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Discussion Starter #1
I'm not sure if anyone can help but I have a question about airflow under the bonnet. As this affects the engine more than anything else I thought I'd post it here.

As I understand it the back of the engine gets quite a bit hotter than the front due to the restrictions on airflow through the engine bay. This is not good for performance (particularly under pressure). As the air enters the engine bay at the front it is hit by the radiator now, as we all know you need to put a fan behind the rad to draw the air through otherwise it would stall and you would form an air dam in front of the car. Therefore no air for the engine at all.

As the air enters the engine bay it is split between the rad and over the rad. I can understand those who install a plate to direct most of the air through the rad would get less turbulence under the bonnet and, hopefully, make a bit more of a difference to the radiator cooling. My question comes after that.

As the air enters the engine bay it becomes very turbulent. Once air behaves in this way it is extremely difficult to get it to calm down again. To prevent this from happening you would need to channel the air. The best way to do this is to reduce the pressure at the back of the engine bay thus drawing the air from the front to the back. As I can see the easiest way to do this would be to install some strips above the engine/below the bonnet that start at the width of the front opening and then curve away towards the back.

This should encourage more air to the back of the engine and thus help keep a more balanced temperature across all cylinders. In addition, reducing the turbulence under the bonnet will reduce the drag the car experiences.

I accept it is not just a matter of installing a couple of strips under the bonnet. There will need to be a rolloff designed around the lower end of the strip but, the aerodynamics of this are all quite rudimentary and already understood.

My question is this.
Has anyone ever done this sort of thing before or have any experience of doing something similar.
 

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Sounds interesting....but i've never done anything like that. I have recently fit a radiator shroud though...hope that helps things a bit
 

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Airflow under the bonnet

Hi,
Please don`t fit any direct airflow piping to your air filters like I did as they direct WATER straight into your engine.I know there are some kits available but I think unless you are running massive BHP then I wouldn`t bother.You could go for a Nismo 400R bonnet,it may solve your worries about engine airflow as it has a huge air vent in the middle & looks fantastic.

Good Luck,
Henry
 

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Henry, the NISMO bonnet is excellent but rather expensive. How about Top Secret?
 

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Underbonnet Temps

<<- Mine turned up like this (the triangles are grilled), done I suspect to ensure air kept moving on throught the intercooler/oil cooler/rad sandwich. I am less concerned with passing air over the engine as it is mainly cooled by the oil and water... I am slightly more concerned about the induction temperatures as pretty much all the air in the engine compartment has come through two or three "air heaters". I may consider instaling an air scoop, to increase the flow of clean, cool air to the cones.

I'd be interested in what you guys think,

Cheers,

Dave
 

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Discussion Starter #8
Air scoops

Dave C, - You mentioned air sccops to keep the engine cooler. I was talking to a part time racing driver friend on this very subject, when we came to the following conclusions.

If you can install air scoops underneath the car you could direct the flow of air up and into the engine bay. This would have several effects. Firstly it would force the warmer air out of the top of the engine bay thus taking heat away. Secondly it would remove the air flowing under the car (for best results just behind the front wheels). This would cause lower pressure underneath the car and higher pressure from the windscreen back, the overall effect being more downforce.

The only problem I see is not losing the air scoops on the UK raods, so our thoughts are this would be a track-day only modification. It could be easily done with the correct arrangement of pre-drilled hols and securing pins etc.

I'll let you know how we get on. Now all I need to do is convince someone with a wind tunnel to let me try it out. I'm already on the case.:smokin:

John
 

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r33....nice!:)
I s that made from FRP???

....the reason why the 400R bonnet is so expensive is that its made from carbon fibre...plus I think its very hard to find!
 

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Sirvroomm, sorry I don't know Top Secret's URL.
DCD, yes, it's FRP. And it's cheap as hell! The whole cost of including shipping (to S'pore) and paint job is only around 700 quid. The carbon fibre looks really cool. Electra quoted about 1700 quid. The design is the same and the weight is just about the same too - about 3.4 kg.
 

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Yes it is very nice...I saw it on a white 34 a while back.
The carbon ones are a pain to paint...plus I reckon they look rather nice with just a few hands of clear finish.
I loooove the Nismo Z-tune bonnet...but my fear is always if water getting in to the engine bay...plus its way too expensive:(
 

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Discussion Starter #15
£500-£600 sounds a lot for a sheet of plastic. And that doesn't include getting it here.:(

Maybe one of the chaps going to Japan in January will take a big suitcase :)
 

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It's not that expensive for a bonnet. I think its actually the cheepest one!!
If you wan carbon...now that gets expensive!:eek:

Have you had a look at Electra? They make loads of body parts, they specialize in carbon bits, but they might have some FRP
 
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