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Turbo boost
Don,
If you would, please describe what your front engine gauges were showing during the takeoff roll from brake release at your unpaved strip, e.g., MP, RPM, fuel flow, oil press & temp. Any anomalies during the run-up, or normal? Did you get any turbo boost at all? Or, did it start coming up slowly during the takeoff roll, or after liftoff? And what about during climb and cruise?
What mine has typically done is come up to about 25-27" and just sits there at brake release, at full throttle, with the out-of-synch wow-wow between the front and rear. Then I get a slow turbo spool up to about 35" and 125-130PPH during the takeoff run. If I land somewhere and then restart and takeoff within say 30-minutes or an hour, I usually don't get any boost at all until after liftoff and in the climb, so I've been reluctant to go into any unimproved short strips.
The manuals say that if everything is rigged properly, you should have full-turbo boost with 2/23 throttle, which is the way things used to work and my rear engine always does, but we're pushing the front throttle all the way forward even to get the 25-27" prior to brake release. Leaving it at full throttle position, it eventually comes up to 35". The engines ususally get synched up and the wow-wow disappears just before liftoff. We've checked the rigging and everything seems fine.
Once into the climb or cruise, everything seems to work just like it's suppose to, i.e., normal throttle positions for a given MP, but the front reacts slight slower than the rear engine. Oil pressure is top green and temps at least 100F prior to takeoff. And normal cyl head temps. Normal indications during climbs and cruise. And I recall one day in cruise at 8,000' running the RPM's up to 2800 redline and bringing the throttles up and no problem acquiring 37" with full-rich mix. And as I noted in a previous post, the other day while at 17,500', noticed that when I pushed the front throttle up from 30" to full at 2400RPM, the MP wanted to oscillate between 33 and 38" like it was bootstrapping... but steady at 30" or 33" with 2400. I should have upped the RPM to see if it would have stabilized, but neglected to do so.
Do you have any of these kind of MP fluctuations at altitude, or are things rock steady?
Got to be some pesky carbon/grime in the system somewhere. Maybe it's the controller instead of the wastegate, as things work normally once airborne.
Be interested in your indications, throttle positions, MP's and RPM's. BTW, my front engine is at 1250 TTSN, and the rear at 150 SFRM. I'll have to check the logs, but it seems the front controller, and wastegate were overhauled a couple of years before I acquired the plane (and probably needlessly!), and I think the front turbo was replaced at 700 hours, but I'll have to check to make sure.
SkyKing
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