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.

 

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. 

 

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.

 

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)