Thread: Will a bonnet scoop reduce heat in the engine bay?

Originally Posted by border0_3

.....

Time for radiator check, replacement?

Regards

If you haven't already flushed the rad .. internally, not just a spray with the hose to remove bugs!), my experience so far in using the CEM(Cost Effective Maintenance) coolant flush/conditioner stuff has been positive.

My normal coolant temp is in the low 80's without fail, no matter the ambient .. maybe 85 on a very hot 40+ day here or there(on a trip recently in 40+ heat, it ran at 83 without issue)
Pre CEM flush, with the A/C on in 30+ days, I'd easily see over 100, regularly saw 103-105 (minutes after I'd backed off and turned off the A/C from the coolant gauge) at any speed above 80k/h, I'd have to manage the A/C(like Val does).
Drove me nuts!

So in went the first does of CEM, ran it for a day or so as they say(or a few hours or whatever) .. time to flush out the cooling system.
1/. first thing I noted was that the reservoir water went murky .. yellowy-brown .. but not much .. just a light murk.
2/. engine flush saw very little murkiness. a bit of residual coolant came out, and mainly clean water.
3/. radiator flush saw initially clean water with (garden)hose from the top and flowing out the bottom hose port, but then back flushing it with garden hose in the bottom port and all the brown muck came flowing out when the hose was removed.
Not much flow out the top of the rad(rad still in car).
I flushed the rad for about half an hour, most of that time, a bit less brown murky crud coming out the bottom .. until it finally flowed out pretty much clean.

On the recent trip up to central NSW, 40+ heat for most of it, I ran both with and without A/C .. mainly as a test.
Without, I saw not much difference from the usual low 80's I see, but with A/C on it climbed much more slowly, would hit 88-90 and then drop again to about 86-87-ish .. obviously the thermostat was at full opening.
I'd never had that before.. once the coolant started climbing, it would just continue on.

Eventually after a few hours of trying to get it to heat up excessively, I finally hit a few hills, at about 100-110k/h in the 40° heat and the hottest temp I saw was a very brief second or so at 100°, but that was under a heavy load, EGT at 700° too .. etc.
I did back off and coolant also dropped steadily down to 95 after a few mins of easing off at 100k/h.

I've been running this CEM flush stuff since, and over the past month or so now, with the second treatment, there's been a slow build up of some rusty looking goop above the water level line in the reservoir.
Looks like steamed up residue of whatever has been left over in the rad broken down by this CEM flush. It's not in the water tho, just above the water line and settled onto the insides of the reservoir now.
Best way to describe this build up would be 'boiled up rust having evaporated and condensed'.

Overall .. I'd say that unless you have a deeper issue, if it's just a partially blocked rad, this CEM stuff will probably help .. or more accurately!! won't hurt

The 'hard part' now is going to be the cleanout of the coolant reservoir of all this brown muck buildup now.
I used to use rice and whatever cleaning agent I could get my hands on, the rice added when shaking acts like an abrasive, but doesn't damage anything .. but it's tedious work to do.
Just thinking of getting a new one to make life less difficult

I know others here have high regard for this CEM stuff, and as of now, I'm a fan myself too. And would recommend this coolant flush/conditioner stuff as one tool to try.
At the least, it's helped me get to a point where I don't have to 'manage' the aircon any more ... just keep an eye on the coolant temp every now and then.

I have their oil flush stuff too, and have plans to get into that ASAP(waiting on some parts first).

There are so many areas of high pressure in air flow stream around moving motor vehicles that plopping on an air scoop without a lot of research is a process which could result in quite the opposite effect to that desired.

The first thing to consider is that, for a vehicle doing what the thing was designed to do, the manufacturer's cooling system, if fully serviceable, is probably the best possible option. Then the next consideration is that people selling add-on cooling products have a distinct barrow to push and might be promising results that are extremely difficult to achieve outside a testing laboratory.

There is simply no more effective way to improve engine cooling than to increase air flow through the radiator. And how to do that is really blindingly obvious. Fan cooling cannot be surpassed. And just how much fan cooling you employ is limited only by the space required to attach more or larger fans, and your ability to pay for them.

But if you must go for scoops, remember that it should be rear facing, preferably with an extractor fan, venting to an area of air flow at standard air pressure or lower when the vehicle is in motion. And I wish you good luck in locating that point.

The fender vents Bill makes in this (and subsequent) videos look pretty trick. (How to Make a Race Car Aero Kit - Part A - YouTube)

I always wanted to add D4 style vents to my d2 and have them vent to under the bonnet somewhere, and somehow.

Originally Posted by Spinner912

And I wish you good luck in locating that point.

Without access to CFD or a wind tunnel, wool tuft testing works well, if you know what you are doing.

Back in the day we'd also use magnahelic gauges (pressure differential gauge) for air box testing too.

A lot can be deduced from real race cars with front engines that have been in a wind tunnel on where laminar flow occurs and where and how the best shape of vents are for best extraction of rad air.

Hi All,

Im working with this guy at the moment to get a 79series cruiser forward facing bonnet vent on my RRC, we sourced a second hand bonnet together and should have pics of first effort within a week.

Good news also is he picked up a defender bonnet at the same time.

So thats Disco 1,2, RRC, Defender and county sorted hopefully.

They are fiberglass and supplies with inset bolts and nuts do up under bonnet, usually under $300

Made in OZ by Vaderworks

Will post up how we go here.

Not worried about water as I have an LS engine, for over bonnet crossings fit a car bra.

Contraptions can be made to divert water to safe areas for bonnet scoops if it concerns you.

Also mesh can be added to these vents to ensure not to much foreign object entry.

If they look good enough for the RRC i will be adding this to mine to force cool air in and down straight onto the engine, and also vent out when standing still or engine off (reduce heat soak)

Imo the 79 series bonnet scoop is the best looking scoop out there.

Attached photos of a disco with 79series vents from him.

You could also fiberglass into bonnet for cleaner look again.

Has anybody considered fitting a digitally controlled electric water pump? I have one on my track car, a 1981 Commodore fitted with an L67 supercharged V6 Holden engine. Before fitting the electric pump I had fitted a V8 radiator mainly because the hose outlets were in the right places for the V6. I had no overheating issues by the way but liked the theory behind the electric pump and the release of a few horsepower. With the digital controller there is no need for a thermostat. However the pump was so efficient in the old Commodore that I had to refit the thermostat so as to reach the predetermined temperature setting. An electric pump must have at least a continual flow even if only a trickle so I drilled a 3mm hole in the thermostat flange. I still had trouble getting the engine up to the 80*C that I had set the controller and now run with 2/3 of the radiator blocked off. If it's really hot I remove on piece of the blocking material, I used pieces of sheet perspex for this. If you consider going this way buy an aluminium bodied pump such as a Davies Craig unit. An electric pump works opposite to a mechanical pump, pumps more water at low speeds and less at high speeds when air flow does the majority of cooling.

Originally Posted by Mick_Marsh

Wouldn't they be vents for bringing air into the cabin? I have similar on the Mercs, Commodore and Camry.
The engine bay is isolated from those vents, usually with a rubber pinchweld section.

Quite correct, Mick.

Originally Posted by blackrangie

Hi All,

Im working with this guy at the moment to get a 79series cruiser forward facing bonnet vent on my RRC, we sourced a second hand bonnet together and should have pics of first effort within a week.

Looks great. Of course, the scoop in a 7X series is there to feed the intercooler. It is not present in cars other than those fitted with the V8, which is pretty much every 7X series other than those shipped here.

Like I said, looks great. I've often wondered about fitting an intercooler up there on one of mine.