Can you use the CHT sensor in the head of a 1.8 Blacktop Zetec (from a focus) instead of a coolant sensor with Megasquirt?

Or do you have to fit a coolant sensor in an other location?

Yes you can use any sencors with Megasquirt but it needs calibrating with their readings using Easytherm.

Basically you tell it the resistances of your sencor :
as cold as you can get it (usually around 0deg surrounded in ice)
Room temperature or higher
And around boiling (usually immersed in a cup of water just poured out of the kettle)

But it can make for problems should the ECU ever have the firmware upgraded or you start tuneing the MS from a different laptop, it requires the information coping again.

Its also not good practice to use 1 sencor for 2 uses (just incase that sencor is already in use for your temp guage)

Oooh just remembered.. obviously if you put it anywhere else it should be in the engine side of the water system where there is constant flow and full engine temperature, not at the other side of the thermostat or similar.

[Edited on 15/5/08 by MkIndy7]

FYI the mondeo thermostat housing also has a CTS location in it.

The focus ones are prone to cracking, both our company focus's have had new ones after cracking, so its worthwhile putting a nice new one (mondeo) on anyway imho.

That said, no reason you couldn't use the CHT as long as you're not sharing it with something else as MKIndy7 said.

If you're fitting aftermarket gauges etc, it may be worth getting a silvertop thermostat housing - this has a 3/8npt hole perfect for aftermarket senders and bolts straight onto the blacktop.