I have been watching my boost gage and keep seeing posts of peeps getting anywehere from 10-15 lbs of boost. Problem is my gage has never gone over 5 lbs. I tried it out today and in 2nd gear shifting at 5500 it went to 5 lbs and stopped. The truck feels like it's pulling pretty well but keep in mind I have never driven one of these before other than the one in my garage. I feel like something might be wrong. I have seen posts of people talking about the turbo whine and the waist gate noises, with the radio off I hear none of these noises. I'm a noob when it comes to turbo vehicles, this is my first one, so any advice would be appreciated. Oh and the air temp was 43 F if that has anything to do with it and the truck has 330 miles on it w/ 93 octane in the tank. I've been taking it easy on it the first 500 miles usually shifting at around 4500 or less.
I'm interested to see some opinions on this especially from the guys that are used to these turbo motors.
Thanks in advance.

 

What boost pressure do you get in 4 or 5 gear? It is my understanding (usually wrong however) that the boost is limited in 1 and 2 gear and is temperature dependent in all gears.

 

boost is not limited in 1st and 2nd gear in the manuals, only the automatics.
can't give you any more advice than that, I'd call the dealer and talk to the service mgr... maybe take it in real quick to see if something is amiss.
that's what I'd do.

 

I've never seen mine above about 13, but it definantly has the inherent turbo noise. Not loud like my other turbo cars, but definantly audible. The car is designed to muffle the lovely sounds from the factory so we can spend major $$$ getting the noise back I actually punched it in 1st the other day and can absolutely, 100% guarantee there is no boost reduction in first My tires were screamin' in pleasure. I'm over 600 miles now and can't stand waiting anymore to play a little.

If the car feels like it's pulling hard, I would bet a bad boost gauge. If you were really only getting 5 psi, it would probably feel pretty sluggish. You'd be off by probably close to 40 hp, 40 ft-lb which would likely be noticable.

 

Some Boost guages are not working correctly (including mine. which works itermittently (stuck at 5 psi or fine)). There is a test document ID #1953174 that explains trouble shooting and repair procedure. Bottom line = take it to your dealer and have it repaired. (ECM or Boost Guage replacement). Here's a (partial-abreviated) quote from the document "The ECM sends a PWM signal to the boost gage via the boost gage signal circuit. The boost gage displays pressure above and below ambient manifold pressure. The ECM controls the boost pressure with the BP control solenoid. The maximum boost pressure is about 83 kpa (12 psi) (????). When the ignition is turned ON and the boost gage is ON, the boost gage performs a power up self test. The dial normally below 0 psi moves up to 0 psi to indicate the boost gage passed the self test. Power is provided to the boost gage via the ignition 1 voltage circuit."

 

How many miles are on the car as I heard that boost is limited during brake-in miles.

 

Yes, if its running well, could be a bad guage or a leak in the line going to it. Its pretty easy to kink those kind of lines, and a kink could cause a leak. How much vacuum does it pull when idleing? Should be 15-17". Much less than that would indicate leakage or a guage problem. If its not running well, now thats a different story.

 

Well, that blows my theory! You were replying just as I was. When I saw the Autometer guage, I never thought electronic. Thanks

 

The below numbered items should have had a diagram, but was lost in the transfer, still gives a basic idea of the turbo



Document ID# 1830792
2008 Chevrolet HHR


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Boost Control System Description




(1) Evaporative Emission (EVAP) Canister Vent Solenoid Valve
(2) EVAP Canister
(3) Non-Return Valve
(4) EVAP Canister Purge Solenoid Valve
(5) High Pressure Fuel Pump
(6) Camshaft Position (CMP) Actuator Solenoid
(7) Charge Air Bypass Valve Solenoid
(8) Charge Air Bypass Valve
(9) Mass Air Flow (MAF)/Intake Air Temperature (IAT) Sensor
(10) Turbocharger Wastegate Solenoid Valve
(11) Turbocharger Wastegate Actuator
(12) Camshaft Position (CMP) Sensor
(13) Ignition Coil/Module and Spark Plug
(14) Fuel Injector
(15) Charge Air Cooler (CAC)
(16) Turbocharger Boost Pressure Sensor
(17) Throttle Body (TB)
(18) Manifold Absolute Pressure (MAP) Sensor
(19) Fuel Rail Pressure (FRP) Sensor
(20) Engine Coolant Temperature (ECT) Sensor
(21) Engine Exhaust Manifold
(22) Turbocharger
(23) Heated Oxygen Sensor (HO2S) 1 and 2
(24) Catalyst
(25) Crankshaft Position (CKP) Sensor
(26) Fuel Pump Module
(27) Accelerator Pedal
(28) Theft Deterrent
(29) Data Link Connector (DLC)
(30) Malfunction Indicator Lamp (MIL)
(31) GMLAN Serial Data
(32) Engine Control Module (ECM)

Boost Control Description and Operation
A turbocharger (TC) is a compressor that is used to increase the power output of an engine by increasing the mass of the oxygen and therefore the fuel entering the engine. This BorgWarner™ dual-scroll TC is mounted on the exhaust manifold and the lightweight turbine is driven by the waste energy generated by the flow of the exhaust gases. The turbine is connected by a shaft to the compressor which is mounted in the induction system of the engine. The compressor vanes compress the intake air above atmospheric pressure, thereby greatly increasing the density of the air entering the engine. The TC is capable of producing up to 20 psi, or 1.40 bar, of power-enhancing boost.

