X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sat, 14 Apr 2012 00:01:40 -0400 Message-ID: X-Original-Return-Path: Received: from blu0-omc3-s3.blu0.hotmail.com ([65.55.116.78] verified) by logan.com (CommuniGate Pro SMTP 5.4.4) with ESMTP id 5478218 for lml@lancaironline.net; Thu, 12 Apr 2012 04:23:21 -0400 Received-SPF: neutral receiver=logan.com; client-ip=65.55.116.78; envelope-from=frederickmoreno@bigpond.com Received: from BLU0-SMTP161 ([65.55.116.72]) by blu0-omc3-s3.blu0.hotmail.com with Microsoft SMTPSVC(6.0.3790.4675); Thu, 12 Apr 2012 01:22:45 -0700 X-Originating-IP: [58.166.87.143] X-Originating-Email: [frederickmoreno@bigpond.com] X-Original-Message-ID: X-Original-Return-Path: frederickmoreno@bigpond.com Received: from Razzle ([58.166.87.143]) by BLU0-SMTP161.phx.gbl over TLS secured channel with Microsoft SMTPSVC(6.0.3790.4675); Thu, 12 Apr 2012 01:22:43 -0700 MIME-Version: 1.0 X-Original-Date: Thu, 12 Apr 2012 16:22:33 +0800 Content-Type: multipart/alternative; charset="utf-8"; boundary="------------Boundary-00=_LXXCX1T3LVC000000000" X-Mailer: IncrediMail (6295180) From: Frederick Moreno References: X-FID: FLAVOR00-NONE-0000-0000-000000000000 X-Priority: 3 X-Original-To: "Lancair Mail (lml@lancaironline.net)" Subject: Re: [LML] Re: Engine "surge" issue X-OriginalArrivalTime: 12 Apr 2012 08:22:44.0493 (UTC) FILETIME=[6F8E5BD0:01CD1885] --------------Boundary-00=_LXXCX1T3LVC000000000 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Luke: =0D =0D You will get a lot of opinions so here is mine based on my experience as = a heat transfer engineer. =0D =0D The fluctuations and problems (except the high CHT on one cylinder in cli= mb) come from fuel boiling- in the lines feeding the fuel pump, in the fuel pump, between fuel pump and "spider," and in the "spider" assembly and th= e little lines where the fuel spreads out to the cylinders. The boiling le= ads to intermittent flow, bubbles, more flow, and its occurrence depends primarily on temperature and pressure, both of which change with time and RPM after start. And the rate of cooling of each of these areas is different once the engine starts, so you can have boiling occuring I seve= ral places at once which greatly confuses the situation and make engine operation even more erratic after a hot start. =0D =0D Depending on the distance between tank fuel elevation (empty or full?) an= d fuel pump elevation and length of line under the cowl leading to the fuel pump, lowered pressure caused by fuel pump suction will cause bubbling (boiling) of fuel in the inlet line with consequent erratic flow at the f= uel pump outlet as bubbles are swallowed, clear, and more are swallowed. Thi= s will also happen in the gascolator if it is mounted in front of the firew= all Same thing happens downstream of the pump where fuel boils in the lines due to elevated temperatures after shut down. =0D =0D And consider this scenario. You start the engine. RPM rises, fuel deman= d increases, the fuel pump sucks harder, fuel boils at the inlet, pump suck= s gas vapor, fuel pressure falls, then fuel pumped above the engine for a moment starts to boil when it hits the hot lines and the fuel pressure fa= lls when the fuel pump falters. Suction falls due to vapor in the pump.=20 Liquid finally gets to the pump inlet, the pump raises its outlet press= ure puts more fuel above the engine, and the cycle repeats with boiling at t= he fuel pump inlet and the fuel above the engine starts to boil again when = the pressure falls again. The cycle repeats. Surge. And the fuel mixture?=20 All over the map. This can continue until things cool off which can tak= e 1-2 minutes, a very long time when you are battling an engine that is running out of fuel (vapor only), then drowning in it, then starvation se= ts in again with a new batch of bubbles.... You get the idea. =0D =0D At higher RPM, the fuel pressure out of the pump rises to meet increased flow rate demand for the engine, and this raises the pump discharge press= ure which can suppress boiling downstream of the pump, but may worsen boiling upstream of the pump due to decreased pump inlet pressure 9greater suctio= n). Reduce the RPM down before the lines cool, and the boiling starts again downstream of the pump and fuel nozzles get squirts of fuel, then vapor, then fuel and this continues until no more vapor is produced as temperatu= re falls due to fuel cooling of the lines. =0D =0D Wrapping lines helps only for a short period after shutdown. The insulat= ion on the lines is insufficient to keep the heat out of the lines and out of the fuel within the lines for more than a feww minutes. Thermal insulato= rs are actually lousy insulators. Think of them as semiconductors, not insulators and conductors in the electrical sense where insulators really insulate. Remember: there is no fuel flow to carry any heat away the hea= t seeping through the insulation unlike occurs when the engine is running. = =0D =0D Under stagnant conditions after shutdown, temperatures tend to equilibrat= e fairly quickly. Under the cowl after shutdown, temperatures will soar to over 150F+ even on a cool day before they start down due to natural cooli= ng which can be very slow with a tightly cowled engine and no wind.