X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Tue, 21 Mar 2006 10:45:41 -0500 Message-ID: X-Original-Return-Path: Received: from imo-m21.mx.aol.com ([64.12.137.2] verified) by logan.com (CommuniGate Pro SMTP 5.0.8) with ESMTP id 1040794 for lml@lancaironline.net; Mon, 20 Mar 2006 19:54:52 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.2; envelope-from=Sky2high@aol.com Received: from Sky2high@aol.com by imo-m21.mx.aol.com (mail_out_v38_r7.3.) id 7.33e.398905 (58677); Mon, 20 Mar 2006 19:53:59 -0500 (EST) From: Sky2high@aol.com X-Original-Message-ID: <33e.398905.3150a8a7@aol.com> X-Original-Date: Mon, 20 Mar 2006 19:53:59 EST Subject: Re: high CHT X-Original-To: jschredl@web.de, lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1142902439" X-Mailer: 9.0 Security Edition for Windows sub 5300 X-Spam-Flag: NO -------------------------------1142902439 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Johannes, =20 You wrote: In a message dated 3/20/2006 1:22:57 A.M. Central Standard Time, =20 jschredl@web.de writes: 1. Calibration of probes: use 4 pc. EGT and CHT thermocouples with the EPI800 system from Vision Micro. I checked one probe years ago with confidential results. But I agree, I have to re-check them all again to be on the save side. Are you using bayonet type probes? Spark Plug Washer type CHT sensors can=20 yield a reading 50F higher than actual. 2. During a normal flight I have following results (+-10=B0F): 2500 RPM; 23,3"Hg; OAT=3D72=B0F; at 4500ft with 185MPH Indicated Airspeed; Oil-Temp=3D193=B0F; Fuel =3D 7,5 gal/hour; (Temperatures converted from=20= =B0C to =B0F) CHT EGT Cyl. 1 390=B0F 1400=B0F Cyl. 2 410=B0F 1436=B0F Cyl. 3 410=B0F 1418=B0F Cyl. 4 390=B0F 1382=B0F I have a standard IO320 Lycoming (new when installed) with standard Bendix injector, Slick magnetos and standard pistons. I notice Cyl. 2+3 have slight higher EGT and same to CHT. Today I braved high winds and cold weather to try to collect similar =20 information. Although the temperature was somewhat cooler, these results a= re=20 consistent with past tests. Note that I have ECI Cermi-Nil cylinders, 9:1=20 compression ratio pistons, about 300 hours SMOH (15 hours on cyl #3 OH), Li= ght Speed=20 Electronic Ignition and a small (7 Vane) Stewart-Warner oil cooler. So.... =20 23.5 MAP, 2500 RPM, 4500 feet MSL, 30.17"Hg (1020 Mb), Dalt 3600, 4C (39F)=20 OAT,=20 176 KIAS, 186 KTAS (these are Knots) and Oil 165F, Fuel 9.7 gph. Note: #3 EGT peaked at 1430F, 8.4 gph (EI timing was 25 degrees BTDC). Afte= r=20 enrichening to 9.7 GPH: CYL CHT EGT 1 340F 1290F 2 330 1320 *3 340 1320 4 340 1310 =20 I then closed the oil cooler air intake door far enough to raise the oil =20 temp to 176F (no change in CHT) and note that my EPI 800 spare temp probe is located at the oil cooler air exit= =20 where it registered 69C (156F). =20 Next I opened the throttle fully (WOT), MAP of 27.4", 2500 RPM, 11.7 gph =20 (100F rich of peak), 192 KIAS (201 KTAS)=20 with all the CHTs dropping about 10F. =20 On return I climbed to 5500 MSL where the density altitude was 4600 feet an= d=20 the temp was 3C. There I ran 23.5 MAP, 2500 RPM, 178 KIAS, 9.6 GPH, 176F oil with the door=20 partially closed and the CHTs were even at 330F. =20 SO, =20 a. Do you really mean 185 MPH or 185 Knots? The difference would be=20 significant in gph and cooling differential pressures. b. Is your oil cooler a Stewart-Warner (other brands are less efficient)? =20 How many vanes? c. Is your Vernatherm correctly set to send all the oil to the cooler when =20 the temp exceeds 180F? Oil accounts for at least 1/3rd of the engine coolin= g. =20 The vernatherm can be tested in hot water to see if it fully shrinks (opens= )=20 at 180F. d. Has your throttle body been checked to see if it is delivering all the =20 fuel it should? Fuel consumption seems a bit low unless your HP is much less= =20 than mine or; =20 e. Are you running at peak or lean of peak EGT? (I tend to see lower EGTs =20 because of the electronic ignition, but not that much lower.) =20 3. Measuring the pressure conditions was my first attempt to get more information about this problem. I have to add I used the static pressure of the cockpit, not from the stati= c ports. Now you tell me there might be a considerable differenc I have to repeat measurement using the exact static pressure! The reason why I used a airspeed indicator was I can compare it better: Aircraft speed v: thats the maximum of pressure I can ever get (knowing p-dynamic =3D 1/2 * rho * v * v) -> max ram