Buckaroo Posted January 12, 2017 Report Share Posted January 12, 2017 Carb balancing is the most critical component of a healthy running engine. Without balanced carbs you get vibrations that can quickly cause component failures and advanced wear and failure. Question? Why hasn't Rotax designed a cockpit adjusting knob that be calibrated from the panel in concert with a vacuum balance gauge or set of lights? It seems to me a linkage to one of the carbs cable fittings could be easily (for engineers) designed to the dash with a detent knob that would adjust the travel. A lit or analog vacuum gauge would be simple to mount to the dash as well. Having to stand by a meat shredder to get to a little wire by finger twisting a little brass bicycle like adjuster seems way under engineered! ???? Then you have to do it with different rpm's. So now you need a throttle man to add to the YouTube hold my beer moment!???? Link to comment Share on other sites More sharing options...
Roger Lee Posted January 12, 2017 Report Share Posted January 12, 2017 Carb sync is only good up to 3500 rpm. After that the tube isn't big enough. That's why syncing carbs should be done at or under 3500 rpm. I tend to use 3300-3500 and that should keep them in good shape for higher rpms. When the carb sync is done every 100 hrs or annual and you use a set of gauges it usually only takes me 5-15 minutes with the CT throttle setup. Sometimes with other aircraft throttle linkages they are not designed well enough and use too thick a cable and or a poor throttle system which won't allow the throttle arm on the carb to return to the exact position every time so these may take me a little longer and sometimes they will never be perfect. Our thin throttle cable is a God send compared to the people that have heavy thick cables, routed poorly for smooth operation and poor throttle hook ups in the cockpit. Once you understand what gauges are telling you setting the sync is very easy and quick. I don't like the electronic devices. Link to comment Share on other sites More sharing options...
Buckaroo Posted January 12, 2017 Author Report Share Posted January 12, 2017 What do you think of my question? At first I thought this was a fuel air adjustment. Then when I learned it was just a cable adjustment it immediately made me wonder why there's not a simple little cockpit mechanism to do the job perfectly each flight. I would guess temp changes and altitude variations throw these carbs off. On YouTube there's a guy who built a adjuster like I asked about. It wasn't a Ct tho. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 12, 2017 Report Share Posted January 12, 2017 Buckaroo, that is a great question! Even if it only worked on the ground, it would take a lot of time out of the process. You could verify sync before each flight, which would be great in helping our engines (and everything else) to last as long as possible and get maximum performance. a twist knob that differentially adjusts throttle cable tension, combined with a vacuum gauge with a center "normal" range would do it. Brilliant! Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 12, 2017 Report Share Posted January 12, 2017 On YouTube there's a guy who built a adjuster like I asked about. It wasn't a Ct tho. Do you have a link to the video? I'm curious. Link to comment Share on other sites More sharing options...
Buckaroo Posted January 12, 2017 Author Report Share Posted January 12, 2017 Thanks flyingmonkey! I'll research yt for that piece. Link to comment Share on other sites More sharing options...
Buckaroo Posted January 12, 2017 Author Report Share Posted January 12, 2017 https://youtu.be/91b0NNI53-M This guy has a electric cable drive fitting that turns both ways. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 12, 2017 Report Share Posted January 12, 2017 https://youtu.be/91b0NNI53-M This guy has a electric cable drive fitting that turns both ways. That's pretty cool, but I'd want a motor that turns a lot slower than what he has there. It takes *very* little adjustment to make fairly large sync changes. In my response I almost mentioned an electric solution, but I'm not sure if that makes it better or worse from a complexity standpoint. Maybe better since you don't have to reroute cables. The setup in that video is pretty elegant, since it makes the adjustment at the point you'd usually adjust manually. Not sure if the idea would be to have that on both carbs and fiddle them with separate switches, or just have a single switch hooked to both sides that runs them in opposite directions to "meet in the middle" on sync. Interesting idea. Link to comment Share on other sites More sharing options...
Buckaroo Posted January 12, 2017 Author Report Share Posted January 12, 2017 I've never done a carb adj on Rotax. Do both carbs have to be adjusted? I would think since your just matching one to the other just adjusting one would do the job? Not true? Another thing is if you have the vacuum gauge constantly attached to a gauge in the cockpit I would imagine the engine would run rough until the vacuum line was blocked? Not sure. Link to comment Share on other sites More sharing options...
Roger Lee Posted January 12, 2017 Report Share Posted January 12, 2017 These have been around for a few years, but aren't practical and don't always keep their set point. If you sync the carbs they should be just fine in between each time. Usually I see anywhere from still synced to 1.5 inches off. The tube can compensate for that. If you install a system like some of these guys you'll eventually just back back and have holes left to fill. Don't over think this engine or life or you'll never sleep or be happy. Link to comment Share on other sites More sharing options...
