Turbo Charging a 912

gyrodeputy

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I am looking for specific information on turbo charging a Rotax 912.

The cost to upgrade to a 914 is huge. I am told that you can do a kit upgrade to the 912 for only a couple thousand bucks.

This is similar to the way Xenon has done it in the RST model.

Does anybody have any experience with this that could share details like an aftermarket kit that may be available? How about model, brands part numbers etc.

I would love to have some feed back and/or input.

Thanks in advance and as always, stay safe!!!
 

bones

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You can only do the 80hp one, not the 100 hp FYI
 

alcar

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turbo charging 912

turbo charging 912

There is a rotax engine rebuilder in Canada that does turbo charging on 912's
Call Bob at 250-832-8786
 

gyrodeputy

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Thanks for the leads...more research to follow.

Stay safe
 

mark treidel

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Heath,
I would be most interested in your results. I have a 912ULS 100HP which I was thinking about turbo charging also. I know the bolt on kit is only for the 80HP engine but would be grateful for any additional info. I'll be monitoring,....Thanks,
 

mark treidel

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Thanks Kai,
I'm aware of that however I'm looking for something on the opposite side of your world....a bit closer to home, if you will. By the way, really enjoyed you article.
 

bones

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Celier aviation (Xenon) have supercharged the 912 ULS as RST engine.

Kai.
This is impossible, without major internal mods, the motors are all 80hp 912, well as far s i know, and they are turbo not supercharged.
 

NoWingsAttached

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You can turbocharge anything. THe question is longevity. If you already have a 100 912 and you do not live at 5000 ASL, why bother? There are a couple of things you need to know: if you are going to boost it over 0.5 bar, you dont' need to do much other than additional oil cooling and intake cooling, and you should have a 1-pint reservoir to cool the oil BEFORE it goes into the snail. But for a measly 0.5 bar boost this is a waste of time, weight and money.

To go beyond that, up to 1.0 bar, you need to reduce the piston crown down to 8:1

For fuel-injected motors, beyond 1.0 bar boost you should add an additional fuel injector somewhere downstream of your intercooler. IF you add it upstream of the intercooler it might blow up. You'll absolutely need this additional fuel to keep the jugs cool and to help prevent detonation. If you can add a knock sensor, that would be good. You don't always hear what is about to destroy your toy..
 

Bill Clem

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There is one rub...

There is one rub...

One problem that is not obvious is that of the wastegate controller. The Rotax wastegate controller keeps the wastegate open until either the throttle position sensor tells the computer that more power is needed, ie. over 5500 rpm or that the airbox pressure is lower than that needed for the power setting. The result is that the turbo isn't boosting most of the time. The mechanical aftermarket auto wastegate controllers use a spring and a diaphragm to keep the wastegate closed all the time, even at idle, until airbox pressure exceeds the set spring pressure, opening the wastegate. This is the configuration used for the Xenon RST. Keep in mind that increased pressure means increased temperature so when boosted, the air going into the airbox is at higher temperature. Higher temperature means less density which means less oxygen for combustion. An intercooler can help. I saw this in real time flying a Xenon 912 RST in Phoenix one Summer without an intercooler. We had to avoid any high power settings, not because of over boost, but because of airbox temperature. Ended up landing by mid-morning as the day heated up.

The way to avoid this problem is to make the wastegate controller so the gate can be held open until needed. My solution, still experimental, was to take the spring out of the canister wastegate controller and attach a push-pull cable to the externally mounted spring, allowing the gate to be manually opened but then, when needed, pull on the spring, closing the gate but allowing it to open under higher pressures. This allows non-boosted operation but inflight adjustment of the airbox pressure as desired. Years ago, a similar system was used in aircraft before the advent of more complicated, heavier oil-hydraulic wastegate controllers.
 

bones

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One problem that is not obvious is that of the wastegate controller. The Rotax wastegate controller keeps the wastegate open until either the throttle position sensor tells the computer that more power is needed, ie. over 5500 rpm or that the airbox pressure is lower than that needed for the power setting. The result is that the turbo isn't boosting most of the time.
Not quiet right, but it is sort of how it works, the turbo on a 914 starts to boost from about 4200rpm, but does not give FULL boost until after 5500rpm,also it is fully closed at idle otherwise the turbo would seize up on idle down. but the down side to this is, if you want full power it is a good 2 secs before you get it.
The mechanical aftermarket auto wastegate controllers use a spring and a diaphragm to keep the wastegate closed all the time, even at idle, until airbox pressure exceeds the set spring pressure, opening the wastegate. This is the configuration used for the Xenon RST. Keep in mind that increased pressure means increased temperature so when boosted, the air going into the airbox is at higher temperature. Higher temperature means less density which means less oxygen for combustion. An intercooler can help. I saw this in real time flying a Xenon 912 RST in Phoenix one Summer without an intercooler. We had to avoid any high power settings, not because of over boost, but because of airbox temperature. Ended up landing by mid-morning as the day heated up.

