REFLECTOR: Fuel Flow for Performance Engines IO-550

[Al Gietzen]

Bill;

My opinion would be that it has nothing to do with the tuned exhaust.  An
exhaust - or induction - system is tuned for a specific rpm.  It is matching
of the standing wave frequency of the exhaust pulse - determined essentially
by the pipe length - to the frequency of when the valve is open.  For an
aircraft it should be tined for the cruise power rpm, and may help by a few
percent of power. Exhaust tuning is generally more important on engine that
run at higher rpm, and performance cammed engines with greater valve
overlap.

So its effect is fairly strongly peaked around the rpm for which it is
tuned.  It would have no effect at idle. Look for the problem on the fuel
supply side.

Al

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of LAURA WALKER
Sent: Tuesday, October 07, 2008 3:13 AM
To: reflector at tvbf.org
Subject: REFLECTOR: Fuel Flow for Performance Engines IO-550

My Performance Engines IO-550 seems to run very lean, both at idle and at
ground run-up. So lean, that if I shut down the Plasma ignition, it won't
idle at all on just the magneto. I also get no rpm rise on mixture cutoff,
and it hesitates to come off idle or low power. By accident, I once started
it with low fuel pump boost on, and it ran much better, even idling on the
magneto side alone. 

I think I have two problems: one, my tuned exhaust is scavenging the
cylinders too well and the mixture needs to be richened to make up for it.
And two, I need to make sure the fuel flow pressures are correct for my
horsepower level.

Back when Ron Monson would talk to me, he figured I would be getting an
additional 30-30HP from the addition of the tuned exhaust/headers which
should total just around 400 HP.  The only fuel flow and pressure charts
that came with my engine are from TCM's 310HP IO-550. My calculations say
that I should be looking at 25% more fuel flow at full throttle or roughly
32-34 GPH. 

Anybody out there with the PE IO-550 experienced this, and if so, what are
your fuel flow numbers?

Bill Walker 

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