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Yep, Ed.
I have your original prop…a
Performance Prop 76 X 88. Tractor configuration…It is a Lancair Legacy.
The air going through the radiator after
the fan is picking up 80*, which seems like a lot to me….This is measured
after the fan and may not be representative of the rest of the core. But prop
blast should be supplying the balance of the core with at least some air….
I was running at 2100-2200 rpm during this
test which I failed to mention. If you look at your calculations you were
doing before you were distracted by the prop question, I think you were about
to arrive at the conclusion that it should be cooling…??
My coolant is a 50/50 antifreeze mix. I
mention this because of the next question.
Back in my car repair days, you could tell
if the thermostat was sticking by removing the radiator cap and watching to see
if the water started to flow as the engine heated up. I don’t have a
thermostat, so can I remove the radiator cap and start the engine to determine
flow, or will the high flow pump shoot antifreeze all over my plane?
I am interested in your completed
calculations to see what you determine my cooling results should be.
Without the folks on this list, only
really gifted people like you and Tracy
could ever hope to “get er done”.
Thanks,
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Wednesday, October 03, 2007
7:19 PM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Problem?
[FlyRotary] Re: Coolant Water Pressure
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.
----- 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
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