IO-540 Idle Speed

What ground idle speed (throttle all the way out) have people been setting on the RV-10's IO-540 fuel injection system? I have an IO-540 C4B5 (d.b.a. D4A5). Minimum ground idle (warm engine, throttle full aft) is 800 rpm, which I think is high.

Thanks,

Tim Lewis

Tim

800 is OK, when idle on the ground, subject to stone damage potential keep your idle speed between 1000-1200 and leaned out so far that the engine RPM peaks and then just starts to fall again.

So in other words leaned beyond best power. For a few reasons, mainly the health of your spark plugs, your fuel wasted is nil, and less build up of deposits in the cylinder and plugs.

Do not worry about lining up and blasting off too lean if you forget, it can't happen. The engine will almost die on you if you open the throttle at such an aggressively lean mixture.

DB

Idle RPM

I have mine set at just over 800 and it is fine. I am curious about what kind of fuel pressure to expect on the IO540 at both idle and cruise power.

Pat

Pat Stewart said:

I have mine set at just over 800 and it is fine. I am curious about what kind of fuel pressure to expect on the IO540 at both idle and cruise power.

Pat

Click to expand...

My fuel pressure is constant at 21-25 PSI.

Pat Stewart said:

I have mine set at just over 800 and it is fine. I am curious about what kind of fuel pressure to expect on the IO540 at both idle and cruise power.

Pat

Click to expand...

I see 27-30 psi, independent of engine speed.

I see fuel pressure fluctuations down to 12PSI with the boost pump off at TOC, I let things cool off a bit and then it will be stable around 22-23PSI.

We fitted the cooling shroud too.

I think quite a number of folk have seen similar.

Interesting.... I'm at 750, and was thinking it should be lower. I suppose it doesn't matter as much with the CS prop.

-Rob

You can set the idle at any speed above 550 rpm you want. Slower if you want, but most won’t run well below 550rpm. The engine doesn't care. It's how much float you get landing and how much brakes you use taxing. Most engines in the certified world, idle between 550 and 750 wherever the engine runs smoothest and accelerates best from.
Fuel pressure shouldn't vary much from idle to full power on engines equipped with dual diaphram pumps. If rotary pump equipped ilde FP and full power FP might vary as much as 20 psi depending on pump relief valve settings.
Good Luck,
Mahlon
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