IO390 fuel flow/ performace chart

[African Bear]

Hi All,
Would anyone have a power/fuel flow chart for an IO 390 x engine. My engine has an API fuel injection system on it.
I have some fairly sketchy numbers coming up especially with the boost pumps on for take-off and Landing. I've contacted API and they tell me that on no account should the fuel flow transducer be on the suction side of any pumps so that is a known problem. I've bought all the new piping and a new transducer and will install ASAP.
I'm now looking for actual numbers to cross-check with the numbers that will be shown.
Currently I run at 36 LPH at 145 MPH TAS. Engine runs really well with a nice lighter grey exhaust with EGT 1480 F and CHT 365
Take-off up to 88 LPH !!
I never used to pay much heed to the Fuel flow as I was taught without one and then don't trust my current set up as an instrument providing useful information, until I had a very low powered take-off and had to do an exceedingly gentle turn and land the way I took off. Transpired that I had a largely blocked filter into the metering body (sintered brass type). It would have been nice to have seen the low flow and avoiding the few minutes of extreme clench!

[jaredyates]

I don't have any data for the 390. But my takeoff fuel flow with the 360 was pretty consistently 19.7 gph and on the 540, around 27-28 gph. Once aloft with the 540 I loaf at 8gph, cruise at 10-12. Subtract 2gph from each of those for the 360.

Your 88Lph for takeoff sounds about right, that's around 22gph.

[DBeaulieu]

I'm interested in what was clogging your filter?

[African Bear]

Jared...thank you for those details... the odd thing is that if I turn on the boost pumps the fuel flow doubles(almost exactly) but absolutely no note change in the engine. When I move the flow sensor to the proper location, I'll let you know what the numbers are.
@DBeaulieu...very fine dust was the culprit...after she had a 100hr service, that filter and the gascolator were all cleaned and blown out. I had actually done about 3 circuits with no problem and only on the 4th did the problem occur. I can only think that with the service some particles were disturbed in the system and became the last straw to blocking that filter. it was removed and certainly looked clean until we ran it in an ultrasonic cleaner and the dust that came out was amazing. A good lesson learnt. Now I clean that filter every 40 hrs.
I do use a 2 micron filter funnel for fuelling . Possibly the dust came from the auxiliary tanks that, at that time , were not used that often.

[DBeaulieu]

Thanks for the details...always adding to my "clue bag" Smooth skies!
Dave

[Nev]

I went through a few similar issues early on with mine. The original location of my fuel flow transducer was aft of the firewall and between the electric fuel pump and the engine driven fuel pump, following some well intentioned advice (the theory was to keep the transducer cool). The result was that the fuel flow readings changed with the electric pump ON, and were often erratic.

After discussing with the transducer company directly, I moved the transducer forward of the firewall, between the engine driven pump and the throttle body. It's now attached to the engine mount. This has solved all the fuel flow reading issues. The actual fuel flow readings did still need to be calibrated and I did this by measuring the amount of fuel I pumped into the tanks during refueling, and compared this to what the transducer said it had used. On the Dynon there is a formula, and a correction factor.

At around the 60 hour in service mark, the low fuel pressure alarm sounded, and the Dynon recorded reductions in fuel pressure on two separate occasions. The normal (boost pump OFF) pressure is 22 PSI, and on these occasions the low pressure alarm triggered at 17 PSI. There was no change in engine sound and no other indications. After extensive investigation, I found some debris in the throttle body finger filter. I don't know for certain that this was the definitive cause of the issue, but in the 370 hours since, it has operated trouble free.

We surmised at the time that as the electric fuel pump may have generated some fine metallic dust as it ran itself in. Next time I will remove and clean the throttle body finger filter several times during test flying. Incidentally, a normal fuel filter would not have filtered these particles if they were generated by the fuel pump. The finger filter has run completely clean after the 100 hour mark.

[African Bear]

Nev,.
Thanks for your response. It looks as if you have basically gone through the same process that I am going through now.
I have been advised to pet the red cube between the metering body and the flow divider, I can do this and take the red cube forward of the front baffle next to the alternator, which is also very close to the metering body so won't add many inches of fuel pipe. 
Any ideas on the fuel flow for an IO390?
I have also added cooling shrouds over the aux pump, gascolator,and mechanical pump, as I find that if I start up ,warm up and fly and land later all is very good. If I do circuits with full stop landings I really suffer from vapourisation and my engine is very "grumpy" until full throttle is applied. I am told by API that this is also a symtom of the red cube on the wrong side of the fuel pumps on fuel injected engines.

[Nev]

Many of the RV's have their red cubes between the metering body and the flow divider, so you should be in safe territory there. I don't know the typical IO390 fuel flow. However, if you start with a full tank, fly for a couple of hours, then fill back up again, you'll know the exact fuel used and can calibrate the transducer. This is a very accurate way to establish the fuel flow. On mine (gold cube) it uses a fuel flow factor, with a formula. Below is an excerpt from the Dynon Installation Manual. In practice it's pretty simple to do, and the "pulses per gallon" number is already on the Dynon fuel flow correction page.

Regarding the fuel vaporization when warm, mine does exactly the same when on the ground at low RPM. When RPM is increased the symptoms disappear. In a nutshell it's never been an issue, so I never worried about it, and on mine the transducer location didn't seem to affect it.

26608FB2-B9C3-480C-A159-79E90830EF52.jpg

[African Bear]

Thanks for all that information.
Incidentally API says for IO 390
15 to 18 GPH at 2700rpm @6000 ft altitude on takeoff
18 to 20 GPH at 2700 rpm @ sea level on takeoff.