Received-SPF: pass
 receiver=logan.com; client-ip=64.12.137.2; envelope-from=WRJJRS@aol.com
References: <list-2193053@logan.com>
To: flyrotary@lancaironline.net
Content-Transfer-Encoding: quoted-printable
Subject: Re: [FlyRotary] Re: carbs vs efi
Date: Mon, 23 Jul 2007 11:13:49 -0400
In-Reply-To: <list-2193053@logan.com>
MIME-Version: 1.0
From: wrjjrs@aol.com
Content-Type: text/plain; charset="iso-8859-1"; format=flowed
Message-Id: <8C99B5334A9C53B-338-2405@webmail-de17.sysops.aol.com>


-----Original Message-----
From: Ernest Christley <echristley@nc.rr.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Sun, 22 Jul 2007 11:31 am
Subject: [FlyRotary] Re: carbs vs efi


Russell Duffy wrote:=A0
> > EFI is a complex system, but when it's working like it does in your=20
car=A0
> every day, it's a no brainer of a choice. Since this is a result of=A0
> millions of dollars of R&D work, such a perfect, turn-key system is=20
not=A0
> going to be available to us. Even if such a system was available, it=20
would=A0
> require everyone to use exactly the same setup, which goes against=20
the grain=A0
> for most of us. > >=A0
=A0
Rusty, all of those arguments can be turned right back around and=20
pointed at carbs. 8*) There has been MUCH more money put in to carb=20
development over the years than has been invested in EFI system. People=20
often ask me what the best program to do "XYZ" is. My canned response=20
is that the best program to use is usually the one that you already=20
know. I think it's the same with carbs vs EFI.=A0
=A0
See, the problem isn't just delivering fuel to the engine in the right=20
amount. Shucks, that's easy. It gets complicated when you start trying=20
to deliver the right amount of fuel at the right time. With carbs you=20
have to figure out jets size, add an accelerator pump, mess with the=20
venturi, and a hundred other things that people have tried over the=20
years. If you change something in the intake, you may have to switch=20
out a bunch of stuff in order to retune. Then you have to fiddle and=20
adjust to get it all working properly again. With EFI, you have to size=20
the injector, learn concepts such as acceleration enrichment and XTau,=20
decide between speed-density vs alpha-N for tuning, and then modify a=20
program to account for all the variables. If something changes in the=20
intake, you'll have to modify the tuning parameters in the program=20
again. When it's all done, you're going to have to learn a lot before=20
you know what you're doing, the learning will only come from fiddling=20
with the thing, and you won't know what you're doing until you learn a=20
lot.=A0
=A0
For me, I like the EFI. I won't necessarily smell like gas after=20
fiddling, and I can do much of the fiddling from my desk. A carb is an=20
analogue computer, with the drawback that you will never get=20
datalogging from it. But the biggest advantage to EFI for me is the=20
fact that I can just hit the AUTOTUNE button to flatten the learning=20
curve. But, while I've rebuilt a few carbs before, I don't really have=20
that Zen understanding of how they work. OTOH, I'm a software engineer.=20
Program a controller is second nature for me.=A0
=A0
Your mileage may vary. Not valid in all states. No user serviceable=20
parts inside. May cause headaches, heart palpitations, or diarhea. Do=20
not take before operating heavy equipment.

Well put Ernest,
  A engine is a dynamic system with a ton of variables. Working with=20
what you are familiar with is a good idea. I built race engines as a=20
young man of 20, and even then the mantra was, "everything effects=20
everything!" Consider it the internal combustion engine law of=20
unintended consequences. A small change can sometimes effect several=20
other systems, in ways both good or bad.
Bill Jepson =A0
--=A0
Homepage: http://www.flyrotary.com/=A0
Archive and UnSub:=20
http://mail.lancaironline.net:81/lists/flyrotary/List.html=A0


________________________________________________________________________
AOL now offers free email to everyone.  Find out more about what's free=20
from AOL at AOL.com.
=3D0