Black insulation type stuff under bonnet.. Any use?

[LeeRoy]

Good heat shielding, still has lots of heat under bonnet.
Just the whole engine bay heats up, rather then a specific site getting blistering.

I agree with the whole area being hot but having a close proximity between say a turbo(or any other hot surface for that matter) and the bonnet will definately have a greater affect on the painted area it is closer to than anywhere else.

Keep in mind that with a car travelling the other side of the bonnet will have heat removed via the air passing over it.

[CrUZida]

Stick some washers under the hinges on the bonnet to lift it up 1/2" and pull that rubber strip off the back along the top of the firewall. You'll see a noticeable drop in temperature, although you could end up sucking in warm air into your cabin.

I've just removed the strip on my Levin and it doesn't get so hot in traffic.

Except that makes it worse...

The base of the windscreen is a high pressure zone, not a low pressure zone.
ie, its good for air intake, not air exhaust.
Air intake from the rear of the bonnet makes it worse for air intake at the front of the bonnet (ie, where air is needed to cooler the radiator)

Engine bays are designed so that all the air flow through the radiator, and out under the firewall.

[oldcorollas]

true, but in sydney, where everything is a traffic jam.. maybe it is better

as soon as you start moving tho, it will suck...

[Kyosho]

Except that makes it worse...

The base of the windscreen is a high pressure zone, not a low pressure zone.
ie, its good for air intake, not air exhaust.
Air intake from the rear of the bonnet makes it worse for air intake at the front of the bonnet (ie, where air is needed to cooler the radiator)

Engine bays are designed so that all the air flow through the radiator, and out under the firewall.

I was trying to remember last night the reasoning behind it causing heat up...
But, that was too late at night...

Not only is it destroying cooling properties, but bonnets etc are designed to sit a certain way for crumpling.
In an accident, if those bolts snap, or strip out (It's easier to happen now that you have less thread in there, and more leverage on the bolt) that bonnet is coming straight through your front windscreen.

[pisso001]

Yeah i think im going to leave it on and not try the raising of the bonnet.. Is there a good way to ecourage more air to flow under the fire wall? My car does seem to run a little hotter than my last one... ( same car)

Thanks for the tips. Plus rep for all.. By the way. No big honkin' turbos in sight of this engine...

Thanks,

Chris.

[CrUZida]

Wouldn't it be better to find out why its overheating rather than do a bandaid guess fix?

[Kyosho]

Wouldn't it be better to find out why its overheating rather than do a bandaid guess fix?

No one has complained of an over heating car...

Original question was why was it there, last one was "I wonder why car B runs slightly warmer then Car A"

I'd be more inclined to find out if the two cars are meant to be at different temps

[pisso001]

Yeah its not over heating just according to the guage its running a little hotter and the only difference in the cars was the old one didnt have the insulation under the bannet..

Im going to put a better radiator and thermo fans in to cool this one down a little...

Thanks for the helps..

Thanks,

Chris.

[CrUZida]

In my experience temp guages rarely move more than a 1mm between freezing winter and boiling summer with the aircon on.

If the guage is creeping a little higher in summer, esp in traffic, then something is not performing at 100%.

Either the radiator is blocked, or the airflow isn't adequete.

If you just have a single thermo bolted to the radiator, then that is your problem.
If you have the stcok viscous fan, and its operating correctly, and you have a stock shroud fitted, then chances are your radiator is blocked.

If its overheating while cruising at speeds over 60kph, then your waterpump is probably on its way out.

[oldcorollas]

the basic thing to do is to exclude air fro going under the car, to suck more air out of the engine bay... if air is currently being allowed to go under car from the front, then it is a battle of high pressure zones to move air..

having bonnet insulation should have little effect on the cooling of the engine bay, or the temp.
without it, you just have a hot bonnet, but it seems unlikely that a hot bonnet will contribute much to the cooling of an engine bay, considering the amount of heat generated, and the airflow.

[LeeRoy]

I guess its sorta the same as wrapping a dump pipe or coating a turbo housing. Both are designed to keep heat on one side will reducing heat on the other. In this case the insulation would help to retain heat on the underside of the bonnet and keep it in the engine bay while reducing heat on the outside of the bonnet.

Keep in mind that as the insulation has come on the bonnet from factory, the car will have been designed to lose heat through other avenues wheras if you were putting it on a car that never came with it you may need to do other things to reduce the temp like increase airflow and so on.

[oldcorollas]

how much heat do you really think is lost out through the bonnet?
tha air and radiant heat result in the bonnet getting warm.... the bonnet isn7t going to cool the air much (ie, lose heat from engine bay air to outside air via bonnet), and the radiant heat will be blocked by the insulation (with the result of the insulation getting as wamr as the bonnet would have...

in both cases, the answer is to lose more heat to the air that is passing through the engine bay, and to increase the airflow through the engine bay. the insulation will have very little effect at retaining heat in the engine bay.

[pisso001]

So in order to get more air flow threw the engine bay i could lower the car or put a lip on the front bumper to reduce air flow under the front of the car, this would then encourage more air through the radiator...

But then its probably not going to make much difference at all so i think ill just get a better radiator and ditch the viscous fan for twin thermo fans...

Thanks,

Chris.

[CrUZida]

If the viscous is properly shrouded (and working) it will flow more air than 2 non-shrouded thermo's any day of the week.

[TERRA Operative]

But if you the shroud the thermo's.....