anyone got a steady hand ??

[SGHOM]

or nerves of steel ??
I know what you felt like now Dave !! /yes /yes :embarasse /help

[Wouter]

/gulp....... :inquisiti

Erhm.... excuse me Mr SGHOM......

I think you need a few pints to steady your hand...... :chugchug:

[SGHOM]

I've got to let the hot air out somehow ?? :rolleyes4
It's been masked up now for 2 hours, & i've not had the bottle to drill the pilot holes yet !! :embarasse I've been painting my wheels & just staring at it ! /help

[Spirit]

If you're not confident Derek, then you could always try Heath's little tip for now.....remove the rubber strip along the back of the bulkhead.....it should help a little.

[SGHOM]

If you're not confident Derek, then you could always try Heath's little tip for now.....remove the rubber strip along the back of the bulkhead.....it should help a little.
I am confident........... & the rubber strip is long gone !! /yes
It's just started raining though ! :embarasse

[Wouter]

It's been masked up now for 2 hours, & i've not had the bottle to drill the pilot holes yet !!

Don't sweat it.... you made the other vents, and they look good! :thumbsup:

What is the worst that can happen? you may have to talk to Mo about a new bonnet!

Good luck and let us see the pics!

[SGHOM]

he who dares ?? :rolleyes4
It's pretty easy cutting through, I just wish I'd made the corners a bit rounder. the jigsaw is not too keen turning on a sixpence !! [ 5p actually ! ]

[Wouter]

Cool!!! :thumbsup: :thumbsup: :thumbsup:

I hope it has the desired affect!

[SGHOM]

looking meaner all the time !! :evil2: :evil2:
just a bit of straightning up to do, then a sliver of chrome strip around the edge, & some fine mesh glued in ! /yes
waddya fink ??

[Nick Mann]

Glad to see the strut brace is still in one piece!! :rolleyes4

Go for it mate, you know the blingometer is going up all the time!! :smug:

[SGHOM]

1.5mm red & earth, singles lighting cable !! :rolleyes4
strip the cores out, bung a bit of glue inside the outer sheathing, & hey presto !! /yes /Steeringw

[ANTHONY]

very nice:thumbsup:

[BraindG]

You know what?! that looks alright Derek! top job :)

[Physician]

Very good Derek ......... I'm impressed /yes

[Kenneth]

Sorry to be negative, but what are you trying to achieve with those vents?

Seeing as that part of the bonnet is a high pressure area, you will not get extra cooling unless pretty much stationary. down side is that you will probably increase air pressure under the bonnet at speed, which reduces the effectiveness of your radiator and intercooler.

I do think they look good though.

[Kieran]

Seeing as that part of the bonnet is a high pressure area, you will not get extra cooling unless pretty much stationary. down side is that you will probably increase air pressure under the bonnet at speed, which reduces the effectiveness of your radiator and intercooler.


Wont the air coming through the front of the car use those holes as an escape route then?

[SGHOM]

Sorry to be negative, but what are you trying to achieve with those vents?


.
It's ok getting cold air in to the engine bay , but It has no effect unless it has somewhere to go !!
with a sealed bonnet, the temperatures are too high. /yes removing the rubber strip helps................................. ask HJM ! /yes
but providing ventilation will help even more.

[Big Ian]

look's quite good Derek nice job :thumbsup: ...also you could have got these on ebay and done a similar job Vent's (http://cgi.ebay.co.uk/50CC-PIAGGIO-NRG-FRONT-PANEL-PAIR-AIR-VENTS-GRILLS-NEW_W0QQitemZ7995432078QQcategoryZ25640QQrdZ1QQcmd ZViewItem)

[SGHOM]

look's quite good Derek ]


only 'quite good '?? :embarasse :embarasse

those vents cost £5 ? way out of my price bracket !! /yes

[Big Ian]

only 'quite good '?? :embarasse :embarasse


oop's i was sleepin then!......that look's FKN AWESOME Derek :thumbsup: , hope it does the trick
(don't know why you just don't take the bonnet of for "The Pod"? /Hmmm )