The TC incorporates a wastegate that is controlled by a pressure differential, that is determined by the engine control module (ECM) by means of a PWM solenoid, in order to regulate the pressure ratio of the compressor. A TC bypass valve is integrated within the unit, and is also controlled by the ECM by utilizing a remotely mounted solenoid to prevent compressor surging and damage from vibrations by opening during abrupt closed throttle conditions. When the valve is commanded open during closed throttle deceleration conditions, the bypass valve allows the air to recirculate in the TC and maintain compressor speed. Within a calibrated range during the closed throttle event, or upon a wide open throttle command the valve will then close to optimize turbo response.

TC Wastegate Closed




(1) Turbocharger Wastegate Solenoid with Duty Cycle at 100 percent
(2) Compressor
(3) Turbine
(4) Exhaust Gas Pressure
(5) Spring Force
(6) Turbocharger Wastegate Actuator

The wastegate is completely closed at idle. All of the exhaust energy is passing through the turbine. There are three reasons that the wastegate remains closed:

• There is a lack of compressor outlet pressure. Lower compressor outlet pressures tend to close the wastegate via the pneumatic connection to the actuator.

• The return spring within the actuator is helping to keep the wastegate closed.

• The low energy of the exhaust gas flow is not enough to overcome the return spring force.

During normal operation, if a wide open throttle were to be requested at lower engine speeds, the ECM will command the boost control solenoid with a duty cycle of 100 percent to minimize any turbo lag. During engine loads in the middle and upper RPM ranges, the ECM will command the boost control solenoid, with a duty cycle of 65-80 percent. Manifold pressures of up to 240 kPa are possible.

TC Wastegate Open




(1) Turbocharger Wastegate Solenoid with Duty Cycle at 0 percent
(2) Compressor
(3) Turbine
(4) Regulating Pressure
(5) Exhaust Gas Pressure
(6) Spring Force
(7) Turbocharger Wastegate Actuator

When certain DTCs are set the ECM will limit the amount of available boost pressure. Limiting boost pressure is accomplished by the ECM controlling the TC wastegate solenoid and maintaining the duty cycle at 0 percent. This means that the ECM will not actively close the wastegate during greater engine loads. The system at this point is limited to mechanical boost. Mechanical boost means that the wastegate will still move, but the amount of motion is limited by the mechanical properties of the return spring within the actuator, the pneumatic properties of the actuator, and the physics of the exhaust gas flow in the exhaust system. In this mode of operation the manifold pressure will attain a maximum pressure of 140 kPa.

The TC wastegate actuator assembly has a threaded rod and nut that connects the diaphragm of the actuator to the wastegate. This rod is adjusted to BorgWarner™ factory specifications and is not adjustable.


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Document ID# 1830792
2008 Chevrolet HHR

 

Here is copy of Document ID# 1953174


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Boost Gage Malfunction
Diagnostic Instructions
• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure

• Review Strategy Based Diagnosis for an overview of the diagnostic approach

• Diagnostic Procedure Instructions provides an overview of each diagnostic category

Diagnostic Fault Information
Circuit
Short to Ground
Open/High Resistance
Short to Voltage

Ignition 1 Voltage Circuit
1
1
--

Boost Gage Signal Circuit
1
1
--

Boost Gage Ground Circuit
--
--
1

1. Boost gage inoperative


Circuit/System Description
The boost gage is a measure of the engine manifold air pressure. The engine control module (ECM) sends a PWM signal to the boost gage via the boost gage signal circuit. The boost gage displays the engine air intake above and below the ambient manifold pressure. The ECM controls the engine boost pressure with the boost control solenoid. The engine boost system pumps more air than the engine would normally use into the intake manifold. The excess air pumped into the intake manifold, creates the engine boost effect. The maximum boost pressure is about 83 kPa (12 psi). When the ignition is turned ON and the boost gage is ON, the boost gage performs a power up self test. The boost gage dial normally below 0 kPa (0 psi) moves up to 0 kPa (0 psi) to indicate the boost gage passed the self test. Power is provided to the boost gage via the ignition 1 voltage circuit.

Reference Information
Schematic Reference
Instrument Cluster Schematics

Connector End View Reference
Component Connector End Views

Description and Operation
Instrument Cluster Description and Operation

Electrical Information Reference

• Circuit Testing

• Connector Repairs

• Testing for Intermittent Conditions and Poor Connections

• Wiring Repairs


Scan Tool Reference
Control Module References for scan tool information

Circuit/System Testing
Ignition OFF, disconnect the harness connector at the boost gage.
Ignition OFF, test for less than 1 ohm of resistance between the boost gage ground circuit terminal D and ground.
⇒ If greater than the specified range, test the circuit for a short to battery or open/high resistance.

Ignition ON, verify a test lamp illuminates when connected between the boost gage B+ circuit terminal A and ground.
⇒ If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

Ignition OFF, connect the harness connector at the boost gage.
Ignition ON, verify that the boost gage performs a self test by the gage dial moving up to the 0 kPa (0 psi) marker.
⇒ If the boost gage does not perform a self test, test the boost gage signal circuit terminal C for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.

If all circuits test normal, replace the boost gage.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the ECM replacement, setup, and programming


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Document ID# 1953174
the above mentioned document