Replies to This Discussion

Permalink Reply by Timothy D. McCall on March 9, 2017 at 9:43pm

John

It's good to know that you have been meticulous in testing the carb install.  I was convinced that the aerocarb had an inherent flaw associated with gravity feed systems but it may be that I was a little hasty in my conviction. There are a few differences in the installations that may or may not have any effect on the results. 

Is your fuel burn rate what you were expecting?

Tim

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Permalink Reply by John Austin on March 9, 2017 at 10:11pm

My fuel burn rate is definitely much better!  At a "high cruise" rpm, I easily burn a full 1 GPH less than previously since I can lean-out the engine properly.  Seems the way the Bing was set up it progressively increases the fuel flow with rpm and of course, there is no way to lean it out.

Look at that picture of the MGL XTreme EMS I posted further down the page - I'm burning 5.6 GPH at 2890 rpm.  Previously with the Bing, I would probably be 2700-2750 to burn 5.6 GPH. Previously at 2900, I'd probably have been 6.5-7 GPH!

There is an aftermarket device called a HACman that "tricks" the Bing and indirectly allows leaning, but if I understand it correctly, it works best at higher altitudes. With the STOL 750, I don't tend to fly very high, but the mixture can still be leaned with the AeroInjector.  BTW, you can use a much cheaper control, but I really like the McFarlane "Vernier Assist" mixture control (recommended to me by a Sonex pilot). It was pricey (about $200), but it is very compact and allows precise adjustments of the mixture but you don't have to push any locking button, etc - just push or pull and then twist to fine-tune - they have good support there, too, as does Sonex/AeroConversions!

John

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Permalink Reply by John Austin on March 10, 2017 at 7:08am

Jeff,

You can get the cable direct from McFarlane in 3 standard lengths:

More details about the cable are here.  I simply called them and a very nice lady assisted me with my order. Be sure to mention AOPA or EAA membership and she will give you a discount - she didn't ask for any membership numbers. ;>)

Obviously, you want to avoid sharp bends in the cable run.  The 72" length was only $5 more, so I ordered it and routed it with gentle bends and then determined the final length, withdrew the solid wire core, and trimmed the outer sheath with a Dremel cut-off wheel.

I am very happy with the AeroInjector.  In researching, there were some negative reviews - mainly dealing with "burps" due to vapor issues.  I think a careful installation with a short, insulated fuel line that avoids heat soaking and high points to trap vapor will avoid problems.  Since it is a gravity-fed carb, it's a natural for the high-wing STOL 750.  However, for low-wing aircraft, it will work with either a header tank and/or a regulated fuel pump.

John

Permalink Reply by Scott Smith on March 26, 2017 at 3:38pm

Hi John, glad you are doing the testing, not me! Nasa might be looking for new test pilots, who knows. Sounds like you fit the mold.
:)

Now to the serious: I would like to put a 3300 into an HD. My plan is to get some airtime flying a super super easy Zodiac before I put some big boy wings on it (HDS). With the HDS wings the Jabiru will come in handy.
However I've heard some complaints about the Jabiru engines as far as reliability goes. Have you had issues with yours, or heard the same things from others concerning reliability?
BTW, I sure wish the Jabiru came with fuel injection.

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Permalink Reply by John Austin on March 26, 2017 at 7:13pm

Scott,

As far as testing, I don't feel much like a test pilot as there is extensive experience with the AeroInjector/Jab 3300 in the Sonex community.  As I've previously stated, the Jab 3300 seems to be the engine-of-choice in the Sonex, which is ironic since Sonex also sells and promotes the "AeroVee," a VW-based aero engine - but, it is 4 cylinders/80 hp vs the 6 cylinder/120 hp Jabiru, so, no contest!  I extensively leaned on the support of one of the Jabiru/AeroInjector gurus in the Sonex community and also had excellent support from "AeroConversions," which is a subsidiary of Sonex.

As far as Jabiru reliability, I feel like I'm beating a dead horse I've discussed this so frequently, but, here goes!  Basically, the most common thing you'll hear about Jabiru's is that, "Yeah, they're relatively light and produce 120 hp, but they have overheating and reliability problems!"

Here's my highly biased take - Jabiru engines have been in production for over two decades.  Apparently, Jabiru "beta tested" on their customers with the first and second generation of their engines, as these engines indeed had a tendency towards overheating/cooling problems and reliability problems.  However, like all modern manufacturers, Jabiru has undergone continuous quality improvement. I was fortunate in that 5 years ago, I got the third generation of the Jabiru 3300, the "late hydraulic lifter" engine, which also had numerous improvements elsewhere including completely internal oil circulation with deletion of external oil return lines and increased cylinder cooling fin area.

I think a major source of bad reviews come from builders who have purchased a "new" engine from another builder - an engine that although is zero-time, it has been sitting around in a crate for a number of years and is a second generation engine or older.  They then proceed to install this engine and experience the problems of the older generations.  Simply put - the engine from  several years ago is not the same engine that Jabiru builds now.

