We tweaked the injectors and Airflow Performance today.

pierre smith · #1 12-02-2010, 03:20 PM

After mailing injector orifices back 'n forth for a week or more and half a dozen phone calls, Don suggested that I just fly up there and get it done, so I did.

We flew and he took EGT readings every .2 GPH down to LOP and we landed and switched inserts around, based on the fuel flows and EGT's and went up again, running 23"/2400 and started leaning at the same rate again and it amazed me to see how close they had become and he suggested 8500' for some full throttle testing. After we got there, he started leaning again, all the way down to 11GPH...something I'd never seen but at an airspeed cost...down to 170 something MPH but getting over 17 MPG according to the Dynon EMS and all the temps were very close.

On the way home, I went for 50 LOP (remember, I'm old school at 65 years old and never leaned this far in years gone by) and fuel flow was around 13 GPH/190 TAS...2GPH better than before and getting 15 MPG instead of 13-13 1/2.

A good day indeed and well spent with a very knowledgeable guy. If you haven't had your injectors tweaked and matched, you can't go wrong up at Airflow, in Spartanburg, S.C.

I still have the choice of running 202 MPH true but now down in the 14+ GPH range, instead of 15 1/2 or more if I just have to go fast, or do 190 at 13 GPH, my choice.

Happy camper,

Kahuna · #2 12-02-2010, 03:34 PM

Quote:

Originally Posted by pierre smith

After mailing injector orifices back 'n forth for a week or more and half a dozen phone calls, Don suggested that I just fly up there and get it done, so I did.

What was the problem doing it from home?

TS Flightlines · #3 12-02-2010, 03:42 PM

that is awesome! Gee, you will have an almost brand new plane!!!!
Gee---I need to come see you!
Tom

N395V · #4 12-02-2010, 06:43 PM

Now I know why he hasn't finished rebuilding my fuel pump.

yakdriver · #5 12-03-2010, 08:10 AM

My 7 gets 196mph true on 10gph/50 rop or 188 true on 8.2gph/50lop after balancing my injectors. My CHTs and EGTs run within 10 degrees highest to lowest and LOP operation yields 40 degree lower CHTs and 10 degree lower oil temps. Love my AFP system. Don

pierre smith · #6 12-03-2010, 03:13 PM

....and it may be my imagination but the engine sure feels a lot smoother now...it should be, since two cylinders were making big horsepower and the other 4 were rich before.

Best,

Tom Martin · #7 12-03-2010, 05:35 PM

A week or so ago there was a thread on using mpg as the most efficient place to fly your aircraft.
I did a simple test at 22 squared at peak EGT and at 50 LOP. LOP did indeed give me better fuel economy. It was 0.5 mpg better but over 10 knots slower. Unless I am trying to extend range I will go 10 knots faster every time rather then save half a mile per gallon. It amounts to less time on your engine. I estimate, in this case, 6 or 7% more time on your engine by burning less fuel. On 2000 hour TBO you have just lost 120 to 140 hours.
Work it out for your plane and see how many hours of engine life you are losing by going slower. 5% of an engine rebuild would buy a lot of fuel.

Geico266 · #8 12-03-2010, 06:01 PM

Pierre, I was able to get my -10 dialed in with Don's help also a few years ago. It is amazing how much better the fuel economy is running -50F LOP, and how much cooler everything runs. I get the fuel flow down to 10.5.

Welcome to the dark side Pierre!

pierre smith · #9 12-04-2010, 05:53 AM

Quote:

Originally Posted by Tom Martin

A week or so ago there was a thread on using mpg as the most efficient place to fly your aircraft.
I did a simple test at 22 squared at peak EGT and at 50 LOP. LOP did indeed give me better fuel economy. It was 0.5 mpg better but over 10 knots slower. Unless I am trying to extend range I will go 10 knots faster every time rather then save half a mile per gallon. It amounts to less time on your engine. I estimate, in this case, 6 or 7% more time on your engine by burning less fuel. On 2000 hour TBO you have just lost 120 to 140 hours.
Work it out for your plane and see how many hours of engine life you are losing by going slower. 5% of an engine rebuild would buy a lot of fuel.

....and I agree with not wanting to go slower. This is my second RV and because I, too, want speed. Now that my injectors are optimized, I have a better choice...speed or some speed plus economy, that I didn't have before.

Best,

N395V · #10 12-04-2010, 06:47 AM

Quote:

On 2000 hour TBO you have just lost 120 to 140 hours.

This is correct if you plan to do a reman at TBO.

Most engines will go beyond TBO.

LOP enthusiasts can make the case that engine wear and thus the time at which you need to reman is a combination of>>>>

(Intracylinder pressures)* (CHT)*(RPM) *(time in hours)*(etc) with heat(CHT) and intracylinder stress being greater contributors to engine wear than hours.

Thus LOP decreases intracylinder stress and heat thereby prolonging engine life to a degree greater than the hours it adds to your collective flights.