Fuel Injection Systems
 

I have started this thread for two reasons
To drag the information exchange about FI away from the discussion on the merits of the 0-340.

To find out as much as I can about different types of FI V Carb.

What I would like information on is real world differences in fuel consumption with Precision/Airflow and Fadec units V carburation. Costs of maintenance for the different systems. What are the starting difficulties and how are they overcome.

I am running an 0-320 in my RV 4 with the standard Marvel carb and at 2400 an using about 9USG/hour which equates to almost $100 for fuel at that RPM. Yes, 1 USG is about $10.50 in the UK. This will help me make a decision about converting to FI

Steve,
I use to own a Twin Comanche with injected IO-320s. We programmed for 8 gallons a side at 160 kts. which was WOT at about 2400 rpm and 7000 feet. this method was used for several thousand hours on this plane.
My RV-10 has the Airflow throttle body injection with the purge valve set-up. That makes it very easy to hot start.
If you really want to get as fuel efficient as possible ($10 per gallon will do that!) I would use the EFII ignition and fuel injection system. I'm installing the ignition system next month and will eventually install the fuel injection.

Hi Steve,
My -4 with IO-360 AIA, Bendix FI, and Slick mags, down low burns 8GPH ROP at 160knots and above 5000 feet I run it LOP at 6.5 to 7GPH at the same speed or more depending on altitude, 10k? would be more like 176 knots LOP at about 7.2GPH.

Hot starting, Throttle open ?? mixture closed, crank, when engine starts open mixture about half or more, works every time.

Cold starting, Throttle cracked, mixture open, pump hand wobble pump 6 times, put shoulder belts and head set on, close canopy, start engine, works every time.

Maintenance costs so far none, My engine was built in 1989, I overhauled it in 2006 with 900 hours on it, it was running good so we did nothing with the FI, just put it back on, the O/H now has 1200 hours on it. 2100 hours over the past 24 years with no problems. The engine O/H was only done because we found the crank case was broken between #2 and #4 cylinders.

Sounds like you could save a lot of $$ in fuel!

Steve,
If fuel consumption is your main goal then the only way FI will help is if you are going to run LOP. Having said that I will give you a real comparison from a flight today.
ROP 72% power, 59f, 150 kts, 4100 DA = 9.2 GPH
LOP 72% power, 59f, 150 kts, 4100 DA = 7.8 GPH

Same direction of flight. I just happened to be reading my data from a flight when I saw your post.
1.4 GPH difference.

Steve - 9GPH on a 320! Wow! I hope thats a typical average with lots of touch and goes and full rich acro.

I get 8.5 to 7.5 in the 200HP -8 depending on how high I want to go. This is based on many hours of cross country time. Preliminary flights in the Rocket seem to indicate I can get it under 11GPH... Pretty good considering it's 260HP.

Hot or cold starts with even the standard Bendix (no purge valve) are no problem once you understand what's going on. I've only flown standard Bendix for the last many years and can count on one hand the number of times I couldn't get it started on the first try.

Hardly. O-320 will see 13-14 or more gph at WOT near sea level. On the other end, LOP, ~50-55% power, I've seen 5.1 gph (IO-320, 152 kts, 15k ft). 9 gph at 75% power is where they run.

Steve, I understand you wanting to make a wise decision and asking the multiple layer question you have. Problem is you will get scattered answers with all sorts of data but mostly inconclusive for diagnosis as it will only ever be an 8/10 answer. Unless you know how to fill in some blanks in some they will be meaningless.

Of course if you knew how to fill in the voids, you would not be asking the question in the first place. This is not meant to be a rude statement, even though it could be taken that way.

Quite simply if you want any chance at running your engine with a BSFC of below 0.40 then the best way to do that is with a IO engine. The difference between a Precision Airmotive and a Airflow Performance is the post code it was made in. Don at Airflow provides great help here on VAF if that helps.

Sure if you get a carb engine with good distribution it may run almost as well, but it will never be quite as good. The laws of physics do not allow it.

Understood, and thats the meaning of my post. I do a lot of cross country work so I'm LOP. If Steve does a lot of the same kind of flying, then 9 GPH is way out of line. OTOH, if he's blasting around at low altitude and short hops, then 9 GPH is understandable.

And David's point is well taken. Just because I spend hours on end at 10,000 feet LOP does not make my fuel burn at all valid for someone who flies differently. Unless you plan on going high and LOP, then injection is not going to give you much economy over a carb.

Good information.
 

Hi Guys

Thanks for all the input so far.... this is exactly what I am looking for, especially the last post by Michael. In England ( a small country), most of our flying is short hops often below 3000 feet.

In my 4 from the midlands where I live I can be over the coast to the south in less than an hour. Over the Welsh coast in an hour and the same out to the east coast. Only venturing down to Cornwall or up to Scotland would put more than 3 hours on the clock. However, I do intend to fly to the south of France at some time.

I guess when I have broken the engine in and can run at lower RPM the burn will drop significantly?

Hi Steve,

I would second the opinion that says there is no practical difference in Airflow & Precision injection systems, that to achieve lower fuel consumption requires aggressive use of the red knob (and a good engine analyser), and that starting problems are myths once you learn an appropriate technique.

The cost to convert will be at least ?3K - and you may have to fit an O-360 air scoop to the cowl as the injector body is longer than the carb. I'm currently running a carb and regularly run at 25 lit/hr for around 135kt (RV-6, leaning as much as I can at all altitudes), a good electronic ignition helps a lot.

Because of the better fuel distribution from FI you should be able to see a drop of 2 or 3 lit/hr with FI (again leaned right off). Means there will be at least a 500hr payback time. I would go EI first and see how your engine responds.

Pete