10 replies to this topic

[01smartc]

Hi all, mite sound stupid but how hot does the intake get?

Reason i ask is that i have some bike carbs and i am making some custom ram pipes as the intake to the carb is oval so conventional rams cnt be used... i have got some polymorph plastic which i am goin to mould into the pipes.. however the plastic is fully mouldable at 62 degrees... so would it get hot enough there to make the custom pipes distort?

Cheers Smartie

[Jammy]

On a standard setup where the exhaust and inlet manifolds are as one you used to get some heat transferring to the inlet and carb, thats why there is the thick plastic spacer there, to isolate the heat. This problem was mostly overcome with the aftermarket seperate alloy inlets you can get.

I doubt it would get 60* hot at the back of the carb, especially if you used a heat reflective sheild underneath it. However I'd watch it closely on the hottest of summer days!

[dklawson]

I'd still worry about radiant heat off the immediately adjacent exhaust manifold/header. With a metal intake, particularly an aluminum one, the incoming charge can carry some of this heat away. Plastic... not so much.

Before committing to this, why not make a plate or block out of this material and wire it onto the side of your Mini's intake manifold? After you've driven around for a while you'll know if it's going to be affected by the heat.

That said, if the material flows at 62oC, I'd be very concerned that the added stress from the weight of the carbs will cause the material to slowly deform. Also, what's the effect of long term gasoline exposure on the material you're talking about using?

[Ethel]

Spun aluminium or CF / Fibreglass moulding? You can get high temperature, fire retardant resin and there are quite a few metal spinners about - suppose you'd still have to work in the oval.

[Jammy]

Could always get an IR thermometer and double check, could save you a lot of work for nothing.

[01smartc]

The car is in pieces so cnt drive it round and see! lol ... erm its only as a ram pipe to smooth the airflow into the carb so petrol resistant etc wont matter... would consider making a mould and pouring somthing into it to set ... but wht would i pour in? :s

Cheers

[Grimmy@JHE]

i would say get a spinner to make some proper ones. they would look the nuts too.
at my uni they use a machine called rapid prototype, which is basicly a cad machine that makes what ever you draw out of some sort of dust and glue i.e. trumpets. but yet again, i have only seen these used on 16v heads and not the mini's design. definatly a couple of layers of exhaust lagging if plastic is used
hope i have been some help.

edit: if your going to get some made, research lengths as they make quite a differance on torque curves.

Edited by grimmy, 23 November 2007 - 10:03 PM.

[Ethel]

Your best option could be to make up a wooden former to match your orifice then use it as a drift to reshape an existing ram pipe

[dklawson]

Ram pipes. Well, that's different. They won't be in as close proximity to the exhaust manifold as the intake manifold is.

[Xiao_Bin]

if that plastic is fully mouldable at 62°C, it would be soft already below that, right?
At idle or even just parked under the sun it definitely can get hotter than 40/50, then on acceleration you'll just suck the ram into the engine

[998dave]

I'd have to say 62 degrees melting is far too low, it's going to go floopy even if it doesn't melt.
You could use a thermoset, Polyphenylformaldehyde (Bakelite), or something similar, but then that can be quite brittle.

Best option might be to make a round pipe, and 'squash' it at one end to make it suit the shape of the carb intake!?

Last option, but the airbox / rubber mounts from the bike, and use them to make a mould then, use that to make the ram pipes?

Dave