X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from [64.129.170.194] (HELO VIRCOM1.fcdata.private) by logan.com (CommuniGate Pro SMTP 5.4.4) with ESMTP id 5433632 for flyrotary@lancaironline.net; Thu, 08 Mar 2012 09:58:03 -0500 Received-SPF: none receiver=logan.com; client-ip=64.129.170.194; envelope-from=cbarber@texasattorney.net Received: from FCD-MAIL05.FCDATA.PRIVATE (unverified [172.16.5.24]) by VIRCOM1.fcdata.private (Vircom SMTPRS 5.1.1024.13396) with ESMTP id for ; Thu, 8 Mar 2012 08:56:30 -0600 X-Modus-BlackList: 172.16.5.24=OK;cbarber@texasattorney.net=OK X-Modus-RBL: 172.16.5.24=Excluded X-Modus-Trusted: 172.16.5.24=NO X-Modus-Audit: FALSE;0;0;0 Received: from FCD-MAIL06.FCDATA.PRIVATE ([fe80::697f:d6aa:b87:78d8]) by FCD-MAIL05.FCDATA.PRIVATE ([fe80::809d:a06e:5913:452e%13]) with mapi id 14.01.0355.002; Thu, 8 Mar 2012 08:56:55 -0600 From: Chris Barber To: Rotary motors in aircraft Subject: Engine cooling Thread-Topic: Engine cooling Thread-Index: Acz9O7IQKpUUeWhWTZGhhgqLFBZmjw== Date: Thu, 8 Mar 2012 14:56:51 +0000 Message-ID: <2D41F9BF3B5F9842B164AF93214F3D30F0543908@FCD-MAIL06.FCDATA.PRIVATE> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [69.148.239.2] Content-Type: multipart/alternative; boundary="_000_2D41F9BF3B5F9842B164AF93214F3D30F0543908FCDMAIL06FCDATA_" MIME-Version: 1.0 --_000_2D41F9BF3B5F9842B164AF93214F3D30F0543908FCDMAIL06FCDATA_ Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable This was posted on the canardaviation.com forum regarding some V8 engine co= oling for aircraft. While some may discount it since it was written by a man who recently passe= d away due to an aircraft crash, I don't think cooling had anything to do w= ith Bud's crash. Just some data points for discussion. PLEASE if you know some stuff that is= rotary specific, or just wrong, CHIME IN!! Chris Houston Cooling Guidelines for V8 Engines in Aircraft by Bud Warren and Phyllis Ridings Introduction: The goal of this article is to share our experiences regarding engine cooli= ng with the Experimental world so that more auto conversion aircraft can be= nefit from our successes and failures. Synopsis: Auto engines in aircraft operate under constant load and therefore produce = more heat than would be produced in an earth bound vehicle. With increased = engine load comes increased heat production by the engine, therefore, an au= to engine in an airplane requires greater cooling capacity than is required= for the same engine in a car or truck. Cooling capacity must be increased = proportionately in order to keep the engine operating in a temperature rang= e that will preserve the engine and increase efficiency. Our description of proper engine cooling is that a V8 engine in an airplane= should never exceed 200=B0F except momentarily during climb out, cooling o= ff to 170-190=B0F at cruise, and never exceed 210=B0F under any but the mos= t extreme circumstances. High engine temperatures only serve to fatigue com= ponents prematurely, and with proper cooling that can be avoided altogether= . Many will argue that their engines run just fine at 230-235=B0F, but we d= o know that high engine temperatures such as this will dramatically shorten= the engine life and contribute to engine failures. Again, there are those who argue that our cars run over 200=B0F and that se= ems to be alright=85but consider this=85auto manufacturers run engines at 2= 00=B0F and above in order to satisfy EPA requirements, not because the engi= nes run better at higher temperatures and certainly not because it is bette= r for the engine. Any long time auto racer will tell you that every effort = is made to help racing engines run cool both for engine longevity and for f= uel efficiency. This system of cooling is based upon each of the following requirements bei= ng met completely. Any one of these recommendations that are not followed c= ould be reason enough for the cooling system to fail. In other words, not o= ne item mentioned below is optional, and is only variable if it is mentione= d to be. When followed to the letter, this system will cool a V8 engine in = an airplane, every time. Formulas The following are the basics upon which we have developed the best and most= complete cooling system that we have ever seen. When followed, under just = about every circumstance, the aircraft will run cool. 1) Requirement: Radiator surface required is 1.5 sq in of surface area per = cubic inch of the engine. For example: LS1 V8 Chevrolet =3D 350 cu in x 1.5= =3D 525 sq in of radiator surface area required. For this purpose, this ap= plies only to the surface area of the radiator that the air flow first make= s contact with. 2) Requirement: Minimum of 3.0 cu in of cooling volume per HP produced. For example: We only utilize up to 300 HP of an LS1 for aircraft use. Using= a dual radiator configuration with two radiators measuring 15=94 x 18=94 x= 2.25=94 thick =3D the total cooling volume is 1215 cu in. Therefore, our cooling volume to HP ratio: 1215 cu in cooling volume =F7 30= 0 HP =3D 4.05 cu in per HP. With this formula, we have been able to maintai= n climb out temperatures of around 200=B0F and 190=B0F at cruise on a 100= =B0F day. With a cooling system like this, we could taxi from Houston to Da= llas with no overheating problems. 