X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mailout2.pacific.net.au ([61.8.0.115] verified) by logan.com (CommuniGate Pro SMTP 4.3.6) with ESMTP id 613413 for flyrotary@lancaironline.net; Sun, 24 Jul 2005 09:32:52 -0400 Received-SPF: none receiver=logan.com; client-ip=61.8.0.115; envelope-from=leonp@pacific.net.au Received: from mailproxy2.pacific.net.au (mailproxy2.pacific.net.au [61.8.0.87]) by mailout2.pacific.net.au (8.13.4/8.13.4/Debian-3) with ESMTP id j6ODW4fg006406 for ; Sun, 24 Jul 2005 23:32:04 +1000 Received: from ar1 (ppp209C.dyn.pacific.net.au [61.8.32.156]) by mailproxy2.pacific.net.au (8.13.4/8.13.4/Debian-3) with SMTP id j6ODVlZb018403 for ; Sun, 24 Jul 2005 23:31:48 +1000 Message-ID: <000f01c59053$c24cb720$9c20083d@ar1> From: "Leon Promet" To: "Rotary motors in aircraft" References: Subject: More on Fuel Flow Rates and Diagnosis was Re: [FlyRotary] Re: FUEL FLOW was Re: [FlyRotary] Lycoming debugging test - -HELP! Date: Sun, 24 Jul 2005 23:29:44 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_000C_01C590A7.92D04CB0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2800.1409 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1409 This is a multi-part message in MIME format. ------=_NextPart_000_000C_01C590A7.92D04CB0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hey Kevin, Before you go trying to diagnose the problem piecemeal, please do a = flow test AT THE CARBY. And before you do that, go and do the sums so = that you know how much you SHOULD have as a minimum flow rate. FWIW, = Air BP have a website, and the relevant info about 100LL AvGas density = is on there. See: http://www.airbp.com/usga/index2b438.html?page=3Dproducts&sub=3Davgas Seems that the relative density varies from a low of 0.6582 to a high of = 0.7238. Let's take the lower density. Each litre will weigh 658 grams, = which is around 1.45 Lbs. (2.2 Lbs to the Kg). Taking the high, each = litre will weigh 724 grams which is around 1.60 Lbs. If you directly = weight the fuel that flows into the container (digital bathroom scalesa = are accureate enoungh), then you don't have to do as much math. Again, I freely 'fess up that I know next to NOTHING about Lycosaurae. = But each Shetland Pony on any Otto Cycle engine will need at least 0.55 = Lbs of fuel per hour per BHP at WOT, and there should be a 25% EXTRA = flow margin for safety. SO do the math, and do the flow AT the carby. = This will tell you if you are getting enough fuel AT the carby to = produce the power of which the engine is capable (all depends on the = spec of your O 320 but they are somewhere in the vicinity of 150 - 160. = So let's say 150 BHP to make the math easy. 150 x 0.55 =3D 82.5 Lbs per hour =3D / 60 =3D 1.38 Lbs per minute. = Now one litre weighs 1.45 lbs, so 1.38 Lbs is 1.38/1.45 =3D 0.95 = Litres. So you SHOULD have a flow rate of somewhere around 1.2 litres a = minute (or whatever that is in US quarts, pints, or US Gallons etc - = we got metricated downunder in the late '70s, and I've always been = confused with US gallons as opposed to Imperial (real blokes) gallons = anyway).=20 Then switch tanks and measure the flow rate from the other tank. If all = is well, look in the carby for a restriction, if not, work back doing = the easy things first like the fuel filters, BUT do the FLOW TEST = first!!!!! (Make sure you have a GOOD fire extinguisher on hand, and = an assistant to turn the pumps on & off). Make sure you also have a clear understanding of the difference between = causes & symptoms. Be systematic, change ONE thing at a time and note = the results. If for example, you switch tanks, and the flow rate goes = up, it means that there is a restriction on the supply from the OTHER = tank. If there is no change, then EITHER both tanks are OK, or there = is a similar problem in BOTH tanks. Similarly, if you change the fuel = filter(s) - (do ONE at a time!), and the flow rate goes up, it means = that the filter was partially blocked. If nothing different happens, = then the fuel filter was OK. If you start fiddling with fuel filters, back flushing tanks