V12 engine cooling info and knowledge, sharing the love:

[K9COP Senior Member Find all posts View Profile Close K9COP]

Guys, I received this as an email, probably as a response to other vehicle enquiries. The sender appears to claim some knowledge of helping to keep cool V12 engines, design of cooling systems etc that I thought may be of use to builders of Countachs etc with V12s, or maybe other engines. I remember after reading the build thread of the Audi V8 engined Lotus Esprit that cooling was a major issue..

I can't verify or vouch for the sender or the information, but thought I'd share it just the same. I'm not responsible for the content etc. etc....

K9

" V12s - Our Passion?

Good afternoon,

if this email has been sent to you in error then we apologize, you can easily remove your name below by unsubscribing.

Although v12s started out 16 years ago with a Jaguar XJS V12 (you can read more about that at our website [www.v12s.com] ), we have since expanded what we do, to cover most British and European makes as well as some American cars.

Our passion for anything that has a V12 hasn't changed, our focus on the things that can be improved with modern technology hasn't changed either.

Cooling V12-engined cars of the 60s, 70s, 80s and 90s isn't that hard with the modern technology that we have now.

Read my article 'Cooling System Design and Your Engine'

There are six essentials to cooling a V12:

• electric cooling fans mounted on an aluminum fan shroud
• a temperature controller that activates the electric cooling fans at the proper temperatures
• post-shutdown cooling
• additional fluid capacity in the cooling system
• an aluminum radiator
• waterless coolant

So, you ask:
Why electric cooling fans?
Because they run fast even when you are idling, unlike a mechanical fan.
Why an aluminum fan shroud?
Because it lets the fans draw air across the whole radiator core, not just the area of the fan. The aluminum acts like a 'heat-sink' and adds more cooling power. It looks nice :-)
Why a temperature controller?
Because it allows you to dial-in a suitable temperature setting to start your fans, remember you want to start your fans before you reach thermostat opening temperature - read my FAQ for more info.
Why post-shutdown cooling?
It's good for your engine if you can keep cooling it after you've turned it off, this prevents 'heat-soak' where internal engine temperatures actually increase even though your engine isn't running.
Why additional fluid capacity?
This allows sufficient time for fluid to be cooled before it recirculates back to the radiator.
Why an aluminum radiator?
As above, aluminum acts like a 'heat-sink' - it heats up and cools down very rapidly. It makes a significant difference to cooling an engine.
Why waterless coolant?
Water, through corrosion, is damaging to your engine. Waterless coolant has a much higher boiling point than water. You can use a lower pressure radiator cap thus protecting your coolant hoses, radiator and heater.

I personally design and handcraft all the electric cooling fan systems that you see at my website (www.v12s.com), and I'm always ready to design one for your car if it is not listed.

Any questions etc. Please feel free to email me.

Thank you,
Wolfgang
www.v12s.com

P.S. v12s is in tax-free New Hampshire - No Sales Tax!"

[jdinner Senior Member Find all posts View Profile Close jdinner]

After countless attempts at trying to maintain a proper temperature I can say that the Spal fan was the only thing that worked.

[TRcrazy Active Users Find all posts View Profile Close TRcrazy]

Thanks K9 and Jim for the info here. I have a question on how to plumb dual radiators. I attached a pic here to assist. I dont know if the hoses criss-cross up and down or top hose goes across to the other top hose. There must be a proper way to do this. On my 512TR I will move the cooling to the rear and would like to have a left and a right radiator. Not v12 by the way, stock 2.8v6 for the time being. Thanks Vinny
.

[JoseOSI Senior Member Find all posts View Profile Close JoseOSI]

Hot goes from the thermostat into the top, cold out the bottom into the motor.
Think of it like aaa batteries & the motor is the lamp :-)

Cheers Jose'

[TRcrazy Active Users Find all posts View Profile Close TRcrazy]

Thanks Jose!, -Vinny

[K9COP Senior Member Find all posts View Profile Close K9COP]

Agreed with Jose, but that's from a layman's perspective. I don't claim knowledge, was just passing on the contact.

Again, I strongly recommend you read this Esprit conversion thread. It's very long, but very thorough and the cooling information/theory is excellent...

K9

http://www.motorgeek.com/viewtopic.php?f=6&t=9648

[Bloozberry Active Users Find all posts View Profile Close Bloozberry]

The way Jose recommends routing the hoses is called "in-series". From an ease of installation point of view, it's often the preferred routing of the hoses. However if you're looking for the greatest cooling capacity, the radiators must be plumbed "in-parallel", like so:



The reason: The cooling efficiency of a heat exchanger (radiator) is directly proportional to the difference in temperature between the water and the air flowing through it. In other words, if the hot water flows to one radiator first, then the water temperature entering the second radiator will be cooler. That cooler water reduces the temperature difference between it and the air flowing through the second rad. That reduction in temperature difference reduces the efficiency of the second radiator.

On the other hand, if you plumb the radiators in parallel, the temperature of the water entering both radiators will be the same, (ie hot) and both will operate at the same peak efficiency as the first one in Jose's example. The end result is cooler water re-entering the block.

Some have disputed this line of reasoning in another thread, citing that the different cores in multi-core radiators are in series with each other, therefore series routing must be better. But many factors influence the internal layout of a multi-core radiator including modular design, manufacturing, and packaging constraints. The thermodynamic laws that govern heat exchange don't lie though: parallel plumbing is more efficient than series.

