: Boost Control logic



coach123
06-22-10, 12:23 AM
FYI... I wanted to share this info with everyone. I couldn't get the pictures to paste but you can figure it out.

Boost Control System Description
Bypass Valve Open

(1) By-pass Valve Actuator
(2) Boost Signal
(3) Boost Control Solenoid
(4) Boost Vacuum Source
(5) Supercharger
(6) Intake Plenum
(7) By-pass Valve (normally closed)
(8) Throttle Body
(9) Air Cleaner
(10) MAF Sensor
(11) Inlet Vacuum Signal

Boost Control System Operation
Bypass Valve Closed

(1) By-pass Valve Actuator
(2) Boost Signal
(3) Boost Control Solenoid
(4) Boost Vacuum Source
(5) Supercharger
(6) Intake Plenum
(7) By-pass Valve (normally closed)
(8) Throttle Body
(9) Air Cleaner
(10) MAF Sensor
(11) Inlet Vacuum Signal

Operation

Supercharger boost pressure is regulated to prevent engine and drive train damage. When the engine is operating under high boost conditions, the engine control module (ECM) limits boost pressure to 83 kPa (12 psi). The ECM disables boost under the following conditions:

Reverse gear is selected.

Drivetrain abuse is detected.

Electronic throttle control (ETC) fault is detected.

Engine coolant temperature (ECT) is greater than 125C (257F).

An intercooler pump failure is detected.

Intake air temperature (IAT) sensor 2 is equal to or greater than 120.5C (248F), boost pressure is limited to 145 kPa (7 psi). The ECM commands the boost control solenoid to default to 62 percent DC.

Vehicle speeds exceed 159 mph in third, second, and fourth gears only, after 150 seconds boost is trimmed actively.

The ECM controls boost pressure by using the boost control solenoid. The boost control solenoid is normally an open valve. Under most conditions, the ECM commands the boost control solenoid to operate at a 99-100 percent duty cycle. This keeps the solenoid valve closed and allows only inlet vacuum to control the position of the bypass valve. At idle, engine vacuum is applied to the upper side of the bypass valve actuator, counteracting spring tension to hold the bypass valve open. As engine load is increased, engine vacuum is decreased, causing the spring in the bypass valve actuator to overcome the applied vacuum, closing the bypass valve and allowing the boost pressure to increase. The bypass valve starts to close when the vacuum measures 250 mm Hg (10 in Hg) and is fully closed at 90 mm Hg (3.5 in Hg). When reduced boost pressure is desired, the ECM commands the boost control solenoid to operate at a 0 percent duty cycle, but may command a partial duty cycle, approximately 62 percent, depending on the operating condition. This opens the solenoid valve and allows boost pressure to enter the bypass valve actuator at the lower side to counteract the spring tension, opening the bypass valve and re-circulating excess boost pressure back into the supercharger inlet.
Results of Incorrect Operation

The following conditions will result in reduced engine power, especially during a wide open throttle (WOT) operation:
An open boost control solenoid control circuit.

An open control solenoid ignition 1 voltage circuit.

An open control solenoid control circuit.

A boost control solenoid valve that is stuck open.

The following conditions will result in full boost to be commanded at all times. These conditions can also result in overboost conditions during high engine load situations.
A boost control solenoid control circuit shorted to ground.

A boost control solenoid valve is stuck closed.

A restriction in the boost source or signal vacuum hoses.

A restriction in the exhaust system may cause an overboost condition and reduced fuel economy.

A restriction in the vacuum signal hose to the bypass valve actuator or stuck closed bypass valve will cause a noisy idle and reduced fuel economy.

Tinmanx
06-22-10, 01:31 AM
That is great! This is the kind of info I love to read.

coach123
06-22-10, 02:24 PM
If anyone decides to increase boost make sure your tuner changes the necessary things in the ECM to fully allow all potential of the supercharger. I'm not sure if these parameters where changed in my initial tune by Vengeance Racing and will have to get Jesse to verify. The following link is to lingenfelter's website discussing it.

http://www.lingenfelter.com/LPEforumfiles/showthread.php?t=158

Here is a excerpt from the link:

It sounds like you might be hitting the overboost limits in the calibration.

To fix this you need to change the high and low limits in the overboost protection area.

In EFILive it is the following locations:
B7006 Overboost Upper Limit
B7007 Overboost Lower Limit

On the ZR1 we set them to 230.0 kPa (B7006) and 210.0 kPa (B7007).

Stock is 192.0 and 172.0 kPa.

To confirm that this is what is causing the problem, you can log or view the boost control solenoid activity with a scan tool or data acquisitition software. I am fairly certain a Tech 2 shows this variable but I don't recall what it is called.

In EFILive the variable is:
Description: Supercharger Boost Solenoid Duty Cycle
Caption: SCBDC
System: Conditions
Parameter: GM.SCBDC

I can get you the variable and location names in HPTuners or other software if you need them in some other format.

If you are using HPTuners then you need to change the variables in the following area:
Engine
- Torque Management
- - Supercharger

Then go to the following section of the "Supercharger" tab:
- Boost Disable

In the "Boost Disable" section you will have the following stock data:
MAP Disable: 192 kPa
MAP Enable: 172 kPa

Change these to:
MAP Disable: 230 kPa
MAP Enable: 210 kPa

I know that this thread pertains to the new CTS-V but I am pretty sure we have the same type of programming in our STS-V's..

coach123
06-22-10, 10:41 PM
Will somone with EFIlive or HPtuners confirm that we have these overboost limits on our STSV's? The variable names and descriptions are above.

TimmyC
06-23-10, 12:13 AM
I have HPtuners and I'm checking into it. I need to download the beta version of the software to open a CTS-V file for some reason. I checked the STS-V file and there is nothing in the supercharger tab under torque management. It might be something the beta software release will let me see though. I should have it by tomorrow and I'll check it out then. Email me your tune in HPtuner format if you can.

coach123
06-23-10, 12:41 AM
My tune is in EFIlive format.

TimmyC
06-23-10, 08:23 AM
Email it anyway, I think I have EFI Live software too so I can at least look at it.

Florian
06-28-10, 12:26 PM
I'll check my EFILive.....

F

GizmoQ
04-05-11, 04:41 PM
BUMP!


What was the final determination on this.

PGA2B
04-05-11, 04:46 PM
Yes the parameters are in HP Tuner as long as you have the beta version. I do not know if they are in 2.2 or not. I have the latest Beta. For you I know for a fact Jesse had access to the tables as he is EFI Live.

GoofyGuy
04-05-11, 05:23 PM
I dont see desired boost in HP tuners, I do see the controls to control when max boost is desired. As it seems all the highlight explanations are vague as best.

TimmyC
04-05-11, 09:30 PM
I dont see desired boost in HP tuners, I do see the controls to control when max boost is desired. As it seems all the highlight explanations are vague as best.

There is no desired boost setting. The computer closes the bypass valve and the blower pumps all the air it can into the motor.

I think there are many bypass valve tables that are not accessible with HPtuners or EFILive. I'd like to keep it open more during cruising to improve mileage.

GizmoQ
04-06-11, 12:08 AM
O.K., Jesse just kicked me under the table again for asking about this.

"You do not want to just change a setting in the ecm because if you set the max boost to be lower than what your car is making then it WILL be putting in recirculated hot air into your intake over and over again at wide open throttle and will potentially cause damage to the engine. The way it cuts boost is opening up a valve inside the blower. That valve in the blower just lets the boost back into the front of the rotorpack. kind of like an egr system on older cars.."