Tunnel scorched by exhaust heat

[Donels]

My +2 is fully disassembled and body work in progress. On the RH front of the transmission tunnel the resin is scorched and degraded by exhaust heat. Has any installed a heat shield in this area? If so what do you use?

[nmauduit]

I've used a corrugated aluminium sheet for the exhaust of my S4 (from Nimbus - no affiliation on py part), the variety without insulation fabric : very easy to work with, to cut and form, held in place with a few pop rivets. It is thinner than the fabric backed variety, which may isolate more (I've used that version on the transmission tunnel of an E type, the adhesive sounds like a good idea but I'm not sure how long it will stick). As for the exhaust header themselves, I've wrapped them in insulating band down to the end of the gearbox.

aluminium heat shield

[JimE]

The S4 and Sprint silencer had it's own heatshield. Jim

[CBUEB1771]

The question is about the front of the tunnel, not the silencer end. This is an unusual problem and I have not seen it before. Is there any chance that your +2 has a 1600 tall block conversion? If so a standard exhaust manifold will be elevated closer to the body shell and could result in the problem you describe.

[Donels]

It's a 701M block so it is correct, however, it has a 3 piece exhaust manifold and I wonder about exhaust gases escaping from the front of the Y piece. There are no slits in the pipework to aid clamping so it has to be crushed to get a seal, not ideal! See below picture.

The engine and g/b had been removed from the car when I bought it so I have no idea how close the manifold was to the tunnel.

[mbell]

That looks like the standard manifold (or same as on my car). I did have a leak of mine so re-fited with a bit of exhaust paste to seal.

I don't think it a common problem with standard headers on the +2 but the temp of the manifolds will vary depending mixture etc, so a weak mixture could cause higher temps and make it more likely to cook the body. Or possible fitment of wrong engine mounts moving the engine closer to the body.

Personally I'd repair the body as need and fit a heat shield to the body between the chassis and body. This will ensure protection for the body from the issue and also reduce the heat soak into the cabin.

[Grizzly]

I found on my 2 seater the very end of the trans tunnel (passenger foot-well) was so dried out by the exhaust manifold i had to replace quite a large section (the resin had dried out to the degree you could poke a screw driver through the mat), after the repair i fitted a sheet of ZircoFlex which has held up well. I also found the grp in the bonnet above the manifold was quite badly dried out, after it went back on the road i noticed the bonnet was almost uncomfortably hot over the manifold if i had been stuck in traffic (i fitted a heat shield on the inside of the bonnet that fixed that)

Moving onto the +2 i had an issue with my +2 boot floor, i didn't have the later heat shield so the stainless exhaust bubbled the paint off the floor in the space of six months or so.

Another heat issue i had was my new Stainless manifold melted the plastic cover on the back of the Alternator and with said manifold i couldn't sit in traffic long before i started having clutch issues, so i went back to Mild steel (ceramic coated).

[Donels]

Yep that sounds like my problem. I too have replaced the grp in the affected area. Sounds like a sheet of Nimbus G11 is required. Thanks.

[Grizzly]

I really like nimbus but i went with Zircoflex 3 because it was self adhesive, easier to work with and frankly looked better.

But if you are feeling flush ceramic coating the exhaust is the most effective solution, i noticed my under bonnet temp drop dramatically (just be sat down when you get the quote)

[Bigbaldybloke]

A few pictures of the mods and additions I?ve made to reduce heat from the exhaust manifold to the body and alternator. The alternator shield is secured using the engine mounting bolts. I have used the zircoflex self adhesive alloy covered sheet on the sides of the passenger footwell, only needed one A4 sized sheet and I managed to fit it with the body on the chassis, by carefully making a paper pattern to cut the heat shield to shape before peeling off the backing on the adhesive. You can just see it behind the servo. I?ve also made a shield using the dimpled alloy sheet inside the silencer recess in the boot floor, mine has the early transverse silencer. For info I?ve also fitted a banjo type connection to the clutch slave cylinder to get the pipe as far away as possible from the exhaust.
I had several alternator failures which I initially put down to vibration, but in the end decided it was heat from the exhaust manifold frying the electronics, hence the heat shield, cheaper than ceramic coating the manifold, but I may go that route in the future if I still have problems.

[Bigbaldybloke]

Just a quick comment, fitting all the blanking plates and foam etc around the radiator to ensure it has a good flow of air through it reduces the flow of cool air that gets to the alternator and around the engine bay in general so can contribute to the heat levels. Has your car got all these in place?

[baileyman]

If a car has an unblanked rad, rad cooling will be diminished, so the thermostat tries to increase flow, increasing the exit temp from the rad, I think. If engine temp remains constant, then total heat in the compartment will be the same, I think. If the alternator does not overheat in a compartment that has the same heat content as before, perhaps it is the lucky recipient of a wee bit of cool air leakage aimed just so. Perhaps the alternator could benefit from its own ducting while also blanking the rad.

I could be way off base. Cooling issues are interesting.

For instance, it sure seems like a better location for the oil cooler under the rad, perhaps mounted horizontally to avoid bashing, since the air there is cool and stays out of the compartment.

[Grizzly]

baileyman, the rad foams actually make quite a difference to the water temps... when i first put my 2 seater on the road on the warmer days i was seeing high 90's when cruising and well over 100 in traffic, since fitting the foams it never goes over 95 even sat in traffic (on a triple core later style small rad).



I know Ceramic coat is ridiculously expensive but it's surprising how little radiant heat comes off the manifold, i have the zircotec performance white and i can hold my hand 10mm away with the engine running quite comfortably but it's still nasty burn hot if i make contact. Strangely the ceramic coating didn't make much difference to the water temps but made a huge difference to the under bonnet temps especially at lower speeds.

[Donels]

Ceramic coating is used extensively on aero engine turbine components, where it?s called thermal barrier coating, which is a more explanatory name. Typically it reduces the surface temperature by around 100 deg C at 1000 deg C metal temperature, so it will reduced underbonnet heat significantly, probably reducing the manifold surface temperature by around 50 deg C, less than the 100 deg C in turbines due to the lower metal temperatures.

It is usually applied in 3 thin layers around .003? each layer, with each layer requiring curing, hence labour costs and heat treatment costs are incurred 3 times, explaining the cost.

A great solution but expensive.