1985-1998 [Subscribe to Daily Digest] |
 | [Main 9000 Bulletin Board | BBFAQ |
Prev by Date | Next by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Works, but not correctly Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Sat, 5 Jul 2008 15:11:23
In Reply to: BPC woes <-> 900apc replacement, 93CSETurbo, Fri, 4 Jul 2008 10:56:08 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The two wire APC valve is set to base boost with no power, and when 12 volts is applied, it allows full boost. It has only those two positions. So it's spring loaded to base boost (C connected to W), and applying 12 volts closes the solenoid (C connected to R)
The three wire BPC valve has two coils, and the position of the valve is a function of the pulses the ECU gives it. Pulse one coil more than the other, and the valve moves that way; pulse each coil the same, and the valve stays put.
So yes, you've got full boost. But that doesn't necessarily mean the system is working. What's happening? The ECU sends pulses to both coils. But you've only got one coil hooked up. The pulses you're getting are enough to energize the solenoid and you get full boost. But if the ECU decides to cut back boost because of knock, all it will do is make the pulses to one coil shorter and lengthen the pulses to the other coil - the coil you don't have hooked up. So if the pulses to the coil that are hooked up are enough to keep the coil energized, you'll still have full boost - even when the engine is knocking. Not good at all.
I'd also worry that the APC solenoid will take out the transistors in the ECU. I'll bet the resistance may be the same, but the inductance of the APC vs. BPC will be different - putting pulses into inductors can make for some interesting issues.
Is it working now? To some extent. Will it reduce boost if you start knocking? Fair question. If you put your foot on the brake, does the boost reduce to Base? If not, you're not getting the APC function. If it does drop back to base, that's a good sign. But I think you're risking the ECU.
The BPC control is a proportional pulsed system, and the APC is an on-off system. The fact that you get boost doesn't imply all the features are there. I don't recommend this as a 'fix.'
posted by 76.200.21...
, Sat, 5 Jul 2008 15:11:23 <-- Viewing This Message
No Site Registration is Required to Post - Site Membership is optional (Member Features List), but helps to keep the site online
for all Saabers. If the site helps you, please consider helping the site by becoming a member.
 |
 |
 |
 |
 |
