Outer Limits 4x4 Board

I was thinking of getting the bonnet on my MK louvred the shed the excess heat from the Chev, rather than fitting rear facing scoops or moulded vents etc.

My questions are -

1) Would it be as effective as a scoop? My thinking is the combined area of all the louvres would be bigger than one rear facing scoop.

2) Anyone know who does it in Melbourne, preferably the Eastern Burbs

3) What would it cost?

Thanks

Rear facing scoop not legal (oil on w/screen, etc...)

Not really effective as you need to have a bit of speed to get the venturi effect necessary to draw air through (I assume you are having overheating probs at slow speeds).

Louvres would be the go, possibly an additional electric fan to the radiator would help the cooling at slow speeds, and keep the air circulating in general.

As for cost/fitting, NFI....but you could try some Ford/Holden wreckers and source some from one of their performance vehicles.

Snorkle would be a better starting point to draw cool air from outside the engine bay.

Having thermo fans attached to the underside of the bonet to push air out of the louvres sounds like a great idea. would look horn too.

I have seen the louvres (or just holesaw holes) on the rear side edges of landie and rangie V8 bonnets. The owners claim that it works well, even without any fans forcing the ventilation. Don't forget that hot air likes to rise, so it is much easier for it to leave via louvres than go down through the trans tunnel.

I've seen moulded plastic louvers for sale at supercheap and the like, that would just glue or pop rivet onto the bonnet, depending on how rough your 4B is, they were only like $20 a pair. They came in several styles too.

I'm sure lots of fibreglass joints sell factory style vents (Cosworth, rex, etc)... maybe try http://www.fibremaster.com.au/

Could be the go.

If a metal plate is put on the engine side of the louvre it should stop any oil splashback and also direct any rainwater away from electrics, etc. This is what the factory louvres and turbo scoops have. Have a look at one to see what I mean.
Apparently late model Falcon louvres are the go.
Some I have looked at:

On the back of my Sierra bonnnet I cut 5 x 45mm holes to improve under bonnet cooling and they work great. They are hard to see from annywhhere but the front seats.

Why not just set the bonnet so it sits slightly higher at the back...

Just a though (and a rip off of what i have seen others do)

Dave

GaryInOz wrote:Rear facing scoop not legal (oil on w/screen, etc...)

Not really effective as you need to have a bit of speed to get the venturi effect necessary to draw air through (I assume you are having overheating probs at slow speeds).

Louvres would be the go, possibly an additional electric fan to the radiator would help the cooling at slow speeds, and keep the air circulating in general.

As for cost/fitting, NFI....but you could try some Ford/Holden wreckers and source some from one of their performance vehicles.

Snorkle would be a better starting point to draw cool air from outside the engine bay.

Planning on doing the twin snorkels, 1 to push cool air into intake, the other to push into the engine bay.

berazafi wrote:Why not just set the bonnet so it sits slightly higher at the back...

1) illegal.. :(
2) Dangerous.. you have an accident, the bonnet is already aimed at your head, more chance of it comin straight thru the screen, into the head rest.. I looked at doin that too.. even have the mounts for it at home

I like BV36 I think it would work the best.. or BV01 looks the best.

Yep fair enough never though about that

Dave, have you thought about making a scoop like andrew cassar's GQ tray? mounted at the front of the bonnet. then have 2 little vents at the back corners.

benhl wrote:Planning on doing the twin snorkels, 1 to push cool air into intake, the other to push into the engine bay.

that will not work. the 2nd snorkel will create a +ve pressure behind the radiator, causing more resistance, this will result in less flow through the radiator and overheating will be worse.

the object isnt to force as much cold air into the engine bay. its to reduce the pressure in the engine bay so more air can flow through the radiator.

GaryInOz wrote:Snorkle would be a better starting point to draw cool air from outside the engine bay.

you have obviously never owned a chev.



MaccA

383FJ45 wrote:Dave, have you thought about making a scoop like andrew cassar's GQ tray? mounted at the front of the bonnet. then have 2 little vents at the back corners.

Thats what Ive been thinking would be most effective..
or vents at front to allow the fresh air in, and maybe even some form of ducting to drag the hot air out the vents at the back for slow workin....

benhl wrote:Planning on doing the twin snorkels, 1 to push cool air into intake, the other to push into the engine bay.

you still have to get the air out..

From what I was told (I thought about this too, you also can stuff up the designed pressure/airflow from the maufacturer (nissan/yota/mitz/landy etc).

If theres too much air pressure in the engine bay from the snorkel, no air flow will happen through the radiator, thus causing more issues.

Couldnt you turn the snokle around, would that create a vacumm effect of sorts

berazafi wrote:Couldnt you turn the snokle around, would that create a vacumm effect of sorts

even lifting the bonnet at the back, can affect the 'pressure' in teh engine bay.. removing the rubber flaps on the inner guards can have the same effect..

its a fine line, I see what your saying, have it aiming down the back, or down transmission tunnel, or even liftin back of bonnet, and aim the air that way..

it may have 0 bad effect on the air pressure, but it may.. then you end up with a hole in the guard for nothing of you end up removing the snorkel.

maybe plumbing the snorkel into the center of the front of engine may work, pointin back? Who knows.. :(

Im thinkin 2 grills in bonnet at front, and 2 at back.

