REFLECTOR:Rough Rider

[Chuck Jensen]

When the engine is cool at start up, it is certainly less pronounced.
Ronnies comments that his 360 runs somewhat similar is comforting but it
still doesn't seem right.  I don't understand why there should be such a
sharp drop-off in engine operation at 1000 rpm when the booster is secured.
Shouldn't the engine run the same on the ramp whether the booster pump is on
or not?  Isn't the booster pump just insurance during TO/LD in case of main
pump failure and not required for normal ramp operations?

I look at the list below and:

1) seems like a credible culprit (hot engine and all) but the likelihood
that the slight amount of additional pressure from the booster would be just
the amount needed to overcome the vapor lock is possible, but small?  In
this line of thought, is it possible to have a chronic continuous partial
vapor lock would always behave the same...cause rpm drop, rough ops but
never completely stops the engine?  Does anyone know the minimum fuel
pressure values for injected 540 at approx. 1000 rpm?  I have seen 17.  Is
that too low?
2) possible if it always ran rough but wouldn't seem to be related changes
in booster pump status.
3) same as 2)?
4) same as 2), i.e. unrelated to changes from booster pump status?

I have not tried mag/EI manipulations nor observed EGT in relation to this
phenomena, though I will do so.  I'll check to see if the last mechanic
looked at the plugs.  However, if it always ran rough, the plug condition
may be more enlightening.  Except for this one condition, the engine starts
great and runs very smooth.  

Unrelated to the Rough Rider problem, I took a couple sets of EGT/CHT
readings per GAMI's (http://www.gami.com/frames.htm) over a range of fuel
flow settings during cruise.  I thought the results were kind of interesting
but am looking forward to GAMI's thoughts/interpretation.

This is a wild, blind guess, but I predict they will recommend a set of
their calibrated injectors to smooth engine ops in the LOP region by
narrowing the variation in peak temp range between cylinders.  I'll post a
link to my results and their interpretation when I hear from GAMI.

Chuck
N27GV XL/RG



-----Original Message-----
From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
Behalf Of Brian Michalk
Sent: Saturday, July 19, 2003 10:42 AM
To: reflector@tvbf.org
Subject: RE: REFLECTOR:Rough Rider


So this only happens after a flight?  When the engine is cool, things behave
properly?

30PSI?  I'm assuming injected?

Things I would look for:
1) possible partial vapor lock.
2) Intake manifold air leak.  Snug up all those bolts.
3) Injector air shroud obstructions.
4) Check all hoses to the fuel servo for cracks/leaks.

Does turning off either magneto make a characteristic change?  Maybe the EI
is doing something strange temperature-wise.  Take out your spark plugs and
read them.  That'll tell you if you are running too lean/rich or show which
cylinder is the culprit, if it is a single cylinder.

What do your per-cylinder EGT's show when this is happening?

 Brian Michalk  <http://www.michalk.com>
Life is what you make of it ... never wish you had done something.
Aviator, experimental aircraft builder, motorcyclist, SCUBA diver
musician, home-brewer, entrepreneur and mostly single

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