[SGHOM]

(don't know why you just don't take the bonnet of for "The Pod"? /Hmmm )


just the bonnet ?? :rolleyes3

[BraindG]

that look's FKN AWESOME Derek :thumbsup: ,

Ah, see, now thats better :)

[Quail]

Jobs a good'n mate! Nice DIY

[Kenneth]

It's ok getting cold air in to the engine bay , but It has no effect unless it has somewhere to go !!
with a sealed bonnet, the temperatures are too high. /yes removing the rubber strip helps................................. ask HJM ! /yes
but providing ventilation will help even more.

there are 2 ways to cool something (that I can think of just now anyway... still a bit jet-lagged...)

1) draw heat away by giving the hot air somewhere to go (convection/radient loss of heat)
2) force colder air against/past the hot object

eithier way you require movement of air.
To move air you need a high pressure zone and a low pressure zone. Air then moves from high pressure --> low pressure. If the pressure equalizes in both zones, you get no air movement. Net result is that your cooling is less efficient than could be.

My understanding of bonnet vents (not scoops) is as follows...
Vent is placed near the front of the bonnet as this is a low pressure zone (pressure drops when air has to move over a curved surface, ie: from front of the car around the bonnet lip and onto the bonnet) which means air is "sucked" out from under the hood when the car is moving
This lowers the pressure under the hood, which has the effect of increasing the pressure differential between the front of the intercooler/radiator and the back. result is more air flow through the intercooler and ratiator, and therfore better cooling.
If you draw air INTO the engine bay, then you literally reduce the effectiveness of your intercooler and radiator. When you open up a high pressure zone to your engine bay, then you essentially do this and risk the pressure inside the engine bay increasing to the point where there is NO air flow across the radiator and intercooler

When stationary, you want vents that allow the hot air to rise out of the engine bay creating a convectional air flow which cools the engine/turbos.


That said, I cannot say if your setup is going to help or hinder the cooling of your engine bay, but logic says that you should aiming to reduce the pressure in the engine bay compared to your high pressure zones (main one being front of car)

My understanding is that to reduce the pressure, you need create low pressure zones that fecilitate air flow.
I also understand that the main low pressure zones are created at the front of the hood, and under the car by having a well designed under-tray.

To be sure of effectiveness I expect that you would need to measure the pressures involved to discern positive or negative change


I ramble... sorry if I have been a bit of a bore.

[Kenneth]

I would like to make it clear that I do not mean to be negative about your mod, but I feel that sharing of knowledge is important and one of the whole points in having a community of people to discuss stuff with. (I believe I have an understanding of the aerodynamics involved, though I don't claim to be an expert)

I do like the way they look, and have actually thought about bonnet vents such as you have... Your implementation is very good as I think the shape suits.

My thoughts on the functional use of such vents would be to shield the back turbo so as to isolate it from the engine bay using the vent to allow heat to escape. That way when stationary the heat would rise out of the engine bay and when moving the high pressure would flow air down past the turbo and out into the air stream below the car.

[SGHOM]

there are 2 ways to cool something (that I can think of just now anyway... still a bit jet-lagged...)

1) draw heat away by giving the hot air somewhere to go (convection/radient loss of heat)
2) force colder air against/past the hot object

eithier way you require movement of air.
To move air you need a high pressure zone and a low pressure zone. Air then moves from high pressure --> low pressure. If the pressure equalizes in both zones, you get no air movement. Net result is that your cooling is less efficient than could be.

