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  • Re: odd dips in fuel pressure, pump problem?

    by » 6 months ago


    Roger

    i think your broad statement is not fully giving the whole story.  On a carb engine, where they run rich in the first place, a wrap may be successful.  Rotax has made it clear that they do not want their exhaust wrapped.  i have included the Service Letter, that has pictures, to prove their point.  Clearly the engines that you should never wrap are the lean burning and mostly turbo versions.  The exhaust temps get extremely high and pipe failure is possible.  The letter does not differentiate between turbo and non-turbo engines.

    Great caution should come when you have a modified engine, like EDGE performance with a lot of HP.  Power will give you some real problems when you push the limits especially with fuel injected engines and lean burn.  

    If you have to wrap your pipes to keep cowling temps normal then perhaps explore better airflow in the engine bay. (?) Remember that the issue is hot fuel and if you are not flowing air correctly around the exhaust and fuel systems I believe there will be issues.  The vast majority of installations do not require header wrap in my view.  

    Just my opinion.

    Cheers

    37187_2_exhaust wrap SL-916 i-008_915 i-010_912 i-016_912-025_914-023.pdf (You do not have access to download this file.)

  • Re: odd dips in fuel pressure, pump problem?

    by » 6 months ago


    Russell

    Do you happen to have a fuel flow transducer installed on your aircraft and either a Dynon or Garmin that records engine parameters? 

     


  • Re: odd dips in fuel pressure, pump problem?

    by » 6 months ago


    Howdy RW,

    More food for thought;

    All stories have paths that can branch off. I'm  a believer in considering ALL things that may influence  fuel pressure and or temps. I fully agree  with air flow and lean running engines.  I just reprogrammed my Polaris Razor 1K engine ECU to run richer because Polaris sets them to run a little too lean. It performs better and runs cooler. Many have done the same. As far as wrapping exhaust I agree on some engines, but even Rotec and other Rotax centers have to re-wrap Stemmie exhaust pipes on the 914 when they remove the aircraft's  Mfg's  exhaust wrap which would be against the service letter. This happens around the world. The failed exhaust pipes that are warpped in the pictures are most likely  caused by over wrapping which caused metal fatigue  and warpping. How would someone explain thousands of wrapped pipes with no damage around the world and only a handful of failures? Wrong installation. Think of all the bad things you've seen in your career that has caused bad outcomes just because they did it wrong vs right. Just because a few do it wrong and cause an issue should the mfg say we aren't  going to do that anymore.

    My whole point in my previous post is to not always blame or jump to conclusions on the fuel vaporization (the main path) and ignore other causes and issues. Look at the broader and overall picture and don't forget to consider ALL possible issues.

    If airflow or other cooling possibilities aren't  possible or legal maybe a wrap may help. It did in my research and testing. 


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


  • Re: odd dips in fuel pressure, pump problem?

    by » 6 months ago


    Man, I go to the hangar for a few hours and come back to 2 more pages :-)   I'm giving up on individual responses, so here are some comments as I remember them. 

    The fuel drain line WAS potentially getting some ram air.  I had left it as a rubber hose that just hung near the bottom of the firewall.  The hose had curved forward, and was trying to act as a bit of a scoop, though it probably wasn't seeing any outside airflow, mostly just what was exiting the cowl.  Anyway, I relocated that to the same place my carb drip trays drain, and that shouldn't be a problem. 

    I do in fact have a fuel flow transducer, and the pattern did change when the flow dipped, but it wasn't a direct correlation to the pressure.  The FF is always an up and down sort of waveform since it changes when the needles open and close.  the peaks weren't much different when the pressure dropped, but they were spaced farther apart in time.  I wasn't able to get a good screen capture that wasn't a jumbled mess. 

    I have been thinking of a way to measure fuel temp, but I'm not sure how practical it is.  You can never have too much data, and it should be illegal not to log data for every flight. 

    Exhaust wrap is something I tried initially to keep the cowl temps down.  I will say that it DID help some, but regardless of manufacturers claims for temp ratings, I never got more than 20 hrs out of the wrap before it started crumbling to bits.  I wouldn't be opposed to using it in some places if I could find some that didn't fall apart.  Any suggested products?  The stuff I used was https://www.amazon.com/gp/product/B0722ZGQH2  which claims 1800F direct and 2500 continuous.  My EGTs are in the 1450 range, so the manufacturer may be lying a bit. 

    Rusty


  • Re: odd dips in fuel pressure, pump problem?

    by » 6 months ago


    You gotta love good fun idea exchanges. It's  a great way to learn and think outside the box. Sometimes there's  more than one way to skin that proverbial cat. Yes some work better than others. This is why I do so much research and testing.

    The wrap should have lasted until you were ready to remove it. Something was wrong.


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


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