifold into the shrouds, or they are being
sucked into the engine compartment thru damaged or missing seals between the
engine sheet metal and chassis or around the lip of the engine compartment.

Historically Yours,
			James

PS to the Lone Haranger:  What you smell after the Mexican dinner is
methane, not carbon monoxide.  It will only make you smell like something
died.  The CO will take you there.



Message: 1
Date: Sat, 15 Mar 2008 15:03:41 EDT
From: HallGrenn at aol.com
Subject: Re: <VV> Kamm Back and Exhaust Fumes
To: ricebugg at mtco.com
Cc: virtualvairs at corvair.org

In a message dated 3/15/2008 1:11:04 P.M. Eastern Daylight Time,
ricebugg at mtco.com writes:

The  Corvair ends where it does because that is all rear overhang needed  to
cover the rear engine/rear structure w/bumpers.

I don't have any  info why the Corvair exhaust comes out the side.

James,  I will agree that the Corvair doesn't have a true Kamm  back.  But
I'm not dealing in absolutes (though in my younger days I might  have).  But
any squared off rear has a similar, but smaller effect  depending on its
size.  GM recognized this and moved the exhaust to the  side.  I believe the
LM had an easier time of it because they moved the  intake ahead of the
engine deck just behind the rear window (why would they do that?).  But as
you have said the
leaking oil expelled from the hot cooling air does end up on the flat rear
of the car because of the  aerodynamics of the car.  I had a '66 Monza
convertible twenty years ago with an engine that burned a lot of oil and
even though I thoroughly sealed the engine so no oil leaked the rear of the
car stayed oily just from the bluish exhaust exiting the stock GM muffler.
Our church's venerable 15 passenger van without a true Kamm back is flat
enough  to create a low pressure area that holds exhaust and has a sticker
warning on  the rear window and in the owner's manual that the rear window
is not to be open when the van is in motion.  And the exhaust is to the
side.  Follow a  pickup truck in foggy weather and watch the rear end to see
the same thing.

Bob Hall
Group Corvair
Washington DC Suburbs
'64 Brier
'65 Corsa
2 '68 Monzas


----- Original Message -----
From: "james rice" <ricebugg at mtco.com>
To: <virtualvairs at corvair.org>
Sent: Saturday, March 15, 2008 10:10 AM
Subject: Re: <VV> Kamm Back and Exhaust Fumes

ALL:

Bob Hall said:  "Exhausts that exit straight back will be sucked back into
the engine
compartment and then the heater due to the Kamm effect at the squared off
back of
the car.  That's why all stock Corvairs had exhausts that exit at the side."

The Corvair does not have a "Kamm back".  I'm not about to get excessively
historical and aerodynamically technical, because I don't want to take the
time to consult my books or files on the subject.  So briefly, the Kamm back
affect was discovered by the German professor Wunibal Kamm in the late '40's
or very early '50's.  He was researching aero questions, and discovered if
the slope of roof was maintained at about 15 degrees or less toward the rear
and then "chopped off", the car would have the same drag coefficient as if
it had a really long tail normally associated with "stream-lines cars".

There've been very few actual cars, race or street, with Kamm backs.  The
first one specifically designed per his research maybe the Cunningham C4RK
from LeMan's in '52.  Later there was the rebodied Ferrari GTO "Breadvan"
and a couple of Maserati 151/3 with Kamm back's.  Station wagons and
vans/Suv's etc are not actually Kamm backs because the bodywork does not
slop.

The Corvair ends where it does because that is all rear overhang needed to
cover the rear engine/rear structure w/bumpers.

I don't have any info why the Corvair exhaust comes out the side.  I suspect
it has more to do with clearance issues with curbs and slopping driveways.

If you are getting exhaust fumes into the cabin, they are not coming from
the exhaust gas coming up and over the rear bodywork and being sucked into
the top of the engine.  If the car is moving, there is a high pressure area
at the base of the rear window onto the engine lid.  Dave Newell has drawing
from GM of where the pressure area is at speed on the EM.  The air flow on
the LM enters the grill area at the base of the back window from the top and
the sides as air flows around the cabin.  At speed, the high pressure area
on the LM moves to the center of the deck lid, and the fan actually has to
suck air thru the grill area at the base of the back window.  This air flow
issue actually contributes to some head temperature numbers.  The Yenko
Stinger has doors in exactly the right place for engine cooling airflow at
speed.  Remember a well prepared Stinger is capable of over 130mph.  The
Fitch top on LM's restricts air flow into the engine at any speed.

Warren LeVeque did airflow/pressure studies on his Stinger about 25 yrs ago.
The inside of the  engine compartment was actually pressurized on his
racecar.

There is antidotal evidence the underside of the Corvair is very turbulent
with little actual airflow and may actually be positive up around the
transaxle.  If you have a leak at the manifold donuts and have holes in the
firewall you could be getting flow into the passenger compartment.  The
passenger compartment being typically lower pressure than the underside,
even with the windows open....! There is a reason the lower shrouds doors
face the rear.  I suppose if the seal on the deck lid is bad, you might get
some flow back into the engine compartment at speed when the fan is actually
working hard trying to suck air.

Empirical evidence.  Of course none of have them today, but do you remember
what the back of a oil leaker looked like when we were all young?  Oil and
dirt all over the rear, but none of it ended up on the deck lid on either
EM's or LM's.

So find out where the CO is coming from in your exhaust system.  It is not
coming up over the back of the car.

 Historically Yours,
 James Rice