I'm now in the mid-400 hr range and have had no major internal problems with the engine - mostly, I just change the oil and go fly!  I will admit, however, that stuffing a 6 cylinder, air cooled engine into a high drag/low speed airframe like the STOL 750 requires careful tweaking of the cooling.  However, I now routinely run CHT's in the upper 200's F in the summer with rarely a cylinder hitting 305F - that's pretty cool by anyone's standards!  It should be even easier to cool the engine in a faster, lower-drag airframe such as the 601/650 series.

The 3300 has continued to evolve and now includes roller cams and recessed pistons that prevent a stuck valve from hitting a piston.  They've just come out with a 4th generation engine, so there is not that much field experience yet, but it is not so radically different from the third generation that I wouldn't be reluctant to purchase one - in any event, Pete Krotje at Jabiru North America provides good support and will take care of you!  They also offer a maintenance and installation course which I highly recommend.

Like I said, I'm biased - I've had a good user experience! There was absolutely nothing wrong with the Bing carb that is standard on the Jab, but I'm an experimenter and tinkerer and simply wanted to be able to fine-tune the mixture for added economy and EGT/CHT control - it's been an interesting, rewarding experience - especially since it turned out well!  ;>)

John

P.S.:  I agree that a fuel injected 3300 would be sweeeet!  However, that's the attractiveness of the Jabiru as-is: 120 hp, direct drive, air-cooled (no fluid/radiator plumbing or weight), magneto ignition, light weight (just slightly heavier than a Rotax and lighter than all the alternatives), not battery-dependent for ignition or ECU's, simple fuel plumbing (no return lines necessary as required for fuel injection), and last time I looked, still less than $20K - and this is for a brand new engine with a warranty.

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Permalink Reply by Scott Smith on March 27, 2017 at 11:33am

Thanks John, sorry to bother you about the reliability. Sounds good. I'm set on the Jabiru then.

Permalink Reply by John Austin on February 25, 2017 at 11:30am

Well, I deleted the airbox yesterday, so I can answer my own question! It weighs 2.4 lbs (with internal air filter) and the smooth rubber duct with 90 degree bend weighed 0.6 lbs. - 3 lbs total.

The AeroInjector testing went very smoothly, with the #3 needle installed, the EGT's are nice and cool on climb-out and I'm able to lean for best economy in cruise with very balanced EGT's and CHT's.  So, I decided I was "committed" to the AeroInjector enough to go ahead and delete the airbox and duct since they're just useless weight.  The K&N RU-1660 that clamps directly onto the intake bell of the AeroInjector only weighs about 1 lb. Although the carb seems very solidly mounted by the 2" i.d. rubber fuel hose intake runner, I safety wired the carb to the intake flange to give it some additional support since the air filter will be cantilevered off the back side of the carb.

As mentioned previously, the Sonex community has extensive experience with this carb and the Jabiru 3300.  They sometimes have problems with the fuel line getting heat-soaked and subsequent fuel vapor issues, usually causing a hesitation they call the "burps."  The solution is fire-sleeving all the fuel lines (good practice, anyway!) and shielding the gascolator and fuel flow sensor from picking up ambient heat.  However, the Jab is rather tightly-cowled in the Sonex, so this contributes to the heat issues.

In the STOL 750, the lightweight Jabiru 3300 sits rather forward from the firewall for weight and balance, and there is a rather large exhaust air outlet in the lower cowl.  I've never felt it was particularly "hot" between the engine and firewall - none of the components in that area appear "cooked" or discolored by heat. The carb sits more aft from the engine due to the extended intake runner, so that should help with radiant heat absorption from the engine. But, I did fire-sleeve the fuel lines (which I do anyway!) and shielded the red cube with reflective insulation.  I didn't shield the lower firewall-mounted gascolator because it sits about 1/2 exposed below the fuselage and is quite some distance from any exhaust components, etc. My fuel line exits the gascolator and runs directly up to the fuel flow sensor and then to the carb with no loops or high spots - the total length is probably a bit over 12," so this should also help prevent heat-soaking and vapor bubbles. Hopefully, there will be no "burps!"

Here's a pic of the final installation - prior to installing the K&N filter:

All this to give me a mixture control!

... that big meaty throttle quadrant ought to be good for 10 knots all by itself! ;>)

But seriously, in addition to the mixture control for more precise engine management, I carefully weighed all the additions and deletions and gained 7.5 lbs useful load!

John

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Permalink Reply by John Austin on February 27, 2017 at 2:30pm

Got the K&N RU-0660 filter today and installed it:

It only weighed 13 oz (replacing the 3 lbs of airbox and duct!), but the best part was that the EGT/CHT balance was even better at cruise with the EGT delta <50 deg F for all 6 cylinders - the very even CHT's seemed to confirm that, too.  Whatever the filter is doing to the air flow, the carb and plenum like it!

So, overall, I'm very pleased with the conversion.  When we get a little better weather and calmer winds, I plan to repeat the neg G's and power-off and power-on stalls to confirm I've got sufficient fuel pressure since this is a gravity feed system.

