Free boost modification

[DrkPhx]

Originally Posted by djnice

Are you sure we only get boost at WOT? Well, anyway that must also be why they integrated the no lift shift. So the diaphragm keeps the blade closed and it doesn't loose boost for a couple seconds during the shift.

You do get boost at some part throttle positions; but max boost is at WOT.

[RLHMARINES]

I did this yesterday and took it out to see if a difference was noticed. I felt a noticeable extra push at WOT and used my dash logic which gave me a boost reading of 11 psi and the factory boost gauge went farther than I have seen in the past. I will keep an eye on my #2 IAT going forward just to ensure there's no issue. Also, it seems to be making more part throttle boost as my needle sweeps faster as it responds to the throttle input.

[ABADZL1]

OperationSupercharger 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.
• An electronic throttle control fault is detected.
• Engine coolant temperature (ECT) is greater than 125°C (257°F).
• An intercooler pump failure is detected.
• Intake air temperature (IAT) sensor 2 is equal to or greater than 120.5°C (248°F), boost pressure is limited to 145 kPa (7 psi). The ECM commands the boost control solenoid to default to 62 % duty cycle.
• Vehicle speeds exceed 256 km/h (159 mph) in second, third or fourth gear for greater than 150 s.

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 % 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 10 in Hg and is fully closed at 3.5 in Hg. When reduced boost pressure is desired, the ECM commands the boost control solenoid to operate at a 0 % duty cycle, but may command a partial duty cycle, approximately 62 %, 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 OperationThe 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.

[HDRDTD]

"Vehicle speeds exceed 256 km/h (159 mph) in second, third or fourth gear for greater than 150 s. "

159mph in SECOND GEAR ?????

Mine won't do that.

[Jeb114]

Originally Posted by ABADZL1

OperationSupercharger 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.
• An electronic throttle control fault is detected.
• Engine coolant temperature (ECT) is greater than 125°C (257°F).
• An intercooler pump failure is detected.
• Intake air temperature (IAT) sensor 2 is equal to or greater than 120.5°C (248°F), boost pressure is limited to 145 kPa (7 psi). The ECM commands the boost control solenoid to default to 62 % duty cycle.
• Vehicle speeds exceed 256 km/h (159 mph) in second, third or fourth gear for greater than 150 s.

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 % 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 10 in Hg and is fully closed at 3.5 in Hg. When reduced boost pressure is desired, the ECM commands the boost control solenoid to operate at a 0 % duty cycle, but may command a partial duty cycle, approximately 62 %, 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 OperationThe 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.

Thank you for that, I guess the answer is leave mother nature alone Chevy knows what they are doing!!

[djnice]

The supercharger control logic cannot compensate for a mechanical component that requires periodic adjustment or is out of adjustment. For example, the logic will say I want 100% closed, but mechanically it will be at 97%.

So yeah, thanks for posting the operation logic. Now I know this really does need to be checked for correct adjustment, and I am not relying on the dealer to do that.

[PsychoZL1]

^ with that said, it sounds like nothing negative should happen by adjusting the set screw so the plate is fully closed.

[SPOOKYGUNNER]

Originally Posted by Dutchman427

I am going to try it.

I am unable to play the video. Can you send a link to a different format?

[djnice]

I just used a 3/32", long allen wrench to get at the adjusting screw rather than moving the whole bracket. I removed the supercharger drive belt to make access to the screw easier.

At stock setting mine was a half turn open. I set it to a quarter turn open. That was cold. I will check it hot too.

[JANNETTYRACING]

Great thread but keep in mind results will vary widely, all dependent on whether it is out of range or not.

There is a tool that sets the preload on the bypass at a certain rod length then you bolt it on while holding the blade open, done carefully the bypass will be in the perfect location for going fully closed without sticking in cold weather and able to go fully open via limited travel of the rod.

The concern I have with this is the same as everyone else, the blade can get stuck in the closed position without any gap.

So it does need a minimal gap to prevent sticking closed.

I think it is a great Idea to check but I don't necessarily agree with the method of adjustment in the video.

The tool is the best method.

It will have no affect on the tune or the AFR, unless it was specifically tuned with a large gap then you close that gap.

Hope this helps.

[DrkPhx]

Well said Ted.

[KaBoom1701]

Originally Posted by JANNETTYRACING

Great thread but keep in mind results will vary widely, all dependent on whether it is out of range or not.

There is a tool that sets the preload on the bypass at a certain rod length then you bolt it on while holding the blade open, done carefully the bypass will be in the perfect location for going fully closed without sticking in cold weather and able to go fully open via limited travel of the rod.

The concern I have with this is the same as everyone else, the blade can get stuck in the closed position without any gap.

So it does need a minimal gap to prevent sticking closed.

I think it is a great Idea to check but I don't necessarily agree with the method of adjustment in the video.

The tool is the best method.

It will have no affect on the tune or the AFR, unless it was specifically tuned with a large gap then you close that gap.

Hope this helps.

How much is this tool?

[97ChameleonTA]

Lingenfelter sells it for $12.95:

http://www.lingenfelter.com/mm5/merc...8#.VP3IiSI5BhE

[unstable vic]

ordered!!