Interesting.... curious, what prop are you running? :-)
Cheers,
PeteZ
On Tue, Jan 31, 2023 at 9:44 AM n7188u <chmgarb@gmail.com> wrote:
>
> Hi Guys (and Gals),
>
> Haven't posted much lately but things going well with my mono. Enjoying i
t
> more every day.
>
> One question, and a puzzler for me, regarding engine vibration (yes, I
> know I am picky about this subject but I hate when things are running wel
l
> and then change):
>
> My new engine (about 70 hrs now) has always ran pretty good. However, as
> of late, I noticed a slight (emphasis on slight) vibration when I power
> down to a low cruise power setting (around 500-5100 RPM). Now, I know tha
t
> some people will start screaming that I should not keep the power that lo
w
> but I had no issues with sensing vibration (slight) at that power level
> before.
>
> Well, I started to suspect that this was happening when the weather got
> colder (50s-60s =C2=B0F). EGT looks good at around 1400. And even though
I have
> blocked maybe 1/2 of the oil cooler, it still runs a little bellow 180
> (160-170). Coolant has been as low as mod 150s.
>
> Sure enough, last flight the vibration was noticeable. Yesterday we had a
> warm and humid day, in the 80s, so I decided to test my theory. Lo and
> Behold the engine ran great. Absolutely no vibration at 5000 RPM.
>
> My suspicion at this point is that the cold air from our ram air inductio
n
> system is just very cold, and maybe adds a little extra pressure, and the
> mixture goes lean with the stock 912S carb setting. # 1 and 2 plugs look
> normal (slight tan) but the #3 and 4 look lean (white). Engine is stock a
s
> it came from Rotax with no changes to the carbs made.
>
> If we get a cold day again I will try moving the needles up one notch but
> I wonder if anyone had an experience like this before.
>
> Best Regards,
> Chris
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=510082#510082
>
>
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