[BiturboS4] Defi Heads-Up display boost gauge and TT

[Edwards, Dave]

Installed mine at the weekend. Many thanks to Keman (who used to post here),
the articles on AudiWorld and the info on MachV's site. Most of all Keman
since he did the R&D work for controlling the coolant afterrun pump from the
TT. For those who don't know it means that my TT does NOT keep the engine
running, instead it keeps the coolant flowing through the turbos and keeps
the radiator fan going for the controlled time after I switch off.

To be honest I wasn't too bothered about having a HUD boost gauge: I wanted
a boost gauge and a turbo timer so it made sense to use a combined unit. I
only know of one other combined type (the Blitz), but of course I'd have the
difficulty of deciding where to mount the display. The Defi HUD is so
simple: Just stick the box on the top of the dash and it's reflected in the
windscreen. It's also great that it has both a digital and analogue display.

If anyone wants to do Keman's install then I have several tips:
1) You only need two relays if one has a change-over contact.
2) You can access all the wiring you need from the terminals under the dash
and the wiring at the back of the fuse-box. There is no need to hack into
steering column wiring as others (including Keman) have written. The wiring
at the back of the fuse box is much more accessible.
3) The only tricky part is splicing into the wires to the coolant
temperature sensor. Don't bother as it's too tricky mainly because the wires
are quite solder-resistant. After failing to do this I ended up cutting the
wires and patching in a new set.

I had a quick test of the boost gauge and got 1.26 bar peak reading. The
turbos are working great then!

Cheers,
Dave