High Airbox Temp

[Jon Bown]

Doing engine runs before its first flight i have noticed that the airbox temp gauge creeps up to 39 deg at over 4500 rpm is this normal when the plane is not moving forward or is there another problem. Water temp 85 deg and oil temp 90 deg. My top cowl has an open slot in it, tried blanking off made it worse.

[K5054]

Mine in my savannah used to do the same on a hot day. If CHT/water temps are ok (as well as oil temps) it should be fine. Detonation is the main concern but it is to a lesser extent on water cooled heads. Use as high an octane as you can (98) to help against detonation and monitor engine temps.

[facthunter]

With airbox temps like those there would have to be a significant power loss. A temp indication for Carb body wouldn't go astray..Nev

[Jon Bown]

Mine in my savannah used to do the same on a hot day. If CHT/water temps are ok (as well as oil temps) it should be fine. Detonation is the main concern but it is to a lesser extent on water cooled heads. Use as high an octane as you can (98) to help against detonation and monitor engine temps.

Thanks for the info. Yes Water temp around 90 oil temp low may need to blank off oil cooler if not reach 90 in flight. Hoping just heat sink from no forward motion, also my need to check gauge.

[Jon Bown]

With airbox temps like those there would have to be a significant power loss. A temp indication for Carb body wouldn't go astray..Nev

Yep I agree

[Thruster88]

My basic aeronautical knowledge says about 1% power loss for each 2.5°C above ambient temp.

[IBob]

Hi Jon, you don't say which model Savannah you have.

The S has a Nascar type air scoop on the top of the cowling, and on mine there was a gap of approx 40mm between that and the port on the airbox. I noticed that during a hard climb I was getting rising airbox temperatures, and figured that the airbox was drawing air via this gap from under the cowling, instead of from outside the cowling, due to the different airflow over the cowling.

I fixed it by extending the airbox port towards the scoop with a strip of aluminium wrapped round the port and held in place with a hose clip, but still leaving a small gap so that any rainwater pooling on the ground would not make it's way into the airbox.

It sounds as though you are getting something similar during your ground runs.

[facthunter]

When you leave the button/lever in hot with a certified and effective system you don't have much performance. I ALWAYS go Throttle open CHECK Carb heat cold

.Nev