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GT6 removing engine bay heat


John Bonnett

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I just wonder if anyone has tried this.

I've found a 5.5 inch bike fan which I'm going to install in a side valence on the manifold side of the engine. This will be switched on when the car is stationary by the thermo switch. Here's a picture of the fan.

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I assume you will use it when the car is stationary/stopped after a run or do you mean when its running/moving?
Any reason for the fan, are you having poblems with vapour lock on the fuel lines or just sweaty legs?
If so i doubt the fan will do anything to stop it  :-/
Thermo line the gearbox cover with heat resistant material if its personal moisture issues (or wear shorts :) )  :o

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There was somebody (who rallied a 2000 IIRC) who suffered high underbonnet temps, and he fitted a small 4" fan from a boat i think. He reckoned it helped, so may be a wise idea. After all, when stationary there is nowhere for the heat to go if there is no manual fan stirring up the airflow. And a fan blowing air out the side may just work.

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Louvres in the bonnet will help.

Exhaust wrap will help.

the original fan on its original pulley will help.  It circulates air a bit more than a kenlowe which just tends to cool the radiator (very well I might add, but it doesn't really blow air elsewhere.)

Consider the engine bay valances etc....are they necessary.  Are they louvred?

you can direct cold air from the front with ducting and do all sorts of things with it if you want.  But when stationary I suppose a fan is the only means of cooling....but just how long do you stay stationary for???


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I've offered this advice so many times.............

My Silverback was experimental, with the radiator at the back.
An obvious consequence was that it was a cold car to drive, and the gearbox cover was always cold.   Not cool, not only a little  bit warm, but cold.
This tells me that the vast majority of the heat under the bonnet, and making the gearbox cover hot, comes from the radiator and almost none from the engine block or exhaust manifold.
Department of Nogreatsurprise, you will cry!   That's exactly what a radiator is supposed to do!     But do we do anything to extract that heat except by allowing it to disappear out under the engine bay or down the transmission tunnel, as best it can?   No, we do nothing.

  Triumph fitted extractor vents to the sides of the Le Mans Spitfires, and then louvres there and on the bonnet for the later Gt6s.    But mere vents do little to 'extract' hot air, and louvres only work if single or double row.

Compared to a simple slot, a louvre extracts about 25% more air, thanks to the vortex in its wake.     But that vortex ruins the boundary flow for the louvre behind, so that it is much less efficient.   A bank of louvres, as on a GT6, might as well not be there.

Nor did Triumph understand that there is a bubble of high pressure air in front of  a relatively upright windscreen like a GT6's.  They must have known it, as it is that pressure that drives air into the heater, but they didn't appreciate that the bubble pushes forward, probably as far as the top bonnet louvres on a GT6.  Those louvres probably contribute nothing to air flow out of the bonnet at speed, let alone extract anything.

The side louvres may be better, but they are still a bank of louvres, and most inefficient.  What is needed is a more effective means of entraining under bonnet air and extracting it, and aerodynamicists do know how to do this.   A relatively wide slot, with a forward lip and a ramp inside will generate a vortex over the ramp that tranfers energy from the airflow outside to the air over the ramp, causing it to move away from the car as the vortex spirals away from the vent.   See examples on the Aston Volante  http://www.cartype.com/pics/1585/full/aston-martin_volante_emblem.jpg or Jaguar XK http://www.cartype.com/pics/1651/full/jaguar-xf_side_vent_09.jpg.  Also on Range Rovers.

This isn't new!  Jackie Stewart's Tyrrell 006 in which he was F1 Champ in 1973 had the tripping lip and ramp
http://en.wikipedia.org/wiki/File:Tyrrell_006_Donington.jpg
And before that in the GT40s from Mk2 onwards, as seen below.

A similar slot in a GT6s bonnet would work well, IMHO, though of course, few owners would wish to take a tin opener in such a radical way to their car!

John

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JohnD wrote:


That is interesting.  It wouldn't be of much use on the top of the bonnet at the windscreen edge, because of the high-pressure area you mentioned, but I wonder if someone more artistic than I could work them into the sides acceptably.

