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From: George Braly <gwbraly@gami.com>
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Subject: RE: [LML] Re: pressurization IV-P
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Brent, thanks for the information.  Here are some comments.


>>T.O. : Full power 36-38" 2700 RPM 38-40 GPM (full rich)

Brent,  based on the peak cylinder pressures that  I am seeing on the test
stand, I would move the full power fuel flow up about 2 gph, to the 41 to
42.5 gph range at full power.  That, alone, will drop your peak cylinder
pressures a good 100PSI or more (~ 10% or better)


>>Race: Full power lean to 1400 TIT OR 400 CHT whichever happens first 
(OAT and altitude dependent)
Climb: MAP 32", 2500 RPM, 30-32 GPM 1350-1400 TIT (OAT and altitude 
dependent)<<

For race,  I would retard the timing to about 16d.  Run the MP up to about
42" or so.   MORE ponies.  Same peak pressures.  Cooler CHTs.


>>Cruse: 75% power, 28", 2500 RPM, 21.5 GPM, 1500 TIT, 385 CHT, 196 Oil
Temp<<

Try  31.5" MP x 2500 and 18 gph at cruise.  Should have about the same Hp,
with cooler CHTs.



>>I rarely use less than 75%. I never let the oil temp get over 210. I 
never let the TIT exceed 1500. Ignition uses Bendix 1200 mags set at 20 
BTDC (25 will detonate at race power settings).<<

Curious,  what is magic about 1500F TIT?   Why that number, rather than 1475
or 1550 or even 1600F ?


Spark timing at 25BTDC will cause massively high peak cylinder pressures (>
1200PSI) and peak torsional loading on the crank and prop, even at normal
full power full rich on a normal takeoff.   


>> Total time is 717 and 
compression is still in the mid 70's. I can hold 34" map at FL250. The 
induction and exhaust systems are typical for a 540K with the exception 
that the deck plenum does not share a common wall with the oil sump. I 
balanced cylinder flows to achieve relative CHTs+-5 degrees F (no Gamis, 
sorry).<<

You sir, are doing well!

Two questions:

If you lean the mixture from rich, through peak, then to lean of peak, at
what fuel does the first cylinder reach peak EGT?

At what fuel flow does the last cylinder to peak, reach peak EGT?

The answer to THOSE two questions is the ONLY way I know of to determine if
the F/A ratios are balanced in one of these engines.



>>Monty Barrett (Barrett Performance Aircraft) is the best engine builder 
in the business.<<

Monty IS first rate.  Excellent engine person.   I had the chance to have
him fly with me in my airplane down to Florida and back, a few months ago.
I enjoy his company and always learn a lot being around him.

>He also has the best dyno available.<   As distinguished from an R & D
facility,  he does have the best engine overhaul shop dyno I have seen,
anywhere.  It can't swing a prop so it can't be used for some certification
purposes.  But it is a clean, well thought out dyno.   He is bugging me to
get him a cylinder pressure transducer instrumentation rig put together for
his stand.  I'm trying to get to that. 

>>I would recommend 
him to anyone needing an overhaul. Monty apparently likes my engine too 
as it is the one pictured in his TAP ads (opposite the shot of the 
captain himself at the helm of his dyno). So be warned, maybe I am just 
blinded by the fame.<<

Enjoy the fame!   But... since he built yours, he has also built up two of
those TSIO-550 engines, and run them, with 8.5:1 pistons.  I think his
opinion of those engines is right up there with your engine, at this point. 

I put cylinder pressure transducers in one of them up at his shop at his
request because he wanted to make sure he had it set up right before he
shipped it to the customer. (Do you know any other rebuilders that would go
to that trouble?  I don't.)  

Those engines were making 365BHp at 37" x 2700 and about 42.5 gph.    At
cruise, we had  265BHp.  BSFC was down at 0.39... sometimes as low as 0.38.
Saw 0.375, briefly.  


>>IMHO the Continental "Tuned Induction" is a joke. You can't split a 
pulsating flow with a "Y"ed runner and get even mass flow.<<

Ah... Brent....  I agree it is not near as good as it ought to be.... and
your phrase "a joke" is well, you said it, but...

OTOH, the typical air flow balance for that engine (TSIO-550), cylinder to
cylinder, is, measurably indistinguishable from a TIO-540AE2A, your engine.
They are both bad when compared to the air flow from, for example,  an
IO-550 with the runner-log-branch  induction system, which has nearly
perfect airflow uniformity to each cylinder over a broad range of RPM and MP
settings.

>>This, I believe is why Gami is so successful with the Continental. The
situation 
is so bad out of the box that it is easy to make a big improvement. <<

The reasons the routine TCMs are so bad out of the box is NOT because of the
air distribution on the engines.  It is a fuel distribution problem.  When
we fix the fuel distribution problem on the runner-log branch engines, the
F/A ratios are damn near perfect.  Better than can be done with a sequential
port injection system.

>>You are likely not seeing the big gains on the Lycomings because they have
a 
much better intake system. But what do I know.<<

The intake systems on the Lycoming engines leave a LOT to be desired, for
exactly the same reasons as the "tuned" TCM induction systems.  Among other
things, the runners (on both the TCM and the Lycoming engines) are two
short.  They "tune up" and "down" with relatively minor changes in RPM.
We typically see very nearly the same gains on the Lycomings as the TCM
tuned induction engines.  Part of the problem with the Lycoming engines is
that their nozzles are so bad.  Poor atomization, and flow spec tolerances
you can drive a fuel truck through.  

Regards,  George