air The "air-speed" at the upper cowling never can be higher than v! In realit= y less than v because the "upper cowling" is not perfect sealed and air is going down through the cylinder fins. My feeling 75% of v (100%) is a good value. While there is a relationship between aircraft airspeed and possible upper =20 cowl pressure, using a % airspeed relationship is not meaningful. It is th= e=20 upper/lower cowl pressure difference that is significant regardless of=20 airspeed. Thus, the pitot/static use of an airspeed indicator is only usef= ul to=20 convert to pressure, such pressure reported in the literature as inches of=20 water, not airspeed% or psi. My friend with an E-Racer (rear engined) is=20 concerned with the pressure differential even when he is idling his engine=20= and the=20 aircraft is at zero airspeed.=20 Very supprising to me is a pressure of about 40% below the cylinder. My first thought was: this is much to high to have a good pressure difference between upper and lower plenum! Here is the biggest potential ot improve cooling by reducing this pressure. Reading all your mail show me that=B4s "normal"... By the way: the airspeed indicator (I use for "pressure-measurement") needl= e is vibrating about +-3knots and gives a not too bad reading. However using some kind of damping should improve this instrument Since this lower cowl "airspeed" was computed from cockpit "static"=20 pressure, it is not understandable except to point out that the engine comp= artment=20 has a positive air pressure with respect to the cockpit (see my separate=20 e-mail) and that is important for other reasons. =20 If I take the speeds in your original e-mail graph (say, aircraft at 180)=20 and convert them to pressure (upper 135, lower 65) and subtract the =20 difference, that should be the upper/lower cowl pressure difference since th= e static=20 source is the same: =20 In Knots, 135=3D11.9" H2O, 65=3D2.8", difference =3D 9.1" H2O certainly enou= gh for=20 cooling. However, if we are using MPH: in MPH 135=3D 9" H2O, 65=3D2", the difference is 7" H2O which should be en= ough=20 for cooling although it is at the lower end and certainly won't be as high=20= in=20 a Vx or Vy climb.=20 4. On the backside of my baffles I have holes for the oil cooler (as described in lancair manual) and cabin air. Both holes are about 2" diameter. Variating the hole for the oil cooler do not have a signigicant change to CHT but of course to the oil temperature (I use different cut out sizes for summer /winter time) Interesting. Note that if you are using the Lancair cabin heat valve =20 (1.5"), when the heat is turned off the hot air is merely directed into the=20= lower=20 cowling rather than the cabin. Also, you are dumping the oil cooler exit a= ir=20 into the lower cowling and it is possible that these air exits may affect t= he=20 engine cooling air's smooth exit as well as creating a low pressure across=20 the top of the cylinders. I found it interesting that your very nice cowli= ng=20 nose gear door made no difference as I was just considering one to improve=20 cooling efficiency and thus reduce cooling drag. =20 5. I building a pressure cowling which seals the baffles perfect. At the ai= r inlet section I tied to have only very small gaps (about 1/8"). Right now I did not consider to have a perfect air flow design with smout ramps less than 7=B0 angle (will be improved). The short and sharp ending of the Lancair cooling air inlets tend to have a=20= =20 turbulence which makes the opening appear smaller to the air flow than it =20 actually is. Conclusion: I see the aim to get a lower CHT is not that simple (as I already know before). But when measuring a "40%-Pressure" below the cylinder I thought that=B4s the reason! But when the air outlet area from the lower cowling is big enoth and is acting like a venturi system there should be a much lower pressure... Maybe there are turbulences or other reasons (like Gary Casey mentioned ) for this high pressure! I also liked the slight flare (away from the fuselage) at the air exit poin= t=20 of the bottom cowl as this should create a slight low pressure and assist =20 the exiting air rather than have the airstream curl back over the sharp cowl= end=20 and slightly close up the exit area in a virtual sense. =20 Verrrrry Interrrrrresting! =20 Scott Krueger AKA Grayhawk Lancair N92EX IO320 SB 89/96 Aurora, IL (KARR) -------------------------------1142902439 Content-Type: text/html; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable
Johannes,
 