3) Requirement: Abandon the conventional front air inlets and close them of= f altogether. Why do we think that front air inlets provide enough air? Bec= ause every airplane you have ever seen with a piston engine has front air i= nlets. If we have always used them they must work, right? We advocate the u= se of side cowl scoops to get enough air into the cowl, and when these are = installed, the front air inlets will literally will negate their value beca= use front air inlets, when combined with the side air scoops, will set up h= igh pressure in the cowl, not allowing enough cool air in and not enough ho= t air to exit the cowl, and the end result is engine overheating. On their own, there is not enough air volume through conventional front air= inlets to cool the engine effectively. One contributor could be because th= e root of the prop blade of most propellers does not have enough of an airf= oil shape to move much air and actively blocks airflow when the blade passe= s the opening, or because the boundary layer of air on the surface of the c= owl behind the prop root is too still to provide much air volume into the c= owl. With the increased cooling requirements of a 300 HP V8 engine under co= nstant load in an airplane, we have found it to be true that front air inle= ts do not provide enough volume of air, nor does it direct what air it does= direct to the right spot within the cowl to effectively cool the radiators= and the engine. 4) Requirement: Move to the side of the cowl and add exterior mounted air i= nlet scoops. The sides of the cowl receive large volumes of air from off th= e prop whether it is taxiing or flying. NACA scoops look great, but are rec= ess mounted inside the profile of the cowl and simply will not force enough= air through the radiators to cool the massive heat produced from the engin= e. We have found that to get enough air volume it is required that exterior= air inlet scoops be mounted on the sides of the cowl. These scoops should = cover an opening on the side of the cowl that is large enough to expose mos= t of the radiator core to the fresh air stream. Scoops that extend 2=94 fro= m the outside profile of the cowl will reach out beyond the quite boundary = layer of air, capturing high velocity air from off the prop and forcing it = through the core of the radiator. Once through the radiators, the air then = circulates around the engine and out the exit air location. 5) Requirement: Fresh air scoop volume recommended at 20 sq inches per side= . The fresh air scoops we recommend are only 20 square inches in inlet size= , and provide ample air to the radiators when mounted on the side of the co= wl as mentioned above, even when taxiing. This is not a lot of inlet space.= RV-10=92s front air inlets average 36 sq inches per side for a total of 72= sq. inches. Our fresh air scoops total only 40 sq inches of air inlet. You= may experiment with the size of the scoop inlets but it is always better t= o have more than not enough. 6) Requirement: Exit air volume. In order to keep the air moving through th= e cowl it is recommended that you utilize 1.5 to 2.0 the amount of the fres= h air inlet for the cowl exit air. Failure to have enough exit air volume w= ill make the engine run too hot or even overheat. This is more difficult to= achieve with a retractable gear airplane but must not be ignored. Ground a= nd taxi testing may produce successful results, only to have the engine ove= rheat on climb out due to insufficient exit air volume now that the gear do= ors are closed, dramatically cutting down on the exit air volume. 7) Requirement: Baffle only between the radiators and the cowl to direct as= much of the air from the side cowl scoops through the radiators as possibl= e. Once the air passes through the radiators, it passes over the engine and= out the exit, also serving to assist in cooling. A V8 engine radiates a gr= eat deal of heat and adding additional baffling to the inside of the cowl o= nly serves to inhibit air circulation around the engine, so do not add any = additional baffling or plenums within the cowl. 8) Requirement: Use water for engine cooling, and add only enough antifreez= e to keep it from freezing. Water takes the most heat energy to change its = temperature than anything else and that makes water the most efficient in t= erms of its ability to conduct heat with minimum temperature rise. Antifree= ze, or ethylene glycol and propylene glycol, have higher vapor points and t= herefore can absorb heat at higher temperatures without boiling. However, e= ven with its lower vapor point, water still carries more heat per unit than= other coolants. 