http://www.honles.com/thomas/supra/index.htm

OK, the continuing saga of my Supra 89 Turbo ... First modifications done to fix the turbo performance and give it a little more kick.

Turbo Blow-Off Valve (BOV)

I checked the stock BOV and indeed it was completely blown out.

The tubing seemed original vintage, and quite brittle. You can see the badly cracked PCV hose furthest on the left, the stock BOV top center, and other old parts that I replaced. Unfortunately I didn't get a shot of the badly cracked "accordion" hose (air hose #7) before the trash service took it all away.

It's a wonder that I got even the +4psi out of that leaky set of tubes and a stuck wide open BOV.

I checked the Saab and the Porsche versions of the Bosch BOV with the dealers. Both were still less expensive than the Toyota stock source.

The stock Toyota BOV was $89
The Porsche dealer quoted me $55 for the Bosch BOV
The Saab dealer quoted me $44 for the same Bosch BOV

I ultimately contacted ABJ in Boston (1-888-885-3500), and opted for the "Porsche" part (my bias for Porsche vs Saab being worth whatever it is, Bosch # 0-280-142-108 ) and shipped to California, got the "SOGI" price, about $30 at my door just 3 days later.

According to the tech tip, the Porsche version has a higher pressure threshold than the Saab version. I found the details here: http://www.supras.com/sogi/techtips/1_engine/1002_MKIII_BOV_upgrade/index.html Fifteen bucks and a quick trip to 2 Kragen Auto Part stores yielded the necessary 3/4" I.D. to 1" I.D. hoses to adapt the larger Bosch BOV to the stock intake fittings, and some stainless steel hose clamps. The unit went in very nicely. Biggest challenge was getting the taller configuration cut down low enough to have the actuator vacuum line clear under the hood.

side view - The Bosch unit has 1" inlets, so adapter radiator hose was used (Kragen Auto Parts) to mate the 3/4" stock inlets to the Bosch unit. top view - The installation was simple, replacement hose clamps were necessary to get the heavy duty vacuum line tubing , upgraded to 1/4 inch i.d. fuel line tubing sealed properly front view - Bosch BOV installed,. note the vacuum line is tied off to intake hose, necessary to clear underneath hood

 

The SAAB unit is virtually identical, and looks like this (not my car, a borrowed pic from Netherlands):
http://www.supras.nl/images/SaabBOV3.jpg
http://www.supras.nl/images/SaabBOV4.jpg

Test drive after BOV and all related intake tubing replacement showed about +5.5 psi on the stock turbo boost gauge, and the low RPM performance was a lot smoother. Total cost of mod: $45. Not bad. The replacement of the "accordion hose" (Air intake hose #7 according to my info) was necessary as it was badly cracked around the turbo intake area, and all intake related hoses and lines were checked and replaced as needed for cracks and leaks. That was a $45 part from Toyota, the PCV hose was $12 and special order. The ICS air hose (idle control valve) was replaced with a 3/4 inch radiator hose, cinched down solidly by hose clamps to get the 3/4 inch hose to snug up to the 5/8 inch inlets. No obvious leaks so it may stay as is, though at next opportunity it will get 5/8 inch hose as to ensure proper fit.

Wastegate Shims

Next, the wastegate got shimmed. 3 washers and +7.5 psi on the turbo boost gauge. The car has got some serious kick happening around 3000 RPM now. The procedure I followed I found here: http://www.supras.com/sogi/techtips/1_engine/1023_MKIII_wastegate_shimming/index.html

Oh, here's the picture of the car.