etc, = BEFORE you know what your flow rate is, and what it should be, you = will NEVER know what the CAUSE of the problem actually is unless you can = compare flow rate results with each systematic change. Moreover, if your fuel flow meter IS reading accurately, and is on the = low side as you suggest, the low flow rate COULD (but not necessarily) = cause the high CHTs because the engine is running lean under load. = Running full rich is just going to more rapidly use up whatever fuel is = getting into the float bowl. All the more reason to do a flow test to = verify the accuracy of your fuel flow meter. However, you then still = have to find out WHY the fuel flow is low. Fix the flow and the high = CHT problem will most probably disappear, and your p[ower will come = back. If they persist, then you need to look for another cause(s). Anyhow, that's about all I can suggest from where I sit in the = Antipodes. Chers, Leon ----- Original Message -----=20 From: kevin lane=20 To: Rotary motors in aircraft=20 Sent: Sunday, July 24, 2005 9:37 AM Subject: [FlyRotary] Re: FUEL FLOW was Re: [FlyRotary] Lycoming = debugging test - -HELP! thank you for the reply. I will start looking into my fuel supply. I = do have a flow meter but haven't been watching it too much since I was = so concerned with the very high CHT's that I've been hitting. the mesh = filter in the carb is good, brand new in fact. I have two auto mesh = fuel filters ahead of the facet pump. they look clean thru the glass, = but I will remove them and look more closely. I have been reluctant to = remove the wing tanks in order to check the pick-up tubes since it is so = much work, plus my tanks are quite full. I suppose I could try to back = flush them first with an air hose if I am VERY careful. now that I = think about it I don't think I have tried switching tanks yet. that = would certainly be an easy task. I believe that my fuel flow meter was showing 8.5+ gals/hr at full = throttle. now that I think about it that may be low, and 10.5 more = typical. thanks for your help. we are having absolutely beautiful weather = here and I was so anxious to do some flying, but....at least I can hang = out at the airport some more. it's nice to find someone who doesn't = immediately say "I'd get rid of that electronic ignition to begin with"! to answer Tracy, yes I have EGT's, shows low 1100's since I am = running full rich, I have manifold pressure but never looked at it(I'd = make a hell of an experimental test pilot-wait, I am one, oops). in my = defense, I have been nervous running my CHT's up past 400 degrees in = order to replicate this problem, since I just had three cylinders welded = because of who knows what? I've been thinking about attaching my leaf = blower to my plenum to help cool things on the ground runups. it = produces 220mph wind, or so the box says. Kevin Lane Portland, OR e-mail-> n3773@comcast.net ----- Original Message -----=20 From: Leon Promet=20 To: Rotary motors in aircraft=20 Sent: Saturday, July 23, 2005 2:48 PM Subject: [FlyRotary] FUEL FLOW was Re: [FlyRotary] Lycoming = debugging test - -HELP! Hey Kevin, Check your fuel FLOW RATE, especially at your normal climb angle = (on the ground). It sounds like it's losing fuel flow on take-off - the = carb is using whatever fuel is in the bowl, and then running lean. You = might have to jack the fuselage to the required angle in case there is = something in the tank that is occuding the pick-up(s). However, if you = can reproduce it on the ground doing a run-up, it definitely sounds = like lack of fuel FLOW (not pressure) to me. If the engine will = maintain 1700 RPM, then it is getting almost but not quite enough fuel = FLOW at WOT. Various things come to mind. FIrstly, (and most easily), a = partially blocked fuel filter (just because it's new doesn't mean it'll = work!!). So change that first. Use a different brand to eliminate = faulty batch manufacture.