9) Requirement: Use the right radiator cap. An overlooked or under consider= ed part of the cooling system is the radiator cap. Use a 22-24 lb radiator = cap, which will raise the water=92s effective vapor point. For every point = of system pressure increase, the boiling point of water will increase by 3= =B0F. A higher boiling point will also reduce evaporation loss, water pump = cavitation and heat soak induced after boil. : 10) Requirement: Use all aluminum two pass radiators. We recommend that you= r high pressure system consist of all aluminum radiators configured to a tw= o pass system, which increases dwell time in the radiator, and enhances hea= t transfer even more. Hard plumb as much of the water line as you can, usin= g minimal rubber radiator hose for increased durability. The fewer rubber h= oses you have to watch over, the better. 11) To thermostat or not to thermostat...There are a couple of schools of t= hought regarding thermostats in auto conversions for experimental aircraft.= You are likely aware that Bud Warren has not been an advocate for using a = thermostat. He has stated numerous times that racers don=92t use thermostat= s because if it sticks-the race is over. In an aircraft, this happening has= more dangerous implications. His opinion has always been to eliminate the = incidence of a stuck thermostat by simply not using one. We have been flying the Ravin 500 with great success since Oshkosh last yea= r, and we have not been using a thermostat. During the peak heat of summer = we have experienced engine water and oil temps at climb out not to exceed 2= 00=B0F, cooling off to 180=B0-190=B0F at cruise. This system utilizes a dua= l radiator setup and we have been happy with the aircraft performance. However, in colder weather, engine operating temperatures have been a lot c= older that we would like to see. These excessively cool temperatures have t= riggered the ECU to keep the engine in warm up mode; adding additional fuel= to the cylinders in an attempt to warm the engine and causing it to run ri= cher than we like. This is turn causes the check engine light to stay on. W= e would rather stop this from happening so that the check engine light will= be available to warn the pilot if there are any other potentially more vit= al concerns. After much thought, Bud decided to install a thermostat in the LS1 engine o= f the Ravin 500 to do some test flying. During cold weather the resulting e= ngine temps have remained stable at 190=B0F at cruise, and near 200=B0F dur= ing climb out; just about what we see during the warm months of the year. T= his has corrected the check engine light coming on due to the engine remain= ing in warm up mode. We can=92t say unequivocally that we recommend you use a thermostat in your= engine as each situation is different. We would suggest however, that you = carefully determine the correct stance for you to take regarding using or n= ot using a thermostat in your engine. It is a personal decision, with each = option offering different potential results. Perhaps using a thermostat in = the colder months, and replacing it with the thermostat replacement from Ge= ared Drives during the warmer months might be a feasible option. If you choose to use a thermostat, we highly recommend that you test the th= ermostat before you install a new thermostat. This can be accomplished by s= imply dropping it into some boiling water to determine that it does indeed = open. Once you take it out of the boiling water it should close again. This= might seem silly, but there have been incidences of new thermostats not wo= rking. In addition, we recommend that you maintain the coolant in system us= ing the lowest percentage of antifreeze to water that will keep the engine = water from freezing. Also supplement with an anti-corrosive additive to con= dition the inside walls of the cooling system which may help to maintain th= e thermostat as well, and make a note in you POH to change the thermostat o= ut for a new one periodically. Bottom line-use a thermostat if necessary if you choose, but do so with the= utmost of care and caution. If temperatures allow, we recommend that you u= se the thermostat replacement to eliminate the potential of a stuck thermos= tat altogether. __________________ --_000_2D41F9BF3B5F9842B164AF93214F3D30F0543908FCDMAIL06FCDATA_ Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable

