Turbo system
Left, the Garrett T03 version that came standard with most 900T's. Compressor inlet size is 34 mm. Right, the T03 turbo off an 1988 9000 Turbo. At 40 mm, the compressor wheel and inlet surface are about 38% bigger, whilst the turbine housings are the same.
In order to use the turbo off a 9000 in a 900 you have to 'clock' the turbine and compressor housings versus the center housing by loosing the bolts, very carefully turning the housings until their positions exactly match those on the original turbo (if it's a degree or two off, you get a massive leak at the oil return pipe, don't ask me...) and retighten the bolts very evenly to prevent the turbine and compressor wheels from rubbing against the insides of the housings. In addition, the wastegate and wastegate actuator mounting plates from the 900 turbocharger must be transferred.
'87 and later 9000T's and '88 on 900 T's have turbochargers with watercooled bearings. In order to retrofit them to older 900's the best way is to order a new lower radiator hose which features an extension for the water return line, and the hard line which goes into it. The supply line can be taken off the thermostat housing on 8v Turbo's.
Unfortunately the TD04 turbo's from 2.3 litre 9000T's are not a direct fit on the Classic 900 due to a difference in bolt patterns on the exhaust manifold mounting flange. There are adapting plates around from hobbyists in Sweden, but then you will have to reroute the oil return and supply lines.
The turbo intake pipes (turbo-intercooler and intercooler- throttle body) off an '89 or later 900T16 are made of mandrel bent aluminium rather than cast alloy on the earlier cars, and have a significantly bigger internal diameter and gentler bends. This makes for better efficiency and less turbo lag. The intake air box-turbo pipe (center) is from a 99T or very early 900T, and made of the same material. I polished them lightly -mainly to clean them up- using waterproof grade sandpaper and rubbing compound, and clearcoated them using a spray can. On Saabine, a fifth injector is mounted on the intercooler-throttle body elbow so the turbo dump valve had to go on the turbo-intercooler pipe. For this reason, the 'regular' Trent Saab athmospheric dump valve shown here has been replaced by an FSE group A dump valve that Trent Saab had originally made for a Subaru Impreza WRX rally car, which also has the dump valve placed upstream of the intercooler which of course means the internals of the valve must take much higher temperatures. For the mounting of a dump valve, a piece of 1" aluminium pipe has been welded to the intake pipe. The plastic fitting on the other side takes a vacuum hose which is connected to the intake manifold using a T-piece.