|
Grass? what grass? {:>)
Yes, it sounds like the air should rise to the top of your
slanted radiator. However, My experience has been that unless I run the
engine up to around 5000 rpm for about 15-30 seconds (does not have to be
long) that I do not have much success getting air out of the block. It
seems to take that velocity of coolant flow to drag the water out of the
block.
You have over 700 cubic inches of core, so that should be
plenty for cooling a two rotor.
A multi pass radiator (two pass in your case) can require
more coolant pump flow as indicated by this extract from a pretty respected name
in racing/cooling circles:
Double pass
Double pass radiators require 16x
more pressure to flow the same volume of coolant through them, as compared to a
single pass radiator. Triple pass radiators require 64x more pressure to
maintain the same volume. Automotive water pumps are a centrifugal design, not
positive displacement, so with a double pass radiator, the
pressure is doubled and flow is reduced by approximately 33%. Modern radiator
designs, using wide/thin cross sections tubes, seldom benefit from multiple pass
configurations. The decrease in flow caused by multiple passes offsets
any benefits of a high-flow water pump.
Again, these are just back of the envelope calculations
based on a great deal of assumption about your parameters. My gut feel is
that 700 cubic inches should have no problem cooling your installation at those
power settings even being a double pass radiator. So I would look else
where.
You indicate you have an approx. 80F delta T across
your radiator core with the coolant temp a 210F. You have a fan which
apparently has the spec to draw 970 CFI across the 11" dia of the Fan.
Lets assume that was the flow through the entire core. Then that would
give you 970*.0765 = 74 lbm/min of air mass.
Q = 75 * .25 * 80 = 1500 BTU/Min just due to the flow
resulting from your fan - it would seem that plus whatever flow you are getting
from your prop - Prop??.
Hey, this dumb question just occurred to me
- I assume you are running with a prop?? in a tractor
configuration. I lose track of who has what.
Ed
----- Original Message -----
Sent: Wednesday, October 03, 2007 5:12
PM
Subject: [FlyRotary] Re: Problem?
[FlyRotary] Re: Coolant Water Pressure
I have an aluminum
double pass radiator with the finned core size of about 18.25 X 18.25 X
2.25. It is behind the engine and leaning rearward at the top at about a
30-35* angle. The water from the engine enters on the left lower and
crosses the bottom half of the radiator to the right side then rises and goes
back across the top of the radiator and exits the top left side and returns to
the engine.
My radiator cap is at
the top right corner of the radiator at the point where the water starts its
second pass through the top half. My pressure port is just below the
radiator cap. The pressure sending unit is in a “T” with the hose which
goes to the ¼” port at the top of the rear iron connected to the other side of
the “T”. I thought that this hose could have some effect on the
pressure, but I am not certain why it would.
Any air in the system
should either rise to the top of the radiator, or if it was trapped in the
block, it could come through the hose to the radiator. All air should be
found therefore? Under the radiator cap. I have never found any air
there.
I think I found out a
little something about the fuel system today. I only put a few gallons
in the right tank and have been checking for leaks and running the engine on
this fuel. I wanted to run it down to the “non-usable” level and then do
the same thing with the left tank. So I have been really low on
fuel. My pressure has been holding, but I thought that I could hear
bubbles from time to time going through the
lines.
Anyway, before, I
could get a good start by setting the mixture at about 4 PM oclock and it
would fire up in a couple of blades. Today, I tried hitting the primer
button a couple of times and it would start and immediately die. I
finally had to set the cold start on and leave it on just to get the engine to
run! Finally after it warmed up, it ran with the mixture set at 12
oclock, but it was not steady. As my fuel ran out, the pressure dropped
finally to about 28 lbs and the engine started its death rattle. I shut
it off at that time.
The temperature had
risen to 210* the ambient temp was 87-88* and the air after the radiator was
168* This is with my radiator fan running. (11” and 970 CFM)
probably about 10-12 minutes of running the
engine
.
My oil temp was only
160* and the air temp after the oil cooler was 145* , I think that this would
gone higher if I ran longer, because the oil in the pan was up to 170-180* or
so. The pan holds 5 qts, 8 qts in the
system.
Water pressure was up
to 22-23 lbs and oil pressure was 70 lbs.
All my temp probes
are within a degree or so of one another and with a mercury thermometer in the
hangar when reading ambient temp and the engine is cold. I think they
are all correct.
