Where do I connect the small 1" hose outlet used for the heater in
the car? What type of hose should I use for the oil lines?
Thanksfor any help Joe Berki
The nipple for the heater is on the top of the rear(car) end housing.
AN8 or AN10.
Paul Lamar
Paul,
Does this heater hose connection get blocked off or does it get
plumbed into the system?
Joe Berki
Block it off if you don't have a heater on a pusher. On a tail
dragger vent it back to the water pump. Here is a jpg from my
book.How to Cool your Wankel.
Paul Lamar
1"?? Most auto heaters have 5/8" hose from the thermostat housing
(engine side) to the heater and 3/4" return to the water pump
suction. Some use both as 5/8". That looks like a de aeration vent
to the surge tank.
Dale Davies
Helps to fill the block as the engine is tilted up in a tail
dragger. You get a big air bubble in there.
Paul Lamar
Paul,
We ought to differentiate between the small 1/4" port on the top of
the rear side housing and the larger 5/8" (?) port just below the
oil filter pad. We typically use the 1/4" port for an air bleed
back to the swirl tank, and the 5/8" port for a cabin heater, if
used, otherwise just block it off. I wouldn't want to route it back
to the water pump as this is heated water. If anything, I would
route it to the inlet side of the radiator.
BTW, it isn't easy blocking the 5/8" port off as it is an oddball
size, and there isn't enough material to drill it out to the next
larger size. I ended up cleaning it thoroughly and then filling the
nipple with Devcon.
Mark S.
You are absolutely right.
However the output part of the water pump is the inlet side of the
rad :)
Paul Lamar
Correct me if I am wrong but does the water pump suction come from
the cool part of the radiator and the pump out pressurize the block?
Dale Davies
Yes.
It is more like the pressure is constant in the entire system.
There may be a small pressure drop across the pump but we use a 30
psi pressure cap to raise the boiling point.
What is rather confusing about the 13B Mazda water pump is both
inlet and outlet of the block water jacket goes through the pump body.
The pump is built into the front cover on the RX8.
Paul Lamar
Being a Journeyman mechanic I realize the cooling system is
pressurized by the expansion of the coolant as it warms up. Once at
operating temperature and stabilized, there is no more pressure
increase. The coolant pump is the circulation "generator".
Dale Davies
Yes and the faster it circulates the better. The rate of heat
transfer from metal to coolant gets better as the flow speed gets
faster. Common sense. The bigger the fire hose the faster it puts
out the fire.
The real way to measure the engine temperature is place a thermal
couple close to the combustion chamber near the lower spark plug.
The metal temperature must be kept below 500 F or 260 C in any
aluminum engine. CHT.
Don't go on the water temperature alone. It takes a 3 HP pump to
get enough water speed. When I first found the restriction in the
13B water pump back about 2002 and published the modification to
eliminated it on here apparently Mazda engineering was listening.
They removed the restriction in the RX8 water pump design. The RX8
WP gearing and impellor size is about the same as the 280 HP turbo
13B RX7 engine but no restriction.
BTW an electric water pump is not going to cut 3 HP.
1 hp is 746 watts. Three HP is 2238 watts. At 14 volts that is 160
amps! assuming 100% eff. Nobody makes an off the shelf electric pump
that uses 160 amps. Been there and done that.
http://www.rotaryeng.net/electric-water-pumps.html
Paul Lamar
A more familiar concept may be wind chill. Everyone understands
that the harder the wind blows the colder it feels. That's because it's
carrying away heat from our skin at a faster rate. That's why we
all know to blow on a bite of hot food before putting it in our
mouth or to sit in front of a fan when the weather is hot.
Air is just another fluid. The same principles that explain wind chill
also apply to coolant fluid inside the engine and, in correlation,
inside the radiator except that the heat is flowing into the coolant
inside the engine and out of the coolant inside the radiator. The
faster the fluid flow the faster the heat is removed by the coolant.
Faster flow causes increased turbulence which mixes the hot fluid
touching the hot surface with the cooler fluid flowing by outside
the boundary layer reducing the thickness of the boundary layer.
The boundary layer acts like insulation. We all understand that thicker
insulation is more effective at reducing heat flow than a thinner layer
of similar insulation. You more often hear about delta T, the
difference in temperature between the air in the system and the
temperature of the heat exchanger surface, in air conditioning systems
than you do in engine cooling systems. Mixing of heated coolant in
the boundary layer with cooler coolant outside the boundary layer increases
the delta T between the coolant at the surface and the inside
surface of the engine block resulting in faster heat transfer and
better cooling.
Any of you ridden a motor cycle at highway speed in hot weather?
