924Board.org

[serz]

Hi,

why it's OK to wrap exhaust manifolds with special wrapping, preventing heat, and it is not done to intake/carge tube on 931? Imho heat influence from an engine and exaust, situated just under charge tube, could be decreased? Isn't it for this reason 931 has NACA inlet/outlet on hood?


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ex Porsche 924 1978
ex Porsche 924 1982
Now Porsche 924 turbo
http://www.thebestporsche.com

[flosho]

The exhaust wrap is insulated to keep the heat contained within the wrap. IMO, the benefits (if any) would be negligible when wrapping the upper charge tube to keep it from heat soaking. It may even do the opposite and not allow the heat to dissipate from the charge tube.

There is also the risk of it unwrapping, or becoming damaged and getting caught in the cam pulley/timing belt. It also would not look great or be the easiest piece to wrap with the different vacuum lines, electrical connections and other items on the charge tube.

Your best method of fighting under hood temps would be to ceramic coat the turbo manifold and down pipe, along with keeping the factory engine belly pan intact.
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[This Space For Rent]

[fiat22turbo]

My uncle used reflective, foil-backed insulation on the intake of one of his non-intercooled turbo cars. Said it made a difference in knock during autocross runs in the summer time. He also would ice the intake tract down between runs.

It could work if you used the proper materials, That thermal wrap would be the wrong material to use. I would look at a ceramic coatings for the valve cover, charge tube, intake, etc and perhaps a phenolic spacer for the intake manifold and/or throttle body.

Use a thermometer to measure the before/after effects if possible (though that may be tricky to get the environmental variables to stay close enough to make a reasonable outcome).
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Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose)

[!tom]

One reason for this is to keep the exhaust temperatures as high as possible prior to entering the turbo, as this maximizes the turbo efficiency.

It's not so much as to keep everything else cool, but more to retain as much energy in the exhaust in order to increase the power available to the turbo.

The exhaust will cool as it expands in the turbo. Having more heat to begin with means more energy can be recovered.
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78 924 NA
5-lug

[ideola]

The biggest cause of heat in the intake tube is the inefficient K26 turbocharger (compressed gasses gain heat), not reflected or radiated heat from the engine itself.

We've had several thorough discussions on heat gain and thermal dynamics in the past (see threads on phenolic spacers). The design of the charge tube is such that the air passes thru it very quickly, and it is NOT designed as a good heat exchanger, so it is highly unlikely that any heat from the charge tube itself will be inducted into the already-hot compressed charge air. It simply isn't in the charge tube long enough to exchange any heat with it.
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erstwhile owner of just about every 924 variant ever made