improving radiator efficiency

Aerodynamics for getting better airflow through radiators. Note that my most recent aero book (replacing the one shown in this video) can be found here - www.amazon.com/Vehicle-Aerody... or Amazon in your country.

[@cillianpower]

much more energetic in these old videos

[@JulianEdgar]

Yes, I deliberately changed the style.

[@TravisFabel]

This is a great video to come across right now. I have a car that has a very narrow low opening grill below the bumper bar. It essentially feeds into a sealed box that has a fake grill above it but the OEM has the back of the grill blocked off so it's essentially feeding through that one opening into the sealed box, and then through the AC/PS/trans/radiator heat exchangers, and then into the engine bay. But this vehicle was originally an off-road style car that was high in the air. So looking at this I had a hard time understanding how they were creating a low pressure area when they have a small area opening going into this larger box and then air flowing through the car. When you mentioned the flat bottom side of the car, I went ah-HA!! Because the entire underside of the car has a flat under tray. Panels all the way down the full length until the rear axle. So that's how it used to work. My problem is is I've lowered the vehicle from off roady to "normal car height" and am adding more flow resistance to the cooling system by putting an intercooler up front and then I'm going to be blocking up the area behind it with a bigger motor too. So looking at your diagrams and thinking about the flow I have now I'm going to remove the flat paneling directly underneath the engine...which I know from testing will reduce my cooling. Now I understand why but I believe now that I'm closer to the ground and am purely and on road vehicle, I think I can convert this to use an air dam directly underneath the rear edge of the radiator outlet. That'll create a nice low pressure area for all of that to be pulled through without having to open up the grill and I'll try to have the air damn go the full length of the front to kick more air out past the edges of the tires... And we'll see how it goes from there. I don't anticipate nose lift at high speed from this but if I do I'll have to reevaluate. Although I realize if I had a splitter it'll just feed more high pressure air into that air box and may create an even larger differential while providing downforce... (Not particularly worried about drag with a large displacement turbo motor, more about maintaining safe steering and stopping)

[@averyalexander2303]

Great information, thank you! Right now I am working on sealing the gaps around my radiator and ducting it in so all the air that passes through the grill must pass through the radiator and can not bypass it in any way, this would have to help cooling at least slightly.

[@JulianEdgar]

Depending on the size of the original gaps, it may help cooling not a little but a lot!

[@averyalexander2303]

@@JulianEdgar I love your videos. The gaps around the radiator were pretty large, so maybe I will gain a lot of cooling performance. The gap was about 1/2 inch on the bottom, 1 inch on the top, 1 inch on the drivers side, and 2-3 inches on the passengers side depending on the part of the radiator support. I cut sheets of aluminium to seal those gaps and secured them to the sides of the radiator support with sheet metal screws. Free, simple, and effective. I haven't taken any measurements, but those gaps surely increase the pressure in the engine compartment and decrease the pressure in front of the radiators measurably. I didn't finish the ducting for the bumper cover and get that back on yet, but the radiator fans don't seem to be needed as much at lower speeds now that air isn't going around the radiator anymore.

[@asharma9345]

Keep it up Sir. You are GEM.

[@JulianEdgar]

Thank you, I will

[@DerptimeTV]

Probably got close to 200-300 views from me alone. Love learning from your videos. Im working on making an aero shell/cap currently for the bed of my truck which im documenting and will be putting on youtube. But also considering an under tray as all your videos seem to suggest:p only issue im finding is that of the tray. Should I leave the area under the engine exposed to help alleviate high pressure at the front for better radiator flow? Or is it better to make a full tray like in most of your other videos and your honda insight where it covers completely but limits cooling efficiency in favour of aero gains. Im leaning towards open engine bay tray as it will need to retain a good amount of cooling as i haul heavy loads regularly as well as a large camper where the better aero might not be worth the extra strain on components due to decreased component cooling. Unlike the insight. This is a 5.7L chevy not a 1.5 or 2L honda that hardly creates heat in comparison. Different vehicles need different solutions id assume. Again would love to have a sub from you and get your insight on what im doing/creating going forward as I used to be a fabricator, meaning this project is going to get done! Not a hmmm yeah ill get around to building it. No, I get my projects finished. And a video should be out in about a month show casing the aero cap with some testing to show it hopefully working :p

[@zip-tv_]

I like this video. i have 4x4 which has an ARB deluxe bull bar, winch and bash plates. Bar and winch constricts the flow to the exchangers. Things i can see after watching this video is air can escape prior to the exchangers so i will endeavor to seal that up. my car also has the wheel curtains. Should i remove them immediately? Have you done a video on bull bars?