=20 I once had a mysterious problem with an RX4. Chased it for weeks. = Turned out to be a bee in the fuel line. (I'm serious - the guy who = owned the car used to work for me and is still around and will verify = this!!). Anyway, Jack's pride & joy would work just fine around town. = But out on the open road, it would run out of fuel in 3rd gear (usually = when overtaking). Turned out that a bee (very dead at this stage) had = got into the fuel tank. (The problem occurred soon after Jack filled up = at some outback petrol station when he was on holidays). The bee = immediately got stuck in the fuel supply line. At normal cruising flow = rates, there was sufficient fuel to run the car. On hard acceleration, = the bee's wings & body would PARTIALLY block the supply line in the = tank. We only found it when we removed the tank, replaced it with = another one, and cut the old one open. You just wouldn't read about it = in Ripley's or the War Cry! I've also had pieces of fuel gum (and one instance a piece of = cardboard) block the fuel pick-up. When fuel sits a long time at a = bowser storage tank, especially if there is water at the bottom of the = tank, it will form a sheet of gum at the fuel/water interface, almost = like condom latex, (but nowhere near as strong). This film of gum gets = broken up the next time a tanker does a dump, and bits of this will = very effectively block a fuel pick-up, or cripple a fuel filter. =20 I've seen it happen on several occasions over the years. It was = particularly prevalent in the early '70s during the phase out of = "standard" petrol before the introduction of unleaded into this country = (all rotaries used to run on standard not super - which was heavily = leaded back then). I found out the hard way soon after I had purchsed = my RX2 Coupe in 1971. Filled up at an "out of the way" petrol station = (where the fuel sales volume on standard was virtually nil), and = immediately had problems. After eventually getting back to Sydney, we = quickly diagnosed it as a tank problem. Even steam cleaning the tank = didn't fix it. The tank was replaced, and we cut open the old one, = and there was all these bits of gum, just like a thin membrane tyhat = had been cut up. So the place I'd be looking is in your fuel SUPPLY system, as it = seems you have done everything else except check fuel FLOW rate. Can't = guarantee that this IS the problem, but the quick and easy way would be = to check your open flow rate at the carb, and then compare it with = somebody else's. Alternatively, you can work backwards as you know = that the engine requires at least 0.55 Lbs per hour per BHP at WOT. = (First convert that to litres or pints or quarts per minute and you can = direct measure it, or run the fuel into a can for 1 minute and then go = and weigh it). Fuel flow rate should be at least 25% more than the max = required at WOT so that your carb doesn't run dry. One other area of the problem could be the incorrect needle/seat = arrangement on the carb, or a partially blocked filter at the banjo - = I'm not privvy to what carb you are running so this is conjectural as I = plead total ignorance of Lycoming carbs. However, all stock Mazda = carbs have fine brass gauze mesh filters, both at the banjo, and on = top of the needle& seats. Additionally, in the racing 13Bs, an IDA Weber would run out of = fuel as the float bowl was just way too small for anything over 250 BHP. = We used to replace the 2.5 needle/seat assys with 3.0 units. But we = would STILL run out of fuel on long straights. Extended float bowls = were then added, which did fix the problem, but welding the Weber = material was tricky, especially if it had been saturated with oil laced = fuel for a long time (sometimes the castings were slightly porous).. My final solution was to add an EXTRA float bowl (from an SU carb), = with it's own needle & seat, and a fuel return. We could then go back = to a 2.5 Weber needle & seat, as the 3.0 one was prone to flooding at = idle and on the over-run. (Nothing good has ever come of fuel dilition = of engine oil in a race engine). This fixed all fuel flow issues. Some = time later, affordable aftermarket EFI came along, and all this passed = into history. But fuel SUPPLY issues are even MORE critical