[Fot] TR8 Water temperature

Mon Jul 11 15:34:55 MDT 2016

The basic thermodynamic heat transfer equations work in an ideal way, but the world is never that simple. The fundamental heat transfer equation Q=SM(Tin-Tout) suggests that the more mass that gets pushed through the radiator, the more heat gets transferred, but we know that isn’t exactly true. Radiators and motors get coated in gunk, the heat transfer coefficient is therefore variable, the primitive headers don’t precisely distribute the water flow and tubes have more or less turbulence, get blocked. airflow isn’t constant. There are simulations available to size a radiator, but aside from running one, I’d say that it’s highly unlikely that a single pass radiator is going to adequately cool a V8 of more than modest displacement unless you become happy with a generally high operating temperature. Here’s why: 

You can transfer a lot of heat with with a high mass flow rate and a radiator that doesn’t drop the outlet temperature very much, but this means the coolant flowing back into the block is close in temperature to the coolant flowing out. That means your operating temperature IN THE BLOCK will be higher, but won’t rise excessively with increased power output. The heat transfer rate to the air is adequate to remove the heat energy, but only operating at a higher general temperature. 

A slower pump or restricted flow will lower the low-load operating temperature because the time the coolant remains in the radiator is longer. But overall heat transfer is lower, so full load temperature will rise more. That may be adequately compensated for with greater airflow at speed. 

All of this is the reason street cars have thermostats with an operating range that suits the general design of the engine/radiator combination. Of course air temperature shifts this balance. 

Your high idle temperature is typical of a radiator running with a higher outlet temperature because of high coolant flow rate. But don’t kill the engine chasing the wrong parameter. It’s full load you need to worry about. If the internal temperature of the block is too high for the system operating pressure you’ll get sheet boiling in the heat transfer surfaces of the engine (like the sleeves of our wet sleeve triumphs). This may not make the coolant boil generally, but it greatly reduces the heat transfer ability of the surfaces. One reason cylinder 4 of TR3’s is so delicate. 

I’d use at least a two-pass radiator to get the radiator outlet temperature down a bit more. That will reduce engine temperature a bit and you’ll have a slightly higher overall heat transfer ability. 

> On Jul 10, 2016, at 1:44 PM, Mordy Dunst <gasket.works at gte.net> wrote:
> 
> Chris your the engineer....
> 
> Heat produced vs heat removed.  There will be a steady state at some point.  You would like it lower.   Don"t underestimate the headgasket component of channeling coolant flow.  In the TR4 motor i made the coolant holes different than original to allow the mass flow of water to occur from the rear of the motor forward.   I also put a pressure gauge on my coolant.  If the pressure is too low it will not cool as efficiently either.  I don"t know what the coolant  dwell time with in the head needs to be to in order to adsorb the heat generated.  Nor the dwell time in the radiator.  There certainly calcs for all this stuff.  
> 
> MDunst
> Headgasket.com <http://headgasket.com/>
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> Triple R Munitions, Inc
> 626.201.9471 T
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> 
> 
> -----Original Message-----
> From: MadMarx <tr4racing at googlemail.com <mailto:tr4racing at googlemail.com>>
> To: 'Marcel Van Mulders' <van.mulders.marcel at telenet.be <mailto:van.mulders.marcel at telenet.be>>; 'MadMarx' <tr4racing at googlemail.com <mailto:tr4racing at googlemail.com>>
> Cc: fot <fot at autox.team.net <mailto:fot at autox.team.net>>
> Sent: Sat, Jul 9, 2016 8:21 pm
> Subject: Re: [Fot] TR8 Water temperature
> 
> I have a 160F thermostat installed.
> Next test will be without any restrictions, maximum flow and see how it goes with that.
>  
> Chris
>   <>
> Von: Marcel Van Mulders [mailto:van.mulders.marcel at telenet.be <mailto:van.mulders.marcel at telenet.be?>] 
> Gesendet: Samstag, 9. Juli 2016 13:01
> An: 'MadMarx' <tr4racing at googlemail.com <mailto:tr4racing at googlemail.com>>
> Cc: fot at autox.team.net <mailto:fot at autox.team.net>
> Betreff: RE: [Fot] TR8 Water temperature
>  
> My diesel BMW runs always at 100°C/212°F when hot. What coolant thermostat is in it? If the T° is steady at 212°F, perhaps it  is intentionally done so with a 212° thermostat.
> Marcel
>  
> Van: Fot [mailto:fot-bounces at autox.team.net <mailto:fot-bounces at autox.team.net>] Namens MadMarx
> Verzonden: donderdag 7 juli 2016 19:21
> Aan: 'FOT List'
> Onderwerp: [Fot] TR8 Water temperature
> Hi guys,
>  
> My TR8 is running way too hot about 212F at full speed and at idle the temps are getting that high also. I have no idea to get them down.
> Radiator core is 68x48cm x 5 cm. I suppose that should be enough. I've experiment with different restrictor plates with no change. Changing pump speed didn't help either. The difference between radiator in and outlet is 10°C (50F). Not enough I would say. Maybe making the pump more slower? It was running on a ratio of 0.8 slower than crank, currently 1:1 speed. Any ideas? 10 Liters are circulating.
>  
> Cheers
> Chris
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