X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from mail11.syd.optusnet.com.au ([211.29.132.192] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTPS id 2195142 for flyrotary@lancaironline.net; Mon, 23 Jul 2007 18:57:50 -0400 Received-SPF: none receiver=logan.com; client-ip=211.29.132.192; envelope-from=lendich@optusnet.com.au Received: from george (d58-105-86-198.dsl.nsw.optusnet.com.au [58.105.86.198]) by mail11.syd.optusnet.com.au (8.13.1/8.13.1) with SMTP id l6NMv3dK010579 for ; Tue, 24 Jul 2007 08:57:05 +1000 Message-ID: <004201c7cd7c$ca732110$c656693a@george> From: "George Lendich" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Carb vs. EFI Date: Tue, 24 Jul 2007 08:57:04 +1000 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_003F_01C7CDD0.9B0842D0" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2180 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 X-Antivirus: avast! (VPS 0657-0, 12/12/2006), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. ------=_NextPart_000_003F_01C7CDD0.9B0842D0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Ernest wrote: Point of interest and it should be kept in mind for any comparison is = how "well-tuned" the components are. The article writers appear to be = professionals, and yet even they had to swapped several components on = both type of systems to get maximum performance. Lynn could probably = make a carb outperform most other's EFI on a particular race day. Give = me another 6 months of study with this EFI, and I might be able to give = him a run for his money, though*. Another point is that I keep reading "Carbs are simpler. You just have = to bolt it on and go." Well, yeah. That's true, IF you want to leave a = lot of performance on the ground. Once you start talking about getting = all the performance out of the engine, especially if you want to = accomplish that over a large range of environmental conditions, then the = carb starts getting VERY complicated. Most people are oblivious that all = that complication even exists and will opt to just take what they get, = power-wise, or bolt on another 'simple' carb. If there is an = improvement, they'll tell everyone the old carb sucks and the new one is = the cat's meow, and at no point will they consider they haven't a clue. = I'm not trying to say EFI is simple, just that a carb is more forgiving = of cluelessness. Ernest, I have worked with carbs and EFI both. I have used throttle body and = also tuned multi-point injection.=20 For the most part the carb and dual point distributor were the bad old = days. You had to tune for the specific track and the specific = atmospheric conditions at that time. EFI was a God send. Dry manifolds, = great torque curves, less peaky operation....and no more blown %*&#(@) = power valves. No springs, jets, and diaphragms to fool with. I would not even think of running anything other than EFI in a car. = That is a no brainer. Carbs are simple in concept, but to make them work = for the varying conditions in an automotive setting they become = complicated nightmares that are prone to failure.=20 That said an airplane is not a car. It is operated at a relatively = narrow band of power settings 65-100%. You (the pilot) have direct = control of the mixture. The carb doesn't have to adjust for changing = conditons, you do. The only time this is a problem is takeoff and = landing. So you run a rich mixture during these regimes. So you burn an = extra couple of pints of fuel per flight. That is your big savings with = EFI in a plane; a couple pints of fuel per cross country. The rest of = the time you lean for cruise and forget it. This is no big deal and = anybody who can fly a Cessna 150 can do this. You don't really need an = accelerator pump. I have yet to fly a Cessna that didn't stumble if I = slam the throttle from idle to full. It didn't seem to cause me any = problems. If you carve off all the crap needed to make a carb work in a car they = become very simple devices. As far as power goes, Theoretically all things equal, a fuel injection = system will make slightly more power due to the drop in manifold = pressure caused by the venturi in the carb. In practice, unless you are = flying a CS prop, you will not be flying at WOT. So there will be no = significant difference in power. Tracy makes a great system and I am not trying to knock it. Ed, Tracy = and others have been running it for a long time. If you want EFI I would = suggest you use Tracy's. Otherwise stick to a carb. The failure modes = for a carb are few and easy to fix. There are far fewer catastrophic = failure modes for a carb than an EFI system. I certainly would not fly = an untried non redundant EFI system. It is not that I am uncomfortable with software, or wiring. I have = built and wired machine tools, and worked on rocket engine test stands = with lots of data acquisition and control equipment. All requiring lots = of wires and software. I just know all the things that can go wrong, and = therefore I am afraid of untested, non redundant electronics. If you = don't know the MTBF of every component and the system as a whole, and = you rely on a single controller that runs your engine, you are playing = Russian Roulette. Any little component, solder joint, you name it can = bring you down (think kill you). Think about that long and hard. Are you = really gaining anything worth that risk? Perceived efficiency? Perceived = benefits? Tracy's system is very reasonably priced for what you get. I = certainly would not use some other single controller system just to save = a few hundred dollars.=20 When things can kill me I like the risks to be easily understood. just my $.02 Monty Monty, You snatched the words out of my (non-professional) mouth. That's how = I see it too - to the extent of looking at developing my own simple = carb, for the single rotor demonstrator. George ( down under) =20 ------=_NextPart_000_003F_01C7CDD0.9B0842D0 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
Ernest = wrote:
 
Point of interest and = it should be=20 kept in mind for any comparison is how "well-tuned" the components = are. The=20 article writers appear to be professionals, and yet even they had to = swapped=20 several components on both type of systems to get maximum performance. = Lynn=20 could probably make a carb outperform most other's EFI on a particular = race=20 day. Give me another 6 months of study with this EFI, and I might be = able to=20 give him a run for his money, though*.

