Xylan coating pumps & superchargers

[Guy Croft]

I do a bit of this from time to time, on the Lancia Volumex unit and some others. I use Xylan 1010 conductive, a Teflon poylmer not unlike the stuff used on non-stick frying pans, except a harder version with nickel in it to stop the build up of static. My coated blowers have been used on methanol powered engines, not just petrol.

Very good on oil pumps too, especially when you cannot get a new one and want to restore clearances. Used a lot in FI, Xylan, on sump scavenge pumps etc.

The flow characteristic of the Roots blower depends to a great extent on running clearances, rotor to rotor casing/end plates. With Coating you can close up some of these and hopefully induce superior flow (less back leakage and higher manifold pressure). Unfortunately so far I have been unable to get any bench testing done to give quantifiable results. Xylan, especially wetted with fuel or oil, is almost frictionless. It is 'sacrificial' in the sense that being a relatively soft plastic, if there is light contact somewhere it will simply rub off and find its own level, go thru the engine without causing damage.

On the Vx I do the rotor sides and the end plates as shown below. I don't coat the ends of the rotors because they run too tight and it might seize. Doing the end plates doesn't affect the end foat and heps redeuce friction. You have to make sure the ends of the rotors are well polished or they will cut the coating to pieces, likewise the inside of the main casing.

The actual spraying takes minutes, but the pre-prep and cleanup after is very time consuming. The Xylan thinners is very agressive and eats into everything, including skin. The polymer comes out in a different shade of dark green each time I use it, seems to vary with age, doesn't affect performance though.