The way to avoid this problem is to make the wastegate controller so the gate can be held open until needed. My solution, still experimental, was to take the spring out of the canister wastegate controller and attach a push-pull cable to the externally mounted spring, allowing the gate to be manually opened but then, when needed, pull on the spring, closing the gate but allowing it to open under higher pressures. This allows non-boosted operation but inflight adjustment of the airbox pressure as desired. Years ago, a similar system was used in aircraft before the advent of more complicated, heavier oil-hydraulic wastegate controllers.
Bill, an intercooler on the RST engine has NO over heating air box temps, i installed one on mine, it dropped the temps by about 20*C, i use mine for flight training on days of 40*C and the air box temp is never a problem.
For what its worth, you know the 914 will drop the boost if the airbox gets hot, i have had it done to me, not a nice feeling just when you really need the grunt nothing, so i would rather have the power there and risk cooking the engine than putting into the trees because a friggin computer decided i shouldnt have power.
 

bones

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To go beyond that, up to 1.0 bar, you need to reduce the piston crown down to 8:1

For fuel-injected motors, beyond 1.0 bar boost you should add an additional fuel injector somewhere downstream of your intercooler. IF you add it upstream of the intercooler it might blow up. You'll absolutely need this additional fuel to keep the jugs cool and to help prevent detonation. If you can add a knock sensor, that would be good. You don't always hear what is about to destroy your toy..
I would call that major internal works :angel:
 

Bill Clem

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Probably a change in the programming...

Probably a change in the programming...

I have two 914 engines, the original is 15 years old with one replacement of the computer about 10 years ago. The wastegate remains open at idle, and on static power run up's I've never seen the wastegate controller move, but it might have partially closed without my notice.

The newer engine is fuel injected with electronic ignition, a larger turbo and a huge intercooler. I agree with the idea that a computer shouldn't decide when I need power. I've placed a linear actuator on the wastegate controller so I can literally dial in any airbox pressure I want, needing adjustment only for significant altitude changes.

I've always thought that Rotax could do better with the 914. A bit more displacement, getting rid of the leaky carburetors downstream of the turbo, better mid-range torque, perhaps including an adjustable pitch prop in the excessive price. I had hopes when they started experimenting with a 6 cylinder but that never got past the prototype stage and even then it weighed about 400 lbs.
 

ckurz7000

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Rumor has it that Rotax is testing a 4 cylinder fuel injected normally aspirated engine delivering more power than the 912. Any one with more info on this?

-- Chris.
 

bones

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I have two 914 engines, the original is 15 years old with one replacement of the computer about 10 years ago. The wastegate remains open at idle, and on static power run up's I've never seen the wastegate controller move, but it might have partially closed without my notice.
Bill, maybe you should throw your cd in your puter and read page 70 on the installation of 914, adjusting the servo and waste gate it CLEARLY states the waste gate is to be closed at idle, even to tension spring is to have 1.5-2 mm of pressure to ensure it is closed tight(cant remember where i read that now) here it is on page 195 of the maintenance manual for the 914.
BTW your welcome.
Bill, with the TCU turned on(motor OFF) if you move the throttle you can hear and see the TCU servo motor moving, if not you have a problem
 

Bill Clem

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Sorry to disappoint...

Sorry to disappoint...

But my original 914 was the first, to my knowledge, to be installed on a gyro. Both my installation manual and maintenance manual are made from paper, perhaps you've heard of it. It doesn't even have 195 pages. And when the engine is not running but the TCU is on and the throttle moves, the turbo controller motor does not move. I suspect that this engine is a few generations behind, at least the TCU is. But I am not anxious to replace it, given the present cost. BTW, you're welcome.
 

bones

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Well then your welcome, i thought that all 914's were the same pice of crap set up seems they made a few viariances of it then :)
 

Mike G

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Mark
There are two different TCU set ups, the older ones had a lower boost pressure at idle and the later ones had a high boost pressure ( waste gate shut) at idle.
See the Heavy maintenance manual section 76 engine control page 5.
Mike G
 
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