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| Subject: Cooling Mods on Rotax 582 Pulsar [TD] | |
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Author: Bob P |
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Date Posted: Sun, Sep 30 2012, 19:17:52 GMT I suffer from CMD (Compulsive Modification Disorder). Instead of counting sheep to get to sleep I lie in bed wondering which bit of my Pulsar I could modify next. A couple of years ago I fitted a replacement Rotax 582 engine and decided to tweak its cooling system at the same time. When I bought the plane it had an early (small big end bearings) silver top 582 engine. The builder (John Webb) had removed the engine thermostat and fitted a manually operated (by knob in cockpit) shutter arrangement in front of the starboard radiator instead. The effect of this is that the coolant always flows around the radiators and the pilot opens and closes the radiator shutter as required to keep the water temp in limits. It seems to me that this arrangement is better than a thermostat as there is no risk of the engine being subjected to a blast of icy water (and cold seizure) if the thermostat popped open suddenly (eg on a go around). Also the maximum cooling might be marginally improved because a fully open thermostat will still slightly restrict the water flow. Another possible problem with my old engine was that small amounts of air kept accumulating in the collector tank (the thing with the filler cap on top). I was concerned that air might also becoming trapped in the cylinder head. My final concern with the old engine was that there is no provision to prevent carb icing (other than the residual heat in the engine compartment). I mentioned this to Alan Gill who reassured me that (I think from memory) Pulsars are not prone to icing, and that thermometers bolted to the carbs showed that they stayed above freezing level). But I was still a bit wary because my engine uses oil injection rather than 2T mix, and I had read somewhere that the oil in the 2T mix reduces the risk of ice build-up (oils the carb walls to stop ice sticking). My new 582 engine is a “blue top” with a 2 way thermostat so that water circulates directly from the head outlet back to the water pump inlet via a bypass hose when the engine is cold. Apart from the difficulty in fitting the bypass hose in my Pulsar ( I’ve even had to modify my plug caps to clear the engine cowl), the bypass hose prevents continuous water flow around the radiator circuit. To overcome the above limitations I’ve modified my cooling system as follows: 1) The 2 way thermostat, and the bypass hose have been removed and the ports for the bypass hose blanked off. 2) In addition to the venting hose at the front of the cylinder head, I’ve fitted a second venting hose into my bypass hose cylinder head blanking plate. This second venting hose returns air/coolant to the collector tank via proprietary (SkyDrive) hot water carb heaters (thus reducing the risk of icing) 3) My radiator temperature control shutters are now (slowly) operated by a small electric motor and gear arrangement, with an open-stop- shut switch in the cockpit. 4) I’ve replaced the overflow bottle with an automotive pressurised expansion tank. This tank incorporated a pressure relief cap that normally remains shut , and is translucent plastic so the coolant level can be easily seen. I’ve replaced the brass collection tank with a (heavily modified) aluminium vehicle “swirlpot” collector. This collector has a filler cap rather than a pressure relief cap, and spigots have been added for the standard cooling hoses plus extra spigots for the carb heater return hose, and an outlet to the expansion tank. 5) All the coolant hoses (except the small bore head venting/ carb heater hoses) are made from reinforced silicon. This seems a good idea as the silicon hoses are more flexible and so they reduce the load on the (have been known to fail) radiator spigots. Also they are less prone to hardening and ageing. A couple of the hoses have customised bends/diameter changes. I’m pleased to say that everything works as intended and the mods have been approved by LAA. The coolant system now remains totally air bubble free, it has not been necessary to top up the coolant system, and (by adjusting the shutters) the engine operating temperature can be kept within Rotax limits (although I do need to 30% blank the non shuttered radiator for cool weather and 60% blank it for cold weather flying. No doubt the standard Pulsar cooling arrangement works fine, but if there are any other sufferers of CMD out there I’ll happily supply further details on request. Bob (G-BVTW. [ Next Thread | Previous Thread | Next Message | Previous Message ] |
| Subject | Author | Date |
| CMD | Captain Pulsar | Mon, Oct 01 2012, 21:02:21 GMT |
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| 582 cooling | croz | Tue, Oct 02 2012, 8:37:18 GMT |
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| pulsar mods | croz | Wed, Oct 03 2012, 10:56:48 GMT |
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| Radiator Shutters | Barry | Sat, Oct 27 2012, 8:56:27 GMT |
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