Jabiru Gen 4

[skippydiesel]

2 hours ago, Blueadventures said:

Don’t see that; looks historical with Aerovee first, then Jab being similar and air cooled also, then the Rotax as some want to fit those and lastly the newer UL range that will fit the Jab mount. The aircraft first designed for air cooled engines and the Jab 3300 is undoubtably the best performer being 25% better climb rate as one example.

In your dreams - the claims are from the marketing department.

[RFguy]

yeah I think the OP is getting confused with where the VW aerovee engines make their best power

Jab 6 cyl :  note flat torque curve

 

[skippydiesel]

30 minutes ago, RFguy said:

WRT sonex - it's unsurprising  that a  the 120 hp jab goes faster  the 100 hp 912ULS rotax .

why ? because  at any altitude, it has more power.  simple......

and power = rpm x torque so forget about talkign about torque. 

I dont 't know why that is in any contention. 

 

ideally, thrust would be presented. that's the final say...

 

If it does go faster (just) I would not be surprised however, when considering the Jab it's not just 20+ hp to  it's advantage,  it's also the inefficiencies of the Jab prop speed and additional weight to its disadvantage.

Then we come to mission objective - if it touring, the Jab will use considerably more fuel/ leg than the Rotax , this may impact on the overall speed if the Jab powered aircraft lands for fuel, while the Rotax motors on.😈

 

As for torque - I would speculate that an engine that delivers more torque, than another can utilise a courser pitch prop, ther by delivering more thrust at a given prop rpm, - what say you?

[Area-51]

1 hour ago, kgwilson said:

The claimed power of the 3300A engine is 90kW or 120HP at 3300 rpm not 3500 rpm. 3300 rpm is the maximum rated power setting for continuous operation. Some individual engines have produced 128 - 130 HP on a dyno.

 

I have set the Bolly BOS 5 prop pitch on my Gen 3 3300A engine to read 3300rpm at full power S&L at cruising altitude. This has reduced the full power climb to about 1200 fpm but that is more than adequate. At 5000 feet in my home built Sierra I have IAS of around 120 knots at full power which is a TAS of 132 knots.

At 3300rpm the gen4 sees 119hp and 189Nm torque where a 68" prop is just shy of supersonic tip speed; the 3300rpm being advantageous for producing thrust over the 9XX unit's 2400rpm; and then there is greater blade root and hub forces upon everything to consider with the added rpm of the gen4. Both units will spin the screw and produce around the same thrust at different rpm and blade pitch combinations; both units will use around the same amount of fuel at similar manifold pressure at equal thrust; both units have different TBO blocks applied. All units are subject to variable end user care during TBO periods.
 

There will never be consensus upon this matter. As a society we need to keep the two camps appropriately separated into easily identifiable "blue" and "red" camps, and "green" for all "other"... Seperate airfields, repairers, and no-fly sky zones... and develop a self sustainable bureaucratic "equality defence & punishment" policy department. 🙂

[jackc]

This turning into a pissing match, just feel lucky we all have aircraft to fly and be happy with.

If you want to fly higher and faster?  Just go buy a plane with a bigger engine?

Me? I would be just as happy to fly a Thruster to Melbourne……or do the trip in a Sonex Jet.

Its still flying, and that is all it matters 🤩

Flying…..is the most fun you can have, with your clothes on 🤩

[Kenlsa]

19 hours ago, justinjsinclair said:

But it’s a colt ❤️❤️❤️❤️❤️❤️❤️❤️❤️❤️, will it be losing the front wheely thingy ?

I can’t dance so it stays a milk stool

[Methusala]

To Area 51, see my post on Thurs. I flew VW as did Markdun  for years. I was attempting diplomacy (yeah, foolish I know). Never works, pistols at 10 paces, I bags second!

Edited April 27 by Methusala
Spell check!

[Area-51]

7 minutes ago, Methusala said:

To Area 51, see my post on Thurs. I flew VW as did Markdun  for years. I was attempting diplomacy (yeah, foolish I know). Never works, pistols at 10 paces, I bags second!