with EFI. So these are just a few areas where you can look. Be systematic, = and start at the connection between the carb and the supply line. You = will then quickly eliminate either the supply to the carb, or the carb = needle & seat itself. If the open pipe fuel flow is more than adequate, = then I'd be looking inside the carb for restrictions. As I have said, = this is only a guide. Feel free to contact me off line if you feel the = need. Cheers, Leon ----- Original Message -----=20 From: kevin lane=20 To: Rotary motors in aircraft=20 Sent: Sunday, July 24, 2005 6:33 AM Subject: [FlyRotary] Lycoming debugging test - -HELP! I realize that this isn't exactly the right forum, but you guys = seem to have excellent debugging skills. my local RV group is totally = worthless ("I find the carnauba wax doesn't show fingerprints as much as = the....")(except Mike!) the on-field mechanics are sick of me coming = by. my O-320 RV-6A is having RAG (rpm attention getter) problems. = it runs fine until about 300' on take-off, then the rpm's drop to like = 1700 (from 2200). switching mags to electronic ignition(Rose) makes no = difference. mixture no diff. pulling the throttle it will seem to run = fine at 1700rpm. I have 4 new cyls that I am attempting to break in. = ground run ups can only go like 2 minutes before CHT's exceed 400 = degrees. I discovered I can get the rpm drop on the ground if I run it = a minute or so full power. cht's will typically approach 415 degrees = when the drop takes place. I don't know if the temp is significant or = not, it does seem that way. I have a brand new slick left mag. rose = checked the electronic ignition and could find nothing wrong, even put = it in an oven to test. I installed a new carb since the old one showed = signs of leakage (and I'm at whits end). no change. my fuel pressure = has been showing 8psi this last year, up from 6 psi when originally = installed.(no idea why) I installed a pressure regulator in-line which = works like a charm. I can dial whatever pressure I like. 2 psi makes = no difference. I bypassed the mechanical fuel pump and ran it just on = the facet electric. 2 psi, no difference. I discovered that you can run = the carb for maybe 30 secs with no fuel pressure while it burns off the = bowl gas. premier engines suggested induction leak making the engine run = lean. no leaks detected cold or hot engine. (pressurized intake with = vacuum, sprayed soapy water) if the engine didn't run right to start with then many = explanations would hold. but it runs fine for several minutes. it runs = the same under mag or electronic ignition both before and after the = problem kicks in. everyone really wants to blame the rose ignition, but = I'm not seeing any connection. with such a quick run-up my oil temp = barely registers, so I doubt parts are seizing. I have new mineral oil = in it for breakin right now. there is a bit of MMO in the fuel too I = believe, left over from a mechanics "what the hell" attempt from way = back. my cyls are all new, rebuilts, so no valve problems. I checked = the push rod lengths when I reinstalled them. the engine isn't missing = when the problems occurs, it simply won't run faster and it seems to = prefer the throttle pulled back to match the rpm it is putting out. I = can't figure out any more lean mixture scenarios to try. the new carb = runs just like the old one did. I recently replaced the mag harness = with a much newer, used one. I tested it and it was fine. the plugs = are all new, but again, no diff between mag and elec ignition. if I = flip the ignition to R and shut off the elect ig then the engine quits = as would be expected, no wiring problems. fuel, spark, air, timing, that's all there is. this damn = lycoming lawn mower has me stumped. my engine has been running fine up = until this (hey, we all have "cracked" cylinders, get out your = microscope and look!). you guys have any ideas? Kevin Lane Portland, OR e-mail-> n3773@comcast.net ----- Original ------=_NextPart_000_000C_01C590A7.92D04CB0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hey Kevin,
 
