Footwell Cooling

[L777JDP]

Hi everyone,

I found this old thread https://www.lotus7.club/forum/techtalk/footwell-cooling-strategy on this topic, and wondered if there was any new insight into this? A commercial solution perhaps. The problem seems to be heat soaking through the metal from the engine.

I've got a windscreen and drive with the side doors fitted, and a wind deflector across the headrests from soft bits, so in this weather I'm sitting in a hot bubble, with the heat coming through the metalwork of the tunnel and footwells.

I figure taking the doors off might give a reasonable improvement, but I've yet to try that as I have the standard door mirrors.

 

[Tazio]

I run aero, and still suffer the same, the heat soak can only be addressed by tackling the source, in my case it's big exhaust primaries, either wrap them or get them ceramic coated, once that's done insulate the tunnel and peddle box.

 

[L777JDP]

Thanks Tazio. The temperature the exhaust will presumably gone up a bit, and as radiative heat transfer is driven by T raised to the power 4, dropping the surface temperature by wrapping it is the way to go. 

Ceramic coating sounds both nice and expensive, but I’d like to hear from anyone whose had it done, and any tips. Similarly anyone who’s wrapped theirs in tape it would be great if you could share your experiences.

[andyl]

DrJ or John,

I have no Caterham bad experience as in the weather I just use a windscreen and let the air have its way. However we did have heat soak problems on a Clubmans (Mallock like) front engine race car, it even used to overheat the diff in a 20 min race. The problem was a mixture of convected and radiated heat. The first problem is that we didn't manage the air through the inside of the body so the engine heated the compartment up and it had nowhere to go. Secondly the front rad also provided hot air.

We ended up putting Nasar ducts in the floor near the exhaust, then we channeled the air from the radiator in a large duct within the bonnet. 

However just as a few thoughts I probably would try:-

1) Ducts in hot air locations.

2) Maybe try this https://www.centaur-ind.com/product/thermcoat-advanced-thermal-insulation/ (of which I have no experience)

3) Stick this around the tunnel area and footwells https://www.demon-tweeks.com/uk/cool-it-heat-resistant-mat-245869/ if you go on the Demon Tweaks webpage and search for "Heat Shield".

I have used ceramic coating, which should incidentally coat not only the outside but the inside of the exhaust/manifold I used Camcoat http://www.camcoat.com/, although I think there was a member also ceramic coating on here, but please coat inside and outside.

Good Luck!

[Jonathan Kay]

Ceramic coating sounds both nice and expensive, but I’d like to hear from anyone whose had it done, and any tips. Similarly anyone who’s wrapped theirs in tape it would be great if you could share your experiences.

• Exhaust wrapping
• Exhaust ceramic coating

Jonathan

 

[Philip L Anderson]

When I built my Caterham 20 years ago I insulated the foot wells / firewall and tunnel with Cool-It insulation by Thermo Tec. It’s a woven fiberglass mat with an aluminum foil face. I banded the cut edges with their Thermo Shield Metallic Insulating Tape (for appearance) and stuck down the edges of the insulation with 3-M Super Weatherstripping and Gasket Adhesive. One only wants to glue the edges as the air space between the fiberglass and aluminum acts as a thermo barrier. The inside of the aluminum is cool to the touch. I have never had any issues with engine heat, and the material has held up very well over the years. However, the engine and gearbox should to be out of the car to do a proper job.

When I had a stainless-steel exhaust system I did not ceramic coat or use insulating wrap. The exhaust system I have now is mild steel that has been ceramic coated for rust protection. It is my understanding if one ceramic coats the exhaust system, and then uses insulating wrap, the pipes will get hot enough to burn off the ceramic coating.

[OliverSedlacek]

I'm still convinced that heat from the gearbox is a significant contributor as changing from 4 speed to 5 speed box made the situation much worse. Insulating the tunnel seems to just bottle up the heat so the gearbox runs hotter and the heat gets out anyway. I'm upgrading my custom heater/cooler fans, and next time the gearbox comes out I'm going to try a fan in the tunnel exhausting the air out of the bottom of the tunnel.

[pugwash]

Running the heater fan with the heater water valve turned off will blow ambient temp air into the foot wells and may displace some of the hotter air.  Of course if you don’t have a heater that’s not much help!  Oh, and try losing the wind deflector between the seats.

Then the doors........

And then the windscreen.....

 

[L777JDP]

The solution I went for was to get the primaries lagged. It has made a huge difference, to the extent that I now appreciate the heater now that it has turned a bit nippier in the South East of England.

[Jonathan Kay]

Thanks for the update.

What did you use, please?

Jonathan

[john milner]

Check that when you think the heater should be off that it is actually off.

[HendrixsWhiteStratReturns]

Have to say - bit of a Heath Robinson fix this but it worked. Huge fan, clipped to dash, plugged into 12v socket and directed at passenger or into the passenger footwell and it worked a treat. Not really fancied wrapping the primaries :-/  

 

[David.Ashley.Poole]

Hello DrJ,

i have always insulated the primaries - but you can only do this if they are made from stainless.  If they are steel they will rust ferociously and not last long.  I always used Thermo-Tec traditional and then transitioned to black when it came out.  I also sprayed them with the insulating coating, which is supposed to provide some degree of waterproofing.  But in heavy rain when I stopped in traffic it used to look as though I had a steam engine under the bonnet... but it did keep the cockpit cool and it reduces the thermal load on the engine from the radiant heat.  The Thermo-Tec also used to look pretty ratty fairly quickly.

The last time I used Titanium wrap with much better results.  The present wrap has been on for about 18 months, and still looks pretty nice even after four hours on the dyno getting a new map - and it does not absorb water, so no more steam.  There is supposedly some minor benefit in performance from keeping the gasses hot (and less dense) until they are out of the primaries, but the link below is to a test on a V-8 in the USA where they did not see any performance difference - but this is a hotly debated topic that may need its own wrapping...

https://www.hotrod.com/articles/ctrp-1203-titanium-exhaust-wrap-wrap-it-up/#ctrp-1203-titanium-exhaust-wrap-wrap-it-up-005

[Jonathan Kay]

Have to say - bit of a Heath Robinson fix this but it worked.

Could you add some photos of it fitted, please.

Thanks

Jonathan

PS: I've often wondered about an array of the little fan units used in personal computers.

[HendrixsWhiteStratReturns]

Hi Jonathan

Yup I'll dig some out this weekend. It's not a particularly pretty fix but it pleased a particularly vocal SWMBO moaning about the heat and she was very happy with the results so that was good enough for me. (and more importantly her !)

 

[Jonathan Kay]

Thanks.

... but it worked.

The Founder would be proud! ;-)

Jonathan

[L777JDP]

Hi Jonathan, sorry I missed your question about the product used. I’ve sent you a PM.

[HendrixsWhiteStratReturns]

Jonathan - here you go, can clamp either way to cool footwell or the passenger. As I say, not remotely pleasing to the aesthete but it works...

[L777JDP]

Jonathan asked me to post what Partridge Green Motorsport used on my car.

The product is called thermo-tec-exhaust wrap. They also used the hi-tec-coating from the same supplier (which is sprayed over the wrap). All held on by stainless steel locking ties.

The hi-tec coating is a high temperature silicone as I understand it, which cures as it gets heated. It produced a bit of a smell for the first couple of short drives, but nothing too offensive.

Best regards, John.