I have the air/fuel
ratio setup that comes with the EM-2, but it doesn’t work till the O2 sensor
gets to about 800* or so, no help on trying to figure out starting
ratio.
The timing brings up
a good point. I got the Renesis out of a wrecked car with 1800 miles on
it, so the timing is set to the factory setting for the Renesis. I have
never checked it. Does anyone know what the factory setting would be for
the Renesis??
Staging is a good
point, but I think that you are correct about having enough fuel to run a low
speeds and not enough to run faster. I was running out of fuel and
probably didn’t have enough to rip it.
You really have good
insights when you are helping folks.. You are pretty right on with your
advice.
Thanks,
Bill B (Must
mow yard…Must mow yard..)
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Wednesday, October 03, 2007 12:53
PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Problem?
[FlyRotary] Re: Coolant Water Pressure
Yes, too hot for that rpm, I
agree.
Assuming you followed the
good suggestions offered by Al, Lynn and others regarding getting all the air
out of the block - really important! I almost cooked engines two times
because of excess air in the coolant system. Here is something
that may quickly tell you something about the air you may have in the
system.
I can't recall what type of
radiator set up you have, but with the Two GM cores I use which are
mounted vertically, you can touch the side tank of the radiator and
determine if there is air in the system. In my case, if I do a
complete drain and refill of the system, on the first run up the core's tanks
will be hot approx 2/3 of the way up and then they are much cooler -
indicating that the remaining 1/3 of my core is filled with air. It
generally takes me 3 runups reaching 5000 rpm before I can touch
the core tanks and find them hot all the way from top to bottom. So
depending on your radiator set up that might be something you can quickly
check.
If the mixture is too lean, you
can get a backfire out the intake, too rich and its generally the exhaust -
where unburned fuel cooks off. So that and black smoke would indicate to
me too rich a mixture. I presume you do not have an Air/Fuel ratio
indicator - strongly recommend you get one, that tells you right away whether
you are running rich or lean. Even a cheap one can be a tremendous help
in finding out whether too rich or too
lean.
One thing you may want to check is
your ignition timing. If using Tracy's EC2 you need to set the static timing
around 35 Deg BTDC. The EC2 backs off 10 deg from that (25Deb BTDC) as
its default starting point for ignition timing. So if you set the static
timing to say 25 Deg then the EC2 would be having the engine operate at a 25 -
10 deg = 15 Deg BTDC which is pretty retarded timing for the
rotary. OR if you set it too far advanced then the timing might be too
advanced.
So just recheck it when you get
the chance.
Another possibility is your
injection system might not be staging properly. IF that were the case,
the engine might work fine below the staging point but not above it.
Could possibly be a sticking secondary injector (if too rich or
lean). But, that is a bit down the likely list. Something
impeding the fuel flow might provide sufficient fuel and low rpm but not
sufficient to run at high rpm.
----- Original Message -----
Sent:
Wednesday, October 03, 2007 11:23 AM
Subject:
[FlyRotary] Re: Problem? [FlyRotary] Re: Coolant Water
Pressure
Ed, this is at
about 2000 rpm. Like a fast idle. I am getting all kinds of fuel
cut like stoppages if I try to run the engine faster. I haven’t seen
more than about 3700 rpm, but I just started it and have not tried to tune
anything. I figure I will have to run longer to get it tuned and the
cooling is holding that back.
Speaking of that,
you guys were talking a while back about the effects you see when the engine
is too lean, or too rich. Talking about backfires, etc and what each
effect represents. I have forgotten what means what…senior days, not
moments!
Do any of you
remember how that went? I am having some problems getting started and
am not certain if I am too rich or too lean. I am getting backfires
out the exhaust at times and smoke from the exhaust at that time.
(black)
I ran the batteries
down yesterday trying to get started due to this. When I originally
started the engine, I flooded it. I am trying to prevent this now and
am concerned that I may not be using enough
mixture.
Bill
B
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Wednesday, October 03, 2007 10:05
AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Problem?
[FlyRotary] Re: Coolant Water Pressure
You indicate you get overheating
after 10-15 minutes run time. I may have missed it, but is this at
idle, max throttle or what. Also what is your OAT. If at idle or
low power then, yes what you are seeing is not what it should be. On
the other hand, if at WOT or high power settings, then 10-15 minutes run
time would be indication of a great cooling capacity. I can not run my
engine more than a minute or two at WOT on a 80F day without temps getting
into the 200F range. But, that is at 5800-6000 rpm. At idle, the
temps stabilize and I can idle all day with safe
temps.
