Engine problem - Seneca II

"BDS" wrote in message
I wonder if the bearings could be changed out as opposed to replacing the
entire turbo.

Yes, along with the seals. However, when you pull the compressor off the
shaft to slide the bearings off, you disturb the balance. Balance is
critical at 130k rpm. Then there is that pesky FAA thing about engine
accessories having to be overhauled at a repair facility.

Do you use Marvel Mystery Oil?

D.

"Darkwing" wrote in message So what happens on a turbo
plane if you pull the power back real fast without a wastegate? On a car
if
the wastegate fails you can damage the engine.

The cylinders shock cool and crack with a strong pssibility of the heads
seperating from the barrels and/or seizure from the barrels shrinking around
the pistons.

I have had the distinct pleasure of driving a Lingenfelter Twin Turbo 01'
vette on more than one occasion, 650hp, 6 speed, BAD BAD BAD!!!

Sweeetttt!!!!

D.

"Scott Skylane" wrote in message That's correct, but it *does* have
pop-off boost valves.

So... I can firewall the throttle levers without overboosting the engines
on a Seneca 2?

D. (stock- as in from the factory)

Capt.Doug wrote:

"Scott Skylane" wrote in message That's correct, but it *does* have

pop-off boost valves.

So... I can firewall the throttle levers without overboosting the engines
on a Seneca 2?

D. (stock- as in from the factory)


Doug,

Doing so would exceed max rated M.P. by about 1". The Pop-offs are
designed to be last chance protection against overboost, and are not to
be relied upon in normal operation. See:

http://www.kellyaerospace.com/articl...bocharging.pdf

Look at the section titled "How do you spell relief" on page 8.

Happy Flying!
Scott Skylane

"Scott Skylane" wrote in message
Doing so would exceed max rated M.P. by about 1". The Pop-offs are
designed to be last chance protection against overboost, and are not to
be relied upon in normal operation. See:

I remember 2 little lights in the upper middle of the instrument panel that
illuminate when overboosting. Are they activated by the PRV?

D.

Capt.Doug wrote:

I remember 2 little lights in the upper middle of the instrument panel that
illuminate when overboosting. Are they activated by the PRV?

D.

No, the P.R.V.'s (Pop-Offs) are purely mechanical in nature. They have
no electrical function.

Happy Flying!
Scott Skylane

"Capt.Doug" wrote in message
...
"BDS" wrote in message
I wonder if the bearings could be changed out as opposed to replacing
the
entire turbo.

Yes, along with the seals. However, when you pull the compressor off the
shaft to slide the bearings off, you disturb the balance. Balance is
critical at 130k rpm. Then there is that pesky FAA thing about engine
accessories having to be overhauled at a repair facility.

Do you use Marvel Mystery Oil?

Not in this aircraft as of yet but I have used it in other non-turboed acft
in the past. Can it handle the heat of the turbo and do you think it might
help clean the bearings?

BDS

"Scott Skylane" wrote in message
...

So... I can firewall the throttle levers without overboosting the
engines
on a Seneca 2?

Doing so would exceed max rated M.P. by about 1". The Pop-offs are
designed to be last chance protection against overboost, and are not to
be relied upon in normal operation. See:

http://www.kellyaerospace.com/articl...bocharging.pdf

Look at the section titled "How do you spell relief" on page 8.

I think our overboost lights come on at just over 40 inches. I am pretty
sure you can go up to 42 for short periods, but I haven't tried. The
throttles on a stock Seneca II are quite sensitive - at sea level ours will
reach 40 in mp at about 75% of throw and you can get +/- 2 in by just
breathing on the throttles. Most of the time with the load and the runway
available I do not need to use more than 35 in so I don't even approach max
boost.

"Kingfish" wrote in message
oups.com...

There were a few good suggestions from others already - Turbo bearing
coking does make sense, but you clearly know to let the turbo unspool
before shutdown so that might not be as likely. (IIRC there is a way to
clean up the turbo bearings without turbo removal if that's what it
turns out to be) My guess would be the fuel control unit gone wonky;
the fact that power returns after richening the mixture might back up
that theory, but what are the chances of both acting up simultaneously?
Maybe the alternate air diverter is partially open? Out of curiousity,
what CHTs are you seeing at 1425 EGT?


I know the fuel controls were double checked and adjusted when the problem
first came up. That doesn't mean they aren't the culprit, but they seem to
act normally when tested.

CHTs never get out of the green arc and typically remain at about 75% of the
scale.

BDS

"BDS" wrote in message
Not in this aircraft as of yet but I have used it in other non-turboed
acft
in the past. Can it handle the heat of the turbo and do you think it
might
help clean the bearings?

Don't know about turbocharged engines. I used it religiously in supercharged
R-985s, but that was to prevent sticking valves.

D.