J230 LSA Visitor

[Guest brentc]

Hi Ivan and welcome.

 

Do you know how old exactly your engine is and what needle / seat combination you are running?

 

There are other threads running where increasing the fuel burn have lowered the temperatures significatly. Mine lowered around 50 deg F with the new seat I fitted recently.

 

I recommend finding out what you have from Jabiru based on your engine serial number and take it from there. Attached is my dash - check the temps. Like I said, it's down around 50 on what it was with the previous seat. The sensor is fitted on number 5.

 

 

[Guest brentc]

Refer to temps in pic.

 

http://www.recreationalflying.com/forum/attachment.php?attachmentid=4384&d=1201507485

 

 

[GlennB]

Hi brentc

 

I have a J230 with mods done and a carbon fiber 3 blade prop. Just wonder what jets and needle you are using ?? I have just fitted Jabirus economy lean kit and feel this is a little light on for this configuration. My cht is still a little high.

 

 

[Guest imap8ntr]

My engine only has 120 hr since new and I am the original owner. By the dates of purchase only the JSL002-2 was out so I am sure my engine doen not have the jets mentioned in 018-2. Thus my jets are 45 idle, 290 and 255. The newest bulletin says that things should change to #35, 285 amd 255 which to me means that all will be even leaner except in idle? Do you agree.

 

Thanks

 

Ivan

 

 

[Guest brentc]

I'm sorry but I don't know the exact seat / jet that I am using, however it's the latest one, running it at around 22 - 23 litres per hour which based on my calculations is the correct amount for that amont of horsepower. I originally had the rich carby, burning 27 litres per hour, then went to the lean kit at 20 per hour and am now up to 22 per hour or thereabouts. I have the 3 blade carbon prop also.

 

Ivan, what would be your exact fuel consumption?

 

 

[Guest imap8ntr]

Hi Brent

 

Thanks for your response. I use 19 l/hr. I may be using a tiny bit more because I do lots of pattern worn but I tried to factor out all those pattern flights. I am definitely sure that I dont use more than 20l/hr.

 

Ivan

 

 

[Guest brentc]

I honestly think that you should be using a bit more than that. Better to be safe than sorry and run a bit richer if you can.

 

I did 130 hours on the original 27 litre set-up, then another 300 on the 19-20 per hour, at which point I had to to a complete top-end overhaul including valves and valve seats because it was running too lean.

 

 

[Guest imap8ntr]

Hi

 

The POH for my airplane says that consumption should be at 19.8gal.hr which is about where I am at. Jabiru USA confirms that I have the correct jetting and are aware of my cruise EGT of 1435. It was also explained to me about the EGT's may run hotter during the cold dense air winters causing the engine to run a little leaner. I am planning on checkin my hottest plugs and head torque bolts to make sure all is just fine.

 

You comments are welcome and appreciated.

 

Ivan

 

 

[Guest airsick]

Remember also -

 

Peak EGT = max efficiency

 

Slightly richer than peak EGT = max power.

 

It can't hurt to run a little richer.

 

 

[Jabiru Phil]

Hi Brentc

 

I too am interested in the discussion on oil temp. My 230 runs at near the 100 mark at cruise. I don't seem to be able to get your pics for some reason, is there a trick?

 

Phil.

 

 

[Guest imap8ntr]

Hi "Airsick"

 

I am a bit confused about what is "peak" EGT. I dont really know what that is for my airplane. Is that listed in the specs or is that something particular to each engine and has to be found out by running the engine. Without a mixture control on my J-250 I dont think I can find out what peak is and thus I dont know if I am lean or rick of peak or at peak?

 

Thanks

 

Ivan

 

 

[Guest airsick]

Hi Ivan,

 

Peak EGT is the highest temp you get depending on mixture. Starting from a full rich mixture as you lean it out EGT should rise. You will eventually get to a point where the EGT peaks and then drops as you continue to lean the mixture.