You wrote:
In a message dated 3/20/2006 1:22:57 A.M. Central Standard Time,=20 jschredl@web.de writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>1.=20 Calibration of probes: use 4 pc. EGT and CHT thermocouples with the
EPI= 800=20 system from Vision Micro. I checked one probe years ago with
confidenti= al=20 results. But I agree, I have to re-check them all again to be
on the sa= ve=20 side.
Are you using bayonet type probes?  Spark Plug Washer type CH= T=20 sensors can yield a reading 50F higher than actual.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>

2. During a normal flight I have following results=20 (+-10=B0F):
   2500 RPM; 23,3"Hg; OAT=3D72=B0F; at 4500ft wit= h 185MPH=20 Indicated Airspeed;
Oil-Temp=3D193=B0F; Fuel =3D 7,5 gal/hour; (Tempera= tures=20 converted from =B0C to =B0F)
        CHT  &nbs= p;=20    EGT
Cyl. 1  390=B0F     1400=B0F
Cy= l.=20 2  410=B0F     1436=B0F
Cyl. 3  410=B0F =20    1418=B0F
Cyl. 4  390=B0F     1382=B0F<= BR>
I=20 have a standard IO320 Lycoming (new when installed) with standard=20 Bendix
injector, Slick magnetos and standard pistons.
I notice Cyl.=20= 2+3=20 have slight higher EGT and same to CHT.
Today I braved high winds and cold weather to try to collect similar=20 information.  Although the temperature was somewhat cooler, these resul= ts=20 are consistent with past tests.  Note that I have ECI Cermi-Nil cylinde= rs,=20 9:1 compression ratio pistons, about 300 hours SMOH (15 hours on cyl #3 OH),= =20 Light Speed Electronic Ignition and a small (7 Vane) Stewart-Warner oil cool= er.=20 So....
 
23.5 MAP, 2500 RPM, 4500 feet MSL, 30.17"Hg (1020 Mb), Dalt 3600,=20= 4C=20 (39F) OAT,
176 KIAS, 186 KTAS (these are Knots) and Oil 165F, Fuel 9.7 gph.
Note: #3 EGT peaked at 1430F, 8.4 gph (EI timing was 25 degrees BT= DC).=20 After enrichening to 9.7 GPH:
CYL CHT   EGT
    1 340F  1290F
    2 330    1320
   *3 340    1320
    4 340    1310
 
I then closed the oil cooler air intake door far enough to raise the oi= l=20 temp to 176F (no change in CHT) and
note that my EPI 800 spare temp probe is located at= the=20 oil cooler air exit where it registered 69C (156F).
 
Next I opened the throttle fully (WOT), MAP of 27.4", 2500 RPM, 11.7 gp= h=20 (100F rich of peak), 192 KIAS (201 KTAS) 
with all the CHTs dropping about 10F.
 
On return I climbed to 5500 MSL where the density altitude was 4600 fee= t=20 and the temp was 3C.
There I ran 23.5 MAP, 2500 RPM, 178 KIAS, 9.6 GPH, 176F oil with t= he=20 door partially closed and
the CHTs were even at 330F.
 
SO,
 
a. Do you really mean 185 MPH or 185 Knots?  The difference w= ould=20 be significant in gph and cooling differential pressures.
b. Is your oil cooler a Stewart-Warner (other brands are less efficient= )?=20 How many vanes?
c. Is your Vernatherm correctly set to send all the oil to the cooler w= hen=20 the temp exceeds 180F? Oil accounts for at least 1/3rd of the engine=20 cooling.  The vernatherm can be tested in hot water to see if it f= ully=20 shrinks (opens) at 180F.
d. Has your throttle body been checked to see if it is delivering all t= he=20 fuel it should? Fuel consumption seems a bit low unless your HP is much less= =20 than mine or; 
e. Are you running at peak or lean of peak EGT? (I tend to see lower EG= Ts=20 because of the electronic ignition, but not that much lower.)
 
