Outer Limits 4x4 Board

Hi all,

How can I reduce the under-bonnet temperature in my 2002 FZJ105 Landcruiser?

I have a Parnell/PRINS VSI injected LPG system, and the computer keeps doing nasty things due to high under-bonnet temperatures (>90 degrees C at the passenger side rear quarter near the firewall, which is where the VSI computer is).

Is it best to put a bonnet scoop, some vents, raise the rear of the bonnet (which is illegal ) or just running another vent in somehow?

Should I heat-wrap / shield my Pacemaker headers?

My engine coolant temp never gets too high (sits between 81-87 degrees C under load according to my guages) but the engine bay is smokin hot.

Can't be good, especially when I want to put in things like an ARB compressor under there.

Could try a heat sheild over the exhaust, move the computer or wrap it so it doesnt get too hot.

sorry to sound like a noob but where is the ECU exactly. under the bonnet? i would sy move it to a better location.

otherwise improve airflow through the engine bay. check raditor, check raditor fan. wrap or ceramic coat the extractors. check bash plate etc for airflow through it.

bonnet vents, but you have to be carefull as it can let water in.

have a look at how the airflow is going out of the engine bay.

Didn't even think about heat shielding the LPG ECU...

That might help the error codes it keeps throwing, but won't really help with the rest of the engine bay.

Heat kills batteries etc too, so I might experiment with some heat shielding on the pacemaker headers.

Putting heat wrap on the extractors wouldn't make them crack or anything would they?

its was mentioned in another thread and i've heard the same thing. the wrap tends to hold mosture in so they rust like crazy. not sure about the cracking tho. but wrapping is a cheap way to try it out.

tweak'e wrote:its was mentioned in another thread and i've heard the same thing. the wrap tends to hold mosture in so they rust like crazy. not sure about the cracking tho. but wrapping is a cheap way to try it out.

Didn't think of that either. Maybe a one-piece heat shield to reflect some of the heat back down under the car - won't hold water or mud in when I go wheeling - rather than wrap that would rust it eventually.

It was talked about in Ezookiel's thread about bonnet scoops.

Installing a scoop can have very positive effects or detrimental ones. It can introduce cool air into your enigne bay, helping your temps overall, or it may create a lower difference in pressure between radiator and engine bay, not allowing as much flow through your radiator etc...

I think heat wrapping won't really solve anything, you just need more cooler air to come in from somewhere.
You could indeed look into the bonnet scoop/vent idea.

talking of more airfow. i was just looking through the surf forum and it reminded me of what someone had done to there surf.....move the number plate basicly anything in front of the raditor, grill, lights and of course number plates.

A rear facing scope won't cause any pressure problems (that is the way I went).

It will allow the hot air to be sucked out of your engine bay and reduce the pressure within - thus increasing air flow through the radiator.

Redboy wrote:A rear facing scope won't cause any pressure problems (that is the way I went).

It will allow the hot air to be sucked out of your engine bay and reduce the pressure within - thus increasing air flow through the radiator.

This was my point.

If your hot air is meant to flow underneath the firewall and under the car, you will disrupt the natural flow of air by forcing some of this upwards and out of the rear facing scoop.

If your model has the rubber seal on the underside back of your bonnet or on the top of the firewall just remove that , it makes a big difference

scotyz wrote:If your model has the rubber seal on the underside back of your bonnet or on the top of the firewall just remove that , it makes a big difference

What about water getting in there?
If that's why the seal is there, probably not a great idea to remove it?

HotFourOk wrote:

Redboy wrote:A rear facing scope won't cause any pressure problems (that is the way I went).

It will allow the hot air to be sucked out of your engine bay and reduce the pressure within - thus increasing air flow through the radiator.

This was my point.

If your hot air is meant to flow underneath the firewall and under the car, you will disrupt the natural flow of air by forcing some of this upwards and out of the rear facing scoop.

I don't understand the problem. If air is being sucked out of the engine bay through top, bottom, or both, it is still sucking more air in from the front, i.e. through the radiator.

Why would air being sucked out through the top cause a problem?

well liftig the back of your bonnet or putting on a bonnet scoop is going to let water in as well ,taking the seal off is a quick easy free way to see if less heat fixes your problem,the water wont bother it

scotyz wrote:well liftig the back of your bonnet or putting on a bonnet scoop is going to let water in as well ,taking the seal off is a quick easy free way to see if less heat fixes your problem,the water wont bother it

Good point - and replacing a seal is cheaper than replacing the bonnet with a bigass hole in it for the scoop....