 

The reasons for this are... When the mixture is too rich there is too much fuel for the amount of air which causes the EGT to cool. When the mixture is too lean there is not enough fuel to burn which also causes excessive cooling. What is the hassle with running the engine too cool?

 

Well there is nothing really wrong with running the engine too cool (unless you go to extremes). The problem stems from the cause of the cooling. Running the mixture too rich or too lean can lead to fouling of the plugs, damage to valves, detonation, etc.

 

As you lean the engine and near the peak EGT you go over the top of the power curve for the engine. Adjusting the mixture to be slightly richer than this point (slightly below peak EGT) will pull you back to the peak power output of the engine.

 

As for the Jabiru - well I haven't got a clue what peak EGT is. I have a mate with a Jab and his manual is extremely vague in this area. He has (from memory) an engine manual and an aircraft manual and both say different things. We recently stuck a Dynon EFIS unit in it and found it very difficult to know what it was meant to look like. And you're right, without a mixture control there isn't much you can do about it in flight anyway.

 

 

[Captain]

G'day Fellas

 

I'm no expert ...... but here is my 2.786 cents worth.

 

In the Jabiru, at full throttle you are basically running on (fuel flow is controlled by) the main jet and therefore the selection or change of the main jet size has a direct influence.

 

At some time as you bring back the power/revs when on cruise, your throttle closes, the needle comes down and your fuel flow is controlled by the needle & seat or perhaps a combination of needle and main. In this case the height of the needle and its shape are a direct influence.

 

The needle that is supplied with the 3300 has been chosen by the factory based on considerable testing. And while I don't have a long experience with Bing carbys I can tell you that in motorcycle racing, the selection of needle profiles is important for ultimate carby tuning and smooth power/torque curves.

 

The largest changes in mixture from the needle coming into play will typically happen between about 2600 or 2700 and 2850 - 2900.

 

As you bring the throttle back to your cruise RPM you will see a decrease in fuel flow and you should see a change in EGT as the needle comes into play.

 

A lambda reading of 0.75 - 0.8 might be typical at full throttle and it might lean off to 0.95 - 1.0 at cruise .... or somewhere in between, and the 3300 engine seems to take that step at about 2700 - 2900 on cruise.

 

If you have an accurate tach and good fuel flow measurement + good EGT readings you should be able to plot it if you adjust throttle in steps of about 50 rpm between say 2600 & 2900 RPM at cruise and record the results.

 

Hope this reads OK, and trust I haven't forgotten anything.

 

Regards Geoff

 

 

[Guest brentc]

Hi Phil, can you see this pic from earlier in this thread?

 

http://www.recreationalflying.com/forum/attachment.php?attachmentid=1368&d=1173659857

 

The oil temp and pressure are about the same as in my dash picture, although my CHT runs at about 250, so 1 notch below this pic although mine is a different guage.

 

If you are running oil temps at 100 degrees I would suggest that they are too high. Have you read in the previous posts in this and other threads on the modification that we have been fitting to reduce temps and the subsequent modifications that Jabiru have produced to combat this problem?

 

At a guess I would suggest that temps at or near 100 degrees will give you rocker bush wear (noticeable by metal created when you pull off the rocker covers), possible damaged rings due to lack of lubrication and potential valve guide wear amongst other things.

 

What is your CHT reading? and do you have an old or relatively new aircraft / cowl combination?

 

 

[Jabiru Phil]

Thanks Brent for the contact. I collected my 230 late October and I assume is the "latest" cowling etc. The cht is a shade above the pic you sent, about 2mm before the yellow. Oil temp is touching the left hand side of the 100 in cruise at 2800 at 2600 it decreases a lot, could be the tight motor as only 35 hours. I do not have pics of that side of panel in flight. I can send pic of cowl if you supply me an email address and you can comment further. Yes I have followed some discissions re oil temps, that's why the contact,

 

Cheers,

 

Phil.

