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From: "Tracy crook" <lors01@msn.com>
To: flyrotary@lancaironline.net
Bcc: 
Subject: RE: [FlyRotary] Re: carbs vs efi 
Date: Mon, 23 Jul 2007 11:52:52 -0400
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Lot of good points made here.  I MUST put something like this thread on the 
EC2 page of my website.

Just as an aside on carbs,  my old Yamaha XS11 was normally a picture of 
perfect carb tuning but it would not run if you took off the air-box for the 
air cleaner.  Same is true of many motorcycles.

On the other hand, the belief that an EFI controller should be a 'Plug 'n 
Play' thing is going to kill me (figuratively) or someone else (literally).

Even an engine that I know intimately will require a different setup 
depending on many details that are variable between builders.

  I'm getting the first feedback from customers of a company that asked me 
to develop an EFI controller for their V8 engines.   I should have known 
this would not go well when they expressed surprise that I needed to know 
things like detailed specs on the crank trigger system.  I then explained 
that to be successful they would have to give me lots of detailed feedback 
on testing because I had no hands-on experience with this engine.   The only 
feedback I got was that it worked great.  The slowly emerging picture is 
that they apparently cranked the engine, it started, and then shipped 
engines to customers all over the world.

Sometimes I want to close the doors and just go work on my toys.

Tracy


>From: wrjjrs@aol.com
>Reply-To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
>Subject: [FlyRotary] Re: carbs vs efi
>Date: Mon, 23 Jul 2007 11:13:49 -0400
>
>
>
>
>-----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: 
>> > EFI is a complex system, but when it's working like it does in your
>car 
>>every day, it's a no brainer of a choice. Since this is a result of 
>>millions of dollars of R&D work, such a perfect, turn-key system is
>not 
>>going to be available to us. Even if such a system was available, it
>would 
>>require everyone to use exactly the same setup, which goes against
>the grain 
>>for most of us. > > 
> 
>Rusty, all of those arguments can be turned right back around and pointed 
>at carbs. 8*) There has been MUCH more money put in to carb development 
>over the years than has been invested in EFI system. People often ask me 
>what the best program to do "XYZ" is. My canned response is that the best 
>program to use is usually the one that you already know. I think it's the 
>same with carbs vs EFI. 
> 
>See, the problem isn't just delivering fuel to the engine in the right 
>amount. Shucks, that's easy. It gets complicated when you start trying to 
>deliver the right amount of fuel at the right time. With carbs you have to 
>figure out jets size, add an accelerator pump, mess with the venturi, and a 
>hundred other things that people have tried over the years. If you change 
>something in the intake, you may have to switch out a bunch of stuff in 
>order to retune. Then you have to fiddle and adjust to get it all working 
>properly again. With EFI, you have to size the injector, learn concepts 
>such as acceleration enrichment and XTau, decide between speed-density vs 
>alpha-N for tuning, and then modify a program to account for all the 
>variables. If something changes in the intake, you'll have to modify the 
>tuning parameters in the program again. When it's all done, you're going to 
>have to learn a lot before you know what you're doing, the learning will 
>only come from fiddling with the thing, and you won't know what you're 
>doing until you learn a lot. 
> 
>For me, I like the EFI. I won't necessarily smell like gas after fiddling, 
>and I can do much of the fiddling from my desk. A carb is an analogue 
>computer, with the drawback that you will never get datalogging from it. 
>But the biggest advantage to EFI for me is the fact that I can just hit the 
>AUTOTUNE button to flatten the learning curve. But, while I've rebuilt a 
>few carbs before, I don't really have that Zen understanding of how they 
>work. OTOH, I'm a software engineer. Program a controller is second nature 
>for me. 
> 
>Your mileage may vary. Not valid in all states. No user serviceable parts 
>inside. May cause headaches, heart palpitations, or diarhea. Do not take 
>before operating heavy equipment.
>
>Well put Ernest,
>  A engine is a dynamic system with a ton of variables. Working with what 
>you are familiar with is a good idea. I built race engines as a young man 
>of 20, and even then the mantra was, "everything effects everything!" 
>Consider it the internal combustion engine law of unintended consequences. 
>A small change can sometimes effect several other systems, in ways both 
>good or bad.
>Bill Jepson  
>-- 
>Homepage: http://www.flyrotary.com/ 
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