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Polishing intake manifolds

in General Tech Discussion 6 years ago

  • Re: Polishing intake manifolds

    by » 6 years ago

    Over the years I have proven several companies wrong and all because they failed to do proper testing and documentation. I haven't ever seen a single document on the before and after affects of a larger tube. Just owners comments and even those are few and far between.

    If it's a truly a better idea and performance enhancer why has it taken off with all the Rotax owners and service centers?

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Polishing intake manifolds

    by » 6 years ago

    Just to avoid any arguments, I thought 5 times before I posted this update and now thought 10 times before posting reply to this. I do respect Roger's knowledge and experience and had been following him for years but do keep in mind that he is wearing a Rotax hat. This is a platform to discuss and share experiences and therefore here is my reply with all good discussion sake only. I am a true believer of keeping every machine strictly to the design standards and also not in favor of milking more than what its designed for.

    Back to this topic - It is very commonly accepted (even by Rotax gurus) that every 912 engines have a rough zone at variable rpm ranges depending on engine setup and other variables. Some have very noticeable and some are worth ignoring. I have flown with many owners in their airplanes and noticed prominent vibrations but they don't even feel it, so, there is a human factor in there as well. This shudder or vibration takes toll on everything starting from engine mount, air frame, hardware and even instruments. I had a student lose display pixels on his garmin GPS twice, guess what it was.
    Quote from Roger - "You need to have made test with instruments before any modifications and then repeat those test under identical circumstances. None ever used test instrumentation to back up any claims."
    I am an instrumentation engineer with 25+ years in industry and do understand the importance of validating a change and its impact assessment. This change in particular doesn't require any further validation when it comes to seeing the benefits of the obvious issue of rough running zone is gone. On the instrumentation side, Its proven by the instruments we already have in the aircraft that there is no change in any parameter of the machine when to comes to WOT RPMs , EGTs, CHTs other then that it runs like a smooth motor throughout the throttle range. In addition, only for testing, I was able to idle it like a 'car engine' to as low as 1000 RPM which is not possible with the original setup.
    So, if there is no validated documentation to say that this should not be done then, being experimental, we do have the right to try and improve the performance. Its not a surprise that people who condemned these actions are all who are (or were) related directly to Rotax operations. To one other comment - "I feel that increasing the size of the tube is simply trying to cover up out of sync carbs." -- Whats wrong with masking a issue of carb-sync if it protects your engine from running rough and give you many other benefits?

    Also, sharing this MOD here by no means imply that I am forcing anyone to do this mod to their engines but it is left at their discretion and neither do I have any marketing/financial interest in sharing as well. I will be more than happy to share my experience with it and can confirm that this changed my total impression about 912. I was always concerned about this rough zone and gear clutter at idle and always preferred flying behind the traditional engines which is now changing. :)

    Time to get back to work - Happy Skies!!
      
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  • Re: Polishing intake manifolds

    by » 6 years ago

    Whats wrong with masking a issue of carb-sync if it protects your engine from running rough adn give you many other benefits?
    Masking the problem. That's the point Roger and I are making. The problem does not need "masked". The carbs just need to be synced properly.
    I am all for pushing for development of newer and better systems. This is a great place to share these experiences. I do not think anyone is arguing that. Just sharing from our many years of experience working on the Rotax engines.
      
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  • Re: Polishing intake manifolds

    by » 6 years ago

    I have no issues with experimentation, testing and research it just needs to have repeatable, factual and instrument backed results to help remove as much as the human factor as possible. So things are just easier to test and prove than others and of course during these adventures it can cause damage depending on wht the research is.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: Harry Walia
      
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  • Re: Polishing intake manifolds

    by » 6 years ago

    You could add a solenoid or manual valve between the carbs on the larger balance tube with cockpit control to do a carb sync check just like a mag check before flight.
      
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