j170 versus j230 fuel consumption ?

[Dayble]

Hi all,

 

The forums and data seem to say about 15 lph for a j170 and 21 lph for a j230

 

If you fly a j230 at just 100 kts, do you get much closer to a j170 fuel rate for that speed ?

 

This question comes about from our soon to be syndicate, where some do

 

not want to go to a j230 coz of the cost of fuel, now and in 3 years time.

 

But we want to carry bikes and if we run a Jab230 at just 100 kts, maybe it would not cost that much more to run, for those that want to do it that way ?

 

 

[Captain]

Ian

 

 

 

I have a 230 and I reckon that 21 lph is low.

 

 

 

It is more like 26. See the latest couple of posts in "J230 @ YSWG" in the Kitbuilding section for a recent discussion.

 

 

 

But then, I suspect that 15 lph is also low for a 170 but others can contribute on that.

 

 

 

If you fly a 230 @ 100 kts you will be at lower than recommended cruise revs unless you reprop it.

 

 

 

The 3300 engine is 50% bigger than the 2200 and that means it will burn more fuel, + the 230 is heavier so the same again.

 

 

 

For me, the fuel burn is fine in the 230 in return for the extra cruise speed and the luggage space in the bigger fuselage. I reckon that to be a reasonable compromise, and I can get long distances for less fuel than my road vehicle uses.

 

 

 

You will almost certainly burn about 50% more fuel in the 230 but cruise approx. 15 - 20% faster than the 170, so the nett is maybe 30% more fuel for the convenience. Good for some and a concern for others.

 

 

 

Hope this helps.

 

 

 

Regards Geoff

 

 

 

PS And there is nothing like the feel of those 6 cylinders when you give it the berries down the strip.

 

 

 

[glenns]

I agree, to fly a J230 at 100kt is not good (unless other influences force this such as turbulance, traffic etc). It will be well below the recommended cruise. There are plenty of other discussion topics here about the damages it causes running engines at lower cruise revs to save fuel. I would think 25 to 26 ltrs an hour is about right for 2850 to 2900 rpm which should give you close if not spot on your 120kt cruise.

 

 

[Captain]

I agree.

 

 

 

Just checked the Jabiru website and they indicate 13 - 16 lph for the 170 and 23 - 25 lph for the 230.

 

 

 

But as posted in the J230@YSWG thread, mine goes a bit higher because I choose to manage the EGT's to have most below 700 C.

 

 

[quentas]

I reckon I burn 23-24 lph at around 118kts with 2800rpm (J230) Tis nice to know you can see over 100 GS on most nice flying days in a head wind.

 

 

[Guest brentc]

My 6 cylinder burns around 23'ish on average.

 

There is an age old argument regarding fuel burn versus speed. If the J230 is 25% quicker and uses 25% more fuel then it doesn't really matter, except that overall when you look at overhaul prices, there's 2 extra cylinders to contend with.

 

I know some RV owners that go as quick as they can all the time because they figure that the extra fuel doesn't cost as much as the extra hours on the engine come overhaul time, so it's better to live for the long term at the expense of the moment.

 

I wish I knww what the price of fuel was going to be in 3 years, but I'm glad I don't have to hire aircraft at the moment. Even if my $42 an hour for fuel doubles, I'll still be better off than hiring (disclaimer - assumes that you own your aircraft).

 

 

[Guest ROM]

A bit off topic but probably of interest to Jab engine owners.

 

The Dyn'Aero MCR's also have a Jabiru 2200 engine option in lieu of the Rotax.

 

Dyn'Aero have apparently done away with the Jab supplied cooling ducts and just use a sealed box right around the top half of the engine which forces the intake cooling flow down through the entire cylinder section.

 

http://fpkit.nexenservices.com/lien/tci/moteur/mplm6j0.htm

 

http://fpkit.nexenservices.com/lien/tci/moteur/mplm6e0.htm

 

 

[Guest J430]

There is a plenom chamver on a J200 at HBA.

 

Very good results indeed!

 

As a guide, I burn 23-24LPH in the cruise, and average 21 over the flight, flying it the way I do. on a recent trip with several legs over a week or so alongside BNP, we used about the same amount of fuel! Might be a tip there!

 

J:thumb_up:

 

 

[Dayble]

Thanks everyone for some very useful comments.

 

I was talking with a very helpful bloke from Jabiru just now, who says that

 

flying a j230 at slower rpm's is not a issue. ( although at some point it will be less efficient as the nose comes up and there is more drag)

 

 

[Guest brentc]

Interesting comment there Ian as the Jabiru engie dept are usually the ones telling everyone to fly at no less than 2,800-2,850 for fear of glazing the cylinders. Also noted in their JabaChat newsletters!

