Lucas Di Pentima Posted April 30, 2013 Share Posted April 30, 2013 Hello, I have an ultralight with a Rotax 532 engine (2 carbs, 2-stroke, liquid-cooled, point ignition) and I'm getting low EGT temps (950F on one cylinder, 1000F on the other, at cruise setting). Also, I noticed that the water temp is a little cold also, around 140-149 F. I'm somewhat new so please excuse my dumb question: is there any correlation between the 2 temps? Thanks in advance! Link to comment Share on other sites More sharing options...
fly_tornado Posted April 30, 2013 Share Posted April 30, 2013 how old are your gauges and probes? Link to comment Share on other sites More sharing options...
Lucas Di Pentima Posted April 30, 2013 Author Share Posted April 30, 2013 how old are your gauges and probes? The EGT gauge and probes are new, I have purchased myself some months ago. The water probe and gauge came with the ultralight (which I bought about 4 years ago). Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted May 1, 2013 Share Posted May 1, 2013 No , no correlation really. The EGT temp is the temp of your burnt exhaust gas, or the temp of your combustion within the cylinder. 950-1000 is ok, but you can go up to about 1250 with no dramas. Would not worry that there is a 50 deg difference, as egt probes lead a real hard life, and a little inaccuraccy can be expected. 950-1000 EGT tends to be a bit on the cooler/richer side, but you won't do any damage, just burn a bit more fuel. You may check that both slides within the carbs are perfectly lined up, by removing the air filters and lining them both up at the top edge of the inlet hole. They will run their best when the slides are lined up, and this can change easily with just a little bit of cable stretch. Adjust one slide to match the other with the brass cable adj screw at to top off carb, then lock off under the little rubber. You may need to re-adjust you idle stops after this, to reset you idle. Big hex type nuts on outside of carb, which are just slide bottom stops really. Coolant temp range for that engine is 60-80C, and if all is well, they usually sit right in the middle at 70C. A bit on the cool side is good, but you don't want to be at the other end !...the best position for the coolant sender is right in the center of the cylinder-head, for the best reading, as this is the hot spot. You must be running a good coolant and have good radiators. If you bumped up you EGTs to around 1200 you probabily would see a slight rise in your coolant temp also..............hope that has helped .................................Maj.... Link to comment Share on other sites More sharing options...
facthunter Posted May 1, 2013 Share Posted May 1, 2013 Your EGT's are good and are the ones that count for reliability. I suppose the colder running head temps would have some effect, but I don't think it would be much. Temporarily block off some of the radiator area and see what happens. Your fuel rate of consumption is helpful too. If it is UP perhaps consider a slight leaning of the mixture, but don't overdo it. Nev Link to comment Share on other sites More sharing options...
Hongie Posted May 1, 2013 Share Posted May 1, 2013 I imagine EGT would be more a function of ignition timing and lambda ratio maj? Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted May 1, 2013 Share Posted May 1, 2013 Well Ign timing on those engine is set electronically, and lambada rate is controlled by pilots' heart beat really............................................................... Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted May 1, 2013 Share Posted May 1, 2013 Oh sorry ...points ignition...Watch out !!!.............................................Maj... Link to comment Share on other sites More sharing options...
Hongie Posted May 1, 2013 Share Posted May 1, 2013 lol not talking about a dance here ross :P air fuel ratio is what i'm on about ya goose... all though i reckon you would be a bit of a lambada mover from what i seen at monto... now BACK ON TOPIC lol 1 Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted May 1, 2013 Share Posted May 1, 2013 You don't mean stoihnochik (or whatever) mixture ratio do you....best air/fuel ratio at about 15/16 to 1 ????????????....I thought I was pretty well behaved at Monto, except when that old chick tried her best to latch onto me, and take me to her caravan !!............ Link to comment Share on other sites More sharing options...
turboplanner Posted May 1, 2013 Share Posted May 1, 2013 his reputation follows him everywhere Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted May 1, 2013 Share Posted May 1, 2013 Indipenti..........With points ignition be aware that as the points wear they have the effect of advancing timing, and leaning out the mixture. You would be wise to mark the normal position on your EGT guage, and always watch for a rise in EGTs, which may be in one or both cylinders. This could be very gradual over a period of time....Additionally become accusmtomed to reading your plugs, probabily every ten hours or so, and watching for a whitening of the burn color. Color is read on the center ceramic, around the center post, and ideally should be a nice rich coffee color, when all is well.............................Maj... Link to comment Share on other sites More sharing options...
