My 185 has an IO-520 that has a max output of 300hp, limited to 10 minutes. Following the Continental SID, my takeoff fuel flow is in the mid-26’s. I suspect this isn’t enough, as I get CHTs above 380 within a minute or so of takeoff. I can control it fiddling with the prop, throttle, and airspeed, but there’s sure no way I could get 10 minutes at full power.

The baffles are relatively new and as good as you’ll find on a 185. There are no D’Shannon options or anything like that.

I’m looking for recommendations on takeoff fuel flow. And, if we goose the max fuel flow, do we have to redo the SID?

Try 28.5, Doc. Of course, the idle, and idle mixture will need to be tweaked as well. Possibly a couple of iterations to get it dialed in.

I suspect that your 185 has no engine monitor, because I think you already know that the target takeoff EGT should be 1250-1300dF or so. If 28.5 doesn’t do the job, carefully increase it. But since it’s a 520, I’d be reluctant to go above 29.0 gph.

Remember that it’s now M-0, not SID 97-3. Not sure if they’ve made changes to the fuel setup. It’s my opinion that the guidance from CMI is just that - guidance. Get it close with the guidance, and make the final adjustments as needed from there.
jh

Stuart,

If you have/add GAMIjectors the STC allows you to set T/O fuel flow appropriately I think.

RAS

I don't have the 520 numbers in my head, but it does vary with altitude. There is a chart somewhere that gives a MINIMUM fuel flow for full power per altitude.

I had a 550 powered 185, at my home airport (KPSO) at 7650 msl the minimum was 27 GPH.

My 520A is set up around 26.4 gph on takeoff. You can run your fuel pump to get another gph on t.o. After you get clear of obstacles dial back the prop to 2350 or so and then follow with the throttle.

Tim

Stu,

Already said, you need just over 28 to make it happy. Make sure you follow procedure so you Are not too rich at idle.

Thanks, y’all!

Here's a TCM chart that shows fuel flows for some of the flavors of 520's at the bottom.

That CMI document shows 24.9 as the max, which is insufficient. Perhaps one of the Three (apparently former) Amigos will step in here.

jh

The 185 has an IO-520-D, which isn’t on that table. On the Bonanza I had it at 28+, IIRC, but it did stumble sometimes when going full rich. The -D model, at 300hp, would presumably need a higher fuel flow than the Bonanza did.

Do you have an electric boost pump you can flip on to boost GPH? On my Bonanza, I have the regular Conti spec fuel flows, and in summer weather there is a minute or so between takeoff and cruise climb where a few seconds of using the electric pump can be useful. It stops the CHT rise instantly. (Note, NA Bonanza... Hi boost on a turbo Bo can flood out the engine). Once I get into cruise climb the airflow keeps the CHT’s in line.

24.4-26.1 gph @2850 rpm per CMI manual M-0. Metered pressure 17.0-19.4 psi.

That’s where it is. It doesn’t seem to be enough.

28 gph for the 520, 30 gph for the 550. Lean it on the ground if it runs rough.