Under Bonnet Temperatures

[Styria]

We all are familiar with the fact that under bonnet temperatures can reach quite high levels. Come to think of, so do outside bonnet temperatures to the extent that one can hardly touch the bonnet to check oil or water levels after, for instance, you have been on a high speed country drive.

I distinctly remember a return trip from Brisbane to Sydney on a particularly hot summer's day. The temperature would have been about 35 degrees (NOT Fahrenheit) and half way back at Coffs Harbour, I was just going to have a peep under the bonnet. Imagine my surprise - the bonnet and catch were so hot that you couldn't even touch them. Yet, doesn't it make you wonder how components can continue to work efficiently, despite all that heat, plus rubber, plastic and all other associated components that need to work properly to keep the car running ! I am sure that most of you are familiar with frying sausages on an exhaust manifold. Many years ago, a Rover P4 owner was quite smug in letting everyone know that he was going to cook his snags whilst driving to our destination. With great expectation he opened the bonnet (with every one looking on, of course) and picking off black cinder off the manifold. Not a sign of any snag, but just hyaneous laughter by the group hanging around ! Regards Styria

N.B. I am sure it sounded like hyenas laughing.....

 

[Patrick_R]

Good post Styria.

I can just imagine the by then hungry driver looking forward to his sausages, only to find burnt offerings.
What a disappointment

In the truck world we are running some very high temps inside the engine for thermal efficiency (along with fuel pressures) to ensure the correct & full burning of fuel to keep the oxides of Nirogen (NOx) at legal levels. We also have to manage soot.

The amount of under cab lnsulatuon (as the drivers sit on top of the engine) is huge to stop heat transfer into the cab.

Our latest engine from Volvo Powertrain even has a clutch on the water pump to cycle it in and out of operation to ensure cooling is kept at a very accurate level.

 

[sean sherry]

The way to best performance is a Cold Air Intake and an 82 degree Thermostat to run the Engine at the best temperature for maximum Power. Hot air expands more to push the Piston down. My 1500cc MGA also had an extractor Manifold and electronic Ignition with a higher MGB Diff. Was still accelerating at 80 MPH .Sat Nav reading. An after market crossflow alloy Head would have been even nicer. A cooler thermostat will not fix a Radiator problem !