Bob Llewellyn Posted April 15, 2014 Share Posted April 15, 2014 David, I actually think that most of those problems have been - at least partially - addressed in this rambling discussion!. I don't have the knowledge or skills to know the numbers, but conceptually, I'd go about it this way:By test, find out the fuel delivery profile using the cd carby only that delivers more or less reliably about, say 90% of the fuel required on average to keep the engine reasonably happy at say 75% power. Set the carby up to do that; needle, jetting. Then add Dafydd's idea of an auto-rich solenoid that simply fools the carby into delivering more than required if in abnormal situation i.e. EFI failure. Perhaps also modify the existing 'choke' function on the carby to provide 'climb-rich' condition, that one simply pulls on at the start of the take-off run and leaves alone until throttling back to cruise climb. Then size the injectors adequately to provide all the additional individual pot supply in normal circumstances so that when everything is running happily, the added injector droplet size is an efficient fuel-air mixture. That is intended to mainly provide even fuel distribution to all pots at the best economy rate.. For electrical supply redundancy, I'd think a fairly small LiFePo4 battery could be plumbed in, utilising the more reliable charging functionality of the CAMit standard-type alternator that has much better protection from dangerous voltage spikes than the Jab style alternator. In fact, I don't think I'd be happy even running the EFI box from anything other than a well-regulated supply, for safety reasons, and certainly NOT any LiFePo4 type battery. Even quite a small (say around 1 kg, 8300 mh-hour HobbyKing battery) should, I'd think, give a decent amount of EFI-running capability - enough to get well along the way to a bug-out destination and set up a get-there height profile that assumes you may need to go back to carby-only power settings. It would take some intelligent system design for both the fuel and electrical supply, but the beauty of the EFI supplementary is that once the EFI is programmed, it should be possible to apply the entire package to any Jab engine and the EFI will handle the different individual engine / operation characteristics. Well, that's my theory... cue the dance of the effema angels-on-a-pinhead philosophers.. Aha! THAT's why you bought #0001 - you're not good with big numbers! I must say, I've long suspected it... Most aircooled aero donks run stoichometric - i.e. the "correct" mixture (nominally 14.2~14.7:1) - up to ~85% power, then progressively richen up to ~12:1 at 100%. The main slide needle in Bings (both by shape & position) controls this enrichment. If you re-needled your Bing to give stoichometric all the way up, then EFI failure should only affect you on takeoff/climb; and you'd kinda notice the rev drop! 1 Link to comment Share on other sites More sharing options...
Powerin Posted April 15, 2014 Share Posted April 15, 2014 Oscar, I may have missed it (feel free to point me to the post number), but I don't get why you want to use both carby and EFI at the same time. Why use supplementary EFI to make up for the deficiencies of a carby when EFI is perfectly capable of doing it on its own? As mentioned above for redundancy you then use a carby or TBI as the throttle body and only supply the carby with fuel if EFI fails. 2 Link to comment Share on other sites More sharing options...
David Isaac Posted April 15, 2014 Share Posted April 15, 2014 Running fuel systems dry for extended periods is a very bad idea. They may not work when needed. This problem has been well identified on duel fuel petrol/LPG vehicles. Better run partial fuel through a carby or dispose of it completely. I'm in favour of the latter, run a multi point EFI system with built in systems and power redundancy. They have proven reliability these days and it any case can easily be built in. 1 1 Link to comment Share on other sites More sharing options...
