How can I stop the area around the tunnel getting so hot!

[alan_thomas]

just got back from Silverstone, beautiful day top down all the way. The car never missed a beat, didn't overheat but that's what I expect. The problem was the amount of heat coming up into the cabin thru the tunnel. The metal shaft of the gear lever (auto) was almost too hot to touch and the whole area was emitting a lot of heat.

I know there is the usual underfelt type insulation under the carpets but that does not go as far as the gear lever. Also I believe the 2 centre exhaust silencers would originally have had heat shields, is that correct?
I could easily fabricate some alloy shields and space them off the floor between the floor and the silencers but I think a lot of the heat in the tunnel is engine heat being directly off the heads and down and into the tunnel and shields above the silencers would not stop this

The heater valve shuts off fully ( ie the lever goes as far as it can possible to go) but I suspect there is a trickle of coolant still going thru the heater, has anyone used an auxiliary, say a 15mm plumbing ball valve to ensure the coolant is fully shut off from the heater?

Any bright ideas guys how I can keep the cabin cooler? - Alan

[barkerwilliams]

Comparing a Stag to a modern car there are a couple of major differences. MPG Stags burn more fuel than a modern car and generates more heat. My car did /does not have heat shields, I'm not sure what cars did in the 1970's I only remember heat shields coming in with catalysts.

Airflow, I'm not sure that the Stag has any meaningful airflow design within the engine compartment and along the underside. It starts with a restrictive front design with limited flow through the radiator and the air is not funnelled over the exhausts and beyond so the under-bonnet space just gets hotter and hotter. When my car is stationary and the electric fan cuts in it is interesting where the hot air exits the car.

The front bulkhead has a foam top half but the lower half is metal and the hot air is forced between the gearbox and the tunnel past your glowing gear lever, the exhausts radiate nicely along the length onto the floor.

If you were starting now the car front would need to be designed to accelerate the air along the sides of the car and create a low pressure area under the car which would draw the hot air out and assist by drawing more air through the radiator, perhaps a front spoiler would help but not just "a spoiler" but one that was designed and tested to meet airflow objectives, and perhaps a modern style under-engine shield. Certainly the bumper being a couple of inches away from the bodywork must agitate the airflow and not guide it over the car in a beneficial way. Similarly the flattish headlamps.

I'm not convinced that you can realistically retro-fit /design airflow or heat shielding. But anything you can do to scoop a greater volume of air through a free flowing radiator can only be a good thing for many reasons. If there are any low pressure areas over the bonnet perhaps a louvre could be fitted but I'm not sure the effect would be significant. There are Stags with air conditioning, I have never been in one so cannot say how effective; with the roof down I suspect totally ineffective.

Possibly a small clip-on duct/scoop to the air intake at the base of the windscreen cabin air intake would funnel more air into the car as per the TR6 "flap"

Perhaps the easiest would not be to concentrate on the cabin but the occupants. Slip 2" air ducting up each trouser leg and couple to a high volume blower, a loose waistband and your sorted.


Alan

[new to this]

Alan

You know the aluminium foil they have behind radiators stick that round the gearbox tunnel,that may help

Dave

[Phil S]

l have the same problem (as do most l'm sure)
l have got hold of some ally foil backed with fibreglass and have some of the same on a roll..got to get round to doing the lower bulkhead and tunnel...helped in my last kit car.
Phil

[Kithmo]

Would wrapping the exhaust manifolds and downpipes reduce the under bonnet temps ?
I would think that, together with heat shields on the silencers and foil underneath the carpet underlay on the tunnel, should deflect a lot of the heat towards the rear of the car shouldn't it ?.

[Motorsport Micky]

Would wrapping the exhaust manifolds and downpipes reduce the under bonnet temps ?

At the cost of increased cylinder head heat, we struggle with that on race cars, if you prevent the heat getting out of the pipes the heat backs up through the airflow.

On a TR7 V 8 the windscreen has a high pressure area in front of it that stretches forward about 18 inches, luckily it finished behind the bonnet vents, to aid under bonnet heat removal we had a full length under tray complete with underbody vents and an underbody spoiler just to the rear of the engine. This helped accelerate the air being pushed into the engine compartment by the high pressure area in front of the windscreen down the rear of engine firewall. The gearbox housing was lined with the silvered anti thermal insulation ( can't remember name), Our exhausts had a balance pipe across under the gearbox and two side exit boxes ( with louvred in the under tray under them with tailpipes just under the sills in front of the rear wheels...hot.

Micky

[redstag]

The exhaust silencers did have heat shields, Not all aftermarket exhausts have them, my exhaaust is made by Bell and does.

Does your car have the insulation panel between the transmission tunnel and gearbox?

Pete

[mole42]

The auto gearbox didn’t have the insulation, it is for noise rather than heat anyway..

i bonded some ĵ inch underfelt to the gearbox tunnel carpet which made a huge difference to the feeling of heat from the tunnel. It’s a real pig to fit though, getting the extra thickness under the heater used a whole months worth of swearwords.

[redstag]

Mine was an auto and has the insulation fitted. Maybe they left it out on later cars.

I wouldn't disagree that it was fitted for noise but it must have an effect on heat transfer as well.

Pete

[mole42]

Intersting, I understood that the WKC0341 "Pad, Sound dead, engine" couldn't be fitted to the auto cars because there wasn't enough space. The description for the earlier version; 910904 is "Pad, Sound deadening, gearbox cover" and I wonder if this one would fit?

I was interested a couple of years ago because my car has a ZF gearbox which is noisier than I like for long-distance work (I was particularly irritated after a 460-mile drive one day on my own) but after I'd heard that the sound-deadening cover wouldn't fit I gave up and went the underfelt route.

[Rubce]

If you think that the tunnel area in a Stag gets hot, try driving a Triumph GT6 and then you will know what real heat from the tunnel is!!!!!!

Bruce

[Hughesy]

I fitted insulation foam with double skin aluminium foil as an under lay. It has reduced the tunnel temps but really needs more treatment on the under side of the tunnel.

[Guest]

I wrapped my headers and exhaust under the footwells as I was unable to drive the car in bare feet. The engine bay runs cooler and I can now drive in bare feet. I think if you run hotter exhaust gases it flows more freely in theory.

[steve.n]

I must admit I enjoy driving in bare feet but beware, apparently it's illegal.

[Motorsport Micky]

I wrapped my headers and exhaust under the footwells as I was unable to drive the car in bare feet. The engine bay runs cooler and I can now drive in bare feet. I think if you run hotter exhaust gases it flows more freely in theory.

"Would wrapping the exhaust manifolds and downpipes reduce the under bonnet temps ?"

At the cost of increased cylinder head heat,

Not what you want in cars and especially Stag ! I think I'll stick with wearing shoes as my sartorial in car fashion choice lol.

Micky