[TRcrazy Active Users Find all posts View Profile Close TRcrazy]

Good info here, My initial concern was forcing the coolant to pump 'uphill' to the 2nd radiator when running the rads in series. I was wondered whether that would create flow issues. The two methods explained here are a real opener. Thank you, -Vinny

[CARBUILDER Senior Member Find all posts View Profile Close CARBUILDER]

Just A Side Note: Pay attention to your rad caps pressure ratings. Make sure your coolant fill cap or caps (water inlet) are highest point(s) in system to ease bleeding air to avoid air locks.

[jdinner Senior Member Find all posts View Profile Close jdinner]

Some of my experiences with cooling system plumbing and overheating engines.
If you decide to run your system in parallel I suggest doing flow and volume tests with the tube routing you plan on doing. Length of tubing, size of tubing, placement of Tee's and construction of Tee's are critical in having your system operate properly.
Don't believe me? Will this system work both rads equally?



If you want a cooling system that works then I suggest a series system. I am a huge fan of 'rad 1' cooling the coolant then 'rad 2' cooling it some more and then return to the engine. I do not understand the issue with reducing the efficiency of 'rad 2'.
When you are in stop-and-go traffic at 105*F you will soon see that 'rad 2' is far more efficient.

I had many issues with my V12 running hot.
I added shrouding, electric inline water pump, engine oil cooler, 4 cooling fans (cheap jobber fans), wrapped the exhaust and nothing made it run cool.
I added two 13" pusher Spal fans and that made all the difference in the world.

I had to fix a car made in a bodyshop that was overheating. Simply by re-routing the radiators hoses from parallel to series made it run twice as long without overheating.
Adding a pressure tank cured the overheating issues.
Just my experience, that's all.

This is how my system is constructed and it works.

[JoseOSI Senior Member Find all posts View Profile Close JoseOSI]

I agree with a series fitment. I do my fitments exactly the same way, single core rads for good airflow, air bleeds from all the highest spots to the expansion tank, & I like to use a computer controlled electric pump by davies craig.It does away with the thermostat,& existing water pump. Controlling the temp electronically by pumping faster or slower. Its nice for getting airlocks out as well, by simply hotwiring the pump, it will flow without running the cars motor.Another bonus, it runs on even after the motor is shut down, until it cools down to the temps you set into the computer, thus stopping heat soak. Just make sure to fit a strong battery.On the midmounts, I tend to fit one larger rad to the front, & one smaller in the back, set the cars ecu to switch on the front fans, & the electric pump ecu to switch on the rear at +-15' higher.It tends to stay so constant that the rear fans hardly ever runs.Cheers Jose'

[Bloozberry Active Users Find all posts View Profile Close Bloozberry]

If you decide to run your system in parallel I suggest doing flow and volume tests with the tube routing you plan on doing.

There is no need to do flow and volume tests. The goal (of course) is to design the system to flow water equally to and from both radiators, but nothing more than a basic understanding is needed to separate the flow into equal streams to both radiators.

Length of tubing, size of tubing, placement of Tee's and construction of Tee's are critical in having your system operate properly.
Don't believe me? Will this system work both rads equally?

The illustration you provided of a parallel system is ludicrous, and gets back to my first comment of basic plumbing skills and knowledge. For starters, a Tee doesn't flow the same as a "Y". Furthermore, the length of tubing isn't "critical" in a system that fits in a typical car. Several extra feet of pipe on one side or the other will produce negligible pumping losses. Nor is the placement of the Tee's critical. No matter where the Tee's are, the water will flow equally to both radiators. Use Y's, and of course you impede the flow to one or both radiators if improperly oriented.

If you want a cooling system that works then I suggest a series system. I am a huge fan of 'rad 1' cooling the coolant then 'rad 2' cooling it some more and then return to the engine. I do not understand the issue with reducing the efficiency of 'rad 2'.

Any system designed without thought of flow requirements is likely to bested by one that is.

[Bloozberry Active Users Find all posts View Profile Close Bloozberry]

I suspect it's not a coincidence, nor the result of an arbitrary decision process that led Ferrari and Lamborghini to plumb the following dual radiator cars in parallel (I'm sure there are other examples):

Lamborghini: Countach, Gallardo, Murcielago, Diablo

Ferrari: Testarossa, F348, F355, F430

[jdinner Senior Member Find all posts View Profile Close jdinner]

I suspect it's not a coincidence, nor the result of an arbitrary decision process that led Ferrari and Lamborghini to plumb the following dual radiator cars in parallel (I'm sure there are other examples):

Lamborghini: Countach, Gallardo, Murcielago, Diablo

Ferrari: Testarossa, F348, F355, F430

Those manufacturers had many overheating issues too but the main thing to notice is the placement of the tee. Exactly in the middle.

[Bloozberry Active Users Find all posts View Profile Close Bloozberry]

What makes you think the placement of the Tee has any influence on the effectiveness of the cooling system? Water isn't compressible so the flow rate through both radiators will be the same if the restriction through both plumbing systems is the same. Adding several more feet to one system or the other isn't going to make any difference in flow rates.

As for your diagram, if the photo manager would let me upload, I would post one of the Lamborghini Countach showing that the Tee's aren't centralized. In fact, the cold water return Tee appears to be right at one radiator and requires perhaps six feet of extra tubing to reach the other.

Edit to add: Try Googling images of the F348 & F355 coolant system. You'll note they don't even have Tees... they have Y pipes that appear to favour flow to one radiator on the hot water circuit and the other radiator on the cold water circuit. To my knowledge, neither car has over-heating issues.

Now show me a production car that has a dual radiator set up where the rads are in series.