GT6 Gearbox tunnel insulation

[Alex Lowe]

Hi All, 

Im about to reinstall my gearbox tunnel into the GT6 and was wondering what people suggest using to reduce the heat coming into the cabin. Iv heard if people using roof insulation as a substitute for the original insulation bag?

Alex

[Steve P]

I used Dynaliner for my Vitesse,not so much for heat but it's definitely a lot quieter.

Steve

[Paul H]

I used SilentCoat, very easy to use .  Heat up first with a heat gun . For the contours use a 2ins roller used for sealing wallpaper joins.

https://www.deadening.co.uk/products/silent-coat-2mm-deadening-mat?

 

[Iain T]

I used Dodo Mat Hex in 2mm thick. Very flexible and doesn't require heating. Has a thin foil hexagon embossed coating which flattens as you roll it on so you can see where you've been. I bought it when on offer. Good stuff. I also applied to front bulkhead. Comes in sheet format. 

Iain 

[JohnD]

2 hours ago, Alex Lowe said:

Hi All, 

Im about to reinstall my gearbox tunnel into the GT6 and was wondering what people suggest using to reduce the heat coming into the cabin. Iv heard if people using roof insulation as a substitute for the original insulation bag?

Alex

Alex,

Heat in the cabin is almost entirely due to, not radiated heat from.the gearbox Yr exhaust pipe, but to connvected heat, hot air from the radiator.    It gets into the cabin via the many holes in the bulkhead and/or a poor seal of the cover to the floor pan.

You will do better (send save money!) By sealing all those gaps!   Get under the dash while someone shoes a torch at the bulkhead from the engine bay - night or a dark garage will help.   And look at the sealing kits sold by the Club Shop.

Why am I so sure about this?  I built the only Triumph AFAIK with a radiator at the back.  It was a cold car to drive, even in hot weather, as all that hot air from yhe rad was behind me!

John

[Paul H]

Can’t agree with the Club Shop sealing kit . Very much overpriced and there are better solutions . 
Paul 

[dougbgt6]

Yes, the Club shop sealing kit is a waste of money. Draught excluder tape is just as good and why carry on with those strange washers?

John is also correct. I used draught excluder and SilentCoat to line the inside of the tunnel and cover the holes in the bulkhead. I have it on the floor as well, but be warned it's surprisingly heavy and will take 10mph off your top speed  However you will be cool and quite.

I never had a problem shaping the SilentCoat with my hands, but it was a hot summer when I did it.

Doug

[Iain T]

Using Dodo Mat or similar and sealing the bulkhead holes has also reduced the fumes in my car however I think most of the fumes enter via a poorly sealed gearbox cover. Wherever the heat is generated even with Dodo mat my gearbox cover still gets hot but with the 631 exhaust there's a lot of hot pipes down there. 

Iain 

[Colin Lindsay]

32 minutes ago, Iain T said:

Using Dodo Mat or similar and sealing the bulkhead holes has also reduced the fumes in my car however I think most of the fumes enter via a poorly sealed gearbox cover. Wherever the heat is generated even with Dodo mat my gearbox cover still gets hot but with the 631 exhaust there's a lot of hot pipes down there. 

Iain 

Using Dodomat to make a seal over the edge of the gearbox tunnel cover has helped my Herald immensely. Once it's fitted and screwed down, just cut a sheet into longwise strips of maybe three inches wide and press it down over the join to completely seal any gaps. It can be prised back if the cover needs to come off, or it's easily replaced.

[Mark B]

This is what I used on my Vitesse replicating the original insulation. I attached the insulation inside the tunnel cover with contact adhesive and home made staple/ clips through thefibreglass cover so no chance it could drop down and melt on the exhaust, somthing to bear in mind.

Photo bottom of thread.

https://sideways-technologies.co.uk/forums/index.php?/topic/7484-vitesse-sound-insulation

Edited November 26, 2023 by Mark B

[Iain T]

34 minutes ago, Colin Lindsay said:

Using Dodomat to make a seal over the edge of the gearbox tunnel cover

A good idea! Sealing is a constant battle and although better I'm still smelling of exhaust fumes when I drive the Vitesse. It's an odour neither I or my wife like👃

I've been using gaffer tape but some fumes still get in. 

Iain 

[JohnD]

I only said "look" at the Club seal kit!  I use a roll of self adhesive, closed-cell foam, half an inch thick, that I bought from a local firm.

An "exhaust smell" is rather worrying.    CO poisoning is insidious, with no symptoms!   I have a CO detector unit in my cellar where the gas boiler is, but they aren't as cheap as the colour changing button designed (it seems - why?) for pilots:

 

Another version is less than £3!  Carbon Monoxide Detectors | Essential Cockpit Accessories - Flightstore

If you do detect CO then please attack the problem.  For a start, exhaust fumes shouldn't escape from the pipe until it's behind the car!     The head to manifold, and  later junctions need to be checked.

John

Edited November 26, 2023 by JohnD

[Iain T]

Correction it may not be exhaust fumes but hot engine/oil fumes. I have checked all the joints and welded angle clamps to seal the 3-1 usual culprit. The pong is definitely coming in through the tunnel cover joint. 

