Lotus Elan

New SS Exhaust

PostPost by: cabc26b » Mon Sep 12, 2016 2:54 pm

I don't coat my stainless headers because 304 stainless does not transfer heat very well . I witness the heat resistive qualities of SS every time I boil water in one of our SS pots.

Maybe Russ will show up and explain the science as I avoided thermals -

FWIW - one of my other cars uses stainless as a heat shield in the engine bay.

George
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PostPost by: Galwaylotus » Mon Sep 12, 2016 4:20 pm

I asked and found that my new manifold is made of 409 SS.
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PostPost by: Galwaylotus » Tue Sep 13, 2016 7:00 pm

Does anyone know the O.D. of the tube between the Y-piece and the silencer on a S3 SE? My local exhaust centre has 43mm, 41mm and can get 38mm tubes but the Y-piece seems to be 41mm and I don't want to go down to 38mm if that's smaller than the Lotus spec. I wish they had a tube swager that could reduce the inlet side by a couple of mm. :o
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PostPost by: alan.barker » Thu Sep 15, 2016 2:18 am

I hope it's a good fit and doesn't touch the Chassis :wink:
With SS there is much more radiant heat. My 3 classics have stainless steel and they are hotter then mild steel.
Elan Sprint, TVR 3000S and TVR 3000M
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PostPost by: Andy8421 » Thu Sep 15, 2016 5:37 am

UAB807F wrote:
Galwaylotus wrote:What am I missing?


I'm not sure myself on that one. If it's any consolation I've got a very similar looking set-up on my Elan, bought back in the days when Chris Neil were the go-to guys for parts not available at Lotus. It's no longer shiny but other than that I can't say I've noticed anything melting nearby. I wouldn't want to touch it after a run but otherwise it's just stayed there doing it's job..

Possibly controversial, but I don't get why you'd want to insulate one. The heat output from the engine is just the same if you've got a cast iron manifold or mild steel thing and it's got to escape from somewhere. AFAIK Lotus didn't insulate them from new ?

I'd have thought that you insulate the pipe effectively you're relying on all the heat escaping through the exhaust itself and consequently raising the actual running temperatures of the steel over a non-insulated one ? I don't know if that's good or bad but it might be interesting to know the wall temperatures before & after insulating.

Brian


Brian,

While the heat output of the engine is the same, insulating the manifold in some way will reduce under the bonnet temperature, and more importantly will reduce radiant heat from the manifold cooking nearby components / bodywork.

As for Lotus not insulating them from new, I have a long list of things Lotus didn't do, which would have made the car better / safer / more durable but cost money to do - so I am not sure Lotus not doing it is necessarily a good yardstick.

I have a big bore TTR manifold on the Elan I race. The pipes curl much closer to the footwell / firewall than the standard manifold and after a race the glass fibre would be smoking. Closer examination indicated the glass fibre was charred and was probably closer to being a 'firewall' than I would have liked. I wrapped the manifold with tape from Demon Tweeks and fitted a heatshield to the glass fibre. Now, after a race, inside the footwell is just warm to touch. I don't doubt the manifold temp is higher than without the insulating wrap, but it seems to have suffered no ill effects.

When I finally get around to restoring my Sprint, I plan to wrap the manifold to give the alternator / clutch slave / footwell an easier time.
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