Before you go trying to diagnose the = problem=20 piecemeal,  please do a flow test AT THE CARBY. And before you = do=20 that,  go and do the sums so that you know how much you SHOULD = have as=20 a minimum flow rate. FWIW,  Air BP have a website,  and = the=20 relevant info about 100LL AvGas density is on there.  = See:
 
http://www.airbp.com/usga/index2b438.html?page=3Dproducts&s= ub=3Davgas
 
Seems that the relative density varies = from a low=20 of 0.6582 to a high of 0.7238.  Let's take the lower density.  = Each=20 litre will weigh 658 grams,  which is around 1.45 Lbs.  (2.2 = Lbs to=20 the Kg). Taking the high,  each litre will weigh 724 = grams which=20 is around 1.60 Lbs.  If you directly weight the fuel that flows = into the=20 container (digital bathroom scalesa are accureate enoungh),  then = you don't=20 have to do as much math.
 
Again,  I freely 'fess up = that I=20 know next to NOTHING about Lycosaurae.  But each Shetland Pony on = any Otto=20 Cycle engine will need at least 0.55 Lbs of fuel per hour per = BHP at=20 WOT,  and there should be a 25% EXTRA flow margin for = safety. SO do=20 the math,  and do the flow AT the carby.  This will tell you = if you=20 are getting enough fuel AT the carby to produce the power of which the = engine is=20 capable (all depends on the spec of your O 320 but they are somewhere in = the=20 vicinity of 150 - 160.  So let's say 150 BHP to make the math=20 easy.
 
150 x 0.55 =3D  82.5 Lbs per hour =3D / 60  =3D 1.38 Lbs per minute.  = Now one litre=20 weighs 1.45 lbs,  so 1.38 Lbs is 1.38/1.45 =3D 0.95 Litres.  = So you=20 SHOULD have a flow rate of somewhere around 1.2 litres a minute (or = whatever that is in US quarts,  pints,  or US Gallons etc - we = got=20 metricated downunder in the late '70s,  and I've always been = confused with=20 US gallons as opposed to Imperial (real blokes) gallons=20 anyway). 
 
Then switch tanks and measure the flow = rate from=20 the other tank.  If all is well,  look in the carby for a=20 restriction,  if not,  work back doing the easy things first = like the=20 fuel filters,  BUT do the FLOW TEST first!!!!!  (Make sure you = have a=20 GOOD fire extinguisher on hand,  and an assistant to turn the pumps = on=20 & off).
 
Make sure you also have a clear = understanding of=20 the difference between causes & symptoms.  Be systematic,  = change=20 ONE thing at a time and note the results.  If for example, you = switch=20 tanks,  and the flow rate goes up,  it means that there is a=20 restriction on the supply from the OTHER tank. If there is no=20 change,  then EITHER both tanks are OK,  or there is a similar = problem=20 in BOTH tanks.  Similarly,  if you change the fuel=20 filter(s) - (do ONE at a time!),  and the flow rate = goes=20 up,  it means that the filter was partially blocked.  If = nothing=20 different happens,  then the fuel filter was OK.
 
If you start fiddling with fuel = filters,  back=20 flushing tanks etc,  BEFORE you know what your flow rate is,  = and what=20 it should be,  you will NEVER know what the CAUSE of the = problem=20 actually is unless you can compare flow rate results with each = systematic=20 change.
 
Moreover,  if your fuel flow = meter IS=20 reading accurately, and is on the low side as you suggest,  = the low=20 flow rate  COULD (but not necessarily) cause the high CHTs because = the=20 engine is running lean under load. Running full rich is just going = to more=20 rapidly use up whatever fuel is getting into the float bowl. =  All the=20 more reason to do a flow test to verify the accuracy of your fuel flow=20 meter.  However, you then still have to find out WHY the fuel = flow is=20 low.  Fix the flow and the high CHT problem will most probably = disappear,  and your p[ower will come back.  If they = persist, =20 then you need to look for another cause(s).
 
Anyhow,  that's about all I can = suggest from=20 where I sit in the Antipodes.