Lucas Di Pentima Posted May 1, 2013 Author Share Posted May 1, 2013 Thanks for the tips Maj, I forgot to say that the carb needles are on its lower setting, I cannot get the fuel-air mixture any more leaner, and that's why I'm worried. The needles, and jets are all new and the right ones as the parts manual describes (I have had a hard time trying to get the 532 manuals but fortunately the nice folks from rotax-owner.com helped). My fellow pilots from my airclub say that it's preferable that the engine run on the hot side of the allowed range, what are your thoughts about this? Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted May 1, 2013 Share Posted May 1, 2013 From memory the needle should be on the second from top of needle notch, but I would have to check that. Yes Rotaxowner.com is the way to go. I ran my 582 on the cool side until It was recommended I bump the temps up, as the main bearings can suffer if running too cold. I did this by fitting a thermostat to the engine whick also gave a nicer warm-up, and kept the temps solid at 70C. The rotax thermostat is way too expensive but the Kawasaki KR250 is the same, and much cheaper from your bike shop. Make sure the small steam hole is at the top. Don't get in the habit of fiddling with things, especially carbs...just get things set up correctly , go fly, and monitor, especially plugs in your case. If you want to get rid of the points chores, adjustments etc...keep your eye out for a good used low-time 582. Basically similiar as the 532, but with bigger cylinders and CDI electronic ignition which doesn't need any adjustments. It also automatically advances the ign timing around 22 deg as you go through 4000 rpms, which was at about wheels off in my old Drifter !!..........yehaa !.....Cheers........................Maj... Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted May 1, 2013 Share Posted May 1, 2013 The position of the needle clip only effects mixture in the mid ranges. At full throttle the needle is fully out, and then the main jet is what is metering fuel. You shouldn't stay at full throttle for too long anyway, as that is when things will want to heat up....How much time on your engine, if it is newish things may still need to settle a bit in respect to rings etc, assuming it was run-in correctly by Rotaxs recommendations in the first place ?.................................................Maj... Link to comment Share on other sites More sharing options...
Hongie Posted May 1, 2013 Share Posted May 1, 2013 You don't mean stoihnochik (or whatever) mixture ratio do you....best air/fuel ratio at about 15/16 to 1 ????????????....I thought I was pretty well behaved at Monto, except when that old chick tried her best to latch onto me, and take me to her caravan!!............ Yeah. A lambda value of 1 equals stoichiometic which is 14.7 :1 with unleaded. I use lambda from when I was working on cars.o2 sensors where really called lambda sensors. Link to comment Share on other sites More sharing options...
robinsm Posted May 1, 2013 Share Posted May 1, 2013 Interesting thread. I have run 2 x 582 engines to date and have not been able to get the EGT's over 950 degrees. They nornally run about 900. or so. I have a thermostat in the engine, correct settings as per rotax on the carbs and still not able to get to the recommended temps. I have run these engines now for 5 years and apart from a little more fuel, they run well. The one time I tried to lean out the mizxture I blew a hole in one of the piston crowns at 400ft above the airfeild on take off (detonation|). The question of temps drove me mad for about 12 months and then I decided that if things were running right and about the right temps (albeit a little cool) then leave the damned things alone and enjoy flying. If some one has a magic fix for this please tell us. Indepenti, you are getting better figures than me so just enjoy the flying. Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted May 1, 2013 Share Posted May 1, 2013 robinsm, yes I have run into that also on occasions, only factors that could have an effect really are position of EGT sensors, plug gaps/type, and possibly fuel and oil types. (Assuming of course your carbs are set per Rotax specs) If your plugs were black or sooty, than yes you probabily were running around 900C. If however you maintained a normal color and burn you would probaily have been running a little higher and the guages telling you fibs !...all good....were you running a pre-air filter set up or an after muffler silencer ?....with these fitted the card settings are different to normal without them...............................Maj... Link to comment Share on other sites More sharing options...
Lucas Di Pentima Posted May 1, 2013 Author Share Posted May 1, 2013 Thanks Maj and Nev for all the great info. Luckily this 532 has its hours counted, as I have a HKS700E waiting to take its place in a near future. Nevertheless, I want to make sure all is running correctly on the 532 before I sell it. All these doubts appear because every approx 6 hours I have had some kind of failure that was corrected by changing the plugs. (I use NGK B8ES, as described in the manual). Reading the plugs as you say, I can see they are (very) dark brown, almost black... but they don't show any carbon deposits. I have available a video from the last time I had a partial failure, I'm attaching the video so you can see it. Check at 0:50, the left camera captured the engine's sound. Another reason that could produce low EGTs is too much load on the engine (prop over pitched, as I learnt from Brian Carpenter's lecture from Rainbow Aviation). I've recently bought a new RPM gauge so I can check if this is the case, I haven't tested yet, but on full throttle I should get 6800 RPM, right? I did tested it on the ground and I got 6400. All this tinkering as Maj says is because of the continuous problems that I've been having. My original idea was to be a simple ultralight pilot (aka: ultralight user) but now I know that I should learn about all this, to properly take good care of my engine. :) I've been receiving help from people here but the problems persist. Thanks for all the help! Link to comment Share on other sites More sharing options...
