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ptag.dev(at)tiscali.co.uk
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 Posted: Wed Sep 12, 2007 2:39 pm Post subject: Rotax 914 performance info request.... |
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Hi! All
Today I began to enjoy fuel economy……!
I and my observer brother did a 2 hour 2 landing trip with a couple of timed climbs commencing initially at 1370 lbs and used only 24 litres(best capable measure since I wouldn’t claim a scientific measure!). Ambient temp/pressure was 22deg C /1024. Generally the Manifold pressure was maintained to 27 inches excepting a timed 1000ft/2000ft… 100% power climb at 85kts
80seconds…….. one hour later (fuel used lighter) 1,500ft/2500ft…..115% power climb at 80kts….60seconds …….I failed to collect the manifold pressures during the climbs. However the intake manifold locally insulated surface temperature was 31.1deg C during the initial climb and 35 deg C during the high power climb. 100- 110kt cruise 5,150 RPM the intake manifold temp at 2000ft was 27.4 deg C. (but in this instance the manifold pressure was 29”)
Intake manifold temp. at 1000ft 70kts was 30.8 deg C . At 100kt cruise the coolant temperature was 92 deg C . Oil temperature was 98 deg C with oil pressure at 2 bar.
I am using “Mobil One” 0w -40w and find myself wanting to increase the oil pressure somewhat although the light viscosity oil must be “reaching places where more viscous oils don’t reach !” Would anyone care to pass comment on the suitability of a higher oil pressure and the generally accepted best climb speed, please?
The engine does not now appear to be using/loosing oil from engine/turbo.
The rising coolant temps. on the sustained 115% climb would not have enabled a 5 minute climb.
Would any capable statistician care to crunch/”nit pick” these figures ? and make appropriate recommendations with regards to the oil pressure ? and does anyone have any comparable intake manifold locally insulated surface temps without an intercooler fitted?
A radio test at 20nm 2,000ft was effected at “fives” abeam and approaching Humberside Radar an item near impossible with the Jabiru installation!
Regards
Bob Harrison G-PTAG
PS the stabilator torque tube clamps worked fine and won’t need any heat to remove them !!!!!!
Robt.C.Harrison
[quote][b]
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Gilles.Thesee(at)ac-greno
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| Posted: Wed Sep 12, 2007 3:16 pm Post subject: Rotax 914 performance info request.... |
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Bob,
| Quote: |
Generally the Manifold pressure was maintained to 27 inches excepting
a timed 1000ft/2000ft… 100% power climb at 85kts
80seconds…….. one hour later (fuel used lighter) 1,500ft/2500ft…..115%
power climb at 80kts….60seconds …….I failed to collect the manifold
pressures during the climbs. However the intake manifold locally
insulated surface temperature was 31.1deg C during the initial climb
and 35 deg C during the high power climb. 100- 110kt cruise 5,150 RPM
the intake manifold temp at 2000ft was 27.4 deg C. (but in this
instance the manifold pressure was 29”)
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Our usual settings are as follows :
39"/5800 => 115 % for take off
35"/5500 => 100 % initial climb
31"/5000 => 75 % for cruise & climb
29"/4800 => 65 % for economical cruise
28"/4300 => 55 % (very rarely used)
I don't know the output for 5150 RPM.
27" seems rather low for break in : you need manifold pressure for the
rings to bed in.
| Quote: | Intake manifold temp. at 1000ft 70kts was 30.8 deg C . At 100kt cruise
the coolant temperature was 92 deg C . Oil temperature was 98 deg C
with oil pressure at 2 bar.
I am using “Mobil One” 0w -40w and find myself wanting to increase the
oil pressure somewhat although the light viscosity oil must be
“reaching places where more viscous oils don’t reach !” Would anyone
care to pass comment on the suitability of a higher oil pressure and
the generally accepted best climb speed, please?
The engine does not now appear to be using/loosing oil from engine/turbo.
The rising coolant temps. on the sustained 115% climb would not have
enabled a 5 minute climb.
|
Our cooling setup allows for close to 5 minutes 115 % climb, but we
never bothered to wait until the 5 minute light flashes.
I usually reduce power to 100 % as soon as I'm airborne.
| Quote: |
Would any capable statistician care to crunch/”nit pick” these figures
? and make appropriate recommendations with regards to the oil
pressure ? and does anyone have any comparable intake manifold locally
insulated surface temps without an intercooler fitted?
|
Unfortunately, we did not make those measurements, and our engine is
intercooled. We focused on airbox temperatures.
Yes the 914 oil pressure seems lowish, but it is the way the engine works.
Remember the oil pressure is usually measured at the oil pump, but we
have no means to know what the pressure actually is at the journals,
etc...Certainly much lower than the healthy number usually displayed by
the gauge on other engines.
Sooo, as long as the pressure stays within the manufacturer's numbers...