I would space the back of the bonnet and remove the seal for a few days and see if it makes a difference

Jimbo wrote:I would space the back of the bonnet and remove the seal for a few days and see if it makes a difference

Is spacing the back of the bonnet illegal?

It shouldnt be ,it would probably go unnoticed anyway,you only need to lift it a inch

Not sure, maybe.....just do it for a few days.

OK I'll give that a shot, now the question...
spacing the back up... How do I do it?

In my gq i just put a nut inbetween bonnet and hinge. The original bolts were long enough

a lot of cars have tapered holes on the hinges and there is enough adjustment to lift it a bit

I'll have a play and see what I can work out.

HotFourOk wrote:It was talked about in Ezookiel's thread about bonnet scoops. Installing a scoop can have very positive effects or detrimental ones. It can introduce cool air into your enigne bay, helping your temps overall, or it may create a lower difference in pressure between radiator and engine bay, not allowing as much flow through your radiator etc...

Well, the twin scoops I installed, at a cost of just $30 each, have definitely reduced under bonnet temperatures. I used to open the bonnet in winter and think it would be a great way to cook my bacon and eggs in the morning. Now even in Summer it isn't anywhere near as hot under there as it used to be.
Temperatures on the gauge are about what they used to be before the head gaveway (twice) i.e. about half the gauge except when under load, and then about 3/4ths of gauge, which i already know overestimates temps a little bit.

At $30 it's a pretty cheap option.
And if it makes it worse, then turn it around and face the scoop towards the driver and make it an extractor instead. So can't really lose either way.

Most engine bays get a lot hotter than you would ever imagine.
Try running a thermocouple on your multmeter around different places somtime. To me I dont see it as a problem other than maybe some semiconductor hardware like your computer.

Ive seen batts with internal temps over 68c. ARB compressors over 120c.
All still work OK.

Of course putting comp under seat is a better idea in the 1st place.

I didnt say cooler would be of no benefit though

Bazzle

My engine bay next to the LPG computer today got to 81 degrees c air temperature - idling in gear (it's auto) in traffic, 30 degree sunshine with no wind and the aircon on full.

I don't think I want to know what it gets to, when I'm towing something heavy up the mountain in 35+ degrees, or slogging through sand in 40+ heat... :(


My LPG computer throws an error over 90 degrees C core temp. :(
I've ordered some heat shield at least for the computer - might be able to eliminate some of the heat.


Anyone know where I could get a spare bonnet for my FZJ105 series landcruiser, so I can get medieval on one of them with a hacksaw?

Get your extractors/headers HPC (ceramic) coated. Not the final solution however its the ideal way to keep the heat out of your engine bay.

The heat tape generally results in rusted headers.

Assuming the gas fitting was arranged and paid for by you, take it back to the guy who fitted the gas and tell him to fix it.

sierrajim wrote:Get your extractors/headers HPC (ceramic) coated. Not the final solution however its the ideal way to keep the heat out of your engine bay.

The heat tape generally results in rusted headers.

Assuming the gas fitting was arranged and paid for by you, take it back to the guy who fitted the gas and tell him to fix it.

Anyone know where I can get my headers HPC coated in Canberra?
I don't want to have to take them off, send them away, and have the vehicle out of action for days or weeks.

The gas system was installed in Sydney, and they don't want to know me at the moment... :(

The system itself is awesome, but the installation and after-sales support has been a little disappointing. The major probs have been sorted eventually, but hey.. still trying.

physh wrote:

sierrajim wrote:Get your extractors/headers HPC (ceramic) coated. Not the final solution however its the ideal way to keep the heat out of your engine bay.

The heat tape generally results in rusted headers.

Assuming the gas fitting was arranged and paid for by you, take it back to the guy who fitted the gas and tell him to fix it.

Anyone know where I can get my headers HPC coated in Canberra?
I don't want to have to take them off, send them away, and have the vehicle out of action for days or weeks.

The gas system was installed in Sydney, and they don't want to know me at the moment... :(

The system itself is awesome, but the installation and after-sales support has been a little disappointing. The major probs have been sorted eventually, but hey.. still trying.

Contact the manufacturer of the kit, advise them of your problems and the lack of support from the installer and see how you go.