Fuel efficiency

[dlegg]

What sort of fuel burn figures are you getting with a 3300? I am pleasantly surprised to be getting 16lph at 2800 with the bing carb, engine serial 1928. I have a sensenich ground adjustable prop and am cruising at 110kts. Anyone else......?

 

 

[Guest Andys@coffs]

Do you have CHT and EGT gauges fitted? I was getting 19lph when I had the lean burn jetting when I first purchased my 230 in 2008 at 1bout 2850rpm and 115 to 120 in cruise. These days its between 24 and 27lph depending on DA/cruising altitude of the day. I would think 16lph, if that is calibrated and backed by refuel amounts, is too low and could lead to damage. CHT and EGT will obviously reveal if that is the case.......Its my view that you need these on all cylinders, when you have you'll see significant variances between cylinders and 1 or 2 on the back cylinders only doesn't the full story tell..... If you do have some or all, what head temps are you seeing?

 

Andy

 

 

[dlegg]

I do have EGT and CHT on all cyls. Cht's sit around 140ish and egt's when in cruise 680 to 700ish.Egt's drop down above 2800 rpm. I too think fuel burn is too low but the numbers seem ok?

 

 

[Guest Andys@coffs]

The numbers are Ok......fine finned heads should I think be closer to 120 than 140 but even so better than the 160 I'm seeing on my thick finned heads....

 

On refuel do the amounts need to refill the tanks align to a 16lph fuel flow?

 

Andy

 

 

[Jabiru Phil]

Sounds pretty lean to me.

 

My 2007 model when upgraded to a larger main jet now works out to 21 lt/ hour on xcountry flights, including warm up and taxying. So actual fuel burn in flight would be nearer 22-23 lt.

 

I usually sit in the rage of 2850-2900 revs

 

Flight plan at 115 kn is about spot on including climb and descent.

 

Phil

 

 

[facthunter]

Most of the problems started with the low fuel burn rates. Equal distribution is near impossible without fuel injection. It's pretty difficult to know what horsepower your prop and engine delivers and the fuel flow relates to power. 16 LPH is very low for a six cyl Jab. Nev

 

 

[Peter008]

I mirror your numbers Phil. The only difference is that I do my flight plan at 110kn and find it works just about right. Revs are always around 2800 - 2850 but notice that the revs will not get above 3000 rpm when under load. This is somewhat less than the Jabiru information. I suspect maybe the prop pitch is not an exact science with the wooden Jab props as an explanation of why the revs are slightly down but that is only a guess.

 

 

[facthunter]

RPM is one thing . The other element is torque. In the absence of some torquemeter the variables are PROP type, condition and pitch blade shape area etc and all the factors with the air you are flying through. Nev

 

 

[jetjr]

Fuel is cheap insurance for jabs, don't try to skimp on it

 

J200, runs 2900, 27 lph @ 125 kts tas

 

2 B Bolly prop.

 

Get 600-680 up to 720 at some settings on one cylinder, cht 90 to 120 deg c.

 

I'm keen to see more Manifold readings now there's a factory adjustable prop, as this is the way to look at load.

 

 

[facthunter]

You have a MP and RPM computation related to fuel flow and this works for big engines especially with superchargers and variable pitch props where you can set both. Man Pressure ( usually shown as cruise altitude), and rpm are what is used for flight planning basic engines, but unless you run Wide Open Throttle above a certain altitude, the altitude factor is not the true picture as you control RPM with throttle with a fixed pitch set up, and that will affect the Manifold pressure. Actual MP and RPM correlates to Horsepower and therefore fuel flow. (assuming the engine is functioning normally). and IS useful Nev

 

 

[Jabiru Phil]

I mirror your numbers Phil. The only difference is that I do my flight plan at 110kn and find it works just about right. Revs are always around 2800 - 2850 but notice that the revs will not get above 3000 rpm when under load. This is somewhat less than the Jabiru information. I suspect maybe the prop pitch is not an exact science with the wooden Jab props as an explanation of why the revs are slightly down but that is only a guess.

Peter, I should have stated that I have fitted the new Scimitar ground adjustable prop, factory set at 52 deg.

 

Big difference in performance noted.

 

I maybe imagining it but also sounds a lot quieter to me.

 

Phil

 

 

[Old Koreelah]

Phil can you tell us more about the performance of this prop?

 

 

[jetjr]

Re MAP, good info

 

The readings should be comparable for same engine, same rpm same prop yes?

 

It should be able to be used to better adjust prop pitch along with max static rpm etc. which right now is the only spec given and it's suggested not totally static but in TO run, so plenty of grey area.

 

Wood props flex, CF don't much so pitch adjustment methods and details need strengthening I reckon

 

 

[facthunter]

Jabiru emphasise NOT overloading the engine. This in plain language means not overpropping it. Your achieving the correct static RPM should be enough. Prop efficiency is another matter. One time a spring balance to a tethered aircraft was the go, and would give some indication of it's ability to take off and the fact that the prop was producing thrust to an acceptable amount as distinct from just absorbing horsepower. Nev

 

 

[jetjr]

Yes I know they say don't over prop, but can't give much more info other than max static rpm, this then let's engine run over max rpm in flight.