=0D =0D Facing the airplane into the wind helps to bring air into the inlets and push heat out the outlets as occurs during flight. But without wind present, the natural convection after shutdown will be in the bottom, ris= ing up through the cylinders, and out the inlets behind the prop. This will = be a slow process because there is not much elevation difference between cylinders and "exit" and thus no "chimney" effect. =0D =0D So the root cause is that ALL the fuel lines (and pump, and gascolator) under the cowl heat soak and then problems occur when the engine starts a= nd needs a steady diet of liquid fuel at the injectors, and gets spurts of liquid, then vapor, then liquid, and it continues for several minutes. =0D =0D The solutions offered to accelerate fuel line and fuel pump (and gascolat= or) cooling are beneficial: circulate cool fuel back to the tank to cool as m= uch as the plumbing as possible before start (takes at least a minute, and on= ly cools a portion of the lines), and opening an oil door other other means = to let hot air escape out the top of the cowl to cool everything underneath.= =20 Otherwise, you have to start, and if you can keep it running a bit, incre= ase RPM, perhaps more than a comfortable amount (like 1700, a lot at a tie do= wn) to get steady operation (high pressure downstream of the pump), and flow lots of fuel under pressure until things cool down. That can take a cou= ple of minutes or more. =0D =0D Also, after starting, insulated fuel lines will cool less rapidly with ai= r blast after starting than un-insulated fuel lines. I have in mind here t= he stainless steel small lines emanating from the spider to the fuel injecto= rs. All others should be fire shielded. =0D =0D On my Continental, both the gascolator and the fuel pump have shrouds and get blasts of cooling air via one inch SCAT lines fed from above the cowl= =2E=20 This eliminates heating in flight from the hot air downstream of the engi= ne. A short amount of low boost prior to start gets fuel moving, and the eng= ine usually starts promptly even with a very hot start, after which I shut of= f the low boost. =0D =0D I measure air temperature at the face of the firewall, and temperatures o= f 150F are typical in cruise operating with CHT of 300F with mixture LOP an= d OAT of 60-70F in the summertime at 6000-8000. In other words, with a 30= 0F CHT, I see temperature rise across the engine of about 130-140F at 65% po= wer Higher CHT and higher power settings will increase the temperature ris= e across the engine. This is the temperature at which everything is heat soaked downstream of the cylinders and on the firewall. Add more temperat= ure rise if the component (fuel pump, fuel line, or gascolator) can "see" the= =20 thermal radiation from the exhaust pipes which are glowing red hot. =0D =0D In short, there are lots of ways to heat soak fuel lines, pumps, gascolat= ors and such both in flight and after shutdown. All contribute to fuel boil= ing and erratic operation after a hot start. =0D =0D The high CHT, being recent and apparently severe suggests to me a cracked spark plug causing pre-ignition which is extremely harmful and causes rap= id excessive heating. Pull the plugs, have a close look, and if you can not find a crack, chip, or flaw even with a magnifying glass and a good light= , I suggest two new plugs into that cylinder and a test flight based on gener= al principles. Preignition and detonation are the quickest ways to convert cylinders and pistons to scrap - sometimes in mere tens of seconds. Seek the cause before next flight. =0D =0D You may now insert two cents in that slot in the front of your computer. = =0D =0D Fred Moreno=0D =0D =0D =0D =0D -------Original Message-------=0D =0D From: Luke Alcorn=0D Date: 12/04/2012 10:51:51 AM=0D To: lml@lancaironline.net=0D Subject: [LML] Re: Engine "surge" issue=0D =0D I have a Lycon built IO-360 with 10:1 compression pistons and I have simi= lar issues. My engine does not surge and idle, but with stumble, pop and sputter, with the EGT's bouncing all over the place. It does it shortly after touchdown on any day about 80 degrees, even after a nice long slow descent and gently cooling the engine down from 10,000 feet. If it sits = to get fuel and then restart anywhere up to 3 hours after shutdown, it will idle like crap, but when you put the throttle to it, above 1700 RPM is smooths out.=0D =0D I have been chasing this problem for 2 years. I've wrapped the injector lines in firesleeve, had my fuel servo rebuilt twice, the injectors, spid= er and fuel servo flow matched, changed to colder REM37BY plugs, and I still run into the same problems. The only thing I can think of is that the ho= t fuel between the gascolator and the lines running to the servo is getting turbulent in the lines, and not flowing properly through the spider and injectors, hence the EGT's jumping around. Mixture and boost pump do nothing. I've rebuilt my mags, new ignition harness, intake gaskets (thinking I had a leak), checked exhaust leaks, etc. All of those change= s and it runs the exact same as the day I bought it.=0D =0D I now have a new issue of my #1 CHT going sky high on my initial climb ou= t when it never did before. My CHT's run warm, like any close cowled engin= e, but mine tries to go above 470 really fast, I have to level off and 500 t= o 1000 feet and bring the power back to 22 inches and let it cool down. Th= en I can add full throttle and it is fine the rest of the climb. That cylin= der has the most airflow of any of them being in the right front. I believe t= his is fuel related as well. As cruise my EGT's and CHT's and 20 to 30 degre= e spread.=0D =0D Any help would be appreciated as well.=0D =0D Luke Alcorn=0D =20 --------------Boundary-00=_LXXCX1T3LVC000000000 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
Luke:
 