This was posted on the canardaviation.com forum regarding so= me V8 engine cooling for aircraft.

 

While some may discount it since it was written by a man who recently pa= ssed away due to an aircraft crash, I don't think cooling had anything to d= o with Bud's crash. 

 

Just some data points for discussion. PLEASE if you know some stuff that= is rotary specific, or just wrong, CHIME IN!!

 

Chris

Houston

 

Cooling Guidelines for V8 Engines in Aircraft
by Bud Warren and Phyllis Ridings

Introduction: 

The goal of this article is to share our experiences regarding engine cooli= ng with the Experimental world so that more auto conversion aircraft can be= nefit from our successes and failures.
Synopsis: 
Auto engines in aircraft operate under constant load and therefore produce = more heat than would be produced in an earth bound vehicle. With increased = engine load comes increased heat production by the engine, therefore, an au= to engine in an airplane requires greater cooling capacity than is required for the same engine in a car or = truck. Cooling capacity must be increased proportionately in order to keep = the engine operating in a temperature range that will preserve the engine a= nd increase efficiency. <= br> Our description of proper engine cooling is that a V8 engine in= an airplane should never exceed 200=B0F except momentarily dur= ing climb out, cooling off to 170-190=B0F at cruise, and never excee= d 210=B0F under any but the most extreme circumstances. High engine temperatures only serve to fatigue components p= rematurely, and with proper cooling that can be avoided altogether. Many wi= ll argue that their engines run just fine at 230-235=B0F, but we do = know that high engine temperatures such as this will dramatically shorten the engine life and contribute to e= ngine failures.
Again, there are those who argue that our cars run over 200=B0F= and that seems to be alright=85but consider this=85auto manufacturers run = engines at 200=B0F and above in order to satisfy EPA requiremen= ts, not because the engines run better at higher temperatures and certainly not because it is better for the engine. Any long time auto = racer will tell you that every effort is made to help racing engines run co= ol both for engine longevity and for fuel efficiency.
This system of cooling is based upon each of the following requirements bei= ng met completely. Any one of these recommendations that are not followed c= ould be reason enough for the cooling system to fail. In other words, not o= ne item mentioned below is optional, and is only variable if it is mentioned to be. When followed to the letter= , this system will cool a V8 engine in an airplane, every time.=  

Formulas
The following are the basics upon which we have developed the best and most= complete cooling system that we have ever seen. When followed, under just = about every circumstance, the aircraft will run cool. 


1) Requirement: Radiator surface required is 1.5 sq in of surface area per = cubic inch of the engine. For example: LS1 V8 Chevr= olet =3D 350 cu in x 1.5 =3D 525 sq in of radiator surface area required. F= or this purpose, this applies only to the surface area of the radiator that the air flow first makes contact with. 