[dougbgt6]

Engine bay smells can also sneak in through the heater air intake. Only a matter of checking the rubber seal on Vitesse/Herald but on a GT6 the bonnet bulge doesn't make contact with the seal and additional sealing is required.

My CO2 monitor has a 10 year life span and cost £15, the manual says test it once a week. John's cheap and cheerful lasts 1 year and you can't test it. I've encountered the cheap ones before I discourage anyone from relying on them.

Dou 

[Alex Lowe]

Thank you all for your comments it sounds like some matting and more importantly focusing on sealing the bulkhead gaps is key to success here

looks like ill be shopping for matting and mastic this evening 

[Ian Foster]

Alex

I have used Thermotec 'Cool it' on the outside of my original tunnel cover and have lined the underside with aluminium foil tape. The Cool it is a heavy aluminium foil on a self adhesive bitumen/plastic type base. Sticks like s**t!

There is not a lot of space between the cover and the gearbox etc. in some places and even with just the foil, I have to do a few repairs after the cover has been wrestled in and out. 

https://www.thermotec.com/

Ian

[Straightsix]

On 26/11/2023 at 11:37, Mark B said:

This is what I used on my Vitesse replicating the original insulation. I attached the insulation inside the tunnel cover with contact adhesive and home made staple/ clips through thefibreglass cover so no chance it could drop down and melt on the exhaust, somthing to bear in mind.

Photo bottom of thread.

https://sideways-technologies.co.uk/forums/index.php?/topic/7484-vitesse-sound-insulation

Hi 

Slightly off topic but thank you @Mark B for the sideways link 👍 It’s new to me, and looks a great forum for the race enthusiasts together with modified stuff, have only spent a short time on it, but I’m not getting much done at this rate!  

Cheers.

[JohnD]

Once again , may I point out that expensive insulation on the gear box cover is unnecessary?

First, heat transfer occurs in three ways, and only three ways:  Radiation, like an electric fire, Conduction, like burning your fingers on a hot saucepan and Convection, like that paint stripper gun!

The gearbox does NOT get hot enough for radiation to be a problem, and the exhaust pipe is well underneath and in the airflow.    There is NO radiative heat transfer from either into the passenger compartment.   They doesn't touch the cover - or shouldn't! - so conduction isn't possible.  Covering your gearbox cover with insulation is futile.

What DOES transfer heat into the passenger compartment is convection.   The Internal Combustion Engine is a disgracefully inefficient beast, that converts less than 40% of the energy supplied as fuel into motive force.    (The very latest designs can achieve 50%)   The rest is lost, as noise and HEAT, which must be disposed of, which is why we have the "radiator", which is really a convective loss heat transfer device.     It puts out at least 50% of the energy burnt as fuel as a very large volume of hot air.     The Triumph bulkhead between the engine, surrounded by all that hot air, and the passenger compartment has a great many holes in it!    They are for cables and wires that may or may not still be here, and  were sealed with rubber grommets, but those have often perished and will let that hot air through.   .

Why am I so sure of this?  Because I built the Silverback, the only Triumph ever to have the radiator in the back, mounted behind the hatchback door.   All that hot air was left behind, here was NONE under the bonnet, and Silverback was a cld car to drive, even in warm weather!

Don't waste your money on gearbox cover insulation! A dark garage and torch will find the gaps in the bulkhead - seal them with gaffer tape/grommets and as above, seal the cover to the floor, and you well remain cool!

JOhn

[johny]

of course noise is something else though!

[dougbgt6]

I agree with everything John says

Except

1 hour ago, JohnD said:

The gearbox does NOT get hot enough for radiation to be a problem,

He doesn't have a GT6 

And I agree with Johny keep the noise down!  JohnD is a racer so he likes the noise.

Doug

[Colin Lindsay]

My gearstick used to get almost too hot to touch, and the tunnel carpets were hot to the touch, so whilst the insulation might not have addressed conduction, it kept road noise down to a cooler degree.

[Iain T]

In the todays driving the gearbox cover does get hot as you can't drive at 50+mph all the time. In traffic the heat from the exhaust, engine compartment and heat blown back from the fan all goes to not only toast the bulkhead but also the gearbox cover. Even with Dodo Mat on the inside my cover gets hot. It's a fact of life on many classic cars. I talked to a Jensen CV8 owner who said the inside is unbearable in summer. 

Iain 

Edited December 9, 2023 by Iain T

[Ian Foster]

1 hour ago, Iain T said:

Jensen CV8 owner who said the inside is unbearable in summer

And Austin Healy 3000s

[Pete Lewis]

there is a lot more clearance around the fixed tunnel of the Mk2 2000 so tunnel heat is less of a problem but as the engine block temperature soaks 

into the gearbox the gear stick ultimately would fry eggs , too hot to handle 

Pete

[JohnD]

The heat you experience comes from the engine via the radiator.

I took sometime to explain this concept, but clearly, I failed.

Noise?   I'll give you that - it's about 90dB in the race car at full chat, but the GT6 or Vitesse model is irrelevant.

John