Quote:
http://www.cartype.com/pics/1585/full/aston-martin_volante_emblem.jpg

Forbidden!  Like the Lambada, The Forbidden Dance!

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I have glued heat reflective material to the underside of the tunnel (fiberglass), REMOVED the exhaust wrap as it does nothing! made sure that ALL of the holes in the bulkhead are plugged and made sure that the tunnel is properly sealed and then gaffer taped just to make sure.  I have also used aluminium sheet fixed to the underside of the chassis to deflect any heat from the exhaust system.  My GT6 Mk3 cabin is much cooler now and will even blow cool air inside if i use the cold setting on the heater controls!  I think I would eliminate the heat issue altogether if i was to put heat reflective material on the inside of the bulkhead and  floors.

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Heat is something I've worried about in my GT, as it lives not far outside the tropics. I've lined the floors, tunnel and bulkhead with Dynamat and Dynaliner and will make sure there are no gaps in the bulkhead. My panel guy added a pair of front wing vents, and I'll add a subtle tripper to ensure that they do what they're supposed to, ie actually help hot air escape from the engine bay. I can't think of much else to do!

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I find this bit interesting, 'cos I've done all this too:

339 wrote:
I have glued heat reflective material to the underside of the tunnel (fiberglass), REMOVED the exhaust wrap as it does nothing! made sure that ALL of the holes in the bulkhead are plugged and made sure that the tunnel is properly sealed and then gaffer taped just to make sure.

But not this:
339 wrote:
I have also used aluminium sheet fixed to the underside of the chassis to deflect any heat from the exhaust system.

....and my car isn't cool (Ahem) under any circumstances, really. Though of course I can put the roof down.  :)
Mine has the "original" radiator type and Tim's doesn't.  :-/
Ummm.....
Next Royvoy, perhaps we could all get a thermometer out (not in an intrusive way you understand) and have a comparison.

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smithy wrote:

Next Royvoy, perhaps we could all get a thermometer out (not in an intrusive way you understand) and have a comparison.


Perhaps we could all just do a 15 minute drive and then see who can squeeze the most sweat from their T shirt. We could do it like its a knockout and each have different coloured sweat as long as we don't have to dress up as giants and pretend we're Belgian :)

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Thank you all for your replies especially JohnD for his in depth consideration of the theory of airflow.

My concern is only when the car is stationary in very hot conditions.  Whilst on the move the tunnel area is reasonably cool because there is sufficient airflow to take the heat away. However once stationary the electric fans are not able to get the heat any further than the tunnel and as an indication of the temperature in the tunnel, the gear stick and gear knob are too hot to touch. This cannot be good for the oil in the gearbox and overdrive or the reverse and overdrive inhibitor switches.

I absolutely agree with john that the main contributor to the heat is the radiator and not the exhaust.

My idea is to duct the air out of the side of the engine bay using the motor cycle fan before it reaches the tunnel. If I do manage to fit the Golf fan which is on the nearside, then if what John and I believe to be correct, the extractor fan will also go on the nearside.

John

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339 wrote:
I have glued heat reflective material to the underside of the tunnel (fiberglass), REMOVED the exhaust wrap as it does nothing! made sure that ALL of the holes in the bulkhead are plugged and made sure that the tunnel is properly sealed and then gaffer taped just to make sure.  I have also used aluminium sheet fixed to the underside of the chassis to deflect any heat from the exhaust system.  My GT6 Mk3 cabin is much cooler now and will even blow cool air inside if i use the cold setting on the heater controls!  I think I would eliminate the heat issue altogether if i was to put heat reflective material on the inside of the bulkhead and  floors.




I'm not too concerned with the cabin temperature. I am worried about all the components in the tunnel area that may be reaching temperatures that they were never designed to see

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5458 wrote:
You could fit an oil cooler to the transmission.  I've heard of it being done....although I guess it wouldn't be easy what with no pump and you'd have to tap the transmission too.  All very frightening.




I'd prefer to solve the problem at source if possible

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