Another point is that I = keep=20 reading "Carbs are simpler. You just have to bolt it on and go." Well, = yeah.=20 That's true, IF you want to leave a lot of performance on the ground. = Once you=20 start talking about getting all the performance out of the engine, = especially=20 if you want to accomplish that over a large range of environmental = conditions,=20 then the carb starts getting VERY complicated. Most people are = oblivious that=20 all that complication even exists and will opt to just take what they = get,=20 power-wise, or bolt on another 'simple' carb. If there is an = improvement,=20 they'll tell everyone the old carb sucks and the new one is the cat's = meow,=20 and at no point will they consider they haven't a clue. I'm not trying = to say=20 EFI is simple, just that a carb is more forgiving of=20 cluelessness.
 
Ernest,
 
I have worked with carbs and EFI = both. I have=20 used throttle body and also tuned multi-point injection.
 
For the most part the carb and dual point distributor were = the bad old=20 days. You had to tune for the specific track and the specific = atmospheric=20 conditions at that time. EFI was a God send. Dry manifolds, great = torque=20 curves, less peaky operation....and no more blown %*&#(@) power = valves. No=20 springs, jets, and diaphragms to fool with.
 
I would not even think of running anything other than EFI in = a car.=20 That is a no brainer. Carbs are simple in concept, but to make them=20 work for the varying conditions in an automotive setting they = become=20 complicated nightmares that are prone to = failure. 
 
That said an airplane is not a car. It is operated = at a=20 relatively narrow band of power settings 65-100%. You (the = pilot)=20 have direct control of the mixture. The carb doesn't have to adjust = for=20 changing conditons, you do. The only time this is a problem is takeoff = and=20 landing. So you run a rich mixture during these regimes. So you burn = an extra=20 couple of pints of fuel per flight. That is your big savings with EFI = in a=20 plane; a couple pints of fuel per cross country. The rest of the time = you lean=20 for cruise and forget it. This is no big deal and anybody who can fly = a Cessna=20 150 can do this. You don't really need an accelerator pump. I have yet = to fly=20 a Cessna that didn't stumble if I slam the throttle from idle to full. = It=20 didn't seem to cause me any problems.
 
If you carve off all the crap needed to make a carb work in a = car they=20 become very simple devices.
 
As far as power goes, Theoretically all things equal, a = fuel=20 injection system will make slightly more power due to the drop in = manifold=20 pressure caused by the venturi in the carb. In practice, unless you = are flying=20 a CS prop, you will not be flying at WOT. So there will = be=20 no significant difference in power.
 
Tracy makes a great system and I am = not trying to=20 knock it. Ed, Tracy and others have been running it for a long time. = If you=20 want EFI I would suggest you use Tracy's. Otherwise stick to a carb. = The=20 failure modes for a carb are few and easy to fix. There are far fewer=20 catastrophic failure modes for a carb than an EFI system. I certainly = would=20 not fly an untried non redundant EFI system.
 
It is not that I am uncomfortable = with software,=20 or wiring. I have built and wired machine tools, and worked on = rocket=20 engine test stands with lots of data acquisition and control = equipment.=20 All requiring lots of wires and software. I just know all the things = that can=20 go wrong, and therefore I am afraid of untested, non = redundant=20 electronics. If you don't know the MTBF of every component and = the system=20 as a whole, and you rely on a single controller that runs your engine, = you are=20 playing Russian Roulette. Any little component, solder joint, you name = it can=20 bring you down (think kill you). Think about that long and hard. Are = you=20 really gaining anything worth that risk? Perceived efficiency? = Perceived=20 benefits? Tracy's system is very reasonably priced for what you get. I = certainly would not use some other single controller system just to = save a few=20 hundred dollars.
 
When things can kill me I like the = risks to be=20 easily understood.
 
just my $.02
 
Monty
 
Monty,
You snatched the words out of my (non-professional) mouth. = That's how I=20 see it too - to the extent of looking at developing my own simple = carb, for=20 the single rotor demonstrator.
George ( down under)  

 
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