Best regards,
--
Gilles
http://contrails.free.fr
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jodel(at)nildram.co.uk
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| Posted: Thu Sep 13, 2007 12:25 am Post subject: Rotax 914 performance info request.... |
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| Quote: | | >I am using “Mobil One” 0w -40w Bob, Page 10-9 of the 914 operators manual which covers Lubricants starts with:- Oil: Motorcycle oil of a registered brand with gear additives. As far as I can see from the Mobil.co.uk site, Mobil 1 is not a motorcycle oil. Over the page on 10-10 fig 13 is a table giving multigrade weights according to climatic conditions. 0W-40 is not listed. |
0123
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davidjoyce(at)doctors.org
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| Posted: Thu Sep 13, 2007 1:02 am Post subject: Rotax 914 performance info request.... |
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Bob, 2 Bar for oil pressure is very low for my 914, for any other than
idling speed with very hot oil.It much more commonly runs around the 4 Bar
level. 2 bar is actually the warning limit for the Flydat system when it
starts flashing lights at you! Shell VSX4 came out in various articles as
the clear top choice as I remember it. I wouldn't be happy running generally
at as low a pressure as that. I would be inclined to check your oil
pressure sender if you can, then change your oil, (for VSX 4) then if still
low put a shimmy in the oil pressure relief valve under the gear box.
Regards, David Joyce, G-XSDJ
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josok-e(at)ukolo.fi
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| Posted: Thu Sep 13, 2007 5:58 am Post subject: Rotax 914 performance info request.... |
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Hi Bob,
As others have stated, it's the wrong oil, it has to have additions for the gears, and should not contain additives which will makes the safety clutch slip in a while.
Mine has now done about 35 flying hours, and the temperatures have come down a lot. I also had to lower the idle running speed, while during the first hours the engine used to stop in the landing run-out. In other words, it needs a lot of breaking in.
Regards,
Jos Okhuijsen
Visit - www.EuropaOwners.org
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Gilles.Thesee(at)ac-greno
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| Posted: Thu Sep 13, 2007 7:47 am Post subject: Rotax 914 performance info request.... |
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Simon Smith a écrit :
| Quote: | In Rotax SI-914-019 there are two tables listing recommended oils.
Read the notes under the table and you will see that some are
“recommended” while others are “highly recommended” None of them are
10W-40. If you ask all the UK 91x owners I suspect that you will find
most are using Shell VSX4 10W40
* *
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Bob, Simon and all,
Just had our French dealer on the phone.
He confirms that 2 bar is lowish but well within the operating limits,
and doesn't see any reasons for concern or mod.
Concerning oils, he says the Mobil 1 oils listed in SI-914-019 are OK :
Mobil 1 SAE 5W-30
Mobil 1 SAE 15W-50
Mobil 1 MX4T 10W-40
Mobil 1 V-Twin 20W-50
All are for unleaded fuel only, the last two are "highly recommended".
FWIW.
Concerning best climb speed, it is a matter of minutes to perform
several timed climbs at different speeds, keeping the same power setting.
BTW, can you elaborate about your "intake manifold locally insulated
surface temps" measurements ? What is the purpose of these measurements
? Ice prevention ?
Best regards,
--
Gilles
http://contrails.free.fr
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mikenjulie.parkin(at)btin
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| Posted: Thu Sep 13, 2007 7:52 am Post subject: Rotax 914 performance info request.... |
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Hello Bob,
Very pleased to see you are slowly being bitten by the Rotax Bug. My oil pressure is usually around 2.4 Bar in the cruise but the oil and water temperatures settle back to more like 70 degs C - a bit too cold. A climb speed of 80kts is about Vx for G-JULZ Vy being not more than a couple of knots higher. But practically, if I am going somewhere I tend to climb on track about 100kts it gives a decent rate of climb, it helps with the cooling on a summers day and it enables better lookout ahead.
Now you have got rid of that other 'lump' I think that you will quickly realise the added performance you now have.
I still think you need to open up the cowling gills though.
fly safe,
Mike
[quote] ---
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mikenjulie.parkin(at)btin
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| Posted: Thu Sep 13, 2007 8:44 am Post subject: Rotax 914 performance info request.... |
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David,
G-JULZ has always run at 2.4 Bar in the cruise since new. I remember
talking to Andy Draper about it and he said it was normal and that G-GBXS
also ran at 2.4 Bar.
regards,
Mike
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ptag.dev(at)tiscali.co.uk
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| Posted: Thu Sep 13, 2007 1:58 pm Post subject: Rotax 914 performance info request.... |
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Hi! Gilles
Thanks for your info. provided re.oils etc.
The temperature I'm giving as "Intake manifold surface temperatures" is
my attempt at discovering the effects of the intercooler. I have a
temperature sensor which I can move around the cowl and in the intake
manifold case it is strapped to the manifold and then suitably insulated
from outside effect
The readings then obtained were a rough indication of the temperature
drop compared to the ambient.
Regards
Bob H G-PTAG
--
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