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Re: Does anyone recall seeing a post on BPC valves Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 6 May 2008 18:00:25
In Reply to: Does anyone recall seeing a post on BPC valves, Noel, Tue, 6 May 2008 15:33:18 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The following is for the Trionic system. The BPC on the LH is slightly different. Early LH had the APC (two wire). I'm assuming that you mean the BPC (three wire) Trionic.
The BPC is a valve that connects to the intake manifold pressure (C for charge), upstream of the turbo (R for return), and to the Wastegate Actuator (W). At low boost pressure, the C ties to the W, and R is blocked off. Left this way, as boost continues to increase, the pressure would build up and push on the wastegate actuator, causing the turbo wastegate to open and boost to drop. However, if the ECU wants more boost, it opens the BPC a bit and bleeds off some of the C to W pressure into the return. Basically a leak. So it takes more pressure in the intake manifold to get the wastegate to open; more boost.
The BPC valve has variable positions. The ECU drives it using Pulse Width Modulation (PWM). Basically, there are two coils, each one getting electrical pulses. If they both get pulses of the same width, their magnetic fields are the same, and the valve stays in the middle. When one coil gets wider pulses, it gets more current, a bigger magnetic field, and it moves the valve that way. Electrically, you'll see three pins - one is the common, and the other two are the coils. The coils should measure about 3 ohms, plus or minus 1 ohm, measured at the pins (not connected to the harness).
The common (pin 2) gets power, and pins 1 and 3 connect to the ECU. Inside are electronic switches to ground that generate the pulses. With a BPC, you will hear it hum all the time. The frequency is around 70 to 90 hertz - a low rumble.
From the manual:
Boost pressure control takes place by means of a 2 coil, 3-way solenoid valve which is connected by hoses to the turbo unit wastegate, compressor outlet and compressor inlet.
The solenoid valve is supplied with 12 volte power (+54 circuit) via fuse 5 and controlled from pins 26 and 2 of the control module. The control voltage is a PWM signal with a frequency of 90 Hz below 2500 rpm and 70 Hz above 2500 rpm. the change in frequency at 2500 rpm is to avoid resonance in the air hoses.
The ECM (Trionic) adjusts the boost pressure by alternately grounding pins 26 and 2. As a result of grounding pin 2 a longer time than pin 26 the boost pressure is reduced, and conversely the boost pressure is increased by grounding pin 26 longer than pin 2.
The control module determines boost pressure on the basis of throttle position and engine speed. The control module obtains the current boost pressure from the manifold absolute pressure sensor. Boost pressure is reduced slightly in 1st gear. The module calculates the gear position by comparing the speed of the car with the engine speed.
If the ECM has been de-energized (Battery disconnected), an number of full-throttle accelerations will be needed to obtain a correct build-up of boost pressure (Adaptation runs.)
If knocking occurs, despite retarding the ignition and making the fuel/air mixture richer, the boost pressure is also reduced.
If there is a break in any of the leads to the solenoid valve, basic boost pressure will be obtained.
In the event of abreak in any of the hoses or a fault in the solenoid valve, excessively hight boost pressure may be obtained. The control module will then shut off fuel injection at about 0.65 to 1.35 bar, depending on the engine version.
Cars with automatic transmission - When the selector lever is moved to a position other than P or N, battery voltage will be applied to pin 14 of the control module. Cars with automatic transmission have reduced boost pressure.
When the brake pedal is depressed, power goes to the ECM on pin 15, reducing max available boost to the Basic Boost level. The same occurs in reverse (reverse light to pin 13 of the ECM)
When the cruise control is activated, pin 36 of the ECM is grounded, reducing max boost.
posted by 76.205.17...
, Tue, 6 May 2008 18:00:25 <-- Viewing This Message
, Tue, 6 May 2008 15:40:48
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