skippydiesel

Hi Blueadventure, Can't quite work out, are you are for, fence sitter, against, the Big Tube (BT)t?? Say for a moment the BT does what its supporters claim - smoother running and lower rpm. Starting with rpm - Rotax advise against extended low rpm operations as this will almost certainly damage the gear box - So no benefit! Smoother running - Without data this is just a perceived benefit. Nothing wrong with perception but when you are trying to promote a product/modification, I will always want data ie proof. Then you need to consider the engines state of "tune" ie Was the engine that the BT was fitted to, recently serviced, carburettors balanced, plugs in good condition , etc On the last point, if the BT smooths out a badly running engine, this is a good thing - assuming its not masking an impending problem. I am not an engineer, however my understanding of the Rotax balance tube is that its there to smooth out/make good, any small differences in vacuum between the two induction systems. No significant volume of air flows back & forth in the tube. The proof for this is simple - when doing the pneumatic carby balance, you run the engine with the balance tube disconnected/shut off and the engine runs just fine (smooth) when carby's are balanced. Fitting a BT, will not improve on the action of the Rotax balance tube. I am certain Rotax would have adopted such a simple enchantments if it works as promoted.😈

This "modification" has been extensively discussed on Rotax Owners Forum. Latest revival can be found at https://www.rotax-owner.com/en/general-tech-discussion/6709-polishing-intake-manifolds?start=50 My summary of the discussion: Supporters rave about perceived smoother running /lower idle speed No empirical supporting evidence. Most can't see how it can work/make a significant difference to engine performance. A few die hard supporters refuse to believe its a con job Note; that Rotax engines should not idle below about 1400 rpm, as gearbox damage may occur, recommended extended idle 2000-2500rpm😈

"Tomorrow" turned out to be 8 days later (yesterday). Did an hour. Bit warm under the bubble ( 20C @ 5500') AvTraffic a non starter, due to this computer luddite not realising that a whole heap of "stuff" needed to be selected ON (hope I have now done it correctly). Will do a review after the next flight. For now - Noticed a change in my intercom; Volume needs to be turned to Max, then turned down on headset. I usually do a "click" check, short press of transmit button, on my intercom - doesn't work any more - cant hear the click. Cant explain it, but headset/intercom seems dead - to the point where I did an Any Station Radio Quality Check - came back 5/5. This is the Six Aviation Bluetooth Adapter - not the AvTraffic Should not be related, iPad / WiFi connection with my SE2 dropped out ?? Also lost OzRunways traffic (blue bubble) alerts, for a brief period?? The third event of this nature. I also noticed, after trying, unsuccessfully , to "fix" the AvTraffic issues, in the air, my OzRunways was very slow to come back on ??😈

The above has a 2 3/4" flange. FYI: The similar filter, with a 2 1/2" flange, K&N part # SN-2540, used by many Rotax 912's, may have been discontinued.😈

Does it strike you as a bit odd, that the Dayco cap you have referred to is a pressure cap - the coolant reservoir should be at ambient pressure. I guess if the cap fits, it can easily be modified, using a 2- 3mm drill bit.😈

Dont know the dimensions but what about an oil container cap? Another thought bubble - the collapsible jerry cans/bladders, have a cap which can be ordered separately 😈

I cant be certain but I think you are incorrect. Rotax will supply a basic 912 ULS engine, for which you can including exhaust , air inlet/management , remote oil tank, coolant & oil heat exchangers at a price($$$$?). What you or the factory do with the component's is the choice of the purchaser. Rotax do not supply, for the 912 carburettor engines, fuel reticulation components other than the fuel distribution manifold . Factory's often opt for locally or inhouse, made components - oil/coolant heat exchangers, custom exhaust system & engine mounts, probably due to cost savings and possibly cowling dimensions. I have seen some really weird looking exhaust systems, that are unlikly to follow Rotax standard's. The exhaust system on your Evector being a case in point. 😈

You are not entirely wrong - many airboxes are made by the aircraft factory, as are mufflers and engine mounting systems, however Rotax make all of these items as well. 😈

The air box pictured looks to be a Rotax product. Mine, a home made, is diffrent in a number of ways - location of float bowl breather tubes spigots, length of carby tubes, presence of a hot air inlet, etc😈

The following is speculative; Yes there will be heat transfer, how much this raises the air temp in the box, will depend on the air flow (speed) & volume. The air temperature entering the carbys will also be effected by the ambient temperature ie if cruising along at 7500ft, OAT - 2C, the temperature rise may only be a degree or two. 😈

"While I was taught to use carb heat when pulling power the instructor commented that on most 912ULS the carb heat did not make much difference. He is not the only experienced Rotax user that I have heard say this." Its a widely held belief that Rotax engines do not get carby ice. For sure they are resistant to icing but to think they never get ice is one big mistake. My advice; If the engine is fitted with a manual carby heat system - use it for every reduction in power (landings,stalls or just going to loitering power). Its a good habit to cultivate and will stand you in good stead should you transition to other engines more prone to carby icing.😈

Coolant heated ie plumbed into the cooling system.😈

"Yes. 912 with carbs on top are. Pretty immune to ice unless they have a ducted carb inlet." I would not go so far as to use the " immune" word - perhaps resistant. My last 912ULS/Zephyr, with individual air filters, under cowl temp, ran a consistent 10C above ambient. In 10+ years of ownership and may 100's of hours, never a suggestion of catby ice. My 912ILS/Sonex has an air box, with direct access to outside air. Under cowl also runs 10C above ambient. However the carby inlets are fitted with Cozycarb coolant heated rings, claimed to prevent carby ice. 😈

Hi BrendAn, I am going down a similar track for my Sonex - flies straight & level, hands/feet off, in Cruise with just me aboard. Stick a good sized adult (75kg+) in the right seat and a load of aileron & rudder trim is required. I had a bungee aileron trlm on my Zephyr, didnt need it for the rudder. Very simple/intuitive & light weight. Worked very well. I have acquired a whole role of bungee/shock cord with which to make the trim system. Will need at least two pulleys and one cam cleat per trim (rudder/aileron). I have been checking out variose marine suppliers for the pulleys & cleats - all available. Yet to work out the location of pullies . I rarely have a passenger, so no rush to do the job- get down to it in the cooler months. I may be able to help you with some shock cord. 😈

Me neither - on the 4/ - would need to get back into the carby heat groove, if ever went back to an engine that needs it😈