Oscar Posted April 15, 2014 Share Posted April 15, 2014 Only reason to still use the carby would be if by so doing one could to get around problems of compliance with standards. I'm not sure if this would be feasible, but if you have to run a TCDS'd model Jab engine (e.g. 2200J) and you retain the standard fuel supply set-up but ADD something to it that can be approved under the 'no adverse effect' provision, then you have a mechanism to get the efficiency of the EFI set-up while still retaining the carby so should not need any huge test and certification programme. I do have to say that this is a fairly big IF, but we don't know it's impossible until it is proven to so be. David's point that not actually using the carby fuel system is a bad idea is I think extremely cogent here, and I would not be at all happy with running one as back-up that isn't demonstrating that it works every time one starts up. HOWEVER: I do agree that this is ultimately less desirable than going full EFI when somebody can do the necessary certification work. Given that we have seen authorities (dragged somewhat kicking and screaming, I think) into more acceptance of electronic flight bags etc., just perhaps somewhere further down the yellow brick flightpath we might get a sensible conjunction of regulations and system developments. I'm not holding my breath here, but IF (not WHEN) that happened - and assuming any EFI controller manufacturer can be persuaded to join in the fun, (which is in no way a given), then I'd think that those who have taken the hybrid path ought to be able to use a fair bit of the EFI system they have added as part of the carby-less next step. Link to comment Share on other sites More sharing options...
Oscar Posted April 15, 2014 Share Posted April 15, 2014 Aha! THAT's why you bought #0001 - you're not good with big numbers! I must say, I've long suspected it... Most aircooled aero donks run stoichometric - i.e. the "correct" mixture (nominally 14.2~14.7:1) - up to ~85% power, then progressively richen up to ~12:1 at 100%. The main slide needle in Bings (both by shape & position) controls this enrichment. If you re-needled your Bing to give stoichometric all the way up, then EFI failure should only affect you on takeoff/climb; and you'd kinda notice the rev drop! If I find out where you are, you are going to get a slapping... Yer missing the essential point that trying to get the Bing on a Jaburi to give decent even mixture is a Sisyphean task - you think people haven't damn well been trying to do this for years? 1 Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 15, 2014 Share Posted April 15, 2014 If I find out where you are, you are going to get a slapping...Yer missing the essential point that trying to get the Bing on a Jaburi to give decent even mixture is a Sisyphean task - you think people haven't damn well been trying to do this for years? Nope, not missing that. As I said about 3,000 posts ago, if one regards the EFI as an electronically calibrated high power jet - replacing the enrichment function of the needle - then the mythical complete EFI failure mode is to be fine at ~80% power or less (post #126). FMEA buddy; you'll learn to love it 1 1 Link to comment Share on other sites More sharing options...
Oscar Posted April 15, 2014 Share Posted April 15, 2014 What do you think I've been -ing saying all along? and isn't FMEA an acronym for Fit a Maypole in an Engineer's Ahem? For you (and only because I'm basically a gentle-natured and considerate soul) , I'll extend the medieval process and include a horse-collar.... Still, I'm encouraged that you got there eventually. Been worth every electron. Link to comment Share on other sites More sharing options...
David Isaac Posted April 15, 2014 Share Posted April 15, 2014 It is rather obvious that you bunch of comedians are all rather fond of each other. It is nice to see this type of vitriol for a change ... LOL Link to comment Share on other sites More sharing options...
Oscar Posted April 15, 2014 Share Posted April 15, 2014 I've met him. And I fixed up his damn Thruster some years ago for him, so I have the advantage of knowing which rivets I left out... (we all need a pension plan). 1 Link to comment Share on other sites More sharing options...
facthunter Posted April 15, 2014 Share Posted April 15, 2014 Well it didn't work, so his theory's must be better than yaws, eh!. Nev 1 Link to comment Share on other sites More sharing options...
