Underbonnet heat

[Andy K]

The following previously posted on TR5/250 forum, but same problem anatomically speaking so seems appropriate for here too...........

 

Evening all. (And good afternoon to our New World cousins).

A question for you all.....

 

Excess engine heat can be disposed of by the use of front wing vents. The rally TR4s had ducts with grilles set into them. Iain Rollo's well-modded (c/o Racetorations) TR6 (see recent TR6 forum) has ducts with louvres let into the outer wings.

 

I sure I have seen correspondence about the inefficiency of louvres elsewhere.

 

I also recall something somewhere about the area between the front inner and outer wings being a low pressure area aerodynamically.

 

So if one wanted to vent hot air out of the underbonnet area, why not just open up the triangular pressed area and put a small shroud on the leading edge on the external side of the new inner wing opening to stop the water and road dirt getting in directly. On the move, it extracts actively, and whilst stationary allows convection to do the job. Also, as a bonus, avoids cutting up the outer wings.

 

Any thoughts?

[Roger H]

I also recall something somewhere about the area between the front inner and outer wings being a low pressure area aerodynamically.

 

Isn't that what you are aiming for??

 

Another alternative when racing is to screw up (raise) the bonnet locating cones and put a packer under the bonnet latch and remove the rear engine bay seal. A ten minute job all up, easily reversible and no cutting.

 

IMO, these mods are only really necessary if you dont have adequate cold air feeding the induction manifolds.

[IanR]

Hi,

Though not strictly related to the cooling vents I have been stunned by the difference that Cool-it copper exhaust wrap makes to under bonnet heat. In my last 5 there was no wrap and the heat from the manifold (SS Phoenix 6-3-1) was incredible. Mine is now wrapped in insulations and I would think there is no need to go to the extremes of making vents unless this is a race car and even then I wonder. Get more power this way too albeit minimal.

 

Highly recommended so far,

 

Cheers

[rpurchon]

Hi,

Though not strictly related to the cooling vents I have been stunned by the difference that Cool-it copper exhaust wrap makes to under bonnet heat. In my last 5 there was no wrap and the heat from the manifold (SS Phoenix 6-3-1) was incredible. Mine is now wrapped in insulations and I would think there is no need to go to the extremes of making vents unless this is a race car and even then I wonder. Get more power this way too albeit minimal.

 

Highly recommended so far,

 

Cheers

if you want some cheap exhaust wrap try buying from the usa. $40 = £20 a roll in there local auto stores

probably work out a lot cheaper even with postage.

i was going to buy 2 rolls while on hols last year, but never quite managed to get back to a store.

perhaps some of our us tr owners could start exporting it.

[Roger H]

Wrapping the manifold can lead to embrittlement of the metal. I have been warned about it but it is not something I have experience with.

 

It has been previously discussed on this Forum (see Archives).

[Tom Fremont]

Ceramic coating is supposed to reduce surface temps by ~ 100 deg. F. Cost here in the 'states works out to about 125 pounds. I'm very pleased with a set of stainless manifolds which look the same after 5 years / 35000 miles, under triple Webers which have not suffered from overheating. Appearance, noise and heat characteristics all improve with this treatment

[john.r.davies]

Isn't that what you are aiming for??

 

Another alternative when racing is to screw up (raise) the bonnet locating cones and put a packer under the bonnet latch and remove the rear engine bay seal. A ten minute job all up, easily reversible and no cutting.

 

IMO, these mods are only really necessary if you dont have adequate cold air feeding the induction manifolds.

 

Roger,

Last year I was told by a Scrutineer to get a seal between the rear of my Vitesse bonnet and the bulkhead, or.........

 

He was concerned that a fire in the engine compartment would quickly spread backwards.

 

Scrutineers - Sigh.

 

John