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Considering a turbo car. The specific model is a Dodge Caliber SRT 2008, but I'd prefer a more generic answer.

How can one prevent the car from boosting while still having a car that can be driven around (on vacuum)?

The process should be reversible to make the car boost again. Ideally, this could be done at will without too much electronic gadget.

Is it possible?

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can you explain why you want this ability? –  Larry Jul 13 '11 at 16:33
Someone else will be using the car and I'd like to prevent him from boosting, as this can lead to excessive speeding and improper cooldown. –  Pierre-Alain Vigeant Jul 13 '11 at 17:17
Not answering the q, but possible solution to the problem: fit tamper-proof GPS tracker, and let the user know. –  Rory Alsop Jul 14 '11 at 12:07

4 Answers 4

up vote 4 down vote accepted

You can't prevent the turbo from spooling up without physically removing it from the car. Depending on how the boost is controlled (ie, if there is a manual or electronic boost controller involved, too, or if it's just standard boost control by the ECU) you might be able to turn down the maximum boost to the pressure controlled by the spring in the wastegate if so equipped. That would reduce the maximum available performance somewhat at least but wouldn't prevent the engine from hitting boost.

You might even be able to rig the wastegate to be open all the time so it'll stop boost from building but that might well irritate the ECU to the point of a check engine light.

To be honest, if you don't trust the person who is supposedly borrowing your car, I wouldn't look for a technical solution but simply not let them drive the car.

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That's why i didn't want to write the reason for it, because it might affect the answers. The ECU of the car might be able to control the boost, since I already got an overboost code once and I was unable to boost (the code got reset using an Aeroforce Interceptor). I am wondering if it is possible to induce an overboost code into the ECU. –  Pierre-Alain Vigeant Jul 13 '11 at 18:11
The overboost code might not be want you want; depending on how the ECU handles that you might end up with fuel cuts, which isn't going to make the car more drivable. If you can set the boost with some sort of scan tool that's probably your best bet to lower it, but you'll still run into the limit set by the spring in the wastegate. –  Timo Geusch Jul 13 '11 at 19:42

Any boost controller (manual or electronic) would allow you to turn down the boost. I have a DiabloSport unit and I can go way down almost to the point where the car is atmospheric (max. boost under 3 psi). When ready to restore it, flash back the original tune map.

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Depends on the car. Most cannot have the boost lowered. For example, my car has a wastegate spring that activates at 8.5psi. My boost controller is able to raise that level by bleeding off air, but cannot lower it any. –  Brian Knoblauch Jan 25 '12 at 14:07

This is solvable at the ECU: one of the profiles that I could install using my AccessPort is called "valet mode." The performance is severely limited in that it prevents boost and significant speed.

Caveat: going this route would cost you hundreds of dollars. Admittedly, I really like the performance aspect of the AccessPort and that's why I purchased it.

Mechanically, the best way to prevent boost is to set the wastegate to be always open. All exhaust gases would then bypass the turbine leaving the engine with no boost.

Likewise, you could set the blow-off valve to be always open. That would allow most of the boost to vent, preventing any significant performance.

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Disconnect the charge piping from the turbo to the throttle body. The turbo will still spin, but the engine will never see positive boost pressure. You will need to connect any and all sensors that were attached up and downstream of the turbo charger to the intake tract ahead of the throttle body. Like:

  • Air filter
  • Air flow meter/Mass flow meter
  • Intake temperature sensors
  • Vacuum signals for PCV system etc.

Another method was mentioned already. Disconnect the wastegate from the wastegate actuator. This should reduce performance enough and I doubt any codes would be thrown.

But a much simpler way is to not lend your car out.

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