ye olde chestnut

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Originally Posted by rick130

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Airflow isn't always what it seems

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Yes. I am reminded of the Britten Norman Islander aircraft. Not long after it went into production the BN-2 was replaced by the BN-2a. The only difference was a changed profile of the rear of the engine housing, from duck tail to a wedge, and a fairing added to the undercarriage legs to increase the chord by about 30%.

The result was a marked increase in short field performance, despite an increase of 5% in both gross weight and load capacity (the modifications had no significant weight penalty). Just reduced turbulence round the engines and undercarriage legs.

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Originally Posted by rick130

Airflow isn't always what it seems

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Thats exactly it. I smirked when Cadogee was into 3nuts about not knowing about the aerodynamics, but falling victim to his own accusations.

I think fluid dynamics is incredibly interesting but what people think they know really has to be tested via CFD or in a wind tunnel because subtle differences like windscreen rake (its a bit more than that), floors etc make such a big difference to flow, drag numbers, lift and aero balance.

Point it out to him. [bigwhistle]

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Originally Posted by p38arover

Point it out to him. [bigwhistle]

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It'd be waste of my time I suspect.

To be honest Ron I see a fair bit of information that I know is wrong and I'm sick and tired of having the arguements with people that think they know, but haven't done the testing. So incorrect information then starts to get perpetuated, gains a critical mass and then becomes incorrect gospel. Incorrect information does my head in, and that other people then take that in good faith only to find out that its incorrect and it just cost them a lot money.... maybe $2500 on a set of tyres that scrub, and then probably don't even get the merest of apologies for their loss. There comes a point where you just have to say.... well I hope they fully research that before they cough up. Cadogee's and 3nuts discussion at the very least is inconsequential to virtually everybody and I have no doubt that he wouldn't hear it or reply to it anyway.

Don't we need low pressure behind the radiator so air from the front is pulled through the radiator to increase cooling? If there was high pressure behind the radiator, such as from a forward-facing bonnet scoop, wouldn't hamper airflow through the radiator and engine temperatures would rise? Having vents in the mudguards back near the doors lets air escape and adds to the low pressure effect. Isn't that right?

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Originally Posted by DiscoMick

Don't we need low pressure behind the radiator so air from the front is pulled through the radiator to increase cooling? If there was high pressure behind the radiator, such as from a forward-facing bonnet scoop, wouldn't hamper airflow through the radiator and engine temperatures would rise? Having vents in the mudguards back near the doors lets air escape and adds to the low pressure effect. Isn't that right?

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If you check out the simulation 1 and 3 on the previous page you will see that there is pressure drop under the car in relation to on the nose which will move the air through. Gills really are just cosmetic and probably just vent pressure from the inner guard. Interestingly Toyota generate the same effect by the shape of the top rear of the guard.

https://www.superiorengineering.co/w...er-71357-1.jpg

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Originally Posted by rick130

Airflow isn't always what it seems

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Tell me about it,i am sure you also have spent half your working life playing with all types of airflow......[bighmmm][biggrin]

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Originally Posted by scarry

Tell me about it,i am sure you also have spent half your working life playing with all types of airflow......[bighmmm][biggrin]

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Yep.

It was also really interesting to see what worked and didn't on race cars where aero stuff was pretty much banned.
Rad placement, boundary layers, side pods, strategic holes, all trying to make a car slipperier.

Even airflow going into the engine.
One dyno gain still has me a little stumped.
I was tasked with fabricating a new mounting so we could turn a K&N 90° to fit inside a new air box design that the engineer hoped would work better on the track. (Shaped a timber buck and then hand beaten aluminum base. It looked like a pressing when finished [emoji4])
Just turning the air cleaner picked up nearly 2HP.
We didn't believe it so removed it, fitted the old PiperX, (yuk by the way) fitted the K&N the way it was designed and even removed it.
The new orientation picked up power over no air cleaner. The standard K&N mount and no air cleaner are equal in HP/torque, the PiperX was worse than any other combination we tried.
It was changing the airflow as it entered the carby venturi.
Stunned but happy!

In those days only F1 and the big Sports Car builders had CFD

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Originally Posted by rick130

In those days only F1 and the big Sports Car builders had CFD

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I'd never thought about that, if they use CFD with the engines, but it makes sense.