Jim Meade Posted September 29, 2023 Report Share Posted September 29, 2023 The manual says warmup for a couple of minutes at 2200 RPM, then advance to 2500 RPM until the oil temperature reaches 120F. I've cussed at the warmup time over the years and have fiddled with some different RPMs after the initial couple of minutes. I've about concluded that no matter the outside air temperature, the engine warms up as quickly at 2500 RPM as it does at 3500 or any other higher RPM. What is your practice and experience? I'm starting this discussion just for information. I have no set conviction or point to make, although I'm beginning to believe the manual. Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted September 29, 2023 Report Share Posted September 29, 2023 Just now, Jim Meade said: The manual says warmup for a couple of minutes at 2200 RPM, then advance to 2500 RPM until the oil temperature reaches 120F. I've cussed at the warmup time over the years and have fiddled with some different RPMs after the initial couple of minutes. I've about concluded that no matter the outside air temperature, the engine warms up as quickly at 2500 RPM as it does at 3500 or any other higher RPM. What is your practice and experience? I'm starting this discussion just for information. I have no set conviction or point to make, although I'm beginning to believe the manual. After getting burned on my gearbox overhaul to the tune of $2500, Leading Edge told me some things I didn't know... They recommend warmup from the moment of startup at 2500rpm *or higher*, in order to protect the gearbox components, and the same for taxi. Previously I would warmup and taxi at 1800-2000rpm, and thought that was okay because I was out of the yellow arc. Apparently not so! This will lead to higher taxi speeds and more brake pad wear, but brakes are cheap compared to the gearbox. Going straight to 2500+rpm on start doesn't hurt the engine at all, according to LE. YMMV, I'm just repeating what I was advised. I asked Roger about it and he agreed with Leading Edge's recommendation. Quote Link to comment Share on other sites More sharing options...
Animosity2k Posted October 9, 2023 Report Share Posted October 9, 2023 On 9/29/2023 at 2:35 PM, FlyingMonkey said: After getting burned on my gearbox overhaul to the tune of $2500, Leading Edge told me some things I didn't know... They recommend warmup from the moment of startup at 2500rpm *or higher*, in order to protect the gearbox components, and the same for taxi. Previously I would warmup and taxi at 1800-2000rpm, and thought that was okay because I was out of the yellow arc. Apparently not so! This will lead to higher taxi speeds and more brake pad wear, but brakes are cheap compared to the gearbox. Going straight to 2500+rpm on start doesn't hurt the engine at all, according to LE. YMMV, I'm just repeating what I was advised. I asked Roger about it and he agreed with Leading Edge's recommendation. Interesting, always felt like when I'd taxi out at 1800-1900 it felt like it was rough, I'll start doing my warmup and taxi to runway at 2500,thanks for the tip. Quote Link to comment Share on other sites More sharing options...
Ulmo133 Posted October 10, 2023 Report Share Posted October 10, 2023 Hi. Not an expert (by far) but what I've been taught and what is recommended in my area by Rotax mechanics, it's : to start the motor go to 2000 rpm for 1 or 2 minutes go to 2200 rpm for 1 or 2 minutes go to 2400 rpm until you reach 50°C/120F And after you taxi in between 2000 and 2400 rpm (more if you need to go out the grass or something) and use the brakes as little as possible to avoid overheating them. Quote Link to comment Share on other sites More sharing options...
Madhatter Posted October 10, 2023 Report Share Posted October 10, 2023 If I have to taxi at 2500 rpm then it's time to get rid of the 912 powered CT. This makes no sense as there are many thousands of 912's around the world that do not do this and have no issues. There is something else going on with gearboxes that have this problem. Maybe it's the overhauler or defective parts. Also geared engines do not tolerate constant sudden throttle fluxuations such as in a Cessna 421. Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 10, 2023 Report Share Posted October 10, 2023 7 minutes ago, Madhatter said: If I have to taxi at 2500 rpm then it's time to get rid of the 912 powered CT. This makes no sense as there are many thousands of 912's around the world that do not do this and have no issues. There is something else going on with gearboxes that have this problem. Maybe it's the overhauler or defective parts. Also geared engines do not tolerate constant sudden throttle fluxuations such as in a Cessna 421. 2500rpm sounds high to me as well, but that's what Brett Lawton, Leading Edge's chief Rotax mechanic told me. He says that is Rotax's recommendation, not his, and his experience is that spending much time below 2500rpm is very hard on the gearbox and causes wear over time. Not immediately, but it's what turns a $700 gearbox overhaul into a $2500 overhaul as happened to me. I'm not 100% saying this is accurate, just what I was told explicitly when I asked why parts of my gearbox internals had worn beyond limits. I'd sure love some of the guys who've been to the Rotax heavy maintenance schools to weigh in with some sage advice. Quote Link to comment Share on other sites More sharing options...
Roger Lee Posted October 11, 2023 Report Share Posted October 11, 2023 Rotax used to be happy at 2K+. I was told this year that too many gearboxes have had issues and that Rotax has now bumped up the warm up rpm to 2500 and they don't even care to 3K. You're not hurting anything and it's better safe than sorry. $2500 - $4500 is being sorry. Quote Link to comment Share on other sites More sharing options...
