Cool it Dude!

Some say he can fix a Mustang using just a banana..
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Spanner Monkey
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Cool it Dude!

Postby Spanner Monkey » Wed Jul 15, 2015 5:00 am

This has been a long time coming, and to date has been the most difficult to write without getting too technical. I hope it's of some use to the Mustang Massive

Cooling:
Cooling of the engine, brakes, intake charge, transmission, steering, differential, fuel.
First off, there is no point fitting bigger radiators and coolers all over the car if you can’t get air to them. Put any cooler in stagnant air and all you have is a larger quantity of circulating hot oil/water.
To understand how to improve cooling you need to understand airflow around, over and under your vehicle, and where the high and low pressure areas are. This is probably a bit technical for your average weekend mechanic, so we’ll start with the easy stuff.

So step 1 is: Ducting.
Essentially getting more air through the coolers you already have by directing airflow.
Whatever age of car you have, look at the radiator and assess how much air can ‘spill’ around it – under the car, into the fenders, above the rad into the engine. Most (if not all) Mustangs have places that can be blocked to increase the flow through the radiator. Seal them off with sheet steel, aluminium or plastic and see what effect it has on temperature.
Design of radiator ducting will also have an effect. Make the opening to the duct smaller than the surface area of the rad and you will get more air to it than if you try to ‘funnel’ the air in. A reverse funnel will work well, whereas a conventional funnel may well have a detrimental effect on cooling as pressurised air can spill out. Look at the design of the vents in production car grilles, they are always smaller that the surface area of the radiator for that reason.
A reverse vent in the bonnet behind the rad that flows into a low pressure area will draw more air through the radiator and help downforce as an added bonus.

Step 2. Go large.
If you are making more power you are also going to be making more heat, so the next step would be to increase the size of the coolant radiator. If you have removed your heater to save weight then you have also reduced the capacity of the cooling system. Adding a larger capacity radiator will add back some of the lost coolant and also help cool it. You can either go larger in physical size (if you have room) or have more ‘cores’. A 4 core radiator will have one more row of core tubes than a three-core and therefore 33% more surface area that the airflow can cool.
At this stage you should be thinking of adding (or enlarging) your oil cooler, but choose wisely as you don’t want to over-cool the oil. Adding or enlarging the oil cooler will also add capacity to the oil system so remember that at oil change times.
The next cooler to add IMHO would be a differential cooler. The rear axle is one of the least loved components (oil-wise) but it does do a huge amount of work, and if you’re working it hard then the oil will be piss-thin. Add a small oil cooler with a recirculating pump that can be switched on & off, again the axle will run cooler and there will be a larger capacity of oil.
Next, the transmission. Most automatics have a cooler either integrated into the radiator or stand-alone. If it has an integrated system as standard get it out! The last thing you want to do with a system intended to cool the engine is to introduce heat into it from another source.
Fitting a stand-alone oil cooler for the transmission whether it is manual or auto will extend the life of the oil and internal components.
Power steering. Again, most power steering systems have some kind of oil cooler fitted, whether it’s just a loop of steel pipe or a ‘proper’ cooler it will be there. Enlarging this on a track car is just as important as any of the other coolers. When the PAS oil boils you lose your steering assistance, and if you’ve been sawing away on the steering wheel for the last 20 laps and you’re catching that Camaro(!)at last, then now is not the time you want that to happen. TBH it does generally happen gradually, but either way it’s not good either from a component/oil point of view or from the driver’s point of view. The resultant laxative effects can also be quite harmful.

