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Throttle body transition casting rework info....(long) Posted by REM in Seattle [Email]  (#4)  [Profile/Gallery]
(more from REM in Seattle) on Thu, 26 Oct 2000 17:45:38
In Reply to: Link to Throttle body transistion casting pictures..., REM in Seattle [Profile/Gallery]
, Thu, 26 Oct 2000 15:39:52
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Smoothing/Porting the throttle body transition casting on the NG900
As first pointed out by Dean on this BB, the throttle body transition casting has a pronounced 3/16” lip where it meets the intercooler outlet tube and again where it attaches to the throttle body. These mismatched transitions are an easy place to reduce the restriction in the intake system by smoothing or porting the throttle body transition casting. The following is the procedure I used to remove the intake restriction caused by the throttle body transition casting.
First I removed the throttle body transition casting from the engine. Be sure to cover the throttle body with a cloth or plastic bag to prevent anything from getting into the intake. Remove the O-ring and sensor prior to porting the throttle body transition casting. I used an engine porting kit, Item #46056, about $30 from Eastwood Company (http://www.eastwoodco.com). It consists of a couple of 1/8" dia. spindles that accept 'cartridge rolls' of sand paper. I used a 3/8" electric drill to drive the spindle. I started with 80 grit and finished with 240 grit. I don't know how many 'cartridge rolls' came with the kit. I borrowed the kit from a neighbor and he had purchased extra 'cartridge rolls'. The job took about 1-2 hours with a couple breaks along the way. A vise, or Stanley Workmate, to hold the casting is a big help. In the end, the throttle body transition casting made a smooth, step less transition from the intercooler outlet tube and to the throttle body.
Thoroughly wash and dry the throttle body transition casting using soap and water prior to re-installing it. Lubricate the o-ring with a little silicone grease (dielectric grease), and then reinstall the o-ring and the sensor. This would be a good time to clean the throttle body and apply some good lubricant to the accelerator cables and linkage.
Next I removed the intercooler inlet and outlet tubes. I needed the car on ramps to reach the hose clamps on the intercooler inlet tube. I wanted to remove the ‘silencer’ from the inlet tube to further reduce any restrictions to airflow. The ‘silencer’ is a black plastic perforated piece wrapped with insulation, installed in the intercooler inlet tube directly after the turbocharger on all 1994-1998 Saab 900 turbos. The ‘silencer’ appears to be designed to act as a muffler for the turbocharger. Remove the ‘silencer’ by grabbing it with a pair of needle-nose pliers and pulling it out of the intercooler tube. The ‘silencer’ is destroyed in the process. Mine tore into a few pieces as it came out.
I then wrapped the intercooler tubes, both the inlet (lower) tube and the outlet (upper) tube, with Thermo-Tec Thermo Shield high temperature reflective insulation (http://www.thermotec.com). I cleaned the tubing first with lacquer thinner inside and out. I don't know that the insulation will make a big difference but it looks 'fast'. As it is cool and rainy here in Seattle now, I will have to wait until summer to see if there is any real difference in the temperature of the intake charge.
Insulating the intercooler tubes took about a 1-½ hours. A little soapy water on the ends of the intercooler tubes helps to slip them back into the rubber fittings. You probably don’t want to use silicone grease on the rubber coupler or the ends of the intercooler tubing, as it might allow the tubing to slip out of the coupling when under pressure. Be sure the tubing is properly seated and the clamps are tight, as the turbo pressure will be trying to blow the tubing out of the joints. If one does pop off, be very careful putting it back as the turbo and exhaust get very hot very quickly.
It may just be wishful thinking, but with the throttle body transition cleaned-up etc., the car has a much smoother accelerator response and a smoother idle. Turbo spool-up may be improved as well.
_______________________________________ REM in Seattle Current: 2013 Volvo XC60 R-Design, Rebel Blue, 3.0L 6-cyl turbo, Automatic 2024 MINI Cooper S Convertible, 2.0L 4-cyl turbo, 6-speed manual Former: 2005 Saab 9-3 Aero Convertible, Steel Gray metallic, 2.0L 4-cyl turbo, 5-speed 1998 Saab 900SET 5-door, Silver, 2.0L 4-cyl turbo, Automatic 1991 Alfa Romeo Spider convertible, Alfa Red, 2.0L 4-cyl, 5-speed 1984 Saab 900T 3-door, Red, 2.0L 4-cyl turbo, 5-speed
, Thu, 26 Oct 2000 15:39:52, Thu, 26 Oct 2000 17:45:38 <-- Viewing This Message
, Fri, 27 Oct 2000 08:57:14
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