I have seen the mod by putting vents in the wheel arch. But has anyone tried using thermal grease to increase the conductivity as the air passes over it

You're addressing the wrong problem. The issue isn't inadequate intercooler metal to atmosphere heat transfer co-efficient, but inadequate airflow through the inner arch to get rid of the hot air out of the back of the intercooler.

In any event, thermal transfer paste is intended to improve conductivity between 2 solid surfaces, like CPU to heat sink in a computer.

Does the arch vent really work then?

I've never done it, but people who have and do trackdays say that it does, by reducing performance loss towards the end of the run. I can confirm that the inside of the RHF arch gets hot enough to melt a snowpack when the LHF doesn't.

Edited 24 February, 201115 yr by KenONeill

Might have to try it i have noticed a difference in performance when i been driving a while.

despite having a FMIC as standard my mk4 Ibiza has a vent behind where I presume the SMIC would be - would the arch liner from a mk4 Ibiza fit a mk1 Fabia?

That one am not sure about it probably will

Andy, is the vent in the lower front corner of the RHF arch liner? If so, that's the place. No idea if that liner would fit a Furbie though.

Might have to try it i have noticed a difference in performance when i been driving a while.

It does make a difference. I cut out the vent from a damaged TT wheel arch liner, cut a hole in my liner and Tigersealed it in.

Actually, further on this, the inner arch grille is there to protect the back of the SMIC, and IIRC is pop-rivetted in, so Andy could drill it out of the Ibiza without any issues that I can see.

Andy, is the vent in the lower front corner of the RHF arch liner? If so, that's the place. No idea if that liner would fit a Furbie though.

yep, that's where it is