1979-1993 & 94 Conv [Subscribe to Daily Digest] |
 | [Main C900 Bulletin Board | BBFAQ |
Prev by Date | Post Followup ]
Member Login / Signup - Members see fewer ads. - Latest Member Gallery Photos
Right, there won't be any difference right now ... Posted by RS [Email]  (#15)  [Profile/Gallery]
(more from RS) on Fri, 15 Aug 2003 10:28:47
In Reply to: Re: Base Boost @ 9.5 PSI...Is she going to blow????, scottgf, Fri, 15 Aug 2003 08:29:23 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The APC only does its work modulating the boost when all of the condtions for letting the boost rise beyond the physical base boost setting are satisfied. If the base boost is set beyond it's ability to back it off, it'll sit there, fuss, fume, and rattle the APC solenoid all day with no effect. That's why base boost is set at a conservative 5 or 6 psi - the safety fallback is that you can't (or shouldn't) get knock at that low boost value.
What you should experience under normal stock conditions with everything working corrctly is decent acceleration under load up to somewhere between 2,500 and 3k RPM. Then you get the kick. Think of it as a mild-mannered, Swedish, Mad Max switch.
A rough description of my understanding of what the APC does and how it works is this (anybody, feel to chime in and correct me or add to it) -
- Monitor RPM through a pulse signal from the ignition module
- Monitor Load on the engine by the pressure in the intake manifold
- Monitor engine knock through the knock sensor
- Control the APC solenoid by pulsing it
- When the RPMs rise to around 2,500 RPM it starts clicking to open the APC solenoid up all the way to close the wastegate and let the boost pressure rise. At 3k RPM the APC solenoid should be open steadily. When it either detects knock or the intake manifold pressure rises to the high pressure setpoint, it starts to pulse the APC solenoid to open up the wastegate a bit and back the pressure off.
- If it detects an open circuit in the knock sensor input, it leaves the APC solenoid closed (base boost) because it has no way to know if there's knock.
- If it gets a bad signal from the pressure transducer, it just sits ther and clicks the APC solenoid almost at random.
- If the brake lights are on, it knocks the boost back to base boost.
The stock APC is a very conservatively-engineered system to protect a turbocharged car.
posted by 63.148.1...
, Fri, 15 Aug 2003 05:05:48, Fri, 15 Aug 2003 10:28:47 <-- Viewing This Message, Fri, 15 Aug 2003 11:12:33, Fri, 15 Aug 2003 12:34:04, Fri, 15 Aug 2003 15:00:57, Sat, 16 Aug 2003 09:50:51, Sat, 16 Aug 2003 09:02:17
, Fri, 15 Aug 2003 10:25:04
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.
 |
 |
 |
 |
 |