Buckaroo Posted January 12, 2017 Author Report Share Posted January 12, 2017 These have been around for a few years, but aren't practical and don't always keep their set point. If you sync the carbs they should be just fine in between each time. Usually I see anywhere from still synced to 1.5 inches off. The tube can compensate for that. If you install a system like some of these guys you'll eventually just back back and have holes left to fill. Don't over think this engine or life or you'll never sleep or be happy. Well said! Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 12, 2017 Report Share Posted January 12, 2017 They do seem to keep sync pretty well. I synced at my annual last June and have not had to touch it since. Probably about time to just check and verify the sync. Link to comment Share on other sites More sharing options...
Buckaroo Posted January 12, 2017 Author Report Share Posted January 12, 2017 Is there a first sign or subtle bob or feel that tells one the carbs Re out of synch? Maybe just a steam gauge showing a unbalanced condition would be cool! Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 12, 2017 Report Share Posted January 12, 2017 Is there a first sign or subtle bob or feel that tells one the carbs Re out of synch? Maybe just a steam gauge showing a unbalanced condition would be cool! The engine just might seem a little rougher (or a lot if it's really bad) than usual. In fact engine roughness is more often a sync issue than anything else. Link to comment Share on other sites More sharing options...
Roger Lee Posted January 12, 2017 Report Share Posted January 12, 2017 The human can't hear or feel a few inches out of sync. You must use gauges. I have seen a few not so bright A&P's tell me they have done things like this for 30 years and can do it by ear. They are always 6+" off and the other thing I found out about old A&P's it makes them mad when you laugh. Just no sense of humor. Link to comment Share on other sites More sharing options...
WmInce Posted January 12, 2017 Report Share Posted January 12, 2017 So Roger . . . what have you got against digital carb balance tools (Carb-Mate)? For the average owner, they seem to work just fine. Link to comment Share on other sites More sharing options...
Tom Baker Posted January 12, 2017 Report Share Posted January 12, 2017 On the CT if you watch the throttle lever it will vibrate if the carbs are out of sinc, or least that has been my experience. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 12, 2017 Report Share Posted January 12, 2017 On the CT if you watch the throttle lever it will vibrate if the carbs are out of sinc, or least that has been my experience. Mine always vibrates, even when in sync. This might be airframe dependent. Link to comment Share on other sites More sharing options...
Tom Baker Posted January 12, 2017 Report Share Posted January 12, 2017 Mine always vibrates, even when in sync. This might be airframe dependent. On all that I have worked on I have been able to get the vibration to almost non existent. Some may vibrate a little, but nothing like they do if they are out of balance. Link to comment Share on other sites More sharing options...
WmInce Posted January 12, 2017 Report Share Posted January 12, 2017 On all that I have worked on I have been able to get the vibration to almost non existent. Is that at all RPM's? Seems as though, anything below approximately 1700 RPM generates considerable more vibration than if you stay above it. To me, vibration is the enemy. I go to almost any length to keep it to a minimum, beginning right at startup. Link to comment Share on other sites More sharing options...
Tom Baker Posted January 13, 2017 Report Share Posted January 13, 2017 I normally don't set idle RPM below 1700, and target 1750. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted January 13, 2017 Report Share Posted January 13, 2017 On all that I have worked on I have been able to get the vibration to almost non existent. Some may vibrate a little, but nothing like they do if they are out of balance. I will pay closer attention, maybe mine vibrates more when out of balance. I need to check balance anyway, if I adjust it I'll make note if the vibes decrease. Link to comment Share on other sites More sharing options...
Roger Lee Posted January 13, 2017 Report Share Posted January 13, 2017 So Roger . . . what have you got against digital carb balance tools (Carb-Mate)? For the average owner, they seem to work just fine. Hi Bill, I have one and would gladly sell it. It takes too long. You can't diagnose with it. You can't look at it and in 3 seconds know which carb to adjust, by how much and if the idle of main jets have a clog and which one. You can't tell at a glance if the cable actually needs to be shortened or lengthened before you even start the sync. All the old timers that have used both have all gone back to gauges. They also need a battery connection. Quicker, easier and you have diagnostic comparisons. When you start an engine with gauges I can tell you what's going on in either carb in about 5 seconds and if they are even syncable. I be doing an in depth carb sync diagnostics class with gauges in my new class and everyone will be doing a carb sync. Not just staring at someone else doing one from 30' away. Link to comment Share on other sites More sharing options...
Anticept Posted January 13, 2017 Report Share Posted January 13, 2017 Tom means at flight RPM. Generally, the higher the RPM, the smoother the impulses caused by carb imbalances. There might be some shake at low RPM, but it will be virtually non existent at high RPM. Link to comment Share on other sites More sharing options...
Buckaroo Posted January 13, 2017 Author Report Share Posted January 13, 2017 I think we get a double whammy in the design. We get the constant argument between the prop and the engine and add lower rpm imbalances in the carbs independently running each side of the engine. No wonder we are asked to taxi at 2000 rpm!???? Link to comment Share on other sites More sharing options...
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