 

 

[Captain]

Ian

 

 

 

Brent is right and you will also find that at some of these lower speeds the EGT's also climb to the max or above Jabiru's stated limits, so IMHO you would be more likely to have valve issues and in my view also more likely to gum up rings, which is also a bit of an issue with these engines.

 

 

 

For normal operations at these reduced throttle/rev settings it is fine (eg in the circuit or in turbulence or due to other constraints) but there is no way that I would operate a 3300 constantly at cruise each time at less than 2800 rpm.

 

 

 

See Brent's post in another area on what it cost him to overhall his top end recently and see how your syndicate members like them apples.

 

 

 

If your syndicate are really set on this, & fuel burn is the predominant issue for you all, then my advice would be to go with the 170 ............. but I have to say that if the $10 - $20 per hour difference in fuel cost between operating them both at normal cruise speeds is such an issue, then you are all likely to also have a little trouble with some of the other costs that come with owning and operating the aircraft.

 

 

 

Regards Geoff

 

 

[Guest brentc]

FYI as a matter of interest - Full overhaul parts only no labour for 4 cylinder, close to $8k. Add 33% for 6 Cylinder - this is for 2,000 hours.

 

 

[Guest Andys@coffs]

4cyl-6cyl is a 50% increase, not a 33% increase no? 8k therefore = $12k

 

Or have I missed something

 

Andy

 

 

[Guest ROM]

50% going up, Andy!

 

33% coming down!

 

Now which way is that horse facing?

 

 

[Guest brentc]

I was coming down, from my 6 cylinder to a 4. (that's my excuse and I'm sticking by it). Easy mistake to make, just asked someone next to me and he made the same mistake!

 

Either way, $12k is a lot of cash!

 

 

[Guest Andys@coffs]

50% going up, Andy!33% coming down!

Now which way is that horse facing?

Just asked my wallet and it voted emphatically for the 33%. At the same time Mr Jabiru was equally emphatic that 50% was the right number....... lies...damn lies.....statistics!

 

Rule of thumb.....If an aviation cost can be interpreted 2 ways.....choose the most expensive and be pleasantly surprised for that 1 in a 1000 times:keen:, rather than deeply dissapointed 999 in a 1000:censored:

 

Andy

 

 

[ianboag]

I fly my J200 at 100 kts - about 2500-2600 rpm - because it's quieter than 120 kts and I get to enjoy more time flying. I have a fuel flow meter and at 100 kts it uses a tad under 15 lph. 120 kts is about 25. Takeoff is 35. I would expect a 230 to be not very different.

 

I get a bit of tsk-tsk and wonder if I'm glazing the bores or whatever.

 

The other day i was flying with a mate who used to fly with me in my old C172A which would rumble along in the low 90s burning 35 lph. I throttled back to low 90's - the plane went a bit mushy but the view was nice and it was real quiet - I don't recall the rpm - fuel burn was just over 10 lph. Suck that up you GA tintops

 

Ian Boag

 

 

[Geoff]

Is about the same as the 230 in Mildura Ian.

 

 

[Guest Ken deVos]

I flew the J230 from Tyabb to Lethbridge last Saturday and at 112Knt TAS at 4500ft she was drinking around 21 ltr/hr @ 2700rpm.

 

Mind you, with the headwind I was only getting 77knt ground speed so was happy the six was up front

 

 

[ianboag]

I have no issues with EGTs or CHTs or oil temp/press when I do my reduced power stooging through the sky. All numbers look fine.

 

I do have a funny one on the oil pressure front though. When the oil and engine are cold the pressure is relatively low (35-odd psi) and it increases (50-odd psi) as the engine warms up after takeoff.

 

Warming the oil before takeoff doesn't seem to happen. I use a CHT of 250+ as my indication of a warmed up engine. I forget who suggested that.

 

I did the oil pump mod ages ago and I have one of the big new Aero Classics oil coolers - same as on the 230's (the Positech one is essentially the same). Provided I tape the cooler off 100% the oil temperature is fine .... Sure NZ is colder than Victoria, but I would expect oil temp to track OAT so the difference should not be more than about 10 deg C. Go figure.

 

IB

 

 

[anjum_jabiru]

Hi Dayble, In case you are still looking for an answer, the J230 cruising at 107 knots is expected to burn 17 litres / hour at 2600 RPM.

 

You can go to the link below and press CTRL+F and type 107 in the search box. It gives a table of RPM/Fuel Consumption/True Air Speed

 

http://adelaidesoaring.on.net/wp-content/uploads/2017/02/J230C_Section0_9_POH.pdf

 

Cheers 🙂 

[facthunter]

There's 12 years between those posts. Called a "thread dredge". Might affect your replies. Nev

[RFguy]

anjum_jabiru - more like low 20s at 107 kts Indicated.