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>

3. Measuring the pressure conditions was my first attempt= to=20 get more
information about this problem.
I have to add I used the st= atic=20 pressure of the cockpit, not from the static
ports. Now you tell me the= re=20 might be a considerable differenc I have to
repeat measurement using th= e=20 exact static pressure!
The reason why I used a airspeed indicator was I= can=20 compare it better:
Aircraft speed v: thats the maximum of pressure I ca= n=20 ever get (knowing
p-dynamic =3D 1/2 * rho * v * v) -> max ram airThe=20 "air-speed" at the upper cowling never can be higher than v! In=20 reality
less than v because the "upper cowling" is not perfect sealed a= nd=20 air is
going down through the cylinder fins. My feeling 75% of v (100%)= is=20 a good
value.
While there is a relationship between aircraft airspeed and possible up= per=20 cowl pressure, using a % airspeed relationship is not=20 meaningful.  It is the upper/lower cowl pressure difference that i= s=20 significant regardless of airspeed.  Thus, the pitot/static use of an=20 airspeed indicator is only useful to convert to pressure, such pressure repo= rted=20 in the literature as inches of water, not airspeed% or psi.  My fr= iend=20 with an E-Racer (rear engined) is concerned with the pressure differential e= ven=20 when he is idling his engine and the aircraft is at zero=20 airspeed. 
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size= =3D2>
Very=20 supprising to me is a pressure of about 40% below the cylinder. My
firs= t=20 thought was: this is much to high to have a good pressure=20 difference
between upper and lower plenum! Here is the biggest potentia= l ot=20 improve
cooling by reducing this pressure.
Reading all your mail sho= w me=20 that=B4s "normal"...
By the way: the airspeed indicator (I use for=20 "pressure-measurement") needle
is vibrating about +-3knots and gives a=20= not=20 too bad reading. However using
some kind of damping should improve this= =20 instrument
Since this lower cowl "airspeed" was computed from cockpit=20 "static" pressure, it is not understandable except to point out that the eng= ine=20 compartment has a positive air pressure with respect to the cockpit (see my=20 separate e-mail) and that is important for other reasons.
 
If I take the speeds in your original e-mail graph (say, aircraft=20= at=20 180) and convert them to pressure (upper 135, lower 65) and  subtract t= he=20 difference, that should be the upper/lower cowl pressure difference since th= e=20 static source is the same:
 
In Knots, 135=3D11.9" H2O, 65=3D2.8", difference =3D 9.1" H2O certainly= enough=20 for cooling.  However, if we are using MPH:
 in MPH 135=3D 9" H2O, 65=3D2", the difference is 7" H2O which sho= uld be=20 enough for cooling although it is at the lower end and certainly won't be as= =20 high in a Vx or Vy climb. 
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>

4. On the backside of my baffles I have holes for the oil= =20 cooler (as
described in lancair manual) and cabin air. Both holes are a= bout=20 2"
diameter. Variating the hole for the oil cooler do not have a=20 signigicant
change to CHT but of course to the oil temperature (I use=20 different cut out
sizes for summer /winter time)
Interesting.  Note that if you are using the Lancair cabin heat va= lve=20 (1.5"), when the heat is turned off the hot air is merely directed into the=20 lower cowling rather than the cabin.  Also, you are dumping the oil coo= ler=20 exit air into the lower cowling and it is possible that these air exits may=20 affect the engine cooling air's smooth exit as well as creating a low pressu= re=20 across the top of the cylinders.  I found it interesting that your very= =20 nice cowling nose gear door made no difference as I was just considering one= to=20 improve cooling efficiency and thus reduce cooling drag.  
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>

5. I building a pressure cowling which seals the baffles=20 perfect. At the air
inlet section I tied to have only very small gaps=20 (about 1/8"). Right now I
did not consider to have a perfect air flow=20 design with smout ramps less
than 7=B0 angle (will be=20 improved).
The short and sharp ending of the Lancair cooling air inlets tend to ha= ve a=20 turbulence which makes the opening appear smaller to the air flow than it=20 actually is.
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000=20 size=3D2>

Conclusion:
I see the aim to get a lower CHT is not th= at=20 simple (as I already know
before). But when measuring a "40%-Pressure"=20 below the cylinder I thought
that=B4s the reason! But when the air outl= et=20 area from the lower cowling is
big enoth and is acting like a venturi=20 system there should be a much lower
pressure...
Maybe there are=20 turbulences or other reasons (like Gary Casey mentioned )
for this high= =20 pressure!
I also liked the slight flare (away from the fuselage) at the air exit=20 point of the bottom cowl as this should create a slight low pressure and ass= ist=20 the exiting air rather than have the airstream curl back over the sharp cowl= end=20 and slightly close up the exit area in a virtual sense.
 
Verrrrry Interrrrrresting!=20
 
Scott Krueger=20 AKA Grayhawk
Lancair N92EX IO320 SB 89/96
Aurora, IL=20 (KARR)
-------------------------------1142902439--