Chers,
 
Leon
----- Original Message -----
From:=20 kevin = lane=20
Sent: Sunday, July 24, 2005 = 9:37 AM
Subject: [FlyRotary] Re: FUEL = FLOW was=20 Re: [FlyRotary] Lycoming debugging test - -HELP!

thank you for the = reply.  I will=20 start looking into my fuel supply.  I do have a flow meter but = haven't=20 been watching it too much since I was so concerned with the very high = CHT's=20 that I've been hitting.  the mesh filter in the carb is good, = brand new=20 in fact.  I have two auto mesh fuel filters ahead of the facet=20 pump.  they look clean thru the glass, but I will remove them and = look=20 more closely.  I have been reluctant to remove the wing tanks in = order to=20 check the pick-up tubes since it is so much work, plus my tanks are = quite=20 full.  I suppose I could try to back flush them first with an air = hose if=20 I am VERY careful.  now that I think about it I don't think I = have tried=20 switching tanks yet.  that would certainly be an easy = task.
    I = believe that my=20 fuel flow meter was showing 8.5+ gals/hr at full throttle.  now = that I=20 think about it that may be low, and 10.5 more typical.
    thanks = for your=20 help.  we are having absolutely beautiful weather here and I was = so=20 anxious to do some flying, but....at least I can hang out at the = airport some=20 more.  it's nice to find someone who doesn't immediately say "I'd = get rid=20 of that electronic ignition to begin with"!
    to = answer Tracy, yes=20 I have EGT's, shows low 1100's since I am running full rich,  I = have=20 manifold pressure but never looked at it(I'd make a hell of an = experimental=20 test pilot-wait, I am one, oops).  in my defense, I have been = nervous=20 running my CHT's up past 400 degrees in order to replicate this = problem, since=20 I just had three cylinders welded because of who knows what?  = I've been=20 thinking about attaching my leaf blower to my plenum to help cool = things on=20 the ground runups.  it produces 220mph wind, or so the box=20 says.
Kevin Lane  Portland, OR
e-mail-> n3773@comcast.net
----- Original Message -----
From:=20 Leon=20 Promet
To: Rotary motors in = aircraft=20
Sent: Saturday, July 23, 2005 = 2:48=20 PM
Subject: [FlyRotary] FUEL = FLOW was Re:=20 [FlyRotary] Lycoming debugging test - -HELP!

Hey Kevin,
 
Check your fuel FLOW RATE,  = especially at=20 your normal climb angle  (on the ground).  It sounds like it's losing fuel flow on take-off = - the carb=20 is using whatever fuel is in the bowl,  and then=20 running lean. You might have to jack the fuselage to the = required=20 angle in case there is something in the tank that is occuding the=20 pick-up(s).  However,  if you can reproduce it on the = ground doing=20 a run-up,  it definitely sounds like lack of fuel FLOW (not = pressure)=20 to me.  If the engine will maintain 1700 RPM,  then it is = getting=20 almost but not quite enough fuel FLOW at WOT.
 
Various things come to mind. =20 FIrstly,  (and most easily),  a partially blocked fuel = filter=20 (just because it's new doesn't mean it'll work!!).  So change = that=20 first.  Use a different brand to eliminate faulty batch=20 manufacture. 
 
I once had a mysterious problem = with an=20 RX4.  Chased it for weeks.  Turned out to be a bee in the = fuel=20 line. (I'm serious - the guy who owned the car used to work for me = and is=20 still around and will verify this!!).  Anyway,  Jack's = pride &=20 joy would work just fine around town.  But out on the open = road, =20 it would run out of fuel in 3rd gear (usually when = overtaking).  Turned=20 out that a bee (very dead at this stage) had got into the fuel=20 tank. (The problem occurred soon after Jack filled up at some = outback=20 petrol station when he was on holidays).  The bee = immediately got=20 stuck in the fuel supply line.  At normal cruising flow = rates, =20 there was sufficient fuel to run the car. On hard = acceleration,  the=20 bee's wings & body would PARTIALLY block the supply = line in=20 the tank.  We only found it when we removed the tank,  = replaced it=20 with another one,  and cut the old one open.  You just = wouldn't=20 read about it in Ripley's or the War Cry!
 
