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912 vs. 914 (mechanically)

GravityKnight

By GravityKnight
in Engine/Rotax

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GravityKnight

GravityKnight

Posted
Posted

Obviously the 914 is boosted. But let's go a little more in depth.

 

The 912 is 1352cc's and has a compression ratio of 10.4:1, where as the 914 is 1211cc's like the older 80hp 912 displacement wise. I saw somewhere it was stated the 914's compression ratio is 9.0:1. Where as the older 80hp 912 is 9.1:1. I'm curious how much difference there is between all these engines internally? With the larger bore of the 100hp 912, I would imagine the cylinder walls are thinner. What about the pistons, rods, crank, valves etc.?

 

The reason I'm asking all this is there are some guys turbocharging the 80hp 912's with good results, and even some people boosting the newer 912's over on the kitfox forums and other places. I have turbocharged some n/a engines in the car world over the years, and dealt with the various issues involved. But info about these engines is harder to come by, and I can't just go get my hands on them either. Is the 914 substantially stronger internally vs. the 912? Is the 80hp version of the 912 a better engine to start with if your going to turbo one of the 912's?

 

Sorry for rambling on, if Roger or any of you other Rotax gurus have any info I'd appreciate it!

  • 2 weeks later...
johnr

johnr

Posted
Posted

I have a Jodel D11 that was powerd by an 0-200. There were 2 other Jodels on the field both with 0-200 but slightly heavier than mine. Mine would climb at 800fpm on a good day the other 2 were struggling to get 750fpm. Max cruise for all was about 108Kn. I replaced the 0-200 with a well used  914F(the certified turbo) it had been used commercially & had 1190 hrs . It had never had any problems, the heads had never been off according to the logs. My first flight saw 1500 fpm & then a misfire. I spent months trying to find the misfire that only occurred on max climb. I realised that it must have to be the extreme angle of climb (1500fpm at 65Kn is pretty steep ) that was either weakening or over richening the mixture. Now I climb out at less than full throttle at about 1000 fpm, never misses a beat.

At the present time I have about 150 hrs on it & never a problem. It runs much smoother than the 100 hp I have in the CTsw, it is also much quieter, probably due to the turbo. I could be comfortable without a headset. The smoothness is all through the rev range, it sems to have its sweet spot between 4500 & 4800 rpm. at that its about 90Kn & burning less than 14lph. The Jodel max cruise is 107Kn & the VNE is 137. I could cruise at 115Kn but at that speed the controls are heavy.

I accompanied friends who were cruising in an ultralight at 80Kn, I followed for over 2000 Km & had a fuel burn of 10.5lph.

The CTs in Europe are often powered with the 80hp 912 &  generally fly with a MTOW of 472Kg. The performance at the lower MTOW with 80hp seems to show about the same performance as I get with near 600Kg & 100Hp.

If I had the choice I would choose 1st the 914, 2nd the 80Hp & my last choice would be the 100Hp. I have no experience of the new fuel injected motor.

The other advantage for us in Aus is the 80Hp wil run on our standard 91 octane whereas the 100hp requires the 95 octane,  91 is 11 cents a litre cheaper & 95 is not available at some remote service stations.

The Jodel D11 is an amazing design, stall (it just nods its head) is 27Kn, it will cruise easily at 100Kn. It is wood & fabric weighs 340 Kg & performs as well as some of the sleek composits.

The best fuel burn with the 0-200 was 22lph @ 90Kn.

The 914 has a very well designed turbo control unit that prevents over pressure, almost idiot proof .I have heard it is  also very expensive to repair.

Maybe others experiences are different. I would love to hear from a CT owner with an 80hp 912.

Johnr

Anticept

Anticept

Posted
Posted

Turbbonormalizing would be fine on a 100hp engine. You would only be compressing the air to sea level pressure.

 

Turbocharging a 100hp is unknown territory to me.

Jacques

Jacques

Posted
Posted

I'm happy with my 80hp SW. Our max allowed is 560 kg and at that weight , I can see the need of an inflight ajustable prop (we are allowed) BEFORE the need of a 100hp.

( But solo,full fuel...80hp is enough)  I'm almost at sea level here and goes rarely above 4000'.

GravityKnight,: the 914 turbo IS a 912/80 with a turbo which gives it 35 hp more. .

Some 100hp (ULS) had the turbo installed... HP is much more..35 more ..not sure..maybe more ^_^

  • 2 weeks later...
GravityKnight

GravityKnight

Posted
  • Author
Posted

 

 

GravityKnight,: the 914 turbo IS a 912/80 with a turbo which gives it 35 hp more. .

 This is what I was curious about, if the 914 internally is basically the same engine....

 

 

See a 100hp rotax is just adequate enough to fly up here. I mean they get the job done, but I like to fly in the mountains and with two people/fuel it gets pretty sketchy (home field is 6600ft, been in/out of Leadville which is 10k, passes are 12.5-14k etc.) Some days you just can't go a lot of places.... or you can't bring someone if you do.

 

I will most likely buy a kitfox, and depending on some variables, I may end up with the 80hp 912 (fair amount of them around, prices are reasonable). Which won't be enough if it's in a model 5 or newer bird that operates up to 1320lbs legally / 1550max at these silly high altitudes.

 

Just looking at options. An actual 100-110hp at this elevation would be unreal. Being able to pull around 100hp at Leadville would be so awesome!

 

Good story about going to a 914 johnr... 1500fpm is no joke. And is exactly my goal for my own plane someday (whatever that ends up being)

FlyingMonkey

FlyingMonkey

Posted
Posted

The 914 is only 15lb more than a 912ULS...to me the 15hp and extra high altitude performance is a better payoff than the 22lb and better economy that the 912iS gives.  Though the 914 is about $5500 more than a 912iS.   :unsure:

Jim Meade

Jim Meade

Posted
Posted

I've also recently been pointed to the Kitfox and other forums with the Big Bore options. Interesting, since my CT is Experimental. Price is an issue. If I get to doing more long distance traveling I'll be more interested.

 

There are also ways to add a mixture control for those of us who fly at 8-10K or even higher.

FlyingMonkey

FlyingMonkey

Posted
Posted

The 912iS now comes in a sport version.  The gap between a 914 and the 912iS is much closer now.  Still, no one orders the FD CTLSi with a 914, they are all being built with the 912iS Sport now.

 

No one orders a 914 because as far as I know it's not offered.  The gap has not really closed, the 912iS engine is now making closer to rated horsepower (100).  The 914 still has a 15hp advantage at WOT and far superior high altitude capability through normalization.

FlyingMonkey

FlyingMonkey

Posted
Posted

What is the cost of a low time 80hp 912 and turbo kit?

 

That's a good question.  CPS lists a 80hp 912UL at ~$16k, and IIRC the turbo kits are ~$4500.  That would make a pretty good deal, but you are instantly giving up all warranty on the engine, I'd guess.  Rotax is not going to want to cover anything happening to their engine with somebody else's turbo kit on it.

Tom Baker

Tom Baker

Posted
Posted

It is a 912ULS with an after market fuel injection system. It lives in the north east.

I'm pretty sure the one I'm thinking of has a turbo installed, and it is in the middle part of the country.

IrishAl

IrishAl

Posted
Posted

Covers for the 912 UL are black.

 

912 ULS/is is Green.

 

914 is Red. 

I recently saw a blue one, built specially for the French market. 100hp.

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