[@michaelsillymoose5556]

Julian, after watching your videos and reading there comments I decided to check the gaps around the radiator of my Jimny - I have been trying to reduce heat build up in the engine bay and now you have me looking at other things too :-). Discovered that the factory foam around the radiator has dislodged so I have been driving for goodness knows how long with huge gaps around the coolers. Quickly went off to a local upholsterer to buy some foam. I will see how this all works out. Now for the noisy airflow around those outside mirrors

[@JulianEdgar]

If you spray the foam black it will look as if it was always meant to be there.

[@thetechlibrarian]

0:54 so with that bit of information would you say it's beneficial to prop the hood open if you were idling for an extended period of time or is it better to keep the hood closed so that the radiator works better?

[@JulianEdgar]

I think it would be car-specific. Do some testing.

[@rustywater3219]

So to help cool headers, it might be worthwhile to modify the engine bay to breathe through to the rear of the engine?

[@JulianEdgar]

Best to reduce pressure in the engine bay, eg by an effective undertray or spoiler. 5 minutes to measure the effect of different mock-ups on the road - just measure engine bay pressure.

[@rustywater3219]

wonder if you could use the under hood high pressure to feed brake cooling ducts.

[@JulianEdgar]

You could, but for brake ducts you want highest flow possible, so best to use stagnation pressure not engine bay pressure. Very easy to directly measure the difference in pressures.

[@highoctanememe3617]

would a functional reverse cowl and a undertray work together ? or is it better to have one or the other.

[@JulianEdgar]

Reverse cowls are pretty useless - they are trying to vent into the high pressure area ahead of the windscreen. So, undertray.

[@R0yL33]

1. I thought the front wheelwells were another place for high pressure. That's why you often see vents at the top of the fender. I suppose the area directly in front of the tires is low pressure? 2. For those of us that don't want to put holes in our hood, could fender vents be used? I'm thinking of the typically fake vents you see behind the front wheel, converted to functional.

[@JulianEdgar]

All easy to find out in 30 minutes of on-road aero pressure measurement.

[@rustywater3219]

Wonder if you could capture the high pressure in front of the tires for cooling use somewhere.

[@JulianEdgar]

Well of course it does cool the tyres!

[@rustywater3219]

@@JulianEdgar I was thinking rerouting the air to the brakes?

[@JulianEdgar]

Yes I understood. My point is that the air is already cooling the tyres/wheels (and so aiding brake cooling) and diverting this air, even if possible, may not provide the advantage you're thinking. Anyway, simple to do some tests with cardboard, ducting and an infrared thermometer.

[@dannys7182]

I installed a FMIC in front of stock radiator. Would installing a vented hood help with radiator efficiency? Thanks.

[@JulianEdgar]

Probably. But no need for guesswork - just do some simple pressure measurements. (Eg fitting or altering the undertray may be more effective.)

[@funkyjunky6574]

Is a bug screen no good for the radiator intercooler?

[@JulianEdgar]

A bug screen, depending on how fine it is, will restrict airflow. It could be by a lot. Easy to measure.

[@kingGar27]

Is the paperback version of the book still on sale?

[@JulianEdgar]

My latest book is available at www.amazon.com/Vehicle-Aerodynamics-Modification-Development-alternative/dp/B0C87VYVL8 or Amazon in your country. It is a substantial update and expansion over the earlier book.

[@funkyjunky6574]

Wouldnt the car manufacturers have already sorted all this out in modern cars?

[@JulianEdgar]

1. Who says everyone is working on modern cars? 2. Most - but not all - modern cars have fairly good radiator aero efficiency.

[@averyalexander2303]

Do you have any suggestions on the spacing of heat exchangers? For example, how close should an AC condenser be to the engine's radiator? Seems to me that they should be close together and preferably sealed together with rubber or foam for maximum cooling efficiency. Thanks in advance!

[@JulianEdgar]

I haven't done any testing, and nor have I seen any tech papers on this, so I don't have any particular view. However, I do think they should be sealed together, just so there aren't any air escape routes.

[@averyalexander2303]

@@JulianEdgar That's what I thought, thank you! I had about a 1 inch gap between my AC condenser and radiator and I moved the radiator forwards so there is less than a 1/2 inch gap that could be sealed with foam now. I should put my AC gauges on and see if the spacing makes any difference to the pressures, I think that would be an interesting test. A drop in the AC's head pressure would indicate more efficient heat transfer.