jetjr Posted April 15, 2014 Share Posted April 15, 2014 JJ - the SDS kit is very impressive - but I think it doesn't have the capability to change distribution to each pot individually, or have I missed something? I think it's kind of one-step-further-removed from being an add-on idea, more a replacement.. and for those interested in taking that step, certainly worthy of major consideration. Im checking individual injector adjustment BUT, back to basics on this problem, are we just seeing fuel distribution problems or air distribution issues too, ie does the swirl effect amount of air headed to each pot or is it just buggering up fuel mist? If its just fuel then there should be no need to play with injectors individually? It doesnt run a EGT feedback loop but can run loop on O2 sensor or maybe AFR It is an add on and running 100% EFI is way simpler than trying to calibrate 3 fuel delivery systems. I do see the certification point though. Keeping carb operational would be as simple as running regularly solely on carb system. This a reason why maybe Rotec TBI would be prefered, no bowl or gaskets to be concerned with. Also flow a bit better. Re certification ......how do Rotax go about certifying their ECU injection system in 912 is? Did they have to get whole thing recertificated? I see they are offering new software and intake plenums etc to owners, how does the system handle this kind of upgrade? Whats their redundnacy arrangement? Shows there must be some acceptance SDS/Edge Performance do some slick EFI setups for these std 912 too Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 15, 2014 Share Posted April 15, 2014 Im checking individual injector adjustmentBUT, back to basics on this problem, are we just seeing fuel distribution problems or air distribution issues too, ie does the swirl effect amount of air headed to each pot or is it just buggering up fuel mist? If its just fuel then there should be no need to play with injectors individually? It doesnt run a EGT feedback loop but can run loop on O2 sensor or maybe AFR It is an add on and running 100% EFI is way simpler than trying to calibrate 3 fuel delivery systems. I do see the certification point though. Keeping carb operational would be as simple as running regularly solely on carb system. This a reason why maybe Rotec TBI would be prefered, no bowl or gaskets to be concerned with. Also flow a bit better. Re certification ......how do Rotax go about certifying their ECU injection system in 912 is? Did they have to get whole thing recertificated? I see they are offering new software and intake plenums etc to owners, how does the system handle this kind of upgrade? Whats their redundnacy arrangement? Shows there must be some acceptance SDS/Edge Performance do some slick EFI setups for these std 912 too Unless the air velocity is extreme, or some sort of resonance or interference exists, the air differential will be very small; fuel is much more sensitive to centrifugal force, partial vaporisation etc. If there's enough fuel at 3 pots but the 4th is wrong, one needs to twiddle the 4th injector only... Rotax, under the ASTM for LSA certification, satisfy themselves. Thierlet were the first, and possibly still only, people to get any National Airworthiness Authority to accept non-aviation electronics on a light aeroplane under any Design Standard requiring an independent umpire to be satisfied..., to the best of my knowledge... Link to comment Share on other sites More sharing options...
Oscar Posted April 15, 2014 Share Posted April 15, 2014 Well, we have quite a few reports - sufficient to make it a believable hypothesis - that the mixture problems on Jabs. tends to waddle around amongst the pots depending on throttle position; however it might well be the case that a bit of research could show there is sufficient latitude that just getting a 'generic' mixture curve correct for the worst pot is sufficiently close that the rest don't matter being a tad over-fuelled. Next better is being able to tweak the curves for individual injectors; best is individual egt-based feedback control.. Personally, I'd prefer to have them all running pretty evenly, both for efficiency and for giving the crankshaft a slightly easier life. I'm not at all sure that ending up with say one or two pots running constantly over-rich is ideal for glazing / coking; it won't cause the thing to go BANG suddenly (as long as one keeps aware of compression figures), but it'd be slightly more comfortable to think all those pots are happy little critters for as much of the time as possible. Link to comment Share on other sites More sharing options...
Powerin Posted April 15, 2014 Share Posted April 15, 2014 Re certification ......how do Rotax go about certifying their ECU injection system in 912 is? Did they have to get whole thing recertificated? I see they are offering new software and intake plenums etc to owners, how does the system handle this kind of upgrade? Whats their redundnacy arrangement? Off topic for a CAMit engine thread (sorry), but from memory the Rotax iS has dual redundant ECUs, dual redundant electric fuel pumps, a dedicated direct drive alternator for the EFI system independent of the main electrical system and battery, plus an automatic switch-over to the main alternator if the EFI alternator fails, and if that fails too the battery can keep you going for a little while. Link to comment Share on other sites More sharing options...
Keenaviator Posted April 15, 2014 Share Posted April 15, 2014 Can someone who is running a Camit engine give some feedback as to how they are going? Laurie 3 Link to comment Share on other sites More sharing options...