My understanding of bonnet vents (not scoops) is as follows...
Vent is placed near the front of the bonnet as this is a low pressure zone (pressure drops when air has to move over a curved surface, ie: from front of the car around the bonnet lip and onto the bonnet) which means air is "sucked" out from under the hood when the car is moving
This lowers the pressure under the hood, which has the effect of increasing the pressure differential between the front of the intercooler/radiator and the back. result is more air flow through the intercooler and ratiator, and therfore better cooling.
If you draw air INTO the engine bay, then you literally reduce the effectiveness of your intercooler and radiator. When you open up a high pressure zone to your engine bay, then you essentially do this and risk the pressure inside the engine bay increasing to the point where there is NO air flow across the radiator and intercooler

When stationary, you want vents that allow the hot air to rise out of the engine bay creating a convectional air flow which cools the engine/turbos.


That said, I cannot say if your setup is going to help or hinder the cooling of your engine bay, but logic says that you should aiming to reduce the pressure in the engine bay compared to your high pressure zones (main one being front of car)

My understanding is that to reduce the pressure, you need create low pressure zones that fecilitate air flow.
I also understand that the main low pressure zones are created at the front of the hood, and under the car by having a well designed under-tray.

To be sure of effectiveness I expect that you would need to measure the pressures involved to discern positive or negative change


I ramble... sorry if I have been a bit of a bore.

Kenneth?................. it's just a big hole !! :rolleyes4 /yes /yes

[bradc]

I would think that vents like that (simply a hole, not a scoop or anything) would allow air to escape at high speeds, sure most of the air will escape under the car, but I would imagine that some would go out through the top vents. The area towards the back of the bonnet is a low pressure zone due to the shape of the windscreen just behind it.

When completely stopped or at low speeds I would beleive there would be quite a bit of convection air that would go straight out of the bonnet. I remember BDA saying he can see heat waves coming out of his vents when stopped.

Kenneth knows the type of bonnet I'm keen on (btw Ken, if you didn't see the thread, I'm importing one through speedfactory) I want to fill up the small vent on the right hand side of the bonnet, simply because I think it looks terrible! I'm also toying with getting an evo 7/8 style vent and mounting it right at the back of the engine bay, basically in the same place Derek has put his new vents.

Derek, correct me if I'm wrong, but your scoops on the bonnet are connected straight to your cold air intake, they aren't just letting air come into the engine bay.

[Kenneth]

I would think that vents like that (simply a hole, not a scoop or anything) would allow air to escape at high speeds, sure most of the air will escape under the car, but I would imagine that some would go out through the top vents. The area towards the back of the bonnet is a low pressure zone due to the shape of the windscreen just behind it.


You would need to run pressure tests to determine this. The results I saw from a car showed that at the front of the bonnet there was less pressure on top of the bonnet than in the engine bay. that pressure equalled about 1/2 way up and was positive thereafter.



Kenneth?................. it's just a big hole !!


lol, thats a nice simplistic way of looking at it! Looks good anyway mate :thumbsup:

[bernmc]

I think Kenneth is making a valid point here - the suggestion is that the area in front of the windscreen is high pressure, ie at speed, air will be forced through those holes into the engine bay, or if the pressure in the engine bay is similar, there will be no net flow in or out.

You'll notice with the EVO's bonnet vents there is a gentle lip on front of the vent - air traveling up this lip accelerates, and creates a negative pressure area as it scoots over the vent itself, so drawing air out of the engine bay. (The venturi effect).

There's an easy way for you to find out which way the air is going, Derek - just tape a few 'streamers' - thin bits of paper/tissue or similar to the front of your vents so they hang back over the hole. Then go for a blast - if they dip downwards, air is going into the bay, if they float upwards, the opposite is happening, and if they float level with the bonnet, chances are there's no net air movement. If this is the case, then you need to get your playdough out and make some lips :kiss:

[bradc]

I guess that would also depend on the car, you're saying at high speed that in this particular car there was more pressure on top of the bonnet than beneath it at the back?

And I reckon that this will definately help under bonnet heat.

bernmc, I'm thinking tassles! I know what you mean with the lip on the evo's, all of them have it, the lip is obviously designed to create an area of negative pressure for air to flow up through the vents.

