REFLECTOR: IO-550N Hot Start Procedure

Sun Aug 14 12:10:32 CDT 2011

Thanks for the detailed suggestions, Scott. I know you've got a ton of
experience, so let me ask for a few more clarifications to make sure I
understand.  Especially with hot starts, it seems like the nuances are
important, and also learning when you're error-ing on the too rich or the
too lean side.   Please see my additional embedded questions below.

Bob

  _____  

From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Scott Derrick
Sent: Saturday, August 13, 2011 2:25 PM
To: bobj at computer.org; Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: IO-550N Hot Start Procedure

Bob,

I don't have a 550, but I do have considerable hours behind TIO520's and
IO520's.  Lots of quick turn arounds in Phoenix and southern Arizona,  many
with ground temps 110+.

My normal hot start is:

both knobs to the firewall,  3 seconds of electric fuel pump. No more than
that!

            Would that equate to 3 seconds HIGH or LOW boost with the
standard Velocity 'Dukes' boost pump?
pull the throttle out half way.
start cranking, if it doesn't hit in about 3-5 seconds of cranking, slowly
start pushing the throttle in. 

You can try this twice though the second time you have to reduce the prime
time to 1-2 seconds

            I only use 2 seconds of HIGH boost as above for a cold start, so
your hot start method sounds like 

what I would call a 'flooded' approach.  3 seconds of boost prime sounds
like it would definitely

clear the vapor out of the fuel injector lines, which I believe is the main
issue making hot starts hard.

But are you worried about the excess fuel washing all the oil off the
cylinder walls and rings, or is 

that not even an issue to worry about?  

If you flood it:

            How do you know you've flooded it - just the fact that it
doesn't start in 8 or 10 seconds?  A basic

            problem I have is knowing whether I'm giving it too little or
too much fuel when its hot.

mixture at idle cutoff
throttle to the fire wall. 
no priming.
Crank for 10 seconds.
If it doesn't start.
Crank again, slowly bringing the mixture in.  
When it starts, remember to bring the mixture all the way to the fire wall
before pulling the throttle to idle.

Scott

-------- Original Message --------
Subject: REFLECTOR: IO-550N Hot Start Procedure
From: Bob Jackson  <mailto:bobj at computer.org> <bobj at computer.org>
To: 'Velocity Aircraft Owners and Builders list'
<mailto:reflector at tvbf.org> <reflector at tvbf.org>
Date: 08/13/2011 11:12 AM

When you go on an extended cross country 'barnstorming' tour like I'm
currently on, you are forced to face little issues that you don't normally
encounter, or can primarily avoid during normal operations at home - or
maybe 'manage' by minimizing the opportunities (like in my case right now,
hot start, situations).

So now, while making an extended cross country through the West -- I'm
making lots of quick turn fuel stops, and it's very hot on the ramp in many
places.  

There are many Velocity's flying with the wonderful IO-550N engine - does
anyone have a reliable Hot Start procedure for the IO-550N -- particularly
for when it's been sitting on a hot ramp and shut down for less than, say,
an hour?  I know the main issue with the IO-550N is fuel vaporizing in the
fuel injector lines that run across the top of (a hot, non-operating during
the fuel turn) engine.  

We have avoided the "flood it, then start it in Idle Cutoff and wait for it
to catch before coming out of Idle Cutoff method", because washing the oil
off the cylinder walls with all that fuel doesn't seem like it could be very
good for the metal or the life of the engine (plus I don't have enough hands
to hold down the starter button, and jockey the Mixture, Throttle (and fuel
boost switch) controls all at the same time with the other hand!  

The best Hot Start method we have so far is:

1.	Mixture to Idle Cutoff - run Fuel Boost HIGH for about 30 seconds
(until you see fuel coming out of the overboard cylinder drain under the
engine) to re-circulate and cool the fuel in the engine driven fuel pump
2.	Mixture - Full Rich
3.	Throttle - WOT
4.	Fuel Boost - LOW (just for a second or so, presumably to 'blow' some
of the vapor out of the fuel injector lines
5.	Crank Engine
6.	Slowly (WOT to Idle in ~10 seconds) pull the Throttle back from WOT,
looking for the position with the right fuel-to-air balance until the engine
catches

This method generally works, but it's not 100% reliable and we still get
into conditions where we seem to either get it flooded or starved, and we
can't tell which one.  We start from WOT throttle and slowly reduce while
cranking rather than the other way around (starting from Idle and slowly
increasing toward WOT) because beginning from WOT and reducing, you are
already moving in the right direction to minimize overspeed conditions when
it does catch.

Can someone share a reliable IO-550N Hot Start procedure that works for
them?

Thanks,

Bob Jackson

N2XF

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