I've also had pieces of fuel gum = (and one=20 instance a piece of cardboard) block the fuel pick-up.  When = fuel sits=20 a long time at a bowser storage tank,  especially if there is = water at=20 the bottom of the tank,  it will form a sheet of gum at = the=20 fuel/water interface,  almost like condom latex,  (but = nowhere=20 near as strong).  This film of gum gets broken up the next = time a=20 tanker does a dump,  and bits of this will very effectively = block a=20 fuel pick-up,  or cripple a fuel filter. 
 
I've seen it happen on several = occasions over=20 the years.  It was particularly prevalent in the early = '70s during=20 the phase out of "standard" petrol before the introduction of = unleaded into=20 this country (all rotaries used to run on standard not super - which = was=20 heavily leaded back then).  I found out the hard way soon after = I had=20 purchsed my RX2 Coupe in 1971. Filled up at an "out of the way" = petrol=20 station (where the fuel sales volume on standard was virtually = nil), =20 and immediately had problems.  After eventually getting = back to=20 Sydney,  we quickly diagnosed it as a tank problem.  Even = steam=20 cleaning the tank didn't fix it.  The tank was replaced,  = and we=20 cut open the old one,  and there was all these bits of = gum,  just=20 like a thin membrane tyhat had been cut up.
 
So the place I'd be looking is in = your fuel=20 SUPPLY system,  as it seems you have done everything else = except check=20 fuel FLOW rate.  Can't guarantee that this IS the = problem,  but=20 the quick and easy way would be to check your open flow rate at the=20 carb,  and then compare it with somebody else's. =20 Alternatively,  you can work backwards as you know that = the engine=20 requires at least 0.55 Lbs per hour per BHP at WOT. (First = convert that=20 to litres or pints or quarts per minute and you can direct measure = it, =20 or run the fuel into a can for 1 minute and then go and weigh = it). =20 Fuel flow rate should be at least 25% more than the max required at = WOT so=20 that your carb doesn't run dry.
 
One other area of the problem could = be the=20 incorrect needle/seat arrangement on the carb,  or a partially = blocked=20 filter at the banjo - I'm not privvy to what carb you are = running so=20 this is conjectural as I plead total ignorance of Lycoming = carbs. =20 However,  all stock Mazda carbs have fine brass gauze mesh = filters,  both at the banjo,  and on top of the = needle&=20 seats.
 
Additionally, in the racing = 13Bs,  an IDA=20 Weber would run out of fuel as the float bowl was just way too small = for=20 anything over 250 BHP.  We used to replace the 2.5 needle/seat = assys=20 with 3.0 units.  But  we would STILL run out of fuel on = long=20 straights.  Extended float bowls were then added,  which=20 did fix the problem,  but welding the Weber material was=20 tricky,  especially if it had been saturated with oil laced = fuel for a=20 long time (sometimes the castings were slightly = porous)..
 
My final solution was to add = an EXTRA=20 float bowl (from an SU carb),  with it's own needle & = seat, =20 and a fuel return.   We could then go back to a 2.5 Weber = needle=20 & seat,  as the 3.0 one was prone to flooding at idle and = on the=20 over-run. (Nothing good has ever come of fuel dilition of = engine oil in=20 a race engine). This fixed all fuel flow issues.  Some = time=20 later, affordable aftermarket EFI came along,  and = all this=20 passed into history.  But fuel SUPPLY issues are even MORE = critical=20 with EFI.
 
So these are just a few areas where = you can=20 look.  Be systematic,  and start at the connection between = the=20 carb and the supply line.  You will then quickly eliminate = either the=20 supply to the carb,  or the carb needle & seat = itself.  If the=20 open pipe fuel flow is more than adequate,  then I'd be looking = inside=20 the carb for restrictions.  As I have said,  this is only = a=20 guide.  Feel free to contact me off line if you feel the=20 need.
 
