Guest Andys@coffs Posted April 21, 2014 Share Posted April 21, 2014 I wasn't there but I think its the pre shutdown oiling system designed to prevent barrel corrosion between runs. The red lines are the oil injection lines that go to each head to inject into the inlet valve plenum for each cylinder. Available soon as a bolt on to existing engines Andy Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 21, 2014 Share Posted April 21, 2014 A few years back I had my hot exhaust squirting into the mouths of a pair of exhaust augmenters (based on 1942 NACA research). They worked well, sucking cooling air past the engine and making a measurable difference to climb performance. The penalty was black muck over the wing root and $1070 dollars for an ANR headset.I removed the augmentors. The 3-4% extra efficiency was not worth the damned noise. Next time you get into a dogfight, you might be sorry... 3~4% can be the difference between victory and defeat! Link to comment Share on other sites More sharing options...
Oscar Posted April 21, 2014 Share Posted April 21, 2014 I wasn't there but I think its the pre shutdown oiling system designed to prevent barrel corrosion between runs. The red lines are the oil injection lines that go to each head to inject into the inlet valve plenum for each cylinder.Available soon as a bolt on to existing engines Andy Andy - yep, that's the inhibitor squirter set-up, but they actually inject into the inlet port just ahead of the inlet valve so the (warm engine) oil hits the warm valve face and gets sprayed around the barrel. I believe CAMit are still testing to determine the optimum time for injecting the inhibitor oil so it is done at the best time for dispersing the oil and not having it all just run off the sides of the barrel and that may be some minutes after initial shut-down. The injectors themselves are very slim tubes of almost surgical-implement quality, when installing them one feels that one should be wearing a gown and mask and calling for the theatre nurse to hand them over.. 1 1 Link to comment Share on other sites More sharing options...
geoffreywh Posted April 21, 2014 Share Posted April 21, 2014 Ian said that the optimum time for a squirt was after switching off the mags and before the prop stopped ! Good Luck! But quite a good idea anyway............ Link to comment Share on other sites More sharing options...
Oscar Posted April 21, 2014 Share Posted April 21, 2014 Ian said that the optimum time for a squirt was after switching off the mags and before the prop stopped ! Good Luck! But quite a good idea anyway............ Aha - thanks for that info, I wasn't sure if the question had been resolved.. The timing sounds a bit tricky, but the CAMit engines are reportedly somewhat freer on shut-down than the normal Jab. engine (can be easily turned over by hand rather than really tight - but JabSP6 is the one who can advise us all there!) so it may not be quite as difficult to get the squirt in as one might think. Link to comment Share on other sites More sharing options...
deadstick Posted April 21, 2014 Share Posted April 21, 2014 Was there any mention of price on the 3300? Link to comment Share on other sites More sharing options...
Gnarly Gnu Posted April 21, 2014 Share Posted April 21, 2014 New CAMit 3300 advertised as $19,525 incl GST Link to comment Share on other sites More sharing options...
facthunter Posted April 22, 2014 Share Posted April 22, 2014 Engines shouldn't be "tight" on shutdown. Have compression but not be stiff. Something is wrong when that happens unless a very new engine, where it might be excused for a while. Nev 1 Link to comment Share on other sites More sharing options...
Old Koreelah Posted April 22, 2014 Share Posted April 22, 2014 Next time you get into a dogfight, you might be sorry... 3~4% can be the difference between victory and defeat! Trying to not get into any more, Bob. Link to comment Share on other sites More sharing options...
Old Koreelah Posted April 22, 2014 Share Posted April 22, 2014 Andy - yep, that's the inhibitor squirter set-up, but they actually inject into the inlet port just ahead of the inlet valve so the (warm engine) oil hits the warm valve face and gets sprayed around the barrel. I believe CAMit are still testing ... The system appears well-engineered, but is a patch on a bad design. Why not line the steel barrels with Nikasil and use appropriate rings? Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 22, 2014 Share Posted April 22, 2014 The system appears well-engineered, but is a patch on a bad design. Why not line the steel barrels with Nikasil and use appropriate rings? Because most of the information on modern cylinder bore treatments is proprietary (and secret!), it's hard to justify the reliability; and doing it in the backyard does not garauntee good results. Lycoming brought out a "cheap" training donk with steel bores and chromed rings, which has the same prob. as Jabiru (some model of O-320, from memory...). The lesson is, don't stop flying for more than a weekend. Ever... Link to comment Share on other sites More sharing options...
facthunter Posted April 22, 2014 Share Posted April 22, 2014 Nikasil is used on alloy . There is not enough room to use alloy walled barrels. They could be nitrided and would wear better but perhaps that is not a problem. Steel doesn't conduct heat too well. That is why I believe the cylinders should be fitted with baffles like Contomings. Nev 1 Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 22, 2014 Share Posted April 22, 2014 Engines shouldn't be "tight" on shutdown. Have compression but not be stiff. Something is wrong when that happens unless a very new engine, where it might be excused for a while. Nev wonder if it's varnish or coking on top piston rings? If so, too hot... good case for silicon based oil! Link to comment Share on other sites More sharing options...
facthunter Posted April 22, 2014 Share Posted April 22, 2014 Different piston skirt design, or maybe oil jets. It is very likely the piston crown runs too hot. We run CHT gauges but have no idea about piston temps, which is the other half of the combustion space. They way some look they are obviously HOT. Nev Link to comment Share on other sites More sharing options...