[V6nut]

sorry to invade people, anyone fitted an evo vent to the galant? Was wondering if it looked anygood and also if anyone knew how to channel any rain water out and keep it as a working vent? Help?

[bernmc]

bernmc, I'm thinking tassles!
Dirty boy!!! :inquisiti

[bradc]

Quite a few people have fitted evo style bonnets to a galant. Pescha is running one with a cover she intends to keep in place during winter.

I think it would be quite hard to make a channeling system on an evo style bonnet. I wouldn't worry about it while you're driving, the heat would be enough to keep any standing water sitting on the engine. The only risk is if you park it outside where water will get into the engine bay and sit on parts of the engine.

[Kenneth]

I guess that would also depend on the car, you're saying at high speed that in this particular car there was more pressure on top of the bonnet than beneath it at the back?


There was more pressure on top of the bonnet than in the engine bay under it (yes, at the back)

How many race cars do you see with cooling vents at the back of the bonnet? (we are talking front engined saloon cars)

You will also find that race cars tend to have air from the front of the car FORCED to go throught the intercooler and radiator before entering the engine bay. You can see this by the "box" built around them sealing the sides top and bottom.

best i could do just now...

http://www.flyinmiata.com/projects/OTC/images/OTC_ducting.jpg

[SGHOM]

believe you me !! those strips of tape are fluttering......... in an upwardly mobile direction !! /yes
we tried them both in front & behind the vents, & dependant on the angle of the blower........... they were almost vertical !! :rolleyes4
I think though, B&Q garden blowers [ £29.99 from any good retailer :embarasse ] only blow at 20/25 mph ?? /Hmmm
Joe was beside himself with embarrassment me thinks !! /yes

anyway........ you cant get any more scientifically proven than that ?? /help :embarasse :embarasse

[Quail]

Whilst driving though, the pressure outside the bonnet may be higher than the pressure inside the bonnet, so this may cause the air entering/escaping to act differently

[enigma]

Get it out on the road you plonker!

[BraindG]

Hehehe... genius idea!

[enigma]

Hehehe... genius idea!

Would require tax, MOT and insurance though :uhoh2: :lipsrseal

Do hope you declared it SORN!

[psbarham]

I think though, B&Q garden blowers [ £29.99 from any good retailer :embarasse ] only blow at 20/25 mph ?? /Hmmm

if you bring the legnum to donny on saturday i'll bring our big one , will 180 mph do ya ???????

[SGHOM]

Would require tax, MOT and insurance though :uhoh2: :lipsrseal

!

& wheels, & front end, & complete engine etc !! :rolleyes4 /yes

[Kenneth]

Get it out on the road you plonker!

ROFL - sound advice with an amusing delivery


The tassle idea was very good actually, much impressed bernmc!

[SGHOM]

The tassle idea was very good actually, much impressed bernmc!

The idea ?? or just the picture !! :rolleyes4 :rolleyes4 :leer:

[Dan_G]

Kenneth?................. it's just a big hole !! :rolleyes4 /yes /yes

PMSL!!!

:rolleyes4

dont forget the venturi effect.... sucky sucky love you long time.........


The end result looks good if nothing else.... so then, you going to put some mesh in to stop large rodents (e.g. hedgehogs and lizards) from climing in...

[Kenneth]

The idea ?? or just the picture !! :rolleyes4 :rolleyes4 :leer:

Picture was not really my sort of thing.... far to small and low resolution :rolleyes4

[bradc]

I had the idea!!!!! It was bernmc that had the picture.

As BDA said, get out on the road and drive it from 20mph to 80mph and see what happens.

[BraindG]

As BDA said, get out on the road and drive it from 20mph to 80mph and see what happens.

He can't its, not 100% road legal.

[bradc]

hmmmm, who wants to swap bonnets with SGHOM?

[BraindG]

thats always an option :)