Air box hot

[raytoews]

A friend recently bought a Savannah and I have to say it is one of the nicest handling aircraft I have flown.

 

It has a Rotax 914 and I assume a factory air box. Very large and professionally built.

 

An issue we have is the air box temperature is quite hot, 20 degrees above ambient.

 

The baffles are working in fact I disconnected the hose coming from the muffler.

 

The cool air inlet has a scat hose running to just behind the prop.

 

There has to be some power loss by running air to the carbs at 40c.

 

Any suggestions.

 

 

[facthunter]

There will be a power loss for sure. with the air at 40 (or even higher if it's 20 above ambient.). BUT if you fiddle with it and it does ICE you could lose more power. Like all of it. Nev

 

 

[fly_tornado]

install an intercooler, pretty standard upgrade option for turbos

 

 

[raytoews]

Not turbo .

 

 

[mAgNeToDrOp]

I thought the 914 was just a turbocharged 912 (80 hp) ? giving it about 115hp

 

 

[raytoews]

I think they call that a 915 .This one is not turboed. I'll take a picture of the airbox .You can tell me if that is part of the kit .

 

 

[Downunder]

I think the engine he has is a 912(80 or 100 hp) if it is not turboed. 914's have a turbo under the engine with a large aluminium tube coming up and around...that is the airbox.

 

If it is a metal airbox perhaps it could be ceramic coated.

 

The exhaust headers could also be wrapped with exhaust wrap to keep the internal heat down but I've yet to find a wrap that will last long term at the temps these get to.

 

What about wrapping the airbox? Something to stop any radiated heat getting to it anyway.

 

 

 

[facthunter]

The airbox is part of the PLANES design. Isn't it like all aspects of the engine installation in any aeroplane?. Because they run a bit hotter intake air they don't need Carb heat (supposedly). If you fiddle with it you are on your own aren't you? nev

 

 

[Kiwi]

Savannah Airbox....... it has carb heat, and all air is filtered.

 

 

 

[raytoews]

Savannah Airbox....... it has carb heat, and all air is filtered.

[ATTACH=full]61142[/ATTACH]

That is the he same airbox we have . My original question was. Is this normal to see the air temp in the airbox under the filter 20 degrees Celsius above ambient temperature.

This is not right. Every other airplane in the world ducts cold ambient air directly to the carb .

 

 

[IBob]

There is a butterfly valve at the cold air intake of the box.

 

If this is opening fully and the cold air hose is correctly located, then it should be flooding the air box intake with cold ambient air.

 

If it is open, but the temperature is still up, then the the cold air inflow pressure is not enough to prevent warm air coming in.

 

The cold air inlet on Savannahs now comes from a port in the top cowl.

 

 

[IBob]

To put it another way, there are 3 possibilities:

 

1. The temp reading is incorrectly located or not working properly.

 

2. The baffles or butterfly valves are not operating correctly.

 

3. The air intakes are blocked or not correctly sited, so that insufficient cold air pressure/flow is reaching the air box.

 

 

[IBob]

I'm happy to be cautioned or corrected here, Ironpot.

 

It would help to learn why???

 

 

[1Phils]

That is the he same airbox we have . My original question was. Is this normal to see the air temp in the airbox under the filter 20 degrees Celsius above ambient temperature.This is not right. Every other airplane in the world ducts cold ambient air directly to the carb .

I have the same setup and yes it runs hot but it doesn't affect the operation of the motor.

 

 

[facthunter]

It MUST reduce the power available. Nev

 

 

[eightyknots]

It MUST reduce the power available. Nev

What would be a better set-up than the one described above, Nev?

 

 

[Downunder]

Having an airbox that runs hot is pretty much the opposite to why you actually want an airbox.

 

A hot airbox is pointless.....

 

The idea of an airbox is to get cooler, denser (oxygen rich) air to your engine which will give more power.

 

Also meaning you could run at a lower throttle setting for the same power, lowering fuel usage.

 

Most airboxes will have a valve or flap to switch over to hot internal/muffler air to stop or reduce potential carb icing.

 

If your airbox is working correctly you WILL notice a drop in rpm when changing over to hot air as less power will be produced.

 

This is the easiest way to test an airbox. If there is no rpm drop something is not working correctly.....

 

 

[Kyle Communications]

Thats a 912 not a 914...no turbo The airbox is 912 airbox..so either a 80hp or a 100hp ULS

 

 

[Kyle Communications]

The orange scat tube hole should always be closed if you do not have carb heat pulled on

 

 

[facthunter]

The hotter the intake air the less power you will make. MASS airflow. Carnot cycle has temp change as index of efficiency. Nev

 

 

[crashley]

My RV12 doesn't have an airbox It has airfilters mounted directly on each carby so the air into the engine is drawn from the area around the engine I have measured it and it varies between 40 and 60 degrees so I am loosing a lot of potential performance I would like to change it but It is a big job because I would then have to make a carby heat system

 

ashley

 

 

[Downunder]

My RV12 doesn't have an airbox It has airfilters mounted directly on each carby so the air into the engine is drawn from the area around the engine I have measured it and it varies between 40 and 60 degrees so I am loosing a lot of potential performance I would like to change it but It is a big job because I would then have to make a carby heat systemashley

A friend put a Foxbat airbox on his Highlander. It comes with a valve and cable mechanism inside the airbox.

It is quite compact and the hot air intake can be just a hose directed at the muffler.

 

An added bonus is that it uses the standard conical air filters.....

 

The important measurement is the carb to firewall clearance I guess...