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Posted (edited)

if you want to apply a turbo , the an old  80hp rotax is what you want (9:1) , not a 912ULS (100hp) because the compession is  too high to be useful for the 100hp. (in my opinion)  

 

Yes, 100hp can be turboed but  it involves either  spacers for the cylinders to reduce the compression, or different piston/bore kits.   I mean sure you can turbo with 10.8, but I think I'll leave that one to when I have a full house in the hand and a joker.

 

what I dont know is if the gearbox is uprated for the 100hp , or is it the same identical gearbox in the 80hp, that might have a bearing.  From what I read in forums is  that essentially, the TBO of the gearbox goes down as you push the friendship with it up. 

Looking in the rotax illustrated parts catalog, I could find no difference between 912UL, ULS and the 914 in the propellor gearbox , nor the clutch except there is a different casing for the 914 I think.  certainly recently there was an SI for 914 exhaust valves which of course take a canning with the turbo. https://legacy.rotaxowner.com/si_tb_info/serviceinfo/si-914-030.pdf

 

 

 

Edited by RFguy
  • Like 2
Posted

There is a guy in Melbourne who does a lot of 912ULS turbo conversions. Mainly for the gyro guys. Everything I have seen he has all good reports

 

Mark

 

  • Agree 1
Posted
On 14/9/2022 at 11:55 PM, Kyle Communications said:

There is a guy in Melbourne who does a lot of 912ULS turbo conversions. Mainly for the gyro guys. Everything I have seen he has all good reports

 

Mark

 

Thanks Mark I have been talking to him👍

Posted

I asked him about doing a turbo for a big bore kitted 912 ULS which is a base power of 114hp  turbo would bring it up another 15 or 20hp. He hasnt done one like that.

 

Mark

 

Posted
On 13/9/2022 at 8:22 PM, RFguy said:

if you want to apply a turbo , the an old  80hp rotax is what you want (9:1) , not a 912ULS (100hp) because the compession is  too high to be useful for the 100hp. (in my opinion)  

 

Yes, 100hp can be turboed but  it involves either  spacers for the cylinders to reduce the compression, or different piston/bore kits.   I mean sure you can turbo with 10.8, but I think I'll leave that one to when I have a full house in the hand and a joker.

 

what I dont know is if the gearbox is uprated for the 100hp , or is it the same identical gearbox in the 80hp, that might have a bearing.  From what I read in forums is  that essentially, the TBO of the gearbox goes down as you push the friendship with it up. 

Looking in the rotax illustrated parts catalog, I could find no difference between 912UL, ULS and the 914 in the propellor gearbox , nor the clutch except there is a different casing for the 914 I think.  certainly recently there was an SI for 914 exhaust valves which of course take a canning with the turbo. https://legacy.rotaxowner.com/si_tb_info/serviceinfo/si-914-030.pdf

 

 

 

Thanks RF I realise I would have to change the compression ratio👍

  • Like 1
Posted
2 minutes ago, Kyle Communications said:

I asked him about doing a turbo for a big bore kitted 912 ULS which is a base power of 114hp  turbo would bring it up another 15 or 20hp. He hasnt done one like that.

 

Mark

 

What I can gather he has done 30 to 40 of the 140hp upgrades

Posted

He isnt sure about the big bore version..he offered me a kit but I would probably have to do other stuff to it...getting the compression right too is another thing so would need sparer rings for the heads to lower compression

Our conversation is below. But I have had good feedback from Gyro guys about his conversions. I have supplied my replacement CDI's to the gyro guys

 

I gather you want to put it in a Hornet. I had a guy drop into my farm with a Hornet with a std 912ULS..the perfomance wasnt that great..it does need about 20 more horses and it would be a great aircraft

 

 

Hi Mark, This would be a one off. I have only done testing on the standard 100 hp with the turbo. Also other considerations like the bore diameter and the current compression ratio would have to calculated. Other companies won't turbo the big bore so I couldn't guarantee how well the engine would hold up. Can you give me some more info on the engine like cylinder bore diameter compression ratio and if the camshaft is standard? Thanks Steve

Hi Steve The bore is 4mm bigger and is 1484 cc once fitted. I believe the compression ratio is the same. The camshaft is std. Its basically just replacing the pots and pistons which are 4mm bigger in size. I had the crank welded and the engine has been totally balanced. I understand the differences in piston load etc although the piston speed is the same as there is no difference in the stroke of course.

 

Hi Mark. I could offer you a turbo conversation kit If you have a mechanic to do the conversion. there may be differences in some parts you would have to work out as you go.

 

 

Posted

Hi ClayT.

The 912ULS on my J230 will be down quite a bit in 7500' cruise on the Jab 3300, so I am stiffing around for options, also.

I'm thinking a 10.8:1  big bore kit will pick up almost all of the slack, and the extra bit picked up with the lower prop RPM slight efficiency advantage.

The big bore kits from some vendors can be ordered in lower compression.

 

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