My coolant system runs with no
air cushion and yes, I get a hydraulic "lock" pressure reading of as high as
25 psi immediately upon engine start up. After a 30 - 60 seconds of
running the pressure drops down to zero and then after a few
minutes running builds back up as the coolant warms up to operating
temperatures.
Plenty of suggestion have been
made about what to check - all good.
----- Original Message -----
Sent:
Wednesday, October 03, 2007 9:30 AM
Subject:
[FlyRotary] Re: Coolant Water Pressure
Bill, the definitive test is
the one I described below. Really encourage you to do it as described.
Resist assumptions. Convert your ideas to
measurements.
----- Original Message -----
Sent:
Wednesday, October 03, 2007 6:08 AM
Subject:
[FlyRotary] Re: Coolant Water
Pressure
I think that I
would see air under the radiator cap if I had a compression gas
leak? I never see any air.
To check a
piston engine for head gasket leaks, you would put the cylinder at TDC
and pressurize the cylinder to about 150 lbs with compressed air and
check the radiator for air bubbles…How do you check a
rotary?
I will check
the pressure sender against a mechanical gage.
There is
obviously a heating problem, but I think the pressure is higher than it
should be until just ready to boil. I shut the engine off at 210*,
and at 22+ lbs, the boiling point should be well above
250*??
Thanks for the
suggestions of where to look, guys…
Bill
B
From:
Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On Behalf Of Al p Wick
Sent: Tuesday, October 02, 2007
7:49 PM
To:
Rotary motors in
aircraft
Subject: [FlyRotary] Re: Coolant
Water Pressure
Your coolant reservoir should be above engine.
1) If it is, remove two cups of air from the
reservoir. Then repeat your test.
2) If you now see pressure rise above 22
psi within 5 minutes of cold start, you clearly have compression gases
leaking into cooling system or bad
gage.
3) Air in the block is 10 times more significant
than any other cooling factor. Make darn sure you don't have any. It
causes local boiling, high temps, strange
behavior.
Operating with two cups of air under cap is an
important safety and diagnosis advantage. Everyone should do it. With
that two cups, you only see 22 psi if you have a genuine problem. You
only see 0 psi if you have genuine problem. The pressure is then a very
fast and reliable indicator of system integrity. So two cups of air has
no negative effect on system efficiency, just a substantial improvement
in safety. Only time it could be a negative would be if your reservoir
was way too small, way too low, or flowed way too much
coolant.
Since you describe high temps AND pressure, I
suspect you have temperature problem.
I deliberately overheated my engine many times
so that I was intimate with pressure and temperature patterns.
Then tested various concepts. Don't recommend you do the
same.
I just recently got my
Renesis started again after finishing my cowl. I seem to be
getting very high coolant pressures. I can only run the engine
about 10-15 minutes before hitting the redline at 210*. My water
pressure is at 27 Lbs at that time. I only have a 22 Lb radiator
cap, so I assume that I am blowing into the recovery tank, but I have
not confirmed that. My oil temp has never exceeded about
165*. It might have gone higher if I could have run
longer???
This whole water pressure
thing has me a little baffled. Since this is a closed system and
the only way pressure can build is due to the expansion of the coolant
after heating???, I am confused by some comments that have been made
from time to time. I remember something that Tracy said about
his pressure would build for a time, then go to zero. It seems
to me that the pressure should correlate to the temp pretty closely
since it is a closed system??
Can someone enlighten me a
little on the science of this pressure? It seems to me that
there could be some pressure build up on the positive side of the
pump, but it would go negative on the suction side, so the net effect
of the pump should be close to zero??
Also, my Renesis had only
1800 miles on it when I bought it, so I did not have to tear it
down. As a result, I am somewhat in the dark as to how the water
flows through the system. Could someone help me with that?
I had to remove the thermostat tower for height clearance , so I made
an adapter plate that takes water from the top outlet of the pump and
sends it to the radiator (double pass), then from the radiator, it
returns to the lower inlet of the pump.
Thanks,
Bill
B
-al wick
Cozy IV powered by Turbo Subaru
3.0R with variable valve lift and cam timing.
Artificial
intelligence in cockpit, N9032U 240+ hours from Portland, Oregon
Glass panel design, Subaru
install, Prop construct, Risk assessment
info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
|