GolfGTIforum.co.uk
Model specific boards => Golf mk5 => Topic started by: RedRobin on 08 April 2008, 12:27
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When I changed my bonnet to an OSIR carbonfibre one (with no real justification!) I had the opportunity to get the first one in the UK with a vent. The vent is above the turbo area - A well-known hotspot but, although the steel bonnet would get warm/hot all over after a good run, overheating was never a problem. I've had the vented cf bonnet for a few months now but have felt (unscientifically) that my car has tended to feel she's flying quicker since. I put it down to cold weather possibly delivering cooler air.
I've noticed that after a long run, heat can be felt from the vent but the rest of the bonnet is cool to touch. This has got me wondering if this minor mod of a vent actually has a more significant benefit than I realised it would have. Does it also contribute to expelling air from the whole engine area and hence more efficiently draw air in from the grills and intake?
Does anyone have any knowledge about the effect of vents please?
(http://i22.photobucket.com/albums/b308/RedRobin_05/RED_vent_closeup.jpg)
(http://i22.photobucket.com/albums/b308/RedRobin_05/RED_vent1.jpg)
(http://i22.photobucket.com/albums/b308/RedRobin_05/RED_MySpace_Feb08.jpg)
Thanx :smiley:
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I have no idea to be honest. I would say that it makes sence for the air to be passed through easier and these is no 'dead end'. How much this would make a difference to intake temps would only be solved with a roalling road session..... probably. :huh:
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You'll probably find that a non-vented carbon fibre bonnet is cool to touch too, and I look forward to seeing you and Hurdy not only admiring each others rear ends but also caressing each others front ends on Sunday to compare :cool:
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You'll probably find that a non-vented carbon fibre bonnet is cool to touch too, and I look forward to seeing you and Hurdy not only admiring each others rear ends but also caressing each others front ends on Sunday to compare :cool:
....You're a voyeur!! ONLY hot females have permission to touch my end!!
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Get a room you guys :grin:
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In my opinion the performance must be increased with the vent in place.
Its like a computer, the colder you keep its working parts the better it will run.
Surely the same can be said about the engine/turbo.
?????
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In my opinion the performance must be increased with the vent in place.
Its like a computer, the colder you keep its working parts the better it will run.
Surely the same can be said about the engine/turbo.
?????
thing is with a computer, the hotter the bits the worse the power efficenty, not actually directed at the metal and moving parts... a car has those, so mayb not as similar as it seems.. but yeah if its keeping the engine cool, and i would have though carbon fiber is better at that then steel anyway. it can only be a good thing..
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....Yes, logic definitely suggests strongly that coolness and air flow is generally improved and consequently there may be some performance benefit. But it won't compare to what a front-mounted intercooler (FMIC) should deliver.
If Hurdy will let me touch his front end on Sunday, I'll check if he finds a carbonfibre bonnet stays cooler. I guess that a steel bonnet will soak and retain more heat than a carbon one and consequently keep the engine bay relatively warmer - But the differentials won't be substantial I expect.
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You'll probably find that a non-vented carbon fibre bonnet is cool to touch too, and I look forward to seeing you and Hurdy not only admiring each others rear ends but also caressing each others front ends on Sunday to compare :cool:
Ooh err missis :embarassed: :laugh:
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the only benefit i can see the bonnet having is the weight saving over the standard one, is the MK5 GTI bonnet actually made of steel and not ali?
regarding air flow, i can't see it really making anyodds as the vent faces backwards, which is only going to allow air to escape (eg not cool air being drawn in) and becuase the car's going to be moving forward this air would have been pushed back through the standard vents anyway
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<insert long boring rabble about syphonic effects and drag>
it will improve airflow, but to what extent i wouldn't even want to guess... i think you can get temp readings from vagcom though, could be interesting to compare a standard gti against robins.
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The only true way to find out would be to rolling road test it. It may have a minimal effect, but the bonnet on a car is hardly airtight anyway. It does make sense to have the vent letting out hot air rather than taking in cool air as most of the cooling is done by the intercooler, but the heat that is generated could be pulled away faster by a vent.