GaryInOz wrote:Rear facing scoop not legal (oil on w/screen, etc...)

Not really effective as you need to have a bit of speed to get the venturi effect necessary to draw air through (I assume you are having overheating probs at slow speeds).

Louvres would be the go, possibly an additional electric fan to the radiator would help the cooling at slow speeds, and keep the air circulating in general.

As for cost/fitting, NFI....but you could try some Ford/Holden wreckers and source some from one of their performance vehicles.

Snorkle would be a better starting point to draw cool air from outside the engine bay.

It is actually for when at speed, idling and slow 4x4ing it is fine. But at 100kmh and up and on hot days it starts to climb a bit. My thinking was the air coming through the radiator can't get out quick enough.

berazafi wrote:Why not just set the bonnet so it sits slightly higher at the back...

Just a though (and a rip off of what i have seen others do)

Dave

Don't want to do this for a couple of reasons -

1) I agree with what Bruce said

2) At speed the area at the base of the windscreen is a high pressure area and will push the air into the engine bay, rather than letting it out like I want to do.

383FJ45 wrote:Dave, have you thought about making a scoop like andrew cassar's GQ tray? mounted at the front of the bonnet. then have 2 little vents at the back corners.

benhl wrote:Planning on doing the twin snorkels, 1 to push cool air into intake, the other to push into the engine bay.

that will not work. the 2nd snorkel will create a +ve pressure behind the radiator, causing more resistance, this will result in less flow through the radiator and overheating will be worse.

the object isnt to force as much cold air into the engine bay. its to reduce the pressure in the engine bay so more air can flow through the radiator.

GaryInOz wrote:Snorkle would be a better starting point to draw cool air from outside the engine bay.

you have obviously never owned a chev.



MaccA

Exactly what I want to do, I have thought of a vent like on Shrek, but I have the fabbing skills of a gnat and I was thinking a louved bonnet would be a bit more subtle

Thi is what I want to do but have more than 2 rows

A mate of mine just suggested removing the rear rubber so the bonnet does not seal at the back. (GQ Nissan) This should not cause any legality problems. When I get my car back I will have a look....

Anyone else heard of this trick?

MKPatrolGuy wrote:

berazafi wrote:Why not just set the bonnet so it sits slightly higher at the back...

Just a though (and a rip off of what i have seen others do)

Dave

Don't want to do this for a couple of reasons -

1) I agree with what Bruce said

2) At speed the area at the base of the windscreen is a high pressure area and will push the air into the engine bay, rather than letting it out like I want to do.

i used some rubber to set the bonnet higher on the back of my chevy cruiser as has been described here. it was running a bit hot at speed, not at idle. the bonnet lift made no difference to the temp so i would not recomend it. the above reasons seem to make sense for why it didnt work.

MKPatrolGuy wrote:Thi is what I want to do but have more than 2 rows

MK and GQ bonnets the same? See if Hayden still has the mold for the fiberglass GQ bonnets... would be easier to insert some grills in yourself.

Im planning on getting a set a bonnet vents similar to the BV01 in the pics here.
Im fitting a turbo and want vents to keep the under bonnet temps down a bit. Added airflow through the radiator will be an added bonus

What are peoples thoughts in regards to bonnet vents and water crossings?
I have heard stories of losing the "air bubble" effect in engine bay when going though deep water. Is this a valid point or just a load of shiat?
Paul.

ausyota wrote:I have heard stories of losing the "air bubble" effect in engine bay when going though deep water. Is this a valid point or just a load of shiat?
Paul.

Get a balloon blow it up, stick it underwater, then put a hole in it - what happens?

MKPatrolGuy wrote:Thi is what I want to do but have more than 2 rows

This is what I thought you meant when you said bonnet louvres. When I used to play with 2wd cars (20 years ago), this was a popular thing to get done. Guys would have their whole bonnet louvred. I don't know how much or even who who would do it.

Talk to an old style hot rod type, not a ricer boy, a real hot rod dude, Castlemaine Rod Shop etc. Post results of your research as I've always thought they look good, and on a 4B, might work to reduce heat.

Regards

grazza wrote:A mate of mine just suggested removing the rear rubber so the bonnet does not seal at the back. (GQ Nissan) This should not cause any legality problems. When I get my car back I will have a look....

Anyone else heard of this trick?

Have done this, Doesn't seem to have made any difference.

Those Healy(?) louvres would be a lot of effort on a 4b, especially with all the ribbing in them.

Maybe the solution is to have a lightly weighted flap put on the bonnet (like truck stacks) that let air out but seal up for water crossings.

I know, I am going too far now.....

Another dumb question which I guess I'm going to get flamed for (getting use to it though ), dosent the extra air flow in the engine bay have a negative effect for water crossing (no pressure allowing lots more water a lot faster under the bonnet)?

Nev62 wrote:Another dumb question which I guess I'm going to get flamed for (getting use to it though ), dosent the extra air flow in the engine bay have a negative effect for water crossing (no pressure allowing lots more water a lot faster under the bonnet)?

it can do.. depending on too many variables.
but even bonnet vents will let the water in anyway, same as rear bonnet spacers...