Rotax 135 HP Engine

[deandob]

I think the bearings in the turbo would fail before any heat damage to the engine (and higher performance turbos have an oil cooler to help). Agree exhaust temp sensor would be sensible for a higher boosting turbo.

One disadvantage of the rotax 914 system is the extra complexity of monitoring the engine and electronic wastegate control - more things to go wrong compared to the simpler mechanical system of an aftermarket turbo. However you trust that the manufacturers have got it right especially after a couple of years (I see rotax are regularly releasing service bulletins based on field experience - a good sign).

Probably not a whole lot to worry about (safety / maintenance wise) if the aftermarket turbo is done by a reputable firm and there are lots of aircraft flying around with the modifications and no issues being raised especially after many hours use. A boost, EGT gauge & oil cooler should be mandatory for models with higher boost and for a used gyro the previous owner should be aware about not operating the motor outside safe parameters (like high boost for too long, not enough time to cool down before boosting again). Is this a reasonable summary of what to consider when buying a used gyro with an aftermarket turbo?

[Waddles]

The core engine is the 80 hp model. My understanding is that you can't turbo the 100 HP 912 due to the high compression ratio. The 80 HP model is a low compression engine. Please correct me if my info is wrong.

Waddles.

[Brian]

After having a factory suby turbo & having lot of trouble with it my advice would be to make sure you thoroughly research the project from start to finish as a turbo will add extra heat .
I love horsepower as well & it seems it's something you can't have too much of, particularly when the situation gets extremely tight!

[RickE]

The core engine is the 80 hp model. My understanding is that you can't turbo the 100 HP 912 due to the high compression ratio. The 80 HP model is a low compression engine. Please correct me if my info is wrong.

Waddles.

At Avalon Airshow this year there was a TAG on display that had a Turbo charged 912. It boasted having 146hp and I believe the turbo conversion was done by Steve Paulette in Melbourne. I do recall a modification was required to the head of the 912 to address the compression issue.
Bert Flood also shared our stand at Avalon and from memory didn't have a lot to say about the modified 912.....
As a matter of interest for all you mechanically minded folk, we were also told there is a way to "trick" a 914 into providing an extra 20 or so hp for a limited time.

[TROOPER]

Bert Flood also shared our stand at Avalon and from memory didn't have a lot to say about the modified 912.....

Rick, were you thinking that the blokes at Bert Flood thought that the modified aftermarket turboed 912 was a 'good thing' or 'not so good'?

[deandob]

Good advice Brian. Agree having the extra horsepower if implemented well is actually a safety benefit to help power out of trouble. Being new to aviation and gyros I can't avoid the temptation to look at the gyro crashes on youtube and sites like gyroaccidents.blogspot.com and it does seem that having more horsepower would have helped avoid a number of accidents especially on takeoff (I'm still learning gyro theory - not having the rotor up to speed before climbing seems to be the most common takeoff accident cause though).

Rick, the trick with getting more boost from a 914 is likely similar to the auto bolt on 'chips' which modify the data coming from the sensors to trick the engine management computer or even remapping the timing/fueling tables.

One thing I don't understand is why rotax don't use fuel injectors for the turbo motor especially if they have added additional electronics / safeguards to control boost. Allan and I discussed this on the weekend at Caboolture as carburettors aren't as reliable as fuel injection and require regular tuning. Fuel injection has been around since the '80s in the auto world, and the new rotax motors with fuel injection apparently costs a bit more (and the fuel savings won't pay back the extra cost). In fact these rotax motors are pretty expensive for what they are, even without the fuel injection.

[RossM]

Looking at the gyro accidents blogspot link, may have to take a photo of the ASRA website now, as G3500 looks a bit worse for wear.

[deandob]

While we are talking about the rotax engines, I just read up about the new 915 fuel injected turbo motor, and it delivers an extra 20HP over the 914, which is nice, as well as the fuel savings, even though it is more expensive. This motor apparently is just about ready for use by the gyro manufacturers, and as I have started to look at a what gyro to buy, I'm wondering if waiting to buy a new gyro with the 915 would be a smart move, not just for the extra power & fuel savings, but for the resale, as depreciation is a large part of the ongoing cost of ownership. I assume in a couple of years time the resale on a good gyro with the 915 would be better / more desirable than the same machine using a 914.

Would be interesting to see the torque curve difference between the 914 and 915, as a fuel injected motor has more flexibility for tuning versus one with a carby. If the torque comes on stronger at lower revs the motor will feel stronger and more responsive.

Also I couldn't find the price list for the 914 and 915 - anyone have these?

[RickE]

Rick, were you thinking that the blokes at Bert Flood thought that the modified aftermarket turboed 912 was a 'good thing' or 'not so good'?

Not sure Trooper. From memory though I think that the guy's modifying the 912 were taking on the warranty side of it as well.

[Waddles]

Thanks Rick for that info on turbocharging. I'll stand corrected.

The Xenon is the one from the hunter that you enquired about in an earlier post.

I reckon that Bert doesn't talk much about these modified Rotax engines because they don't come from Rotax and he is the exclusive Rotax dealer here.

Waddles

[WEST OZ FLYER]

I think the bearings in the turbo would fail before any heat damage to the engine (and higher performance turbos have an oil cooler to help).

I doubt that.

[WEST OZ FLYER]

One thing I don't understand is why rotax don't use fuel injectors for the turbo motor especially if they have added additional electronics / safeguards to control boost.

The 914 has an enrichment solenoid operated by the TCU. It's not an injector but does what you describe.

[deandob]

I doubt that.

West Oz Flyer - care to explain? That hasn't been my experience with auto turbos - local heating by an overdriven exhaust turbine is severe, causes the oil to breakdown, warping and even metal fatigue. But the failure modes for a turbo on the rotax motors may be different, so I could be wrong.

[Brian]

I can fully understand Bert not commenting on turbo 912 's & why would he condone someone adding a turbo & then wanting Floods to honour a possible warranty problem which could be as much as a blown motor.
Gets down to the owner taking the risk for paying for a stuff up should it happen which is the way it should be !

[Brian]

Quote from Dean "Good advice Brian. Agree having the extra horsepower if implemented well is actually a safety benefit to help power out of trouble. Being new to aviation and gyros I can't avoid the temptation to look at the gyro crashes on youtube and sites like gyroaccidents.blogspot.com and it does seem that having more horsepower would have helped avoid a number of accidents especially on takeoff (I'm still learning gyro theory - not having the rotor up to speed before climbing seems to be the most common takeoff accident cause though)." End of quote.

Crashes on takeoff can be mainly attributed to rotor management & I'm not going to delve into that here except to say that the lack of this basic skill is a big factor into all sorts of things going pear shaped & resulting in destroying beautiful machines. Extra power being applied during takeoff where the rotors are NOT up to flying speed will see disaster happen very quickly.
All instructors should be able to teach the student pilot all about rotor management. The big influx of the European gyros that call for the pilot to run the blades up to 200 revs or whatever specified for that particular gyro whilst being held stationary by the brakes & then release brakes whilst applying power if not done exactly right will see lots of pretty gyro being spread over the runway ! So it pays to learn, practice until you can do it in your sleep !

Extra power can get a inexperienced pilot into trouble as well so my humble advice is get yourself a second hand single seat gyro powered by a suby EA 81 & go fly that around for a couple hundred hours & then you will have excellent base to work off.

[deandob]

Thank you Brian for the advice.