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.
Supercharging, turbocharging, charge cooling
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- This 'gloopy' stuff is Xylan, not quite as easy as spraying cellulose paint unfortunately. Like spraying, well, .. glue actually.
- Xylan 1010.jpg (112.02 KiB) Viewed 7119 times
- Spray booth and nice spray gun, good evacuation of particles is vital or you end up with 'polymer flu'.
- Dewilbiss gun.jpg (110.81 KiB) Viewed 7119 times
- Rotors for a non-Lancia blower coated & ready for 'fashing off' at 10o deg C prior to next coat. It can blister if you coat quite thick (1 thou" plus) - it all has to be done again.
- rotors first pass ready for 'flashing off'.jpg (109.94 KiB) Viewed 7110 times
- Lancia Volumex blower partly built up after coating.
- Vx coating 02.JPG (18.07 KiB) Viewed 7092 times
- Xylan 1010 used on rotors and inside face of front and rear housing. It's not possible to coat inside the main casing with any certainty of achieving a consistent layer thickness, and baking at 240 deg might well distort it.
- Vx coating 01.JPG (14.82 KiB) Viewed 7099 times
- Polymer coated Fiat TC oil pump. With care, I can coat all the rubbing surfaces, but I emphasise 'care', too much Xylan and it will overheat and seize - or won't turn at all.
- polymer coated oil pump_01.JPG (25.77 KiB) Viewed 7100 times
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