RR does your car still run at 90 degrees when warmed up? - I suspect it will and therefore the benefit is negligible.
Looks mint though :cool:
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<insert long boring rabble about syphonic effects and drag>
it will improve airflow, but to what extent i wouldn't even want to guess... i think you can get temp readings from vagcom though, could be interesting to compare a standard gti against robins.
vagcoms only going to give you the coolant temp isn't it (not sure what sensors you've got in the MK5)? at which point the thermostats going to be keeping the engine at 90, so could mean the radiator doesn't have to do as much work if the cooling improved?
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When in motion surely the vent will be sucking cold air in ?
Dont quote me but I remember reading something about bonnet vents and majority of people thinking they would help release the hot air when in fact when moving the draw the air in - like when you open a sunroof on tilt you feel a draft coming in not out ...
I could be talking bollox though :huh:
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Look at his vent in the full bonnet pic Neg, it's facing the other way to draw air out :wink:
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it will not make any difference what so ever, that you can possibly feel!!
looks AMAZING thow and i want one, couldnt afford one at the moment thow :sad:
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....Good point about the temp gauge at 90, Hurdy - I'll check it out.
It seems that IF there is any benefit, it's only subtle or very slight although the whole engine bay has felt cooler when I've opened the bonnet after a run. Yes, even though I say it myself, it does visually look cool :cool:. Nothing wrong with some nice eye-candy :evil:.
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....Good point about the temp gauge at 90, Hurdy - I'll check it out.
It seems that IF there is any benefit, it's only subtle or very slight although the whole engine bay has felt cooler when I've opened the bonnet after a run. Yes, even though I say it myself, it does visually look cool :cool:. Nothing wrong with some nice eye-candy :evil:.
Wait till you see my all new eye candy on Sunday :evil: :wink:
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Wait till you see my all new eye candy on Sunday :evil: :wink:
....Methinks we should try and park next to each of on our stand - A carbonfibre fest!! :evil:
[I'm visiting the TTshop tomorrow]
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Wait till you see my all new eye candy on Sunday :evil: :wink:
....Methinks we should try and park next to each of on our stand - A carbonfibre fest!! :evil:
[I'm visiting the TTshop tomorrow]
OHHHHHHHHHHHHHHHH my new bit is much sexier than carbon fibre :rolleyes:
and you'll have to wait and see on the day :wink:
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Just a thought, but doesn't steel (or alu) conduct heat? Wouldnt any heat build up in the engine bay be conducted (or radiated)
out (as heat rises) from the bonnet into the atmosphere?
As far as i understand, doesn't carbon fibre insulate, not conduct? Carbonio make a point of this by stating they dont transfer heat from the engine bay into their intake to allow colder air in to combustion, making it denser and more potent.
Quote
"Unique Thermal Barrier composite construction ensures low inlet temperatures"
I'd guess any performance gains would be power to weight, i.e. the CF bonnet weighs a lot less? Or perhaps the vent is introducing the "Venturi" effect, and sucking cooler air in?
Only my thoughts! :grin:
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Just a thought, but doesn't steel (or alu) conduct heat? Wouldnt any heat build up in the engine bay be conducted (or radiated)
out (as heat rises) from the bonnet into the atmosphere?
As far as i understand, doesn't carbon fibre insulate, not conduct? Carbonio make a point of this by stating they dont transfer heat from the engine bay into their intake to allow colder air in to combustion, making it denser and more potent.
Quote
"Unique Thermal Barrier composite construction ensures low inlet temperatures"
I'd guess any performance gains would be power to weight, i.e. the CF bonnet weighs a lot less? Or perhaps the vent is introducing the "Venturi" effect, and sucking cooler air in?
Only my thoughts! :grin:
Exactly what I was thinking!
Johnny Ball would be proud!
:cool:
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....Swings 'n Roundabouts re carbonfibre vs metal bonnet insulation from/to the outside. I think that the vent is very likely to promote a 'Venturi' effect.