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PostPosted: Wed Jul 24, 2013 8:07 pm 
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Group N

Joined: Fri Mar 31, 2006 7:29 am
Posts: 447
Location: Up North
Car Model: ST205
I was thinking about adding some louvres to the bonnet, probably onto the raised centre section, or alternatively running each side of the raised section. BUT.....what effect would this have of he aerodynamics of the bonnet? it would let more heat out and help keep the charge cooler colder......would it have any detrimental effects.....other than allowing more water into the engine bay.

What does everyone think?

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PostPosted: Wed Jul 24, 2013 8:31 pm 
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Clubman

Joined: Sun Apr 29, 2012 4:23 pm
Posts: 90
Car Model: None
May increase drag slightly but the ST205 bonnet is awful for this anyway.
Probably reduce bonnet stifness which could be significant on a contoured aluminium bonnet but again couldn't say definitively to what degree.
If you locate them too far up the bonnet they could be counter productive as the area covering the top 1/3rd of the bonnet and bottom 1/3rd glass is traditionally a high pressure zone.
Are you looking to increase airflow under low or high speed (50mph+) conditions? Complimenting the natural airflow of the engine bay is an essential consideration if the latter.
Also don't underestimate the water ingress problem. When people remove the engine lid rain try from an mr2 turbo and replace with fans they often report running issues (probably from dizzy cap o-ring missing) and find things such as the injectors rust up quickly and water pools on the cam cover.


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PostPosted: Wed Jul 24, 2013 8:31 pm 
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Club Staff
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Joined: Mon Mar 26, 2007 5:53 pm
Posts: 1736
Location: Another Shire County
Car Model: ST185
The 185 already has louvres in the bonnet (the ones either side that are detachable) to aid heat dissipation.
From what I can see there is no detrimental affect on aerodynamics.
Therefore, I don't see any reason why you couldn't do it on a 205 bonnet.
However, placement would be key due to under/over bonnet pressures.

I'm trying to find somewhere that does/fabricates louvres...
I'm looking to do my front/rear wings "a la DTM" on my project 185 (Heat and water dissipation).

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PostPosted: Wed Jul 24, 2013 10:17 pm 
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Group B
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Joined: Sat Sep 02, 2006 3:13 pm
Posts: 3679
Location: Bournemouth
Car Model: None
It looks to me like the 205 setup is designed to get the heat away from the turbo by the shortest route possible. If you add further exits on the bonnet, some of that hot air will pass to those exits too.

The 185 is a completely different scenario in that the air is meant to go IN through the scoop to cool the charge and then escape any way it can, including the louvres. The engine bay on a 185 is MUCH MUCH hotter than a 205, even with a CS bonnet (which also has air exits either side) where the bonnet vent works in the same way as a 205.

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