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Takeoff power and fuel flow in RV-10 (with IO540)

vas4vans

Active Member
Friend
Hi,

I recently bought an RV-10 which has an IO540 that was rebuilt by Barrett Precision with 9:1 compression pistons. The injectors were tuned for high DA operations (since the previous owner was based at a high DA airport). A blurb from the POH:
"Each injector is tuned to ensure that all cylinders reach peak EGT at the same fuel flow. They are optimized for operation at high altitude with the fuel injector restrictors centered around 0.025” for increased pressure at the fuel distribution spider. For frequent flying at low density altitudes re-tuning around .028” restrictors may be advised."

My home airport is (nearly) at sea level. I had a pilot friend record a video at takeoff (I guess I could have obtained the same data by downloading the EFIS logs). With mixture at full rich and a WOT for takeoff, here's the data that was captured right after things stabilized after takeoff (probably at 400-500 AGL):
Power: 94%
Fuel flow: 25.1 gph
RPM: 2630
MP: 27.5
EGTs: 1245-1297
CHTs: 324-357

I have a few questions:
-is this power and fuel flow normal for this kind of engine on takeoff? I guess the other way of asking the question is what power and fuel flow do you see on takeoff in an IO540?
-Is this level of power and fuel on takeoff damaging to the engine and should I be considering using a lower throttle/mixture setting for takeoff?
-My practice is to back off the power at about 500 AGL to 24" MP/2500 RPM/18-19 gph for a cruise climb at about 125 KIAS. Any concerns on any of those numbers?
-Should I be seriously thinking about getting the fuel injectors re-tuned?

Thanks,

Vas
 
Vas,

Don’t change anything. As you can see from your high fuel flow, going from stock 0.028” to an average of 0.025” injector nozzles provides more than enough fuel. Your low CHTs and EGTs indicate you are still way ROP on takeoff.

Talking with Don at AFP he has reason to suggest the smaller nozzle for our standard engines. If you want a second opinion, I suggest you give him a call.

Carl
 
Vas,

Don’t change anything. As you can see from your high fuel flow, going from stock 0.028” to an average of 0.025” injector nozzles provides more than enough fuel. Your low CHTs and EGTs indicate you are still way ROP on takeoff.

Talking with Don at AFP he has reason to suggest the smaller nozzle for our standard engines. If you want a second opinion, I suggest you give him a call.

Carl

Pretty much spot on advice.

Fly it-----enjoy it.
 
No need to change anything. Lots of us have .025" injectors. Speak to Don at Airflow Performance if you are concerned. It ends up with the same fuel flow at slightly higher pressure.

27.5" MAP seems low for sea level. Dial up your rpms too, a few more ponies left in those missing 70 rpms.

Lenny
 
Just my humble opinion but…… I would recommend not pulling your power back on your climb out. Keep the throttle all the way in, but you can bring the prop down a hundred or so less RPMs if you want. Remember, these engines are designed to run full throttle and max RPMs without issue. At sea level you can get away with pulling your power back, but if you develop the habit of pulling your throttle back on climb out, you might do it from an airport with high altitude and/or density altitude, which may not work out well.
 
Vas, I agree with the others. 25 g/hr is where you want to be for 100% power operation. What does your MP read before engine start? At RHV (essentially sea level) the gauge should read what ever the atis says for altimeter setting. If it’s lower, check the gauge. If it agrees, check the air filter, maybe it’s dirty/obstructed.
You’re losing a bit of power by not getting all the way to 2700 rpm. Adjust the governor, check that the prop control can move it stop to stop. If you can get 2700 in cruise but not for takeoff, the internal pitch stop needs adjusting.
I personally pull back to around 25”/2500 RPM after take off, and do some leaning. Less noise, better economy. But watch the cht’s. Depending on climb airspeed you may need some extra richness to keep cht’s below 400 F (or whatever number you think should apply!).
PS. If I missed any emails from you last week, my server was down.
 
My Thunderbolt runs 25.1 gph at takeoff, and has been running that way for over 800 hours. Your EGT’S and CHT’S look great as well. I also have some .025” injectors in some, but not all of them (due to tuning).

Here’s a good test to see if you are too lean. Got to 3000’ MSL or thereabouts, and set up for 24 squared. Look at EGT’s and then lean until you peak. You should have about a 250 degree spread.

Also, as mentioned, just pull the prop back to 2500 RPM’s after 800-1000’ and don’t touch the throttle until level off.

Vic
 
Thanks to everyone for your responses. It sounds like things are mostly fine - I will check the prop to see why I am not getting to 2700 RPM.

To answer Bob's question - it looks like my MP was 29.7 after the engine was shut down.

Vic, I'll try your test the next time I fly it and check the spread.

Thanks,

Vas
 
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