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

Originally Posted by johntins

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 abuot fitting an intercooler up there on one of mine.

LRA tried top mounted intercooling and bonnet scooping Andrews D2 on the 2.8 TD5 project, cooler mounts kept breaking, and they decided to can it due to being complicated etc and just LS'd it. He is very happy with the LS3/6L90 combo.

Factories will avoid using scoops for many reasons,but mostly the clean look, will only use them if 100% nessesary like the Cruisers.

To force fresh cool air onto the top of an engine via scoop will no doubt help to cool engine and parts and could even help to suck more air through rad, will help to reduce heat soak at speed, bonnet scoops will also create a spot for rising hot air to escape when switching off, reducing heat soak.

Cant see many negatives of a sleek good looking forward facing scoop.

Sorry, complete waste of time installing a letterbox in your bonnet.
If you want to reduce temps in your engine bay start at the top end of the temperature table first.
Your headers and exhaust system are by far the hottest place and if you have one of those stinking tractor engines with a turbo charger on it blowing black smoke your exhaust gas pipe work is even hotter.
Wrap your headers and associated pipe work or better still get them ceramic coated (expensive) doing this will improve performance as well.

Bonnet vents are only going to allow hot air our when the vehicle is stopped and engine is shut down, its a cosmetic boy racer enhancement.
Primarily "ducted" air scoops are installed on performance cars to get cool air into the induction system, diesels benefit greatly from this.

Take a look around your bell housing firewall area.....there is a significant hole there isnt there, hot air from the radiator passes through this space at great velocity as your speed increases pretty much in a straight line from the radiator. As a few people have already noted the plenum area in front of your wind screen is a high pressure area (at speed) this is useful for getting cool air into the induction system, but realistically its going to have very little effect on cooling unless there is a significant amount of design applied to it.

Take a look on facetube at some video of engines under full load, headers and exhaust run cherry red at times, isolate this heat and push it through the exhaust system and you will see significant drops in under bonnet temps.

Maintaining higher gas temperatures allows lower density of the gas (it flows faster the hotter it is, think about cold and hot honey) which increases engine performance.
The cooling system in any older vehicle is probably the most poorly maintained part of the car, no one bothers to look at it until it boils over.

Maintenance

Originally Posted by blackrangie

Factories will avoid using scoops for many reasons,but mostly the clean look, will only use them if 100% nessesary

They don't really care about the clean look (aesthetically) so much as the fact that it's cheaper for them to manufacture without a scoop.

Originally Posted by Mick_Marsh

Or you could get a few louvres punched in.

The Classic bonnet has the advantage of having 'sides' where a series of the above vents would work well. Remember, the object of the exercise is to keep the engine room cool... and shoving more cold air IN may not help, if the warmer stuff can't escape.
Another idea would be a strip of louvres, either made of a single strip, or several singles, overlapping, the idea to look sort-of like a Spitfire (aeroplane) exhaust.
Google Images 'boat ventilation louvres' and here's some examples below.
AAA single louvre.jpgAAAlouvre strip.jpg

Personally, I prefer the look of the stamped-in louvres, but $$$?

Another route is to install a vent etc in a similar place as later RR's do, on the fender's side between door and wheel arch. A triangle of metal needs to be cut out inside engine bay to let the air into this area.

Originally Posted by Ace

Hi all,

I've got the disco running pretty sweet these days, engine was done back in 08 and a new head was fitted late in 2016. I've had the radiator rodded and had a new aluminium cowel made up that bolts onto the top of the fan shroud to replace the brittle plastic one. The viscous fan coupling is new and overall it runs pretty cool, there are a few decent hills around here that see the temp increase on the digital gauge, nothing to alarming.

I've ordered a new hard top camper which wont be here for a while so i want to look at ways to keep it cooler.

So, my question is, would fitting a bonnet scoop help drive cooler air in and force the hotter are out or does it do buggar all?

Matt

Hi matey, I have a p38 RR but similar when it comes to heat. I removed the bonnet seal so that the engine bay vents better. If you have a turbo a small scoop in the bonnet above the turbo will work well and force cooler air onto the turbo and force the heat out as well.

Hi Folks,

I added two scoops to my D2, Td5, one to send air down either side of the engine was the plan, and reduce overall engine bay temps.

I have an engine watchdog, measuring head temp and gearbox temp (metal temps) and nanocom for water temps, and a before and after had my under bonnet/head temps down roughly 5 deg C. No real change on water temps, as you would expect with a working radiator and thermostat, but with the lower under bonnet temps, I find the temps definitely recover faster when pushing hard or towing, when the ambient air is cooler, I put a couple of solid blanks in.

All up about $75 (paint and scoops) and one grinding disk

cheers lads

I've been thinking about louvres as well.

I tow a reasonable size enclosed trailer with my V8 D1 (think brick towing a brick). I live just off a freeway exit and have found with last few cars, Holden LS1 V8 and XR6 Turbo and now with my D1 especially that they all used to go right up on the temp guage when I pulled up and started the slow reversing process into my garage (100kph -> 50kph -> stopped). The D1 started spitting out fluid out the overflow on the last really hot day when doing this. Radiator, coolant, fan all good on it and temp is mostly normal while towing on a hot day.

I just want to find some louvres that don't look like floor vents, although they could be handy for when it rains. Not sure whether to position behind the radiator or over the exhausts.