ianboag Posted April 22, 2014 Share Posted April 22, 2014 The requirement for carburettor air preheat is a temperature rise of 50 C minimum in the air entering the carburettor. Normally one gets about half that from the heat coming off the engine cooling fins, and the other half from an exhaust muff. The amount of heat needed to do that would be around five kilowatts, I'd guess. At least an order of magnitude more than the alternator output. Electric preheaters are a bad joke. Not really. There are a lot of 912s flying round with zero carb heat and/or electric/coolant heated jackets on the manifold downstream of the butterfly. The aim being not to heat the air but just to melt ice off the manifold wall which of course needs far fewer kW and does not significantly change the air inlet temperature. 1 Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 22, 2014 Share Posted April 22, 2014 Not really. There are a lot of 912s flying round with zero carb heat and/or electric/coolant heated jackets on the manifold downstream of the butterfly. The aim being not to heat the air but just to melt ice off the manifold wall which of course needs far fewer kW and does not significantly change the air inlet temperature. The certification requirement is that an energy input sufficient to raise the air temperature 50C, is sufficient to control icing. It's not actually a function of energy input; it's a function of lifting the temp out of the zone in which icing can occur. If you fly in marginal icing in VFR conditions (been there), holding an electric cigarette lighter under the slide often helps. But if you're ever caught in serious icing, the Rotax electric system is useless. The Merlin - which normally fought day VFR - used a water-heated butterfly... with a 1,200hp heater... 1 Link to comment Share on other sites More sharing options...
facthunter Posted April 22, 2014 Share Posted April 22, 2014 If ice forms in the carburettor besides losing flow you don't have a functioning carb. The coldest part is where the fuel is vaporising. and downstream of it. (Butterfly and low speed system, depends on design) Nev 1 Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 22, 2014 Share Posted April 22, 2014 If ice forms in the carburettor besides losing flow you don't have a functioning carb. The coldest part is where the fuel is vaporising. and downstream of it. (Butterfly and low speed system, depends on design) Nev Earnest K Gann, richening up to get a backfire to clear the ice before it stopped the engine... every few minutes... Link to comment Share on other sites More sharing options...
facthunter Posted April 22, 2014 Share Posted April 22, 2014 Yes read the book and flew the same aircraft. Don't know about richening it up to make it backfire. If you opened the throttle too much on start up THAT will cause a backfire but that is a LEAN start. The start us done on the primer solenoid which is a fixed flow if you hold the switch down continuously. Backfiring damages the carburettor as it is a four chamber affair, with diaphragms. The carb anti ice was from the engine heat but may have been augmented with alcohol ?? Nev Link to comment Share on other sites More sharing options...
Oscar Posted April 22, 2014 Share Posted April 22, 2014 Not really. There are a lot of 912s flying round with zero carb heat and/or electric/coolant heated jackets on the manifold downstream of the butterfly. The aim being not to heat the air but just to melt ice off the manifold wall which of course needs far fewer kW and does not significantly change the air inlet temperature. Let's just hang on a moment here. Physics doesn't change with engine manufacturer. I don't care what is sucking on the carby, if the airflow pressure differential through the carby throat and ambient temp and humidity is the same, ice will form, no matter what label is on the engine. Ice typically does NOT form on the manifold wall, FFS. It may be that the dual carbys on 912's do not have the pressure gradient situation of the single carby on a Jab, but in the right (er, perhaps that should be the WRONG) situation they will have IDENTICAL icing problems if the combination of airflow through the carby (ies), temperature and humidity occur. 3 Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 22, 2014 Share Posted April 22, 2014 Yes read the book and flew the same aircraft. Don't know about richening it up to make it backfire. If you opened the throttle too much on start up THAT will cause a backfire but that is a LEAN start. The start us done on the primer solenoid which is a fixed flow if you hold the switch down continuously. Backfiring damages the carburettor as it is a four chamber affair, with diaphragms. The carb anti ice was from the engine heat but may have been augmented with alcohol ?? Nev mmf, it's been a long time since I read the book... but I still find the idea of mishandling the engine in order to stay aloft, mildly horrifying. Wasn't it actually ice forming on a gauze stone filter or something? I have had icing in a Thruster, and I was pretty disgusted at that... flying along a bit of low-altitude wave, and a wisp of cloud started to form around me, out of the blue... then the trusty ring-a-ding began to splutter. Sawed the throttle and left the cloud... Link to comment Share on other sites More sharing options...
facthunter Posted April 22, 2014 Share Posted April 22, 2014 With SOME installations makers seem to think the Rotax doesn't need carb heat as the air supply is hot enough. Pushing your luck in my opinion. There are stipulated performances required, and I think that has been alluded to a few times. The Gypsy 1 c gets it off the side of the crankcase except when the throttle is fully open. Not a really inspiring set-up Nev 1 Link to comment Share on other sites More sharing options...
facthunter Posted April 22, 2014 Share Posted April 22, 2014 There's NO airfilter Bob. Just a big scoop on the top of the engine for the cool air. I'm not into abusing things to keep them going. Maybe a bit of poetic licence for effect with the EK Gann Book, but a lot of it is a good read as I recall and keeping them free of ICE was difficult, and quite a handful in bad weather. Todays jets get right over the top of most of the crook stuff or you can use radar to get around it. Nev Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 22, 2014 Share Posted April 22, 2014 With SOME installations makers seem to think the Rotax doesn't need carb heat as the air supply is hot enough. Pushing your luck in my opinion. There are stipulated performances required, and I think that has been alluded to a few times. The Gypsy 1 c gets it off the side of the crankcase except when the throttle is fully open. Not a really inspiring set-up Nev CS-VLA allows use of a sheltered intake for carbys that are "inherently resistant to ice formation", whatever they might be... Link to comment Share on other sites More sharing options...
XAIRVTW Posted April 22, 2014 Share Posted April 22, 2014 For Anyone that was at Natfly and attended the Camit stand: - what's the cable system bolted to this 3300 crank case? I have sent an email to Ian with picture attached as soon as I get a reply I will post it for you. 1 Link to comment Share on other sites More sharing options...
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