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MG Midget and Sprite Technical - heat shield exhaust
|Anyone some results with a heat shield under the exhaust running under the floor.|
Mine is getting so warm it melts my my shoes
|And burns away body coating|
|Are you sure your mixture and timing is OK. Running with a weak mixture can cause the exhaust to heat up.|
I run a supercharged EFI sprite with a larger exhaust (and a WB sensor in the exhaust).
Mixture is perfect.
Exhaust is maybe 1 cm under the floor
|In that case it's self inflicted!!!!|
Not sure what to suggest. You need to create a greater surface area without enlarging the pipe which I think is difficult. Ceramic coating inside and outside of your exhaust pipe maybe. Many cars have heat shields between floor and cat.
My Mini MPI has such a heat shield which is quite small and relatively cheap.
|I drove the 1971 midget across the Mohave Desert in June one afternoon. We stopped for fuel and the ambient temperature was 49 C. We filled the foot wells with ice which never melted. It just evaporated straight away.
I now have an insulating mat under the carpet with rubber mats and carpet mats on top. This keeps the feet from blistering but it gets warm all the same.
Driving up a sustained climb in the Mohave, it always impresses me to pass an overheated Lexus or two with the temperature gauge in the Midget still below "H".
Technically water going from solid to gas would be sublimation not evaporation and I don't think that happens under normal conditions above the triple point of water IIRC 0.01C . I have seen what you describe though with a hot surface were the melting ice produced water which evaporated so quickly you'd hardly notice, I'm glad I wasn't in the car in those conditions.
Regarding the original question both my Lancias, a Beta and Delta turbo had stainless heat shields above the exhaust running down the centre of the car so I think a thin stainless plate placed between the exhaust and underside of the car, maybe half way between, would help reflect heat and allow a barrier layer and airflow between the sheet and floor pan. Something like bright annealed stainless would be my choice as the shiny surface will reflect heat from the exhaust better than a dull surface.
Amazing story on driving at Midget at 49 degrees C. You must have a really well flushed radiator, heater and clear engine block and using a good quality anti-freeze/rust inhibitor? (Nigel style backlfushing or perhaps a superior 'Glenn Method' worth sharing?). Did you run with the heater tap on but with the heater fan switched off?
You use of ice reminds me of a hot 24 hour saloon car race at Snetterton (Norfolk, England) in 1994 when a tuned Nissan Skyline GTR (Andy Middlehurst run and driven IIRC) started having problems during the night with the exhausts making too much heat for the rear mounted fuel tank (!) so at subsequent pit stops the pit crew filled the boot (trunk) with ice and water. Pic of the car - without water and ice streaming out: https://www.flickr.com/photos/trackside/32385409017
|Fed up with wrinkles in the carpet of my BV8 I decided to cut sheets of 9mm plywood to fit the whole floor each side and glued the carpets down to the ply.|
The effect of this is also to insulate the carpet from the steel and even on the hottest day after a long run, the carpet is barely warm.
|Chris at Octarine Services|
This thread was discussed between 24/06/2020 and 27/06/2020
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