skippydiesel

I will have to go back & check what I wrote some many moths back but from geriatric memory Rotax recomend a Mikuni #35 Restrictor Jet. My original return fuel rate was 7.6L/hr at about 3 psi I later installed a small jet which did not solve my problems at the time (low fuel pressure during climb out). Later again a read the Vans document below - sounded similar to my problem - went out & purchased a new higher capacity Boost pump - worried about overpressure - reinstalled the #35 restrictor jet - all good! I also redesigned/plumbed my three tank fuel system, so I can choose (which I do) to use the tank with the return flow for all ops (previously couldn't). https://www.vansaircraft.com/wp-content/uploads/2018/12/Notification-2018-07-12.pdf The RV-12 recommended Facet Cube, PN 40135, delivers Pressure Max/Min 7.0-4.0 psi and 32GPH (US) . This is well above Rotax recommended Max 4.5 psi https://facet-purolator.com/specifications/ Mikuni web - https://mikunioz.com/shop/bs3096-pilot-jet-bleed-type-for-cv-carbs/?v=13b249c5dfa9 I used the VM22 style (that was originally fitted) but on reflection the N151.067 might have been a better bet. Jet fitted in to the end of one of the spigot tube push on fittings. In short the return line restrictor jet selected will be governed by the fuel system configuration, Boost & Mechanical pump performance

"That was an issue with the kit (they supply 27mm!)" Kit???? 27MM ID???? Gates Au will supply: - a molded 90 degree bend, in diffrent "Arm" length options PN 03-0010 ID 25.4mm, Arm 1 125mm, Arm 2 125mm ($10-12) PN 03-0011 ID 25.4mm, Arm 1 300mm, Arm 2 300mm ($15-37) Multi Fit Coolant Hose with two bends, a 135 & 90 degree PN01-007 ID 25mm Length 550 ($?) Then there is 25 mm connectors Straight PN28606 ($20) Elbow PN28626 ($19) Tee PN28638 ($51) Unfortunatly the above connector must be purchased in a minimum of 2/bag From "Started a Spare Parts List" - I have used the above - nice fit on the Rotax radiator spigots (25mm). You will almost certainly have to use a connector, the Gates ones are a very secure fit.

No gravity flow in most low wings - pump all the way. In a 912ULS installation, I would question the sanity of anyone relying on gravity feed - particularly when it comes to fuel vaporization mitigation.

Hi Danny - I hear you Note that the coolant (17mm ID) from Floods is 85.80/m + delivery. Gates Silicone (16mm ID) $16 -$28.50/m + delivery from UK or Australia about $38/m + delivery (some are offering free) Then there is all that good stuff from Mackay ( should be cheaper again). Personally, if I can shave $500 or so off an estimated $1,500+ (from RoTAX) 5 year rubber replacement, using good quality materials, I will be very happy. Convenience can come at quite a cost - as always your choice😈

I agree with you Nev however many get confused by the relationship between flow & pressure. In a 912 ULS (fitted to a Pipistrel) no fuel pressure is required to run the engine. However to get the fuel from wherever it is being stored (tank), pressure (gravity & or pump) will be required to deliver the fuel. Depending on the height above/below delivery point (carb float bowl) that the supply is, plus the effects of tube/hose ID and length (frictional losses) will determine how much pressure is required to deliver the appropriate volume/flow, to the engine at full power (max demand). Note: Other effects will be pipe bend radius/valve types & number/ filters types / return line jetting. Hope I have covered all/most of the issues.

To the best of my understanding, the current price per meter from Floods: Coolant Hose Part No 922250: $0.78/cm + GST + $85.80/m ( you will need over 2m depending on installation) Formed 90 degree hose Part No 9222192: $47.33 +GST = $52.063 (one of) Oil Hose Part No 956394: $1.02/cm + GST = $112.2 / m (you will probably need about 3m depending on installation) So around the $560-$600 + delivery

"Friction losses are significant in small tubes over any distance, an example most people can understand as the water pressure at the tap comes out screaming but at the end of the 10 m hose it is nowhere near the same pressure, this my friends is friction loss." Me thinks you are confusing flow & pressure - The pressure should remain constant, while the flow is reduced, due to such factors as friction. In small (carburettor) aircraft we monitor the health of the fuel supply system in pressure (kph, psi, Bar) but actually use the fuel in volume (L/hr). All the pressure in the World may not deliver sufficient volume of fuel for your engine to run.