2) Requirement: Minimum of 3.0 cu in of cooling volume per HP produced.
For example: We only utilize up to 300 HP of an LS1 for aircraf= t use. Using a dual radiator configuration with two radiators measuring 15= =94 x 18=94 x 2.25=94 thick =3D the total cooling volume is 1215 cu in. 
Therefore, our cooling volume to HP ratio: 1215 cu in cooling volume =F7 30= 0 HP =3D 4.05 cu in per HP. With this formula, we have been able to maintai= n climb out temperatures of around 200=B0F and 190=B0F<= /a> at cruise on a 100=B0F day. With a cooling system like this, we could taxi from Houston to Dallas with no overheating= problems. 


3) Requirement: Abandon the conventional front air inlets and close them of= f altogether. Why do we think that front air inlets provide enough air? Bec= ause every airplane you have ever seen with a piston engine has front air i= nlets. If we have always used them they must work, right? We advocate the use of side cowl scoops to get enou= gh air into the cowl, and when these are installed, the front air inlets wi= ll literally will negate their value because front air inlets, when combine= d with the side air scoops, will set up high pressure in the cowl, not allowing enough cool air in and not = enough hot air to exit the cowl, and the end result is engine overheating.<= br>
On their own, there is not enough air volume through conventional front air= inlets to cool the engine effectively. One contributor could be because th= e root of the prop blade of most propellers does not have enough of an airf= oil shape to move much air and actively blocks airflow when the blade passes the opening, or because the boundary = layer of air on the surface of the cowl behind the prop root is too still t= o provide much air volume into the cowl. With the increased cooling require= ments of a 300 HP V8 engine under constant load in an airplane, we have found it to be true that front= air inlets do not provide enough volume of air, nor does it direct what ai= r it does direct to the right spot within the cowl to effectively cool the = radiators and the engine. 


4) Requirement: Move to the side of the cowl and add exterior mounted air i= nlet scoops. The sides of the cowl receive large volumes of air from off th= e prop whether it is taxiing or flying. NACA scoops look great,= but are recess mounted inside the profile of the cowl and simply will not force enough air through the radiators to = cool the massive heat produced from the engine. We have found that to get e= nough air volume it is required that exterior air inlet scoops be mounted o= n the sides of the cowl. These scoops should cover an opening on the side of the cowl that is large enough to ex= pose most of the radiator core to the fresh air stream. Scoops that extend = 2=94 from the outside profile of the cowl will reach out beyond the quite b= oundary layer of air, capturing high velocity air from off the prop and forcing it through the core of the radi= ator. Once through the radiators, the air then circulates around the engine= and out the exit air location. =


5) Requirement: Fresh air scoop volume recommended at 20 sq inches per side= . The fresh air scoops we recommend are only 20 square inches in inlet size= , and provide ample air to the radiators when mounted on the side of the co= wl as mentioned above, even when taxiing. This is not a lot of inlet space. RV-10=92s front air inle= ts average 36 sq inches per side for a total of 72 sq. inches. Our fresh ai= r scoops total only 40 sq inches of air inlet. You may experiment with the = size of the scoop inlets but it is always better to have more than not enough. 


6) Requirement: Exit air volume. In order to keep the air moving through th= e cowl it is recommended that you utilize 1.5 to 2.0 the amount of the fres= h air inlet for the cowl exit air. Failure to have enough exit air volume w= ill make the engine run too hot or even overheat. This is more difficult to achieve with a retractable gea= r airplane but must not be ignored. Ground and taxi testing may produce suc= cessful results, only to have the engine overheat on climb out due to insuf= ficient exit air volume now that the gear doors are closed, dramatically cutting down on the exit air volum= e. 


7) Requirement: Baffle only between the radiators and the cowl to direct as= much of the air from the side cowl scoops through the radiators as possibl= e. Once the air passes through the radiators, it passes over the engine and= out the exit, also serving to assist in cooling. A V8 engine radiates a great deal of heat and addi= ng additional baffling to the inside of the cowl only serves to inhibit air= circulation around the engine, so do not add any additional baffling or pl= enums within the cowl.

