EXHAUST INSULATING WRAP

Jim Isaacs wrote:

Much of this discussion has been centered around the potential benefits and adverse effects of wrapping the pipes on components under the cowl, in particular their longevity. I am aware of the adverse effect of warm intake air to engine performance but also wonder about the benefit of heat under the cowl to the carb throats. My 912UL has the ring mount, so no air box, and no heat for the carburetors to prevent carb icing other than what the tight cowling provides to them as they sit atop the engine. I don’t know, but suspect that like me, the vast majority of other owners do not have the Rotax manifold carb heat system.  I wonder if the risk of carb ice accumulation could be increased by wrapping the pipes.  In other words, is the performance trade off of using exposed K&N filters instead of the cold air intake (factory air box) year-around carb ice protection?  Does the factory air box kit include some a carb heat capability or is the manifold heat system still required? 

FYI - My last aircraft, an ATEC Zephyr/912ULS, just had the two conical air filters - just like your set up.

In 10-11 year and about 600 hrs I never (knowingly) experienced carburettor icing.

Other than some home made shielding of hoses close to the exhaust system and insulation on my over engine fuel lines there was no  heat control (wraps/ceramic).

I wanted to get an idea about the in flight temperature of the air entering the carburettors.

Purchased one of those digital indoor/outdoor temperature gauges with a long lead to the outdoor thermocouple (about $20 AU).

Passed the long lead through the cabin air system to the outside of the aircraft and in under the cowling - a bit of tape here & there to prevent damage/hold in position. Thermocouple right beside the left air filter (did the right latter).

Result; In cruse, the air entering the carburettor is a fairly consistent 10C above ambient.

Deduction; Negative - some loss of performance but I never noticed it Positive probably a reasonable anti icing environment/set up.

Note: I live and fly from NSW Australia - our winter temperatures are  not even remote similar to the northern USA, Canada and much of Europe. Carburettor ice is however a  very real danger.

Rotax-Owner wrote:

Please Read SL-914-023 - https://legacy.rotaxowner.com/si_tb_info/serviceletter/sl-912-025.pdf

Use of exhaust insulation materials for ROTAX® Engine Type 916 i (Series), 915 i (Series), 912 i (Series), 912 and 914 (Series) ATA System: 78-10-00 Exhaust system

1.3) Reason Insulating the exhaust pipes (e.g. with exhaust wraps or ceramic coatings) leads to a significant increase in the component temperatures of all exhaust-relevant components. The significant additional thermal load generated inevitably reduces the proven durability of exhaust components. Exhaust wrap may also hold moisture, promoting corrosion. The use of any insulation material is not approved by ROTAX® and may result in exhaust component fatigue and damage.

Doesn't Rotech (main Canadian Rotax distributor) in Veron, Canada put the Stemmie motorglider exhaust wrap (factory installed) back on when they do maintenance instead of removing it?

Doesn't that go against the SL-914-023? Stemmie has been wrapping for years. After chatting with Stemmie they aren't having melt downs. 

I think the crux of the whole thing is proper installation and proper engine maintenance so that doesn't lead to issues.

Stemme Motorglider certified their aircraft with an exhaust wrap.

Rotax-Owner wrote:

Stemme Motorglider certified their aircraft with an exhaust wrap.

I know, but it's still on there and it works and has been for years. The exhaust pipes don't care if it's certified the exhaust are all the same for all intents and purpose. Certified many times is just recorded extra paperwork over a non-certified.  Flight Design and other MFG's have approvals for the exhaust wrap and it seems to work.

So the question I would ask Rotax is "Why does it work on many and then others get blamed if the exhaust breaks or deforms?" 

.

I think my point is that if you apply it wrong and or have other engine conditions that add to a heat issue then you may have a problem, but with probably thousands that have and still do use it shows it works when used correctly.

This same analogy applies to many engine problems when things aren't done correctly.

Maybe another analogy. Some owners or mechanics don't believe in carb sync and never have done one. Has this ever had a negative impact on the gearbox and have some gearboxes ever been rebuilt because of vibration issues caused by no carb sync vibration? We know it has, but it wasn't the gearbox's fault it failed it was poor maintenance.

Poor maintenance and installations cause issues. 

re: carb heat.

In the absence of any investigation of the subject, if running an experimental, I'd install a coolant based carb heat setup, just like has been on about every car for the past 30 years. Mine has muff heat routed into the standard intake log and I still can get carb ice on occasion.

https://www.aircraftspruce.com/catalog/eppages/15-05919.php