Bonnet Ventilation

Well it is a Saxo by the looks of it, which should speak volumes about the owners technical knowledge... but I have seen them on a fair few modified cars, the most powerful of which was a 590 bhp cosworth engined bmw e36, it didn't have any other vents but it did have a meshed area where the normal bmw front plate is so that was a major air feed.

However due to the vent design is should create a small air vortex behind the lip of each louver (unless they are too close together) which in turn should suck air down into the engine compartment when moving at speed.

That venting method is also quite expensive I think, in comparison to most vents.... or stabbing your bonnet with a big screw driver/pick axe ;)

You are worried about cooling on a ford ka!?

Hello,

What on earth for on a 1300cc Ford Ka that does 0-60 in 16seconds and raches

89mph on a really good day. It's not a car that gets hot enough to be worried about vents, that's why they were never installed. The engine is so tiny it can't be driven ard enough to heat up that much. I wouldn't waste your money or reduce the resale value by sticking bits on it or doing pointless damage. save your money and buy a decent car instead. Plastic stick on bits can be found on the barryboys web site.

Does the Ka have insulation under the bonnet? Removing that might help out a bit. Presumably if you're fitting vents you're not so worried about the extra noise.

Fit loads of these:

to your bonnet and look like a cool dude as you cruise the McDonalds car park. Paint them green first obviously. (c; Hell, just take the bonnet off man.

Douglas

LOL. I don't consider an underbonnet temperature of 90 degrees "not heating up much."

Aha, it's Mr. Astra man, out-dragged by Corsas, and dropped on the head as a nipper.

Incidently, what does "raches" mean?

Yet again you're spouting bollucks.

ROFL. Actually motorbike fans would work better! :)

Indeed. The issue I have isn't engine cooling, but airbox cooling. The condenser sits in front of the radiator, sits in front of the airbox. It's not unusual for airbox temperatures to hit 60 degrees within minutes of slowing down. When intake temperatures are this high, I have very much reduced torque.

Riiiight. So I guess it could be put right behind the radiator?

Yeah, but not engine cooling, airbox cooling.

Would seem to me that the massive heat from exhausts as well as engine block and radiators etc is far far greater than a couple of bonnet vents can ever remove. Sensibly you would need to remove the bonnet... And wherever you put the vents on the bonnet, they will do nothing exept let 2 percent of the heat out while stopped, and cant let any cold in when moving because the large open front (rads ETC) pressurises underbonnet area, and the air escapes underneath.. Do what racers did for years and add spacers to the rear edge of the bonnet to raise it up a couple of inches in hot weather. Some of the heat can escape up the rear . sides and its cheap!

Well if you take the mitsubushi evo style vent for instance, that is just a giant styled louver. If you were to have that done to the bonnet tip, maybe two or three louvres then I believe you should get the desired effect.

Why not run a close air feed or two to it?

Cold*

Before you start chopping the bonnet there are some other things you could try. You could try insulating the airbox by coating it with something so it doesn't absorb heat so quickly. Get some exhaust wrap to cover the manifold and downpipes so there is less heat under the bonnet to start with. If it's possible on a Ka, try modifying or adding spacers to the bonnet hinge so that the rear of the bonnet is raised slightly to let heat out. You could also try experimenting with a simple water injection setup, you could easily make a cheap one with off the shelf parts since it wouldn't be critical to the engine if it failed.

Job's a good un.

Rob does have a slight point though, even a 500bhp M3 does not have bonnet vents, so a 80bhp Ka will not need them, most people change the way the airbox picks up its air, and I don't know how yours does it, but a front insulated air scoop will be the best method, like on the front grill etc.

90c is not really that hot, but you will defo benefit moving the location of the air intake.

If you have a Turbo engine, fitting vents might be a good idea to keep the heat down., but on a Ford Ka it's not needed.

You should feel the heat under the bonnet on mine after a 1 hour drive home today through town, with the aircon with a 32c outside temp. And this weather won't last :)

Just lift the back of the bonnet up with washers. It will suck the hot air out.

Fraser

Won't do anything - the airflow through the bonnet area is *huge*. A couple of teeny vents will do pif-all :)

You need to be looking at a heat-shield approach instead. Get the exhaust and manifold wrapped, and get a thin sheet of shiny aluminium plate around/in-front-of the airbox to reflect the heat away from it, etc. etc. As others have said, the only way to *really* remove underbonnet heat, is to raise the back of the bonnet. The lower-air pressure there (cos the air is rising up over the windscreen) will suck out a bunch of the underbonnet air (the rest exists underneath the car).

The trick is to get underbonnet airflow. Normally, air comes in the front of the car, through the radiator and other places and has nowhere to go other than into the intake or escape where it can (under the car etc). Louvres allow some of the hot air to escape out through the bonnet, so you get good airflow through the engine bay.

Mostly I don't want to replace the standard induction system, if I did this I'd need to device some cunning sealed intake otherwise there would be no advantage other than the looks, and I don't show off the donk (it does the hard work so I don't have to, heh). There is also the matter of space: I could run cold air feed pipes from the lower grill area but they all would have to go behind the radiator at some point, so would still get heated.

Maybe: the main problem is that hot air entering the bonnet via the front has nowhere to escape to until it's swilled around the entire engine bay.

Yes. But getting cold air in wouldn't help, the hot air needs to escape.

There's an idea worth investigating...

There is some logic with this. Unfortunately, if it's insulated, it'll also keep whatever heat is in there for longer.

Have a look at

- this illustrates the underbonnet area. Fortunately, the manifold is to one side. Manifold heat doesn't bother me as much as the additional heat from the condenser and radiator when I'm using the air conditioning system in hot weather.

Aye that can be done.

Yes, this too...

Hmm - the M3 has side grills. :)

It might be - but getting more air into the induction system isn't what's needed. Speeding the air through the system helps - so high load engine conditions are useful. But even with the biggest induction scoop in the world, it's not going to help at low speed and high temperatures.

Can you touch the bonnet support without getting burnt (although it's cool to see the Ford part number on your palm because you've burnt it on).

Part of the problem is that it's very compact under there. The other part is that the only place for hot air to escape is down the bottom of the engine bay. At slow speeds, little hot air escapes and the stuff that does it the cooler air. Putting a vent at the top should provide a means for the air to escape, especially when the cooling fan is stuffing the hot air into the engine bay.

If you look at the vast majority of cars, they have vents in one or two wheelarchs, specifically designed to help remove hot air from the engine bay. Stand at the front doors of many cars with the cooling fan running (if there's a vent in that wheelarch) and feel the heat. With the Ka, the majority of the heat comes from *under* the car because there is no wheelarch vent. Worse, no scope to put one in... :-x