GrassStripFlyBoy Posted October 11, 2023 Report Share Posted October 11, 2023 My standard practice is 2500 from the moment it starts, and as soon as the oil temp needle (mine is analog) starts moving off the 100F min mark, I'll bump RPM closer to 3k if it's colder season. This suggestion from higher RPM once oil temp begins to rise over 100F comes from Rainbow aviation when I took maintenance rating class, but it also seems logical. If you can go WFO at 120F, easing into ~3k at 100F mark makes sense, and speeds the warming process. Airtime also explained 2500 right from the start when I bought the bird. I wonder what the viscosity curve on these multi weight oils is? That's probably the dynamic at play, building pressure throughout the viscosity change. Quote Link to comment Share on other sites More sharing options...
Ulmo133 Posted October 11, 2023 Report Share Posted October 11, 2023 It probably also depends to the oil. FD France when they made a full check on the engine used Yacco AVX500 and everybody tell me that at the next service I have to use AVX1000 instead. Quote Link to comment Share on other sites More sharing options...
Madhatter Posted October 11, 2023 Report Share Posted October 11, 2023 Maybe a heavy prop has something to do with it, maybe the 5 lb E-Prop is less of an issue. Maybe Rotax needs to address this with data if it's a widespread issue. Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 11, 2023 Report Share Posted October 11, 2023 6 hours ago, Ulmo133 said: It probably also depends to the oil. FD France when they made a full check on the engine used Yacco AVX500 and everybody tell me that at the next service I have to use AVX1000 instead. I believe Rotax currently *only* recommends Aeroshell Sport Plus 4, but maybe that's only in the USA...I'm sure Europe has its own environmental standards. Quote Link to comment Share on other sites More sharing options...
Ulmo133 Posted October 11, 2023 Report Share Posted October 11, 2023 Yes in Europe it's now the AVX1000 and with old engine AVX500 but we also can use the Sport Plus 4. Why ? Good question. Quote Link to comment Share on other sites More sharing options...
FlyingMonkey Posted October 11, 2023 Report Share Posted October 11, 2023 2 minutes ago, Ulmo133 said: Yes in Europe it's now the AVX1000 and with old engine AVX500 but we also can use the Sport Plus 4. Why ? Good question. I'm sure the answer has something to do with a bureaucracy somewhere! Quote Link to comment Share on other sites More sharing options...
Jacques Posted October 11, 2023 Report Share Posted October 11, 2023 different '' properties and advantages '' https://www.yacco.com/en/our-products/light-planes/avx-500-4t-sae-10w40-186 https://www.yacco.com/en/our-products/light-planes/aero-avx-1000-4t-sae-10w40-294 Quote Link to comment Share on other sites More sharing options...
FredG Posted October 11, 2023 Report Share Posted October 11, 2023 The AERO AVX 1000 4T SAE 10W40 is a full synthetic oil that meets JASO MA standards. JASO MA designates oil intended for use in motorcycles that have the gearbox and clutch lubricated by engine oil (like the 912). Other oils, such as Mobil 1 Racing 4t, also meet JASO MA standards. In the past, several motorcycle oils meeting JASO MA standards (including Mobil 1 Racing 4t) were acceptable to Rotax for use in the 912. Although not stated anywhere, from the oils that Rotax used to approve for the 912 family of engines, I infer that the 912 lubrication system was designed for oil that meets the JASO MA standard. As we know, over time, Rotax has limited acceptable oils for use in the 912 to AeroShell Rotax Sport4 (in the USA) although it seems that XPS 5W-50 full synthetic oil will be approved for the aviation fleet (from the LEAF web page: "Fully synthetic 4T SAE 5w-50 multigrade oil for use in ambient temps from -40F to 122F. Approved for all 4 stroke Rotax 9 series aircraft engines. Suits the requirements of integrated gearbox and overload clutch."). I cannot find any information about XPS oil to indicate that it meets JASO MA standards nor that any Rotax document states officially that the XPS 5W-50 is OK for the 912. Quote Link to comment Share on other sites More sharing options...
procharger Posted January 13 Report Share Posted January 13 I think sudden stop with heavy prop does the damage kind of noisy on shutdown. But not with the e-prop its quiet. When engine is running should not be to much stress on gearbox unless the engine carbs. are not balanced. Who knows the real answer?? Quote Link to comment Share on other sites More sharing options...
Anticept Posted January 14 Report Share Posted January 14 The reason for the dog gears being designed they way they are is to absorb some of the impulses at low RPM and high load (such as ground idling). The overload clutch also will slip a little in certain conditions. The 80hp engine doesn't even have the extended lands in the gears nor an overload clutch. It also has much lower compression. Rotax has, as part of their installation manuals and a service instruction, to calculate mass moment of inertia of a prop. If it is too high, it voids the warranty. brett at leasing edge has had to refuse warranties for shredded gearboxes because the owners used props that were too heavy. Gearboxes have always been a rough point in aviation piston engines. Rotax isn't the only one that has issues, though they certainly have won the award for most creative (and complex) solutions. Quote Link to comment Share on other sites More sharing options...
GlennM Posted January 19 Report Share Posted January 19 I use XPS oil in the Rotax in my Can Am. It does not have an integrated gearbox. Personally, I would not use it because I can get the Aeroshell Sport. The XPS oil is not cheap, either. Quote Link to comment Share on other sites More sharing options...
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