Just got some 0.7 mm ali sheet that I will use to panel the underside of the engine bay. This is to control air flow beneath and channel air through the radiator and oil cooler.

Question is really about the air exit. It is simplest to stop the paneling short by about 6 inches (area should be approx equal to nose cone vent?) but will this have adverse effects i.e. will it then to lift the centre of the car up? And is this effect significant i.e. do I need to worry about it?

I have seen that some builders have put in vents on the side so should I do that instead/as well? Again I assume the area should be equal or greater to incoming air area? Or louvres in the bonnet top? (I have small deflector screen so will the hot air make things looks wobbly/affect vision?

What I thyink I am asking is what is the best way to vent the air out of the engine bay?

(inbstead of vents, a mexhed filled hole with some ali sheet to direct air from insdie the engine bay should be a good and SVA cmpliant?)

[Edited on 3/3/06 by 02GF74]

I personally would not vent it under the car at the middle. I have seen a couple of pictures of side venting on this site that I think would work very well. Both side panels are tapered out a couple of inches by the time they get to the cockpit and leaving a vent area.
Dale

The best exit approach is to vent it either up through the bonnet or out through the sides of the engine bay. Venting it underneath will cause unecessary lift and drag penalties.

There is no need for the exit aperture area to equal the intake area. If you locate the exit in a suitably low pressure area then the hole could be as little as 30% of the intake area. Towards the rear of the top of the nosecone is good for this, if you don't mind warm air being blown over the passenger compartment. Just make sure that the air is smoothly ducted from the back of the radiator to the exit and that, if possible, the ductwork is tangential to the external bodywork where the two meet up (the duct will end up a sort of s-shape).

You may also have to consider where rainwater would go if you have a vent on the top but a sealed underbody. A couple of small drain holes in the floor might do it.

cheers rob & dale.

low pressure, hmmm that wold help. I doubt I cna use the rear of the nose cone as a vent but how about the rear part of the bonnet (i.e. near the bulkhead)?

And again the same position on the sides? Good places for low pressure?

My current thinking, and this changes - is to cut out a hole and mesh it over, inside have a curved piece of ali sheet to direct air out to the side vent.

rear sides of the bonnet is popular as per
stuart talyor.

Ned.

quote:

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Originally posted by ned
rear sides of the bonnet is popular as per
stuart talyor.

Ned.

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The Stuart Taylor style vents would help but are unlikely to be enough on their own. They help because you get a collection of hot air inside the engine bay on top of the front bulkhead in front of the scuttle. Letting that out is important. Fortunately it will almost certainly be a higher pressure than most of the region immediately outside the scuttle and so opening holes anywhere around there *should* help, with one caveat...

I use a small set of louvres at the rear of the bonnet but i don't have a full-width windscreen or wind deflector. If i did i would have a high pressure in front of that which would render any vents there pretty redundant. If you have no screen or a small, steeply-raked screen then you could probably get away with it.

With a blank sheet of paper and for road use (no race regulations etc) i would go for vents on the sides of the car but with fairly comprehensive ducting of the air from the back of the rad to the exits.

The ducting is important since at work we often have to fix cooling problems where someone has got a vent that they are expecting the air to leave from but no-one told the air that and so it leaves wherever it feels like. If it's ducted it has no choice. Keep the duct smooth and take it to somewhere that isn't an especially high pressure on the exterior and you're away!

I'll be making dax rush stylee stepped off side panels for mine - like we did on my mates westy a while ago...

Liam
Rescued attachment DSCF0063.JPG

Liam, thats the exact picture I was trying to find to post.
Looks good and would easily vent the air out.
Dale

I have seen piccies of bonnets with round holes in the same position as the stuart taylor vents (whether they are for show or not) and they had a bit of mesh behind them. another car which i think uses vents is the westfield seight as the rv8 gets very hot..

Ned.

<<------ take a gander here

You notice the bonnect has a mesh covered pannel each side; v8 sitting inside for the same reasons as ^^^^ say.

Fitting a second fan behind the radiator help pushh the air through the pas. side vent.

Again as you ^^^^^ say; it is iunkinown whether these holes are the sole methods of ventialtion; as suspect not, so the situation is like here <<<<<; more helper vents really.

What I think I am truying to do is to improve(?) the venting by channeling the air more precises rather than just let it exit wily nilly from the underside of the engine.