John

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Permalink Reply by John Austin on March 2, 2017 at 9:22pm

Flew 2+ hrs cross-country today and this was the end result of the carb mod:

Nicely balanced EGT's and CHT's at a "fast cruise" rpm and leaned out to 5.6 gph. At these settings I was averaging about 88 kts/101 mph TAS (no slats).

John

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Permalink Reply by John Austin on April 12, 2017 at 4:51pm

Update:

None of the components in that area ever look like they get unusually hot or "cooked," so I'm thinking my carb and fuel lines will be relatively cool and not subject to vapor issues.

Well ... so much for wishful thinking!  The Jab/AeroInjector performed flawlessly 'til time to fly down to Sun 'n Fun and I had a great flight down!  Couldn't make it the first night to Cedar Key (our favorite stop-over!) due to weather and stopped at Perry, Fl.  However, it was very hot (in the 90's) at Sun 'n Fun when I flew in the next day.  I started getting some "burps" in-flight - seemed to help to slightly enrichen the mixture.  But on the ground with the extensive taxi to Homebuilt Camping, it was "burping" frequently.  The "burps" are little hesitations or drops in rpm - barely lasts a second, but gets your attention!  

So, I'm undertaking a progressive set of tweaks to see if I can eliminate this annoyance.  The primary mode of attack is to prevent any vapor from forming by keeping the fuel as cool as possible (By the way, I see no difference with 93AKI mogas/no ethanol vs 100LL).  Apparently the gascolator can act as a heat sink, so one tactic is to eliminate it and install an inline fuel filter on the cabin (cool) side of the firewall.  A Jegs billet filter with AN6 male/female fittings is a popular filter for this installation, so I got one.  On the engine side of the firewall, I teed the bulkhead fitting so I could have a drain valve:

The fuel line runs out of the top of the tee to the red cube flow sensor and then to the carb.  I fully insulated the red cube with aluminized radiant heat insulation and firesleeved the fuel lines:

I trimmed and fitted foam insulation to wrap the line and also trimmed and fitted a Thermotec aluminized radiant heat barrier sleeve that will protect the foam.  I coated the trimmed ends of the foam and the Thermotec with high temp silicone sealant - thought it might cut down on deterioration and keep the Thermotec's cut edges from fraying and also secure the stitches on the Velcro closure that runs down the side of the sleeve.  Here's the foam with the sealant drying prior to installation - I stuck it on the handle of a 100 year old mule-pulled planter that's in the hangar!

Tomorrow, I should get the foam and radiant barrier installed.  I'm still down for a few days, however, as I need another AN6 fitting to accomodate the new fuel filter.

Some wonder if removing the gascolator is wise, but the best way to shut down the AeroInjector is to turn off the fuel selector valve.  So, very little fuel resides between the fuel valve and carb after shut down.  However, it there was a slug of water in the line, the AeroInjector doesn't have a bowl to accumulate it and the water would immediately hit the carb long before the taxi and take-off is accomplished - in short, it will be obvious if there is a contaminated fuel problem very quickly!  Fortunately, I'm refueling at my strip 95% of the time and the fuel tanker trailer is stored in an insulated building and the pump has a large gascolator with a transparent bowl and also a filter.  In 25 years, I've never had a drop of water in the fuel. I did install the drain, however, so I could completely drain the tanks to unusable fuel levels if I'm recalibrating my fuel senders, etc.

John

 

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Permalink Reply by John Austin on April 14, 2017 at 6:45pm

Finished up the fuel line insulation yesterday,  I put the foam pipe insulation over the firesleeve and secured it with zip-ties:

I then covered it with Thermotec radiant heat barrier:

Although that area doesn't seem to get excessively hot, I'm going to keep a check on the ties for brittleness and if they become brittle, replace them with stainless zip ties.

Today, I put a new Earl's forged AN6 90 degree fitting on my fuel valve outlet hose that was supposed to connect to the Jeg's fuel filter on the inside (cool side!) of the firewall.  However, even with the low profile 90 degree connector, I still had clearance issues and could not install it that way.  Luckily, I had enough room to install the fuel filter with male/female AN6 connectors directly on the outlet port of my Andair fuel selector valve.  I connected the outlet hose to that and that left plenty of clearance for the hose to connect to the firewall's bulkhead fitting.  I'll try to get pics tomorrow as I button up.  That turned out to be a lucky break, because the fuel filter is on the back of the vertical portion of my center console and it will much easier to access at annual for removal, inspection, and cleaning of the filter screen.

I did a test run-up and no leaks or fuel odors in the cabin, so I hope it stays that way!  ;>)

John

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Permalink Reply by John Austin on April 15, 2017 at 9:15pm

Today, I got everything secured and buttoned-up and did a test flight.  It was warm (83F) and I had zero "burps," but of course that's not the low 90's like I had at Sun 'n Fun when it "burped" so much during taxi.  But, when I got back from the test flight, I taxied around and aggressively leaned the mixture and still could not induce "burps," so I remain hopeful!

John

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