Manifold Pressure Values?????

by geoffrey klestadt in 912iS Technical Questions 8 years ago

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Re: Manifold Pressure Values?????

by Glenn Martin » 7 years ago

Glenn Martin

3 281 801

Hi Geoffrey,
I was unaware that Rotax made a Pilots Operating Handbook. I have only ever seen a POH from an airframe Manufacturer. From Rotax I have seen Service, Installation Heavy Maintenance and Operators manuals none of which have that information. Therefore can you include a link to the Rotax POH so I can look at page 5-4 ?

I have also recently seen the latest 30 December issue from Rotax, but am unsure if it relates to an IS sport engine.

As you say it does say "all 912" but the graph specifically says UL/ULS not IS.

Secondly when I search on the Rotax official website for bulletins etc relating to the IS engine this document does not appear.

As an ex engine developer I would expect that Rotax would program the ECU to adjust fuel/ignition to ensure the engine does not go anywhere near detonation. What is standard is to retard the ignition and add a little fuel in the areas of low rpm and high throttle (MAP) to be safe.

For your situation I would have thought CASA would be OK with the Rotax "approved data" being the 912IS Operators manual. For my aircraft the POH says "must be operated in accordance with the Rotax Operators manual" , and the CAA approved documents just says the same.

I suppose that if there are newer recommendations as may be implied from the 30/12/2016 document then either Rotax will confirm that that document does indeed apply to 912IS engines and/or there will be an update to the 912IS Operators manual.

I suspect that you could use either (912IS OPS manual or the bulletin) for the documentation required by CASA.

When will your aircraft be ready for flight and what is it ??

Cheers

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Re: Manifold Pressure Values?????

by RotaxOwner Admin » 7 years ago

RotaxOwner Admin

59 1.58k 13.9k

Point of clarification: 912iS (series) is a completely different engine, and it gets its own "912i" service bulletins, service letters, and service instructions.

References to "All 912" in the 912 documents exclude the 912iS series engines.

Thank you said by: Glenn Martin

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Re: Manifold Pressure Values?????

by geoffrey klestadt » 7 years ago

geoffrey klestadt

27 94 94

Thank you for the clarification. The 912 letter is irrelevant.

Would I be correct in expecting that the 912i engine is bullet proof or will Rotax eventually tell us what the operating limitations are and how and why they differ from the carbureted version? Apart from the limitation of 5800 rpm at wide open throttle for five minutes.

The CAN bus outputs manifold pressure data, presumably for a reason.

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Re: Manifold Pressure Values?????

by Glenn Martin » 7 years ago

Glenn Martin

3 281 801

No Engine is Bullet proof,
If you want to confirm that then get a Lycoming and a 50 cal rifle and do an experiment.

Rotax has been telling you the operating limitations of the 912IS engine in the Operators manual for years...you just will not believe them.

There is an old saying about teaching old dogs new tricks, look it up, and another about taking a horse to water...

Good luck with your new aircraft, hope you has as much fun as I have been having.

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Re: Manifold Pressure Values?????

by Gilles Thesee » 7 years ago

Gilles Thesee

2 9 0

Hi all,

My understanding is that at the moment relatively few 912iS are flying, and most have fixed pitch propeller.
So few pilots are aware of the absence of a power setting table in the operators manual.

For instance, with a 912, the OM gives such a table :

With our 914, we usually cruise at 75% power, according to the table in our OM :

Whenever the pilot wants to set 75%, he adjusts the pitch lever to 5000 rpm, and the throttle to 31 inHg.
The engine performance is repeatable, so performance measurements are possible.

The injection doesn't change the means of setting a definite power.
Otherwise it is not possible to know the power the engine is delivering, since for a given power, you get more than one fuel flow value.
Without an MP gauge and a definite setting, it is impossible to estimate a fuel economy : you have the fuel flow, but you don't know the corresponding power setting.

Obviously Rotax did their homework, since Mr Stock uses the values in his engine management system, but at the moment they have not been released to the public.
But to fly with a CS prop, we definitely need the data.
Maybe in the near future ?

Best regards,
Gilles

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Manifold Pressure Values?????

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