 

Bottom line is their recommendations are all based around old fixed wood prop which flexed a lot and wasn't adjustable.

 

New types can see different performances had by adjustment.

 

They are now talking about manifold measurements (with a Dynon this is cheap extra sensor to have) however without some field info I think we might be guessing as to what the numbers should be.

 

Not over propping seems to run against their old advice to run the engines hard

 

Currently I have advice that so long as 2750 rpm is reached in take off run then it's OK. Sure won't do it static but once moving does it easy.

 

My prop is the same blades as new jab type but Bolly hub, done 100 hrs on it, very impressive performance

 

 

[Jabiru Phil]

Phil can you tell us more about the performance of this prop?

The only figures I have are from Jab factory prop guy.

 

He recommended to set at 52 deg as opposed the original of 53 deg. I commented that this seems to be going backwards in performance.

 

He talked me into it as the take off distance, climb rate and a few extra knots together with smoother running, less stone damage and wet weather operation were its attributes.

 

So far all of the above except the wet weather operation which I avoid have been spot on.

 

As stated earlier, it does seem a lot quieter.

 

Actual figures are hard to judge, the take off roll is by far the most noticeable feels like another 20 hp.

 

Climb rate is sure better but I don't use it due to my getting to 80- 90 knots ASAP for cooling reasons. At a guess I would say over 1000 ft min. At 65 - 70 knots all up weight.

 

I was under the impression that it is ground adjustable, but was told today by a pilot that is is factory set to what you want and pinned. So maybe I was wrong there.

 

I probably get an extra 100 static revs if this is useful information to you. (3100)

 

The extra 4 or so knots at cruise revs is handy and the smoothness is quite noticeable and appreciated.

 

Hope this is some help.

 

Jabiru should have the performance figures for the various pitch settings if you give them a bell

 

Phil

 

 

[Peter008]

Do you recall the difference in price to the standard wood prop Phil?

 

 

[ruffasguts]

Do you recall the difference in price to the standard wood prop Phil?

$19.00 for prop need different spinner approx. $200.00 dearer

current price as it should be in the hanger this week being fitted to a J170C

 

Mick W

 

 

[Jabiru Phil]

Do you recall the difference in price to the standard wood prop Phil?

Yes, I was taken aback somewhat when quoted 2k but was told that the old original was now quoted at $16 hundred

 

The Scimitar has a different spinner and flange with all accessories supplied so was reasonably happy with the price when this was explained

 

I got a lame to fit, about an hours work to install. No balancing needed as all fits perfectly

 

Happy chappie

 

Phil

 

 

[Keenaviator]

Just bit the bullet and ordered a Jabiru scimitar prop for my UL 450. Seems a bit pricey but in reality not that much dearer than the Patroney I put on the Starlet when you include prop, hub, back and front plates and spinner (painted Jab white). And it's pre assembled and approved.

 

I've been chasing a slightly high egt on no. 4 cylinder and have tried 4 different props: Jab 60 x 42 - 3300 rpm @ 75 knots, Jab 60 x 44 - rpm a bit lower on climb but not very smooth so I didn't persist with it, Sweetapple 58 x 44 - 3400 rpm @ 75 knots and Sensenich 60 x 46 - 3200 rpm @ 75 knots). I've fitted a new stepped needle, 045 main jet and 290 needle jet but no. 3 is still a bit over 700 at WOT (flowing 27 litres per hour). After fitting the new prop I'll check the egt at WOT at 75 knots.

 

The next step is to update the induction set up - mine is an early 2200a with the induction manifold cast into the sump and induction tubes coming out of this at 90 degrees.

 

Laurie

 

 

[AVOCET]

H

 

Peter, I should have stated that I have fitted the new Scimitar ground adjustable prop, factory set at 52 deg.Big difference in performance noted.

I maybe imagining it but also sounds a lot quieter to me.

 

Phil

hi Phill , your not imagining it , or going deaf , they are alot quieter and smoother .

Cheers Mike .

 

 

[jetjr]

Dynamically balance them and they improve further

 

 

[Jabiru Phil]

Why do you say that JR? Surely they are balanced before delivery.

 

Mine has no noticeable vibration. Agree with Mike`s comments, very smooth and quiet,

 

Phil.

 

 

[jetjr]

Yep they are and they are WAY smoother than Jab timber model no doubt.

 

Not balanced dynamically though and this does much better job

 

I swapped to Bolly version some years ago, (blades almost same as new Jab version but different hub I think)

 

Decided to run balancer as I had it for a week, came back with "significant" vibration, added washers etc and now its even better. Often noted by pax.

 

Your actually balancing the whole rotating assembly, spinner, adapter, crank the lot.

 

As discussed elsewhere I have bought balancer now and will be done as annual service.

 

 

[Jabiru Phil]

OK, thanks for the explanation.

 

Guess its the same system used on vehicles where the brake drum and other items are balanced too, not just the tyre and rim.

 

Phil.