Today's Message Index:
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1. 03:25 AM - Re: Re: Hacman Gen 3 Mixture Control (Kingsley Hurst)
2. 03:58 AM - Re: Re: Hacman Gen 3 Mixture Control (Kingsley Hurst)
3. 04:15 AM - Re: Hac-man gen 3 mixture control (Kingsley Hurst)
4. 11:08 AM - Carbon Monoxide test for 914 (rparigoris)
Message 1
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| Subject: | Re: Hacman Gen 3 Mixture Control |
Hello Remi,
Thank you for your input which as usual, I appreciate.
I hadn't considered the effect of lower temperature at altitude but do
understand your reasoning albeit our temps are a far cry from yours. At
the moment, freezing level is above 10,000 ft. Regarding my fuel flow
meter, I do keep impeccable records of fuel used and my totalizer is
very accurate. I therefore have no reason to doubt the accuracy of the
flow meter.
In my quest for a better understanding of Bing carbs and there
idiosyncrasies, if you have any info available which you would be
prepared to share on your leaning system Remi, I would very much
appreciate same please.
Thanks again
Kingsley
On 12.12.19 8:11 pm, Remi Guerner wrote:
>
> Hello Kingsley,
> One reason for a higher fuel flow at altitude for the same MAP and RPM is that
your engine is developing more power. Taking your example, full throttle/20"
means you are at around 10000 ft. At this altitude, the outside temp is minus
4,5C (standard atmosphere) This is almost 20C less than at sea level. Then your
engine is developing 7% more power (293/273). The Rotax runs richer at altitude.
Based on my experience, this over rich mixture increases the fuel consumption
about 10% at 10000ft compared to low altitude at the same power. You say
your fuel flow is 40% higher: that is surprising and I assume your flow meter
is not accurate.
> I do not have any experience with the Hacman, but I have done some testing on
my 912ULS with my own mixture system (using an electric pump to suck pressure
out of the carb bowl vents). The system worked fine, was fail safe, but there
was no power gain at full throttle at altitude. This was disappointing and I
decided that the possible 10% fuel saving was not worth the additional complexity.
>
> Remi
Message 2
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| Subject: | Re: Hacman Gen 3 Mixture Control |
Thanks Ron,
You say, "full throttle will provide a richer mixture". From my
experience in a previous life flying aircraft with mixture controls, I
understand that a richer mixture on full throttle is usually the result
of the Power Jet. To my knowledge, the Bing Carb has no power jet.
As I alluded to in another post, it appears to me that the lack of
pressure differential across the butterfly valve on the Bing, causes the
mixture needle to rise, enriching the mixture and effectively acting
like the power jet on GA aircraft type carbs. The difference between
the GA type carbs and the Bing then being that the GA ones can be
manually leaned.
looking forward to hearing of your first flight Ron.
Kingsley
On 13.12.19 6:42 am, rparigoris wrote:
>
> Hi Kingsley
>
> Carburetors mix fuel to air by volume of air. Going up in altitude decreases
the number of air molecules per given volume of air a lot more than the decrease
in temperature. Thus since there are less air molecules for a given amount
of fuel the mixture will be richer than optimal. I will speak general but often
full throttle will provide a richer mixture than less than full throttle. The
reason is to cool the fire by throwing more gas on it! I have a 914 which complicates
the life of the poor Bing type 64 constant depression carbs but am installing
a Hacman that will work on the 914. Have not yet tested but should be
fine. Mind you if you have control of mixture it can be a good thing, but if
you run hard and lean that can be a terrible thing. If you lean at altitude when
you come down or pull the throttle it will be leaner than desirable so you
will need to add this extra bit to your piloting tasks.
> see Mixture 1 and 2
> http://www.europaowners.org/main.php?g2_itemId=27305&g2_page=2
> I am installing 2 EGTs and a Split Second monitor. It uses a O2 sensor to drive
it. It allows you to monitor mixture. Unlike a fuel injection system that needs
very fast response time of the O2 sensor, using one in this capacity only
needs a very slow response time. Thus even using Leaded Fuel, should be able
to get 100 hours out of O2 sensor from what I'm told.
> Ron P.
Message 3
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| Subject: | Re: Hac-man gen 3 mixture control |
Creighton,
Like you, I have a 912 (80hp) and a CS prop but as yet, no Hacman. I
fully concur with your statement that the Bings do a good job up to
about 4000 ft and your fuel flow at WOT at altitude of 3.5 GPH is very
much the same as what I get down low on the same power setting.
Your figures are what I would expect at altitude (with leaning) so I am
much encouraged by your experience.
Thank you for your input and I would be interested to know what sort of
tubing you have found to be more reliable please. If I am reading the
Hacman information correctly, I think they may have changed the tubing
type on their Gen 3 unit.
Best regards
Kingsley Hurst
On 13.12.19 9:31 am, crouton wrote:
>
> I have been using a Hacman for several years at this point. The Bings do a good
job of keeping the mixture sweet up to about 4000ft (80hp 912).
> On some of my longer legs I have climbed as high as 11500ft and have been able
to keep EGTs up and fuel flows down (WOT and 3.5GPH). Obviously I only fly
this high in order to ride a smoking tailwind.
> The vacuum lines in my kit were aquarium tubing and were not up to engine compartment
conditions and had to be replaced with more durable tubing.
> I like the Hacman and the addition of a constant speed prop rounds out the package,
Affording better climb, faster cruise, and more consistent fuel flows.
Consistent rpm reduces my tendency toward fugoid of a hundred or so feet which
affects rpm and power.
> Creighton Smith A-009
>>
>>
>>
>
>
Message 4
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| Subject: | Carbon Monoxide test for 914 |
Hi Group
Has anyone performed the Carbon Monoxide Test as per Rotax to make sure that the
leanest cylinder is not too lean when running at 115%? If the answer is yes,
what was the richest and leanest cylinder readings and did you need to richen
mixture to pass test?
Thx. Ron P.
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http://forums.matronics.com/viewtopic.php?p=493824#493824
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