That would place oneself firmly in the "green" camp that is gaining footholds in surrounding low lying valleys surrounded by high peaks and ridgelines! 😂😂😂

[kgwilson]

What is the point of a 68 inch prop when efficiency gets lost with the 3300A. The Jabiru Scimitar props for the 3300A engine are 60" diameter. My Bos 5 is also 60" & a little better than the Scimitar. No problem with supersonic tips & less engine stress.

[RFguy]

the only practical  way the 3300 makes >115hp is with a pitch adjustable prop. then it is fantasic, can run it down at 2400-2600 etc 

[Thruster88]

1 hour ago, Area-51 said:

At 3300rpm the gen4 sees 119hp and 189Nm torque where a 68" prop is just shy of supersonic tip speed; the 3300rpm being advantageous for producing thrust over the 9XX unit's 2400rpm;

I don't believe that is correct. The 2400rpm propeller will be more efficient and produce more thrust if the hp was same.

 

Rotax could have chosen any ratio for the gearbox.  

 

[facthunter]

Till the torque curve starts to dip a lot more revs will give more POWER, but high(er) revs is more friction..   Nev

[turboplanner]

2 minutes ago, facthunter said:

Till the torque curve starts to dip a lot more revs will give more POWER, but high(er) revs is more friction..   Nev

The power curve is a product of the torque curve.

Friction is a power demand function.

[facthunter]

Power  is rpm and torque but the RPM  and friction are squared law.   Nev

[RFguy]

yes, fuel flow *may* edge up due to square law related losses.

and

and volumetric / airflow behaviour + efficiency has its own curves for each engine system with RPM/ MP

Edited April 28 by RFguy

[facthunter]

Max HP is always above peak torque. . Centrifugal forces are Squared law and very significant forces that load bearings.. Conrods usually fail in tension. Nev

[danny_galaga]

E=MC²

[turboplanner]

17 minutes ago, danny_galaga said:

E=MC²

I'd be getting that flying machine finished; we already have thousands of academics.

I'll pull the very basic data so people can do their own calculations.

[danny_galaga]

Biogeny recapitulates phylogeny 

 

(Or is it the other way 'round?)

[turboplanner]

No that's the correct order, but so many people try to start downwind so to speak.

[sfGnome]

12 hours ago, danny_galaga said:

Biogeny recapitulates phylogeny

I’m impressed (and yes, I did have to go and look it up 😵‍💫). 

[justinjsinclair]

Did a quick run down to Boonah this morning. 80lts fuel, me 100kg. 25kg tools. No spats. Closeish  to ISA, even got to say hello to a Jab going southbound 

[danny_galaga]

ill be there tomorrow.

[kgwilson]

It was a nice day for flying. I went South to Coramba at 2000 climbed to 3800 through the Mount Moombil gap down to Bellingen to check things out, coastal to South West Rocks & returned coastal past Coffs turning inland at Brooms head (it was raining around Yamba) & back via the Clarence to South Grafton. The Coffs tower was grappling with some Chinese students but managed to figure out what they were saying (I think) as I couldn't.

[Thruster88]

On 15/04/2024 at 3:39 PM, Methusala said:

Was in Tumut this weekend. Lying forlornly in the field 300m north of 35's threshold was a Foxbat. It had declared an oil pressure related engine failure. Rotax 9 series engine I would suppose. So, they  don't all run like the veritable Swiss watch. I'm certainly not attempting to bad mouth the pilot who suffered a little physical shaking but otherwise unharmed. Any engine can fail. Don

The ATSB is investigating this one because it is VH reg. Diverted from track about 15 Nm north east of Tumut, shame it fell 300 metres short. At least we will know what actually happened, hopefully. Aircraft is a A32 Vixen.

 

 https://www.atsb.gov.au/publications/investigation_reports/2024/report/ao-2024-010

Edited April 29 by Thruster88