Powerin Posted April 15, 2014 Share Posted April 15, 2014 Can someone who is running a Camit engine give some feedback as to how they are going? Laurie Like any new engine or mod, I guess we'll have to give them 1000hrs before they can give useful feedback of any failures or shortcomings....unless they start failing sooner. Hearing about what CAMit have done you certainly feel a bit more confident. Link to comment Share on other sites More sharing options...
Oscar Posted April 15, 2014 Share Posted April 15, 2014 Back at Post #10 (first page) is a report on what is probably the highest-time CAMit engine (at least in general flying, not testing!); at the rate it's been putting up the hours, probably has around 180 by now. 1 Link to comment Share on other sites More sharing options...
jetjr Posted April 15, 2014 Share Posted April 15, 2014 Got a good reply from Ross @ SDS No you cant vary individual injectors, not required Nev and my assumption that air distribution is very good seems correct, by putting fuel in at the inlets solves egt spread problem Interestingly he says Rotax have poor egt spread too with carbs, not many would be measuring i guess. Reliability, they have 125,000 flight hours, plus military, on the systems plus 11,000 units in automotive and off road racing. Estimates 24 mill hours in that market. Definitely well tested Can install dual ecu and dual pumps but no room for dual injectors on Jab. No surprise good installation is key to reliability. They believe MTBF is in tens of thousands of hours on the electronics parts, well beyond that of carb setups. Being honest, many aircraft in Raa are lucky to do a few hundred hours per year, and I dont know of any nearing 10,000 hrs esecially on the one engine. Im sure they are out there 1 1 Link to comment Share on other sites More sharing options...
Oscar Posted April 15, 2014 Share Posted April 15, 2014 JJ, that's useful. (incidentally, I've been keeping a quiet eye on SDS for about five years now,: I first noticed them when I was researching a possible EA81-powered project, and I've been consistently impressed with what they do.) Suggests to me that there are a few different paths that one could take, probably driven by what registration group one wants to fit in. As things stand, I suspect that the 'retain the carby and add supplementary fine-tuning by EFI' approach MAY be a way to get around having to use a certified engine - though that would need to be tested as a concept with CASA before embarking on a project to try it. IF it can be accommodated in the regs, I still think an option for 55 and 24-certified reg aircraft. For 19-reg and VH-exp, a straight SDS system (and maybe clean up the pre-TB intake tract, it's pretty squashed for the Bing and early airboxes at least are not a pretty sight, to my eyes). I think I'd like some electrical supply redundancy, and I also think using a conventional alternator with conventional regulator (CAMit or Rotec) would be sensible. On that score, I like the CAMit one as it provides a bit of crankshaft damping and uses toothed belt, not v-belt. A possible, I'd think, degree of redundancy for the SDS installation that wouldn't stuff things up could be to use a TBI unit rather than just a plain TB with a second system and a manual switch-over. Depending on the sort of flying one wants to do, I guess that could be a 'full-on' TBI set-up if you really feel the need for high-level performance from the back-up unit (you fly out of difficult sites etc.) or even, given that the SDS system is pretty damn reliable, something as simple and pretty cheap as a megasquirt with say dual injectors in a simple tube just before the plenum. Aftermarket TBI set-ups come in at around $2k all up, the megasquirt I think can be set up for about $1k. So, an SDS kit PLUS a redundant back-up set-up might come in around $6k; you'd probably want to be pretty well assured that you'd extend the real, attainable TBO by about double that of what people are typically getting now to look at it as cost-neutral. So, I think, there are a number of options one could consider. The result of all of our ponderings here is, to me an indication that this whole area of getting better fuel mix into Jab engines is very much a work in progress and I am of the opinion that the potential of the CAMit engine to provide (we hope!) something worth adding some thousands of $$ worth of extra-quality fuel delivery gear onto is the reason that all of this consideration becomes worthwhile pursuing. Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 15, 2014 Share Posted April 15, 2014 JJ, that's useful. (incidentally, I've been keeping a quiet eye on SDS for about five years now,: I first noticed them when I was researching a possible EA81-powered project, and I've been consistently impressed with what they do.)Suggests to me that there are a few different paths that one could take, probably driven by what registration group one wants to fit in. As things stand, I suspect that the 'retain the carby and add supplementary fine-tuning by EFI' approach MAY be a way to get around having to use a certified engine - though that would need to be tested as a concept with CASA before embarking on a project to try it. IF it can be accommodated in the regs, I still think an option for 55 and 24-certified reg aircraft. For 19-reg and VH-exp, a straight SDS system (and maybe clean up the pre-TB intake tract, it's pretty squashed for the Bing and early airboxes at least are not a pretty sight, to my eyes). I think I'd like some electrical supply redundancy, and I also think using a conventional alternator with conventional regulator (CAMit or Rotec) would be sensible. On that score, I like the CAMit one as it provides a bit of crankshaft damping and uses toothed belt, not v-belt. A possible, I'd think, degree of redundancy for the SDS installation that wouldn't stuff things up could be to use a TBI unit rather than just a plain TB with a second system and a manual switch-over. Depending on the sort of flying one wants to do, I guess that could be a 'full-on' TBI set-up if you really feel the need for high-level performance from the back-up unit (you fly out of difficult sites etc.) or even, given that the SDS system is pretty damn reliable, something as simple and pretty cheap as a megasquirt with say dual injectors in a simple tube just before the plenum. Aftermarket TBI set-ups come in at around $2k all up, the megasquirt I think can be set up for about $1k. So, an SDS kit PLUS a redundant back-up set-up might come in around $6k; you'd probably want to be pretty well assured that you'd extend the real, attainable TBO by about double that of what people are typically getting now to look at it as cost-neutral. So, I think, there are a number of options one could consider. The result of all of our ponderings here is, to me an indication that this whole area of getting better fuel mix into Jab engines is very much a work in progress and I am of the opinion that the potential of the CAMit engine to provide (we hope!) something worth adding some thousands of $$ worth of extra-quality fuel delivery gear onto is the reason that all of this consideration becomes worthwhile pursuing. Or you could just stick two Rotax 462's on the wings, and have twin engined reliability!!!! 1 1 Link to comment Share on other sites More sharing options...
Oscar Posted April 15, 2014 Share Posted April 15, 2014 You are a worryingly sick puppy. Four exclamation marks are the sure sign of someone wearing their underpants on their head. Get back in your basket and don't come out again until you have gotten well, or I'll send someone around with a BIG thermometer to take yer damn temperature.. 1 Link to comment Share on other sites More sharing options...
jetjr Posted April 15, 2014 Share Posted April 15, 2014 Or two 2200 on the nose.........being done currently. Going to be a upgrade kit Im told. I agree on Oscars options, getting full EFI certified would be tough. Might be possible with someone like Ian steering as I sure he knows what will or wont fly with regulations. Although I really like these detailed discussions I now have serious issues. I clearly require upgrade of perfectly good Jabiru built Solid lifter engine to a Camit variant, then adding SDS injection.......looking at $20K and Im around $18 K short. Love dreaming but waking up isnt as much fun. I too have been watching SDS for around 5 years or more. Was very interested in what the South Africans were doing but Im bored waiting for this and they were on a different path. Link to comment Share on other sites More sharing options...
deadstick Posted April 16, 2014 Share Posted April 16, 2014 What about 2-3 psi from a small turbo? would that help normalise the uneven mixture distribution? Link to comment Share on other sites More sharing options...
Bob Llewellyn Posted April 16, 2014 Share Posted April 16, 2014 What about 2-3 psi from a small turbo? would that help normalise the uneven mixture distribution? not unless you used a suck-through carby or injected into the eye of the compressor... 1 Link to comment Share on other sites More sharing options...
facthunter Posted April 16, 2014 Share Posted April 16, 2014 That's not as silly as it sounds. We still don't get over the problem of the all supplying manifold as you can still get a backfire which really overloads an unlucky cylinder by shoving a lot of extra combustible mixture into it . It splits a block on a Holden V6 shortens conrods on other motors. Why wouldn't it break a stud on a Jabiru? Nev Link to comment Share on other sites More sharing options...
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