You will get a lot of opinions so here is mine based on my experienc= e as a heat transfer engineer. 
 
The fluctuations and problems (except the high CHT on one cylin= der in climb) come from fuel boiling-  in the lines feeding the fuel= pump, in the fuel pump, between fuel pump and "spider," and in the "spid= er" assembly and the little lines where the fuel spreads out to the = cylinders.  The boiling leads to intermittent flow, bubbles, more fl= ow, and its occurrence depends primarily on temperature and pressure, bot= h of which change with time and RPM after start.  And the rate of co= oling of each of these areas is different once the engine starts, so you = can have boiling occuring I several places at once which greatly confuses= the situation and make engine operation even more erratic after a hot st= art. 
 
Depending on the distance between tank fuel elevation (empty or= full?) and fuel pump elevation and length of line under the cowl leading= to the fuel pump, lowered pressure caused by fuel pump suction will= cause bubbling (boiling) of fuel in the inlet line with consequent&= nbsp;erratic flow at the fuel pump outlet as bubbles are swallowed, clear= , and more are swallowed.  This will also happen in the gascolator i= f it is mounted in front of the firewall.  Same thing happens downst= ream of the pump where fuel boils in the lines due to elevated tempe= ratures after shut down.   
 
And consider this scenario.  You start the engine.  R= PM rises, fuel demand increases, the fuel pump sucks harder, fuel bo= ils at the inlet, pump sucks gas vapor, fuel pressure falls, then fuel pu= mped above the engine for a moment starts to boil when it hits = the hot lines and the fuel pressure falls when the fuel pump falters.&nbs= p; Suction falls due to  vapor in the pump.  Liquid  final= ly gets to the  pump inlet, the pump raises its outlet pressure, put= s more fuel above the engine, and the cycle repeats with boiling at the f= uel pump inlet and the  fuel above the engine starts to boil ag= ain when the pressure falls again.  The cycle repeats.  Surge.&= nbsp; And the fuel mixture?  All over the map.  This can contin= ue  until things cool off which can take 1-2 minutes, a very long ti= me when you are battling an engine that is running out of fuel (vapo= r only), then drowning in it, then starvation sets in again with a n= ew batch of bubbles....  You get the idea.  
 
At higher RPM, the fuel pressure out of the pump rises to meet incre= ased flow rate demand for the engine, and this raises the pump discharge = pressure which can suppress boiling downstream of the pump, but may worse= n boiling upstream of the pump due to decreased pump inlet pressure 9grea= ter suction).   Reduce the RPM down before the lines cool,= and the boiling starts again downstream of the pump and fuel nozzles get= squirts of fuel, then vapor, then fuel and this continues until no more = vapor is produced as temperature falls due to fuel cooling of the lines. =
 
Wrapping lines helps only for a short period after shutdown.&nb= sp; The insulation on the lines is insufficient to keep the heat out of t= he lines and out of the fuel within the lines for more than a feww minute= s.  Thermal insulators are actually lousy insulators.  Think of= them as semiconductors, not insulators and conductors in the electrical = sense where insulators really insulate.  Remember: there is no fuel = flow to carry any heat away the heat seeping through the insulation unlik= e occurs when the engine is running. 
 
Under stagnant conditions after shutdown, temperatures tend to equil= ibrate fairly quickly.  Under the cowl after shutdown, temperatures = will soar to over 150F+ even on a cool day before they start down due to = natural cooling which  can be very slow with a tightly cowled engine= and no wind.
 
Facing the airplane into the wind helps to bring air into the inlets= and push  heat out the outlets as occurs during flight.  But w= ithout wind present, the natural convection after shutdown will be in the= bottom, rising up through the cylinders, and out the inlets behind the p= rop.  This will be a slow process because there is not much elevatio= n difference between cylinders and "exit" and thus no "chimney" effe= ct. 
 