facthunter Posted May 1, 2013 Share Posted May 1, 2013 What are your full throttle EG temps and do they increase when you come back to cruise power? nev Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted May 1, 2013 Share Posted May 1, 2013 Yes enjoyed the video....the engine faulter sounded to me like a fuel-supply problem, or a fouling plug. The 532s only had a single plug per cylinder didn't they ?....022-.024 thou is good on the plugs. Don't know if your choice of the HKS700E is the right choice for that aircraft and horsepower range, you'd be better off with a new bluetop 582 I reckon. The latest HKS has a turbo...it may be fine however.........................maj... Link to comment Share on other sites More sharing options...
Lucas Di Pentima Posted May 1, 2013 Author Share Posted May 1, 2013 What are your full throttle EG temps and do they increase when you come back to cruise power? nev Hi Nev! I will check those temps in my next test and come back to you. I did notice an increase on EG temps when reducing throttle when in final approach to landing, don't remember how much, maybe 50F or so. Link to comment Share on other sites More sharing options...
Lucas Di Pentima Posted May 1, 2013 Author Share Posted May 1, 2013 Yes enjoyed the video....the engine faulter sounded to me like a fuel-supply problem, or a fouling plug. The 532s only had a single plug per cylinder didn't they ?....022-.024 thou is good on the plugs. Don't know if your choice of the HKS700E is the right choice for that aircraft and horsepower range, you'd be better off with a new bluetop 582 I reckon. The latest HKS has a turbo...it may be fine however.........................maj... Yes, the 532 are single plug per cylinder :( I think the problem are the plugs being fouled, but what I can't still detect is the reason for the fouling, so I thought the low EGTs were some kind of hint. The HKS 700E is used a lot in Chile with Flightstar ultralights, here in Argentina the Rotax is the standard, but I wanted a 4-stroke (912s are too much for an ultralight as far as I know) for enhanced reliability. As for the gapping, the manual states that 0.5 mm (19.68 thou?) is the correct one, on some websites I read that the gapping should be between 0.40 - 0.50 mm, you say a little more is better? I didn't checked the gapping on plugs, always installed as is... I'll check them as soon as I go to the hangar. Have a nice labour day! (it's an international holiday, isn't it?) Link to comment Share on other sites More sharing options...
Guest Maj Millard Posted May 1, 2013 Share Posted May 1, 2013 Yes happy labor day to you also....... NGK plugs generally come out of the box gapped at .025 " for auto use, you need to close that a little for 2-stroke use. The HKS is a fine engine, however revs = horsepower, and I just don't think you'll get the same power response from the HKS 4-stroke, as you would from a new 582 when you need it. Reliability is of no use, if you don't clear those trees at the end of the runway in the first place with your passenger on board !.....From the sound of your plug color you are running a bit on the rich side, hence the low EGTs,....what oil are you using , is the engine pre-mix or auto lube ?............................... Maj... Link to comment Share on other sites More sharing options...
Lucas Di Pentima Posted May 2, 2013 Author Share Posted May 2, 2013 Yes happy labor day to you also....... NGK plugs generally come out of the box gapped at .025 " for auto use, you need to close that a little for 2-stroke use. The HKS is a fine engine, however revs = horsepower, and I just don't think you'll get the same power response from the HKS 4-stroke, as you would from a new 582 when you need it. Reliability is of no use, if you don't clear those trees at the end of the runway in the first place with your passenger on board !.....From the sound of your plug color you are running a bit on the rich side, hence the low EGTs,....what oil are you using , is the engine pre-mix or auto lube ?............................... Maj... Hi Maj! I didn't know the NGK required re-gapping for 2 strokes, nobody on my airclub told me, thanks! I'm using pre-mix (2%) Esso's Aquaglide Oil for 2-stroke marine engines, it's the one all the people here use (the same one that our flight school uses without any issues with an Rotax 503) with 95 Octane (RON) gas. Maybe I should try with the high octane (98 RON) gas, as I've read that pre-mixing gas decreases the octane value from the very beggining. Best regards, Lucas (please can you tell me how to change my name on the forum? I didn't found the option in the account preferences! hehe...) Link to comment Share on other sites More sharing options...
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