Step 3. Tech.
The way an engine cooling system works is by water absorbing heat from the engine which (by means of the water-pump and the natural thermo-syphon effect) is circulated through the radiator where it cools and is then returned to the engine.
It’s a very mis-understood system where the speed of flow is one of the most important – and overlooked – aspect. Imagine you have successfully added enough power to your engine to make the cooling system marginal (even more-so in the near-tropical English summer…). The radiator seems to be almost coping, but you figure more flow will be the best thing, so you pull out the thermostat. The result could be it runs hotter as the coolant is flowing so fast that it no longer absorbs as much heat as it should. The coolant system needs that restriction in the thermostat, so if you are removing the ‘stat you will need to fit a restrictor of similar internal (open) diameter in it’s place.
The water pump itself is relatively inefficient as a pump, but it does agitate and encourage the flow. When you’re buzzing the engine fast the water-pump can cause cavitation which will also cause the cooling efficiency to be badly compromised. This is one of the reasons that people fit smaller crank pulleys as this will slow down the water pump to a more efficient level.
Modern cooling systems are pressurised which increases the boiling point of the coolant. Without pressurisation the water would boil at 212 degrees and disappear into the atmosphere as steam. When water boils it has the same effect as cavitation – air bubbles are introduced into the system and the water content therefore becomes less. Usually your cooling system will run at around 15-16psi. Increasing the pressure of the cap will increase the boiling point, but it will not cool any more efficiently.
There are such things as water wetters which help remove the bubbles from the system and assist cooling. There are also products like the Evans range which totally replace the coolant with a water-less fluid. This typically raises the boiling point of the system to around 350f. Neither will cure overheating problems, but both will allow the engine to run hotter without losing all of the coolant.

Please feel free to ask questions!

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Re: Cool it Dude!

Postby Mustang Barry » Wed Jul 15, 2015 9:06 am

Another informative and entertaining post Spanner Monkey! All makes a lot of sense when explained. Great food for thought! More for the track guys I'd imagine, but great to know the principals.

Any tips for day to day use. Someone here (I forget who) was commenting on how different their car feels depending on time of day. Cool evenings v hot daytime scenario.

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Re: Cool it Dude!

Postby badhand » Thu Jul 16, 2015 5:50 am

Love it. Thanks oh great monkey of spannerland.

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Re: Cool it Dude!

Postby Spanner Monkey » Sun Jul 19, 2015 7:09 am

Mustang Barry wrote:Another informative and entertaining post Spanner Monkey! All makes a lot of sense when explained. Great food for thought! More for the track guys I'd imagine, but great to know the principals.

Any tips for day to day use. Someone here (I forget who) was commenting on how different their car feels depending on time of day. Cool evenings v hot daytime scenario.


I think the car feeling different depending on time of day is probably due to density of air. Denser air (cooler air) in the mornings and evenings will always make your car feel faster - because it is! The denser the air, the more oxygen gets into the cylinders and therefore more power production. It's like strapping a low-boost supercharger to it. Simple as.

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Re: Cool it Dude!

Postby bigkeeko » Mon Jul 20, 2015 9:13 am

Great post. I`ve always wondered about ducting and it`s effects. Even cool air getting into the engine bay through the front during driving has had me thinking. Some people become obsessed with getting cold air into only their airbox/cone filter. Now i get this bit (cool air denser/better etc) but how would cold air directed onto say your transmission fare?
I had a transmission cooler for my last Mustang as it was an auto and would I be right in saying heat is the number one enemy in an auto box? I found that it could have been possible to channel flowing air onto the box using ducting/pipework that might have reduced tranny temps as they (IMO) according to my Diablosport handheld doofer were kinda on the high side, especially after a hard time.
Would this approach have helped? Or am I off the mark? :?:


Brian

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Re: Cool it Dude!

Postby Spanner Monkey » Wed Jul 22, 2015 3:25 am

bigkeeko wrote:Great post. I`ve always wondered about ducting and it`s effects. Even cool air getting into the engine bay through the front during driving has had me thinking. Some people become obsessed with getting cold air into only their airbox/cone filter. Now i get this bit (cool air denser/better etc) but how would cold air directed onto say your transmission fare?
I had a transmission cooler for my last Mustang as it was an auto and would I be right in saying heat is the number one enemy in an auto box? I found that it could have been possible to channel flowing air onto the box using ducting/pipework that might have reduced tranny temps as they (IMO) according to my Diablosport handheld doofer were kinda on the high side, especially after a hard time.
Would this approach have helped? Or am I off the mark? :?:


Brian


Any cooler air directed at hot components will help. The transmission has a huge surface area, and if you can get cooling air to that it will act as a great cooler. The problem with the transmission being where it is (ie being behind a big, hot thing and enclosed in a close-fitting tunnel) it's very difficult to get a good enough supply of cooling air to it, hence the virtually universal fitting of transmission coolers.
And yes, heat is probably the biggest enemy of the transmission.


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