 

 

[Guest brentc]

Are you still on run-in oil? If so, it may drop after you change it. 35 hours, that's a different story, so perhaps related to your higher temps. Remember that if it's hot that a richer mixture will cool things down, so instead of nursing it, it needs to be above 2,800rpm to cool and try to keep the speed up with 95-100 knot climb-out.

 

 

[Jabiru Phil]

Thanks brent. I will up the revs a bit and see if any change in oil temp. The discussion I had with Jab re the running in oil was to change over to w100 when the oil burn settled down, which was at 28 hours. I have not added any oil in the last 7 hours although perhaps down a 100 mils. Climb out temp OK just the cruise at 2800 has me a shade concerned. Flying at the weekend and I will take some readings at different revs. I estimate that the burn is 20 /Hour, mostly longish trips of 60/120 mins, not much curcuit work.

 

Cheers

 

 

[Guest brentc]

You might find that your tacho is over-reading (which is fairly common) and you may be running a tad under 2,800 which is warming things up a little so trying 2,900 might help a bit. That being said though, even if I run mine at 2,700 rpm where it's leaner, I don't get your kind of temps.

 

Do you have a cowl like the one in this pic or are you missing the flappy bits?

 

 

 

[Guest imap8ntr]

Thanks Airsick,

 

I understand the principles you mentioned. I have an idea from these posts as to the next step. Fly at different RPMs in cruise and see what the range of the EGT's are. I cannot read fuel usage. These readings will allow me to determine something about where the peak is and when in cruise if I am above or below it and which side of the curve. Without a mixture control this becomes a bit more difficult but atleast the Jabiru factory has researched the "best" jetting for the Bing carburetor. This in addition to inspecting the exhaust and intake pipes for leakes and plug colors would allow for a good assessment.

 

Note: I have had both a Rotax 582 and 912 for years and never had an issue with the Bing carburetor nor temperatures. Never changed jetting even though it was not an altitude compensating carburetor. The engine manual did have me change plugs every 25hrs on the 582 and 100 hrs on the 912. All always looked very good.

 

Thanks

 

Ivan

 

 

[spooky]

Ahh... Innisfail, a bunch of us were stuck there for 18 days due weather on a trip around OZ. It was so wet and humid the propeller on my SP started to delaminate. When I told Rod Stiff of this months later he replied " Innisfail...its a wonder it didn't grow leaves!"

 

Cheers

 

 

[Jabiru Phil]

You might find that your tacho is over-reading (which is fairly common) and you may be running a tad under 2,800 which is warming things up a little so trying 2,900 might help a bit. That being said though, even if I run mine at 2,700 rpm where it's leaner, I don't get your kind of temps.Do you have a cowl like the one in this pic or are you missing the flappy bits?

Hi Brentc,

 

I replied to the oil temp on a different post so you may not have seen my latest temps since installing the oil cooler cowl mod.

 

All OK now and temps are 80 oil and 240 CHT (same as your pic) 3 hours at the weekend and no variation.

 

Thanks for the help.

 

Phil.:thumb_up:

 

 

[Captain]

All OK now and temps are 80 oil and 240 CHT (same as your pic) 3 hours at the weekend and no variation.

Phil,

 

 

 

I also see 80 C for the oil temp at cruise and maybe 90 C at top of climb to 5000, but I never see anywhere near 240 C for CHT.

 

 

 

In climb my CHT's sit around 160 - 180 C and my 3300 engine manual says max CHT in climb 200 C and Max continuous 180 C. (Section 14.2.3 of the latest manual on the J website talks about max 150 C in cruise and max 175 C in climb), and section 3.7.2. of that manual stipulates that the max time for CHT to be between 180 C & 200 C is 5 minutes.

 

 

 

If that is correct, your 240 C might need some attention to get it down.

 

 

 

Regards Geoff

 

 

[Jabiru Phil]

Hi Captain,

 

I have reread my notes of the week end. I can now explain the different reading that you show. The CHT gauge is in fahrenheit and the OT is centigrade!!!

 

I erred in the reading also, should have read 280deg F