As the air temperature increases the relative wind against your skin
begins to feel hot instead of cool. When the air temperature
exceeds your skin temperature the heat starts to flow in the
opposite direction heating you up instead of cooling you off. And
you thought that dude on the bike in the hot summer weather was
enjoying the nice cool breeze. NOT!
Mark LaPierre
Air is compressable as u stated Mark L, hydrodynamics is not aerodynamics
just ask boat designers. Cooling is effected by conduction. The boundary
layer impedes conductive cooling, the larger the boundary layer
(this is what insulation does) the less effective the conduction.
Increasing flow rate can induce greater turbulence and thus greater
boundary layer disruption
( consider the difference of turbulent flow compared to laminar flow)
. increasing flow rate also reduces the time the coolant spends in
the radiator reducing the delta T of the radiator. liquid conducts
heat away from the surface better than air, but an aerated liquid
conducts even better due to its ability to induce boundary layer
disruption. Think of the energy cavitation removes from a boat
propellers thrust by inducing turbulence.
Next time you go flying, if there is a bit of dirt/dust on the
fuselage/wing, try writing your name in it. When you land your name
will still be there ( baring rain), this will demonstrate the effects
of the boundary layer, this is also known as the friction layer or
transition layer.
feel free to comment.
Graeme Riley
Air is a fluid. Water flowing past a boat hull builds a boundary
layer too.
"Fluid dynamics textbooks usually begin discussions of this topic by
explaining the no-slip condition. This stipulates that the fluid
molecules against a moving surface do not slide (slip) over it.
Instead, they are pressed against it and adhere to it. The region of
water pulled along with the hull is known as the boundary layer, and
it can take one of two forms -- laminar or turbulent."
"When the boundary layer is "laminar," it's thin and presents little
drag. It's also fragile, so it quickly breaks up into a thicker
"turbulent" boundary layer as it flows aft on the hull or foils.
When turbulent, the boundary layer pulls more water with it,
creating more drag. Therefore, the first goal of bottom preparation
is to extend the laminar boundary layer as far aft as possible on
your hull and appendages by creating practically perfect surfaces in
the areas where it can exist."
http://www.sail.ie/SW/Bottom%20Finishes.htm
Since the coolant coming out of the block is hotter the heat
transfer rate to the cooler rad is also higher.
http://en.wikipedia.org/wiki/Heat_transfer_coefficient
http://www.physicsclassroom.com/class/thermalP/u18l1f.cfm
Now it comes down to rad configuration. A few facts. Having tubes of
the same diameter and area the more tubes the slower fluid flow in
the tubes and the less the pressure drop across the rad. Less tubes
less area mean higher flow rate in the tubes and the more the
pressure drop. The coolant cools as it passes down the tube so the
heat transfer rate also decreases. Putting all these variable rates
together gets very complicated indeed. The bible on this subject is
a book called Compact Heat Exchangers by Kays & London. Here is a quote.
"It can be readily shown that for most flow passages that might be
used for the heat transfer surfaces of an exchanger, the heat
transfer rate per unit of surface area can be increased by
increasing fluid-flow velocity, and this rate varies as something
less than the first power of the velocity. The friction-power
expenditure is also increased with flow velocity, but in this case
the power varies by as much as the cube of the velocity and never
less than the square. It is this behavior that allows the designer
to match both heat transfer rate and friction (pressure-drop)
specifications, and it is this behavior that dictates many of the
characteristics of different classes of heat exchangers. If the
friction-power expenditure in a particular application tends to be
high, the designer can reduce flow velocities by increasing the
number of flow passages in the heat exchanger."
Here are a few jpgs from my book How to Cool Your Wankel.
Paul Lamar
We instrument technicians deal with measurement of gases and liquids. Many of
the oil field measurements are derived from an orifice plate. This is as the
name indicates, an orifice in the pipe that causes a restriction and thus a
pressure drop. There is a long formula to calculate the flow rate and volumes.
"Differential pressure" is the prime value with "static" pressure in the pipe
and then fluid temperature to trim the value. The "meter run" where the
measurement takes place requires flow straighteners, 10 pipe inside diameters
upstream and 5 pipe diameters down stream of the orifice plate. The location
of the taps is also very important to proper measurement. You want laminar
flow to measure. The pipe wall has fluid attached which moves along slower and
the velocity increases as it gets closer to the center of the pipe. The
different "layers" of flow cause friction to slow the flow. Pipe lines need
compressor stations about every 100 miles or the friction would stop the flow
through the pipe eventually.
I know this is not AC related exactly, but explains what goes on in the
"pipe", whether the heat exchanger or the block of the engine.
Dale Davies
--
The Rotary Engine News Letter. Powered by Linux.
ACRE NL web site.
http://www.rotaryeng.net
You Tube key word PaulLamar2
Copyright 1998-2012 All world wide rights reserved.