So the root cause is that ALL the fuel lines (and pump, and gascolat= or) under the cowl heat soak and then problems occur when the engine star= ts and needs a steady diet of liquid fuel at the injectors, and gets spur= ts of liquid, then vapor, then liquid, and it continues for several minut= es. 
 
The solutions offered to accelerate fuel line and fuel pump (and gas= colator) cooling are beneficial: circulate cool fuel back to the tank to = cool as much as the plumbing as possible before start (takes at least a m= inute, and only cools a portion of the lines), and opening an oil do= or other other means to let hot air escape out the top of the cowl to coo= l everything underneath.  Otherwise, you have to start, and if you c= an keep it running a bit, increase RPM, perhaps more than a comfortable a= mount (like 1700, a lot at a tie down) to get steady operation (high pres= sure downstream of the pump), and flow lots of fuel under pressure until = things cool down.   That can take a couple of minutes or more.&= nbsp; 
 
Also, after starting, insulated fuel lines will cool less rapidly wi= th air blast after starting than un-insulated fuel lines.  I have in= mind here the stainless steel small lines emanating from the spider to t= he fuel injectors.   All others should be fire shielded.
 
On my Continental, both the gascolator and the fuel pump have shroud= s and get blasts of cooling air via one inch SCAT lines fed from above th= e cowl.  This eliminates heating in flight from the hot air downstre= am of the engine.  A short amount of low boost prior to start gets f= uel moving, and the engine usually starts promptly even with a very hot s= tart, after which I shut off the low boost.
 
I measure air temperature at the face of the firewall, and temperatu= res of 150F are typical in cruise operating with CHT of 300F with mixture= LOP and OAT of 60-70F in the summertime at 6000-8000.   In oth= er words, with a 300F CHT, I see temperature rise across the engine of ab= out 130-140F at 65% power.  Higher CHT and higher power settings wil= l increase the temperature  rise across the engine.  = This is the temperature at which everything is heat soaked downstream of= the cylinders and on the firewall. Add more temperature rise if the comp= onent (fuel pump, fuel line, or gascolator) can "see" the  thermal r= adiation from the  exhaust pipes which are glowing red hot.
 
In short, there are lots of ways to heat soak fuel lines, pumps, gas= colators, and such both in flight and after shutdown.  All contribut= e to fuel boiling and erratic operation after a hot start.
 
The high CHT, being recent and apparently severe suggests to me a cr= acked spark plug causing pre-ignition which is extremely harmful and caus= es rapid excessive heating.  Pull the plugs, have a close look, and = if you can not find a crack, chip, or flaw even with a magnifying glass a= nd a good light, I suggest two new plugs into that cylinder and a test fl= ight based on general principles.  Preignition and detonation are th= e quickest ways to convert cylinders and pistons to scrap - sometimes in = mere tens of seconds.  Seek the cause before next flight.
 
You may now insert two cents in that slot in the front of your compu= ter.
 
Fred Moreno
 
 
 
 
-= ------Original Message-------
 
Date: 12/04/2012 1= 0:51:51 AM
Subject: [LML] Re:= Engine "surge" issue
 

I have a Lycon built IO-360 with 10:1 compr= ession pistons and I have similar issues.  My engine does not surge = and idle, but with stumble, pop and sputter, with the EGT's bouncing all = over the place.  It does it shortly after touchdown on any day about= 80 degrees, even after a nice long slow descent and gently cooling the e= ngine down from 10,000 feet.  If it sits to get fuel and then restar= t anywhere up to 3 hours after shutdown, it will idle like crap, but when= you put the throttle to it, above 1700 RPM is smooths out.

 

I have been chasing this problem for 2 year= s.  I've wrapped the injector lines in firesleeve, had my fuel servo= rebuilt twice, the injectors, spider and fuel servo flow matched, change= d to colder REM37BY plugs, and I still run into the same problems.  = The only thing I can think of is that the hot fuel between the gascolator= and the lines running to the servo is getting turbulent in the lines, an= d not flowing properly through the spider and injectors, hence the EGT's = jumping around.  Mixture and boost pump do nothing.  I've rebui= lt my mags, new ignition harness, intake gaskets (thinking I had a leak),= checked exhaust leaks, etc.  All of those changes and it runs the e= xact same as the day I bought it.

 

I now have a new issue of my #1 CHT going s= ky high on my initial climb out when it never did before.  My CHT's = run warm, like any close cowled engine, but mine tries to go above 470 re= ally fast, I have to level off and 500 to 1000 feet and bring the power b= ack to 22 inches and let it cool down.  Then I can add full throttle= and it is fine the rest of the climb.  That cylinder has the most a= irflow of any of them being in the right front. I believe this is fuel re= lated as well.  As cruise my EGT's and CHT's and 20 to 30 degree spr= ead.

 

Any help would be appreciated as well.

 

Luke Alcorn

 
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