Cheers,
 
Leon
 
 
----- Original Message -----
From:=20 kevin lane=20
To: Rotary motors in = aircraft=20
Sent: Sunday, July 24, 2005 = 6:33=20 AM
Subject: [FlyRotary] = Lycoming=20 debugging test - -HELP!

I realize that this = isn't exactly=20 the right forum, but you guys seem to have excellent debugging=20 skills.  my local RV group is totally worthless ("I find the = carnauba=20 wax doesn't show fingerprints as much as the....")(except = Mike!)  the=20 on-field mechanics are sick of me coming by.
    my = O-320 RV-6A=20 is having RAG (rpm attention getter) problems.  it runs fine = until=20 about 300' on take-off, then the rpm's drop to like 1700 (from=20 2200).  switching mags to electronic ignition(Rose) makes no=20 difference.  mixture no diff.  pulling the throttle = it will=20 seem to run fine at 1700rpm.  I have 4 new cyls that I am = attempting=20 to break in.  ground run ups can only go like 2 minutes = before CHT's=20 exceed 400 degrees.  I discovered I can get the rpm drop on = the=20 ground if I run it a minute or so full power.  cht's will = typically=20 approach 415 degrees when the drop takes place.  I don't know = if the=20 temp is significant or not, it does seem that way.  I have a = brand=20 new slick left mag.  rose checked the electronic ignition and = could=20 find nothing wrong, even put it in an oven to test.  I = installed a=20 new carb since the old one showed signs of leakage (and I'm at = whits=20 end).  no change.  my fuel pressure has been showing = 8psi this=20 last year, up from 6 psi when originally installed.(no idea = why)  I=20 installed a pressure regulator in-line which works like a = charm.  I=20 can dial whatever pressure I like.  2 psi makes no = difference. =20 I bypassed the mechanical fuel pump and ran it just on the facet=20 electric.  2 psi, no difference. I discovered that you = can run=20 the carb for maybe 30 secs with no fuel pressure while it burns = off the=20 bowl gas. premier engines suggested induction leak making the = engine run=20 lean.  no leaks detected cold or hot engine. (pressurized = intake with=20 vacuum, sprayed soapy water)
    if = the engine=20 didn't run right to start with then many explanations would = hold. =20 but it runs fine for several minutes.  it runs the same under = mag or=20 electronic ignition both before and after the problem kicks = in. =20 everyone really wants to blame the rose ignition, but I'm not = seeing any=20 connection.  with such a quick run-up my oil temp barely = registers,=20 so I doubt parts are seizing.  I have new mineral oil in it = for=20 breakin right now.  there is a bit of MMO in the fuel too I = believe,=20 left over from a mechanics "what the hell" attempt from way = back.  my=20 cyls are all new, rebuilts, so no valve problems.  I checked = the push=20 rod lengths when I reinstalled them.  the engine isn't = missing=20 when the problems occurs, it simply won't run faster and it seems = to=20 prefer the throttle pulled back to match the rpm it is putting = out. =20 I can't figure out any more lean mixture scenarios to try.  = the new=20 carb runs just like the old one did.  I recently replaced the = mag=20 harness with a much newer, used one.  I tested it and it was=20 fine.  the plugs are all new, but again, no diff between mag = and elec=20 ignition.  if I flip the ignition to R and shut off the elect = ig then=20 the engine quits as would be expected, no wiring = problems.
    = fuel, spark,=20 air, timing, that's all there is.  this damn lycoming lawn = mower has=20 me stumped.  my engine has been running fine up until this = (hey, we=20 all have "cracked" cylinders, get out your microscope and = look!). =20 you guys have any ideas?
Kevin Lane  Portland, OR
e-mail-> n3773@comcast.net
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