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Bonnet shaking at high speed

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Old 20 April 2013, 11:40 AM
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Scooberpete
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Default Bonnet shaking at high speed

Yesterday on my first trip out on the autobahn. I was doing about 120mph when the bonnet started to shake. I'm guessing the scoop provides a certain amount of lift at this speed. Has anyone else experienced this? Any cure needed?
Old 20 April 2013, 11:43 AM
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4evernewbie
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My classic does this also.
I've purchased some aero bonnet catches but not fitted them yet.
Also on the "autobahn" my bonnet stayed attached at 160 so I wouldn't worry too much

Paul
Old 20 April 2013, 11:45 AM
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aero catches or bonnet pins bud. the catches look better than the pins.
Old 20 April 2013, 11:49 AM
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Rodger!! Many thanks.
Old 20 April 2013, 01:58 PM
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Markyscoob
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Not the scoop! The air passing over the front of the bonnet turns and increases speed as it passes onto the bonnet. This causes a pressure drop and temperature drop according to classic Benoulli's theorem. The low pressure pulls the front edges of our lightweight alloy bonnets up. At 120mph the outer front edge sits about 1" up from usual. Quite worrying.

I also will go down the aerocatch route but my Hawk is a bit too new to be devalued like that yet.
Old 20 April 2013, 02:04 PM
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But surely as long as it doesn't/won't flip that's all that matters. Very interesting tho thank you.
Old 20 April 2013, 02:59 PM
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logger
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Had the same myself, wont be as bad once i get a front mount as im gonna fit a reverse scoop. But i still fancy some, where is the best place to get them ?
Old 20 April 2013, 05:58 PM
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CREWJ
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Does it have any slack if you push down on it?

A possible simple fix would be to adjust the bonnet adjusters. The rubber thingies behind the lights are a screw fit that you can raise and lower.
Old 20 April 2013, 06:07 PM
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Had same problem. Aerocatches sorted it
Old 20 April 2013, 06:27 PM
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how much did it cost to get the catches fitted tommy or did you do them yourself?
Old 20 April 2013, 06:34 PM
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Originally Posted by yabbadoo4
how much did it cost to get the catches fitted tommy or did you do them yourself?
Mattyb fitted mine. I dont like cutting holes in my car.
Old 20 April 2013, 07:26 PM
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Originally Posted by tubbytommy



Had same problem. Aerocatches sorted it
Where did you get them from bud?
Old 20 April 2013, 09:24 PM
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Just as a side note, Scoobs don't like prolonged high speed without FMIC and Oil coolers.

As your in Germany where from personnel experience it gets bloody hot in summer, you might want to look into this if your planning on making it a regular thing.
Old 20 April 2013, 09:30 PM
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Newbie here FMIC?
I generally don't run at that speed, (the wife gets angry really quick if I do)
70-90mph normally.
Old 20 April 2013, 09:35 PM
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Originally Posted by Scooberpete
Newbie here FMIC?
I generally don't run at that speed, (the wife gets angry really quick if I do)
70-90mph normally.
Front mounted intercooler. The silver bit behind the grill at bottom of my bumper
Old 20 April 2013, 09:41 PM
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Rgr makes sense. Just wasn't sure of the abbreviation is all thanks.
Old 20 April 2013, 10:18 PM
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Originally Posted by tubbytommy



Had same problem. Aerocatches sorted it
Pic *****.
Old 20 April 2013, 10:34 PM
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you dont need bonnet catches to devalue a hawk.... just own it... it devalues all on its own.
Old 20 April 2013, 10:41 PM
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My bonnet was lifting bad on a top speed run so we removed the scoop and it cured it, my car now runs with a reverse scoop and I have never seen this problem since
Old 20 April 2013, 10:54 PM
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Rbon91
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Originally Posted by tubbytommy



Had same problem. Aerocatches sorted it


Where you get your hella horns from mate?
Old 21 April 2013, 01:57 AM
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be carefull if you fit them yourself, lining them up is a pita on a hawker cos of the bonnet shape.
Old 21 April 2013, 05:50 AM
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94impreza
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Are the locking ones the best?.
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