More info on 16mm (5/8) silicon hose - https://vansairforce.net/threads/5-year-rubber-alternatives.186607/

ll you Rotax drivers ; Check this out - https://vansairforce.net/threads/5-year-rubber-alternatives.186607/ Seems that 5/8 (16mm)ID silicon is being sued quite often onto 17 mm OD spigots

Just found a Pommy supplier of Gates Heater Hose 17mm ID, 24mm OD , Part No. HTH017 $16.00/m (+ delivery)

Well there you go - must of missed that. Will get a price and compare with RoTax AU supplied 17mm ID coolant hose. Thanks Found it! https://www.shop.flylight.co.uk/engine-service-parts-72-c.asp Straight 17 mm ID silicone hose $28.50 per M (will need 3M) 90 Elbow 17 mm ID silicone hose $23.75 each (will need one on standard configuration) Subtotal $109.25 Above as a kit is now $151.98 but includes hose clamps which can be purchased locally (ie a saving) Then the cruncher DELIVERY ?? - in common with the USA, Pommy delivery is almost exclusively courier and very costly? (RoTAX Au starting to look like it may be competitive - will get a price during the week)

Thanks Blue - my question is not about using silicon hose as such but about using 5/8" (16mm) ID hose pushed onto 17mm OD spigot/barb. (I assume your 25mm ID is going on to 25mm OD spigot). From earlier post: My questions are; Will the Gates silicon 5/8" hose fit, without damage, on to a 17mm OD spigot/barb? Are there other factors that I should consider? The reason for my question is the lack of straight (as in not shape molded) 17 mm ID coolant hose, on the open market - You can purchase it from RoTAX at an exorbitant price.

Does the lack of response mean that no one has tried using silicone coolant hose ????

So you agree, the entry criteria is likely to focus on equipment carried ( ie com, transponder, etc) rather than build type.

Mackay are astonishing in their range of products. This will get you their universal products range (25 mm ID radiator hose being of most interest to Rotax drivers) https://www.mackayrubber.com.au/hoseproducts https://www.mackayrubber.com.au/_files/ugd/478d7d_f2637e84ee494d8ca160b52dd68de25c.pdf https://www.mackayrubber.com.au/_files/ugd/17eaaa_9774ebec8334488e94706a9951ddfacd.pdf

Update: It seems that Mackay (Australian manufacturer of automotive hoses, amongst other things) make a wide range of 17 mm ID molded hoses - the above question is now moot but I would would still be intersted in the experience of anyone fitting silicone hose to a larger OD spigot.

I stand to be corrected - Dont see the logic in that - GA experimental (home built/modified) are not so restricted.

Back to 17mm ID Coolant Hose: Mackay PN CH4195 17mm ID x 430mm Long. $11-$27 various vendors in Au While you are checking this out - have a look at Mackay Catalogue, you may never have to purchase from RoTAX again. Heater hose 17mm ID, pages 44-45. Radiator Hose 24-25mm ID, Page 53-55 https://mackayrubber.com/pdf/hose_ID_listing.pdf For list of Australian sellers see bottom of page https://www.mackayrubber.com.au/automotive

https://automotivesuperstore.com.au/ngk-vd05fmh

Rotax Spark Plug Caps - NGK VD05FMH 8425 https://www.ebay.com/itm/283890969752?epid=14059118977&itmmeta=01HV56GBJRFTKZ5ZPRG8A0DC4H&hash=item4219386c98 https://www.ebay.com/itm/166686792115?itmmeta=01HV56GBJRN5ANQ10Y8GFFMK5T&hash=item26cf4e99b3 https://www.amazon.ca/NGK-VD05FMH-Resistor-Cap/dp/B0068O7NSE

Should have done this before posting - K&S Technologies part number is 10-4222MH K&S caps, they are an exact duplicate of the NGK ones, except the rubber is silicone." Seem to be only available from the USA - sorry!

While I am fanatical about using the correct size (ID) of hose relative to its spigot (OD) I recognise that sometimes a smaller ID hose may do the job just as well. (NOTE: I said smaller ID - never use a larger ID hose, it is almost guaranteed to leak and be insecure on the spigot/barb) EG Rotax specify that 17mm ID coolant hose. A little over 2m in length is required for most 912 engines. 17mm ID is awfully hard to come by, unless you purchase from Rotax, at an exorbitant cost. The well known/respected brand Gates, only do 17 mm in some preformed/shaped hoses - you would have to purchase several to achieve the 2m + required a potentially a costly exercise. Gates do supply silicone coolant hose in ID 5/8" (15.875mm). I am under the impression that silicon hose is considerably more flexible (stretchy) than the usual "rubber" hose. My questions are; Will the Gates silicon 5/8" hose fit, without damage, on to a 17mm OD spigot/barb? Are there other factors that I should consider?

Rotax (& others?) spark plug caps. Just found, on Rotax Owners Forum, this alternative to OM: "K&S Technologies part number is 10-4222MH K&S caps, they are an exact duplicate of the NGK ones, except the rubber is silicone."

Area 51 Wow! the Pipistrel way of addressing, the fuel return system, what I see as relatively simple concept, is very (unnecessarily?) complex. Perhaps there is just no space, closer to the engine, for a header tank.