The Cologne V6 had always been an engine that seem ideally suited to turbocharging, something that was not missed by Turbo Technics. They had already had experience with the XR4i and the Capri 2.8i so a turbocharged XR4x4 always seemed to be a logical step forward. TT offered several packages for the 2.8i engine ranging from 200bhp up to about 300bhp. TT also offered two packages for the 2.9i engined XR, a 210bhp single turbo version and a 230bhp twin turbo version. In all TT converted somewhere in the region of 1,000 cars.

2.8i Engine
On the 2.8i induction was provided by a large Garrett AiResearch T.03 turbo. Generally this was available as a 200 or 230 bhp package, but many other power options were available. When introduced in 1986 the 230 bhp conversion cost about £2,500.

These power figures were achieved by replacing the exhaust manifold with a new casting to feed the turbo via a large intercooler. The plenum chamber is modified to improve flow, compression is reduced to 8.9:1 (230 bhp version). The fuel system is also modified to ensure adequate fuel can be delivered. Finally a larger oil pump is also added.

Again revised dampers, springs and bushes were added.

2.9i Engine
The 2.9i twin turbo version featured a pair of Garrett T.02 turbos coupled to custom built manifolds, one per bank of three cylinders. A revised air cleaner assembly, extra fuel injectors and revised EEC-IV engine management system are also installed, the compression ratio is also reduced to 8.6:1. This gives a revised power output of 225bhp and 273 lb/ft of torque. No revisions were made to the driveline or suspension just a slightly beefier clutch to handle the extra power. In 1989 this conversion would have cost about £4,500.

In 1990 TT took delivery of a Sierra 4x4 GLS and breathed their magic upon it. At the end they had a car giving 280 bhp @ 5000rpm and an amazing 340 lb/ft @ 2500 torque reading. This was achieved again with twin T.02 Garrett turbos but with a lot of tweaking to the rest of the engine. This included forged pistons, balanced and polished con rods, large diameter exhaust valves and a milled and ported cylinder head.

The suspension was also looked at and improved by the addition of RS spec bushes, a second front anti-roll bar and improved shock absorbers and springs. Brakes were also uprated to 284mm ventilated at the front and 273 solid at the rear. Last but not least an AP Racing clutch was also fitted.

All this could be had for £8,700, a considerable sum when added to the price of a new GLS or XR4x4 in 1990. A review of the car in Performance Ford came up with the following observation. "The effect with this car is not so much of driving a turbocharged machine, but rather of driving a Sierra 4x4 which has five or six litres of V8 sitting inside its engine bay; this is the closest we have ever known to driving a turbocharged car which felt more like a supercharged one."

Below can be found some of the original sales specification sheets from Turbo Technics for the various conversions they offered. To download them right click and select "Save Target As".

This information has been been supplied via John Colquitt from the Re-Performance Centre. Visit their website at Re-Performance Centre.

View Sierra 2.0i Turbo Technic File Part 1 :
View Sierra 2.0i Turbo Technic File Part 2 :
View Sierra 2.8i Turbo Technic File Part 1 :
View Sierra 2.8i Turbo Technic File Part 2 :
View Sierra 2.8i Turbo Technic File Part 3 :
View Sierra 2.8i Turbo Technic File Part 4 :
View Sierra 2.9i Turbo Technic File Part 1 :
View Sierra 2.9i Turbo Technic File Part 2 :