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PT Cruiser GT Stage II
By Michael Triffon

Many of us have been lamenting Daimler Chrysler Motor’s (DCM) unwillingness to release the Mopar Stage II upgrade for the PT Cruiser GT, especially when they have released Stage II AND III for our feisty little brethren, the SRT 4. This has led to much discussion of converting SRT 4 Stage II components for use in our beloved manual PT Cruiser GT’s. The automatic is not a contender because all SRT 4’s are manual.

At the time of this writing, no one to my knowledge has actually tried this. Theories have been bandied about and some seem convinced it can be done while others say the A/C and other functions will not work. My point of view is, why bother?

There are not only better options, but they can be more functional, flexible, and cheaper as well! But before we get to them, we need to take a close look at the SRT 4 Stage II components to truly understand the system.

Stage II Components for SRT 4:

1. Stage 2 PCM (Power Control Module)
• Increased WOT and part throttle boost.
• Waste gate control was retuned for better turbo response
• Boost hold feature during WOT shifts.
• Enhanced first gear boost schedule.
• Increased Rev Limit 6500 RPM from 6200 RPM.
2. 682 CC Fuel Injectors
3. Waste gate Actuator
4. 3.0 Bar MAP Sensor (Manifold Absolute Pressure)
5. 3.0 bar TIP Sensor (Throttle Input Pressure)
6. Turbo Toys
• Turbo Intercooler Sprayer
• Dial-A-Boost Switch

Street price of $1350.00, Turbo Toys included.

Very simply put, the Stage II core upgrade will allow more boost to develop and hold it longer before venting it. Increasing the boost means more pressure so the new wastegate has a stronger spring to hold the higher boost. More air will also lean out the fuel mixture which is why they include bigger fuel injectors. All of this lovely boost will overshoot the stock 2.25 Bar MAP (Manifold Absolute Pressure) sensor, so that needs to be upgraded to a 3 Bar sensor so the PCM can see and properly react to the higher boost and supply more fuel.

The last, and optional, components are the turbo toys which are a turbo intercooler sprayer that sprays water on the intercooler body to further refrigerate the air, and a pretty trick little boost wheel that tells the PCM to increase spark advance to take full advantage of 100 octane fuel.

Now that we understand what the components do let’s look at what we can do to get stage II performance in a PT GT. The very first thing you will need is Stage I:

Manual Transmission
• Increased WOT and part throttle boost
• Enhanced 1st gear boost schedule for a higher performance launch
• Optimized calibration for the MOPAR blow off valve conversion kit
• Improved turbo response
• Boost hold feature during WOT shifts
• Soft rev limiter

Automatic Transmission
• Increased WOT and part throttle boost
• Optimized calibration for the MOPAR blow off valve (BOV) conversion kit
• Improved turbo response
• Performance optimized transmission calibration

So far so good but to get Stage II performance we need more boost, and there are 2 ways achieve that goal. The first way is a wastegate upgrade.

The wastegate sits on the exhaust side, where exhaust pressure drives the turbo. It is also plumbed with a line from the pressure side of the turbo. There is a solenoid in between but we will explore that later. When the boost pressure builds up beyond the spring’s capacity to hold it, the wastegate gives and vents exhaust pressure to slow down the turbo and bring boost pressure back under 15 pounds.

It stands to reason that if you install a bigger spring in the waste gate, you could build and hold more boost. Unfortunately the PCM senses the higher boost through the MAP sensor and will immediately reduce the power output by pulling the timing. In order to realize any power gain we will have to keep the PCM from seeing the extra boost by modifying the MAP sensor output.

A MAP sensor works by converting ambient exhaust pressure into an electrical voltage, the higher the pressure, the higher the voltage. In ord