Best Slide Metering TBI for Jabiru 3300

[157YX]

I'm switching to a Gen 4 Jabiru 3300 and would like to know which TBI fuel injector runs best and is easiest to tune correctly (AeroInjector or Rotec TBI)?

[fastj22]

you didn't specify reliability. I think that overrules all.
I've run both. AeroInjector hands down. Simplicity is king. Only two moving parts.

[tx_swordguy]

please don't take this the wrong way. True fuel injection will not be found with either the rotec TBI or the aeroinjector. They are both types of throttle body injection fuel systems similar to a carburetor without the fuel bowl. true fuel injection will need a computer, fuel pump, plumbing etc. I have tried both rotec and aeroinjector on a solid lifter 3300 (started with the aeroinjector). I was having some minor issues with tuning running really rich at idle so I bought a rotec thinking I could make it work better. Trial and error on both units had me going back to the aeroinjector and have it working very well now. My major problem was the slack between the needle holder and the adjustment screw. There was probably .015" slack and that is a lot of bouncing around to allow a big difference in fuel usage creating a tuning nightmare. I fixed it by cutting some small shims out of beer,,, I mean coke cans to take up the slack. It seemed to help and I have been happy for the last yr plus with it. It is a bit of a pain to tune the aeroinjector but it is inexpensive and once you get it where you want it, it works well.

[157YX]

you didn't specify reliability. I think that overrules all.
I've run both. AeroInjector hands down. Simplicity is king. Only two moving parts.

You and I have very similar objectives. I’m building a B conversion Waiex and have switched from an AeroVee 2.1 w/AeroInjector to a Gen 4 Jabiru 3300 w/TBI cuz I need the horsepower here in the mountains of Idaho. The whole reason for going TBI is because of simplicity/reliability/performance. I’ve read a lot about AeroInjector tuning and have been taken back by the sheer amount (many hours) of fiddling it requires to get right. “Burping” and stumbles continue to plague the AeroInjector even when tuned properly. That tells me it’s maybe too simple or course in it’s adjustability. The Rotec TBI appears to have put more thought into adjustability, hence being slightly more complex. I wanted to get first hand knowledge from people who have dealt with both TBIs on the same engine. What was the “tuning and functional” reason you went back to the AeroInjector. I’m all ears and not adverse to the AeroInjector at all.

Thanx in Advance, Rob

[157YX]

please don't take this the wrong way. True fuel injection will not be found with either the rotec TBI or the aeroinjector. They are both types of throttle body injection fuel systems similar to a carburetor without the fuel bowl. true fuel injection will need a computer, fuel pump, plumbing etc. I have tried both rotec and aeroinjector on a solid lifter 3300 (started with the aeroinjector). I was having some minor issues with tuning running really rich at idle so I bought a rotec thinking I could make it work better. Trial and error on both units had me going back to the aeroinjector and have it working very well now. My major problem was the slack between the needle holder and the adjustment screw. There was probably .015" slack and that is a lot of bouncing around to allow a big difference in fuel usage creating a tuning nightmare. I fixed it by cutting some small shims out of beer,,, I mean coke cans to take up the slack. It seemed to help and I have been happy for the last yr plus with it. It is a bit of a pain to tune the aeroinjector but it is inexpensive and once you get it where you want it, it works well.

Sorry, I meant “slide metering” TBI, not port fuel injection, corrected the post title. The “slack” you describe I assume is with the AeroInjector. It sounds like shimming should be used to tune the AeroInjector rather than adjustment screws. Have you had and “burping or stumbling” issues?

Thanx for you input, Rob

[fastj22]

you didn't specify reliability. I think that overrules all.
I've run both. AeroInjector hands down. Simplicity is king. Only two moving parts.

You and I have very similar objectives. I’m building a B conversion Waiex and have switched from an AeroVee 2.1 w/AeroInjector to a Gen 4 Jabiru 3300 w/TBI cuz I need the horsepower here in the mountains of Idaho. The whole reason for going TBI is because of simplicity/reliability/performance. I’ve read a lot about AeroInjector tuning and have been taken back by the sheer amount (many hours) of fiddling it requires to get right. “Burping” and stumbles continue to plague the AeroInjector even when tuned properly. That tells me it’s maybe too simple or course in it’s adjustability. The Rotec TBI appears to have put more thought into adjustability, hence being slightly more complex. I wanted to get first hand knowledge from people who have dealt with both TBIs on the same engine. What was the “tuning and functional” reason you went back to the AeroInjector. I’m all ears and not adverse to the AeroInjector at all.

Thanx in Advance, Rob

The simplicity of the Aerocarb/Injector is the reason for the fiddling to get it tuned to your satisfaction. It really can't be tuned to work well across the entire RPM range without mixture adjustments. So tune it to work best at the RPM you will be running mostly. I set mine to be a too rich at full throttle and full mixture but still run reliably at full mixture and idle. Then pull back the mixture to tune in flight.
The Rotec is a fine piece of machinery. The spray bar atomizes the fuel much better than the AeroInjector. Its easier to tune and works well across the entire RPM band. This is because of a very delicate and intricate on demand pressure regulator. If that regulator sticks open, it runs very rough. If it sticks closed, you land. If Rotec could engineer a more robust regulator, I'd probably give it another chance.
The AeroInjector doesn't seem to atomize as well causing cyl 5 and 6 to go lean on climbout. I've thought of mounting it further from the intake manifold like they do with the aerovee turbo.
Running rich solves some of the burping issues, as does insulating the fuel lines, a burp tube, orienting a smooth path and slow acceleration. If I do a short field takeoff, I still get some burps on takeoff roll, never in the air.

[157YX]

John,

Do you think it's possible to remove the regulator from the Rotec TBI and run it strictly gravity feed like the AeroInjector? I went ahead and e-mailed Rotec, I'll report back when I get their answer

[fastj22]

John,

Do you think it's possible to remove the regulator from the Rotec TBI and run it strictly gravity feed like the AeroInjector? I went ahead and e-mailed Rotec, I'll report back when I get their answer

No, the heart of the Rotec is the on demand pressure regulator. It gives just the right amount of fuel for the situation.
I have the second gen one, with the regulator integrated into the TBI. The previous model had it remotely mounted. I'm wondering if that might be some of the issue. With it integrated, the fine movements are subject to engine vibrations. Its basically a rubber diaphragm with a needle valve and spring. With it remote, vibrations could be isolated.

[WaiexN143NM]

Hi all,
Some people have had bad luck with both the aerocarb and rotec. most people have had good luck with both.
The rotec had an upgraded diaphram. This is needed , it has a molded oring in diaphram. the origional design had a floating oring. its easy to take apart and swap out. yes a needle valve, spring , seat and diaphram.

WaiexN143NM
Michael.

[tx_swordguy]

To answer your question. I personally have not had the burps in my sonex. I run ethanol free mogas as exclusively as possible. I do not have a gascolator and i have insulated and wrapped my fuel line with reflective tape. The burps are a heat thing. Keep as much heat away from the fuel lines as possible and the burps should be controlled or eliminated. Gascolators seem to allow vapors to form more easily too. If you run 100ll you should not have an issue as it is a more stable fuel. I tried my ethanol free gas in my O320 biplane and it cant do it. I HAVE to use 100 ll in it or it stumbles and stalls horribly when hot. With 100 ll no issues. Like what was said you get the aeroinjector to run a hair rich at wot and lean it out at other rpms. It is super simple and i like it once you get it set. I feel mine is still running richer at idle than i would like but it runs so nicely i dont want to change anything.