If you pull on Carb Heat, does the vibration smooth back out?
Mike Duane
N377EA Europa Conventional Gear
Jabiru 3300A
Sensenich 2Blade Ground Adj. Prop
Sent from my iPhone
> On Jan 31, 2023, at 7:47 AM, Pete Zut <peterz@zutrasoft.com> wrote:
>
> =EF=BB
> 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 kn
ow I am picky about this subject but I hate when things are running well and
then change):
>>
>> My new engine (about 70 hrs now) has always ran pretty good. However, as o
f late, I noticed a slight (emphasis on slight) vibration when I power down t
o a low cruise power setting (around 500-5100 RPM). Now, I know that some pe
ople will start screaming that I should not keep the power that low but I ha
d no issues with sensing vibration (slight) at that power level before.
>>
>> Well, I started to suspect that this was happening when the weather got c
older (50s-60s =C2=B0F). EGT looks good at around 1400. And even though I ha
ve blocked maybe 1/2 of the oil cooler, it still runs a little bellow 180 (1
60-170). 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 Beho
ld 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 m
ixture goes lean with the stock 912S carb setting. # 1 and 2 plugs look norm
al (slight tan) but the #3 and 4 look lean (white). Engine is stock as it ca
me 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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