8) Requirement: Use water for engine cooling, and add only enough antifreez= e to keep it from freezing. Water takes the most heat energy to change its = temperature than anything else and that makes water the most efficient in t= erms of its ability to conduct heat with minimum temperature rise. Antifreeze, or ethylene glycol and propylen= e glycol, have higher vapor points and therefore can absorb heat at higher = temperatures without boiling. However, even with its lower vapor point, wat= er still carries more heat per unit than other coolants.

9) Requirement: Use the right radiator cap. An overlooked or under consider= ed part of the cooling system is the radiator cap. Use a 22-24 lb radiator = cap, which will raise the water=92s effective vapor point. For every point = of system pressure increase, the boiling point of water will increase by 3=B0F. A higher boiling point will = also reduce evaporation loss, water pump cavitation and heat so= ak induced after boil. :

10) Requirement: Use all aluminum two pass radiators. We recommend that you= r high pressure system consist of all aluminum radiators configured to a tw= o pass system, which increases dwell time in the radiator, and enhances hea= t transfer even more. Hard plumb as much of the water line as you can, using minimal rubber radiator hose f= or increased durability. The fewer rubber hoses you have to watch over, the= better.

11) To thermostat or not to thermostat...There are a couple of schools of t= hought regarding thermostats in auto conversions for experimental aircraft.= You are likely aware that Bud Warren has not been an advocate for using a = thermostat. He has stated numerous times that racers don=92t use thermostats because if it sticks-the race is= over. In an aircraft, this happening has more dangerous implications. His = opinion has always been to eliminate the incidence of a stuck thermostat by= simply not using one.

We have been flying the Ravin 500 with great success since Oshk= osh last year, and we have not been using a thermostat. During the peak hea= t of summer we have experienced engine water and oil temps at climb out not= to exceed 200=B0F, cooling off to 180=B0-190=B0F at cruise. This system utilizes a dual radiator s= etup and we have been happy with the aircraft performance. 

However, in colder weather, engine operating temperatures have been a lot c= older that we would like to see. These excessively cool temperatures have t= riggered the ECU to keep the engine in warm up mode; adding additional fuel= to the cylinders in an attempt to warm the engine and causing it to run richer than we like. This is turn= causes the check engine light to stay on. We would rather stop this from h= appening so that the check engine light will be available to warn the pilot= if there are any other potentially more vital concerns. 
After much thought, Bud decided to install a thermostat in the LS1<= /a> engine of the Ravin 500 to do some test flying. During cold= weather the resulting engine temps have remained stable at 190=B0F= at cruise, and near 200=B0F during climb out; just about what we see during the warm months of the year. This has c= orrected the check engine light coming on due to the engine remaining in wa= rm up mode. 

We can=92t say unequivocally that we recommend you use a thermostat in your= engine as each situation is different. We would suggest however, that you = carefully determine the correct stance for you to take regarding using or n= ot using a thermostat in your engine. It is a personal decision, with each option offering different potential r= esults. Perhaps using a thermostat in the colder months, and replacing it w= ith the thermostat replacement from Geared Drives during the warmer months = might be a feasible option.

If you choose to use a thermostat, we highly recommend that you test the th= ermostat before you install a new thermostat. This can be accomplished by s= imply dropping it into some boiling water to determine that it does indeed = open. Once you take it out of the boiling water it should close again. This might seem silly, but there have= been incidences of new thermostats not working. In addition, we recommend = that you maintain the coolant in system using the lowest percentage of anti= freeze to water that will keep the engine water from freezing. Also supplement with an anti-corrosive additiv= e to condition the inside walls of the cooling system which may help to mai= ntain the thermostat as well, and make a note in you POH to cha= nge the thermostat out for a new one periodically. 

Bottom line-use a thermostat if necessary if you choose, but do so with the= utmost of care and caution. If temperatures allow, we recommend that you u= se the thermostat replacement to eliminate the potential of a stuck thermos= tat altogether.
__________________
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