Bonnet Raisers

[ilogikal1]

[un1eash]

You see it quite a bit down Santa pod, friends 600+ bhp RX7 has it. I did see it on a Focus ST the other day though which didn't look right.

[Tarmac@TarmacSportz]

 

Hmm wheres the MARMITE smiley,

 

Actually no, I quite like Marmite, not convinced on this but interested in seeing the pics.

[The Chubby Ninja]

I was actually thinking about doing this too to try and let more air flow through the intercooler but could never decide whether it would look good or not. put some pics up if u go for it . I like things a bit different from the norm, not just the usual spacers and stubby mods that are the only ones normally allowed on the forum

[LloydV]

from what ive heard, generally it makes air flow worse, only reason to do it is to make more space under the bonnet. but who knows i may have been informed wrongly!

[AliveBoy]

from what ive heard, generally it makes air flow worse, only reason to do it is to make more space under the bonnet. but who knows i may have been informed wrongly!

 

Heard the same, there was an article which I saw ages ago about the high and low pressure areas it creates. Can't remember where I saw it to dig it out though.

[The Chubby Ninja]

I cant see how it would make the airflow worse but at least it would defrost your windscreen quicker, although you would need to drive about with your head out the window to get the air flowing . dedman has a point about it being dangerous if you crash

[OllyB]

I may be wrong but when driving the turbulence there will cause a high pressure region and possible actually cause air to flow into the engine bay.....

[The Chubby Ninja]

maybe, id like to see it tested in a wind tunnel to see if it is actually any use

[OllyB]

Bonnet vents are more effective as they actually draw the air out of the bonnet as it passes over the top. With risers youve got an opening right where the air hits the windscreen which will cause it to split and push in both directions, normally this just goes up the windscreen but with an opening there the air will flow into the engine bay. Path of least resistance

[jumping350]

For £8 a go i doubt it would get any wind tunnel testing lol

[AliveBoy]

http://www.teirney.net/civic/BonnetSpacers.htm

[GT4 Zed]

Olly is right the raised bonnet will not aid cooling but would make it worse.

The bonnet vents remove air through the Venturi principle as the air rushing above creates low pressure. The angle between the bonnet and windscreen is a high pressure area with turbulence and will impair air venting out off the engine bay from the top. It will also decrease radiator efficiency as air is trapped within the engine bay.

However most of the cooling happens at the underside where low pressure air suck air out of the engine bay through a well designed under stray. So similarly if you ran without your engine under tray you would not only affect the aerodynamics but cooling too.

 

[OllyB]

Physics is allot like me.

 

lazy

[Ekona]

Anyone who does this mod is a complete and utter mongbucket of the highest order. I've never seen anything more stupid in my entire life, and I've watched Hollyoaks since it started.

[GT4 Zed]

Dan, you have an eloquence I admire

[AliveBoy]

I was looking at having louvres put into my bonnet to get hot air out, but decided against it as I couldn't guarantee it would work.

[mattross1313]

Anyone who does this mod is a complete and utter mongbucket

 

Best insult EVER!!! Kudo's Dan!

 

I'm not sure on the raised bonnet on a Zed, if it has gnarly bodykit then it could work really well (by work, I mean look). I agree that it won't do wonders for air flow.

However this is the same sort of argument I used to see on the MR2 forums. When people fitted those snorkels over the roof to push more air down into the induction, or onto the SMIC. If anything all this air being rammed in from the top of the engine used to ruin the air flowing in from the side vents behind the doors. Which then leaves all the hot air swirling around the engine.

[ilogikal1]

Bonnet vents are more effective as they actually draw the air out of the bonnet as it passes over the top. With risers youve got an opening right where the air hits the windscreen which will cause it to split and push in both directions, normally this just goes up the windscreen but with an opening there the air will flow into the engine bay. Path of least resistance

 

Strictly true about the vents, but it won't necessarily decrease under-bonnet temperatures.

Air like water always flows downhill. Downhill in terms of air is from a high pressure area to a low pressure area. The area above the bonnet vent is low pressure and this pulls air out of the engine bay. This is not necessarily good. Air is pulled out of the engine bay, no cold air is pulled in through the same gap, and pulling the air out of the engine bay in this area interrupts the air flow as Nissan designed it in through the front/underside of the car.

 

Vents (unless designed specially and very precisely), as with raisers, will stifle the airflow efficiency and actually increase under-bonnet temps.

[OllyB]

Bonnet vents are more effective as they actually draw the air out of the bonnet as it passes over the top. With risers youve got an opening right where the air hits the windscreen which will cause it to split and push in both directions, normally this just goes up the windscreen but with an opening there the air will flow into the engine bay. Path of least resistance

 

Strictly true about the vents, but it won't necessarily decrease under-bonnet temperatures.

Air like water always flows downhill. Downhill in terms of air is from a high pressure area to a low pressure area. The area above the bonnet vent is low pressure and this pulls air out of the engine bay. This is not necessarily good. Air is pulled out of the engine bay, no cold air is pulled in through the same gap, and pulling the air out of the engine bay in this area interrupts the air flow as Nissan designed it in through the front/underside of the car.

 

Vents (unless designed specially and very precisely), as with raisers, will stifle the airflow efficiency and actually increase under-bonnet temps.

 

Agreed, also may pull hot air from the bottom of the engine/headers over the intake and raise intake temp, robbing bhp....

Edited November 22, 2013 by OllyB

[Richf]

Can actually cause the gearbox to overheat as well , totally pointless IMO

[ZEUS]

Anyone who does this mod is a complete and utter mongbucket of the highest order. I've never seen anything more stupid in my entire life, and I've watched Hollyoaks since it started.

:lol: Brilliant

[glrnet]

Held you in higher esteem than that Dan