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Thread: Use of Plenums?

  1. #1

    Join Date
    Jan 2012

    Use of Plenums?

    I fly a Pazmany PL2 (N446DL) with O-290 D2B, wood prop Hegy 70-61. About a year ago, I bought carbon fiber plenums from Renegade Aircraft, via Doc Bailey, but haven't installed them yet. I'm wondering if anyone has experience with plenums and their effects on engine cooling. According to Renegade, I should remove existing baffling and all the inner-cylinder cooling baffles -- but I'm timid about doing that. I'd think that inner cylinder baffles would help in directing the cooling intake are around the cylinders completely -- and without them, the air might just rush past leaving potential hot spots.

    Does anyone have anyone have any experience with this cooling mod. My engine is O-290 D2B in which the 3 and 4 cylinders run a little hot on climb out. They run up close to 500F during climb (unless I reduce power to 75%0 and the cruise temps on those two cylinders runs about 400F. I'd like to see it in the 300's -- but again, I've been reluctant to pull all the baffling...

    Thoughts on this would be appreciated. Thanks.

    Semper Fi

  2. #2
    cub builder's Avatar
    Join Date
    Nov 2011
    North Central AR
    Simply put, plenums are a good way to capture all the air from the air inlets and not allow it to leak out except through the cylinders where it gets used for cooling. The temps you quote are well beyond what I would allow in my planes. I would not eliminate the inner cylinder baffling as it is necessary to keep the air flow in the lower cooling fins and also so you don't just spill air out in the dead space between the cylinders. Whether you install plenums or not, you have some serious cooling work to do if you want those cylinders to live for very long. With the temps you're showing, it won't take long before your heads start developing cracks.


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