Fuel pressure too high at takeoff power?

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3 months 3 weeks ago #3263 by STEVE ELLS
Replied by STEVE ELLS on topic Fuel pressure too high at takeoff power?
Hi Dave;
I'm having a little trouble with these numbers.

When you say "the fuel pressure to well above the Riley 21 psi max spec. at takeoff power. "

I believe you're referring to the max unmetered fuel pressure.

The Continental spec (in both SID97-3G and Continental Manual M-0) for unmetered fuel pressure adjustment at full power is 35-39 psi at 2700 and 35.5 MAP. With the unmetered FP set to those values (and the unmetered FP set to 5.5-6.5 at 600 rpm you should get fuel flow of 180-186 pounds and 30.7- 31.7 gph.

If you're getting those fuel flows/gph readings the engine is set up correctly.

I don't have a copy of the Riley Intercooler temperature delta/manifold pressure adjustment tables of the installation instructions so don't really know where the 21 psi comes from.

When I was setting up the take off FP on turbo-charged Cessnas, I liked to set them up on the "fat" side, figuring that too little fuel flow can cause hotter than desired temperatures. It wasn't uncommon to see the FF needle go past the redline with this "fat" set up during the first take off of the day.

We would instruct the pilot to pull the mixture back to redline during the take off roll or after cleaning up on the climb.

You an always adjust down, but you can never adjust up above the maximum set up pressures.

If I've missed something, or didn't understand your post, please let me know,

Best,
Steve

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3 months 3 weeks ago #3258 by Dave Fisher
Fuel pressure too high at takeoff power? was created by Dave Fisher
1981 P210 with TIO520P and Riley intercooler. Fuel flow was below min spec with 36.5 MP and 2700RPM takeoff power (around 27gal/hr). My mechanic checked the set up of the fuel injection by the service bulletin SID97-3E. Pressures were spec. In order to get the minimum fuel flow specified (31.7gal/hr ) he had to increase the fuel pressure to well above the Riley 21psi max spec. at takeoff power. I am monitoring fuel pressure and flow with my new MVP50 display. Engine seems to run great at both settings with lots of power. Does anybody have any suggestions as to why the fuel flow would be too low when the fuel pressure is at max spec at takeoff power? Should I be concerned that the fuel pressure is now well above spec for takeoff power?
Thank you

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