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Beginning Boost Targets

Practical Reflash Tuning

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Discussion and questions related to the course Practical Reflash Tuning

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How do you know where to set your original boost targets. for Instance I have a 2004 USDM WRX with a VF-43 Turbo from an STI. Cobbs Stock map file will have a lower boost target than I am assuming I can use. How do I know where to begin my boost targets compared to the stock file?

Why don't you start with the stock values. Then, I would go up in 200kPa increments (or 2-3 psi). If you know your eventual target was a big jump (like +20 psi), you might start with half that.

Yeah that makes sense, I am not looking to go crazy with this car nor will I be tuning professionally, so I cant imagine needing to go much above Cobbs map targets around 17 psi. I just wondered if there was a set point to begin if say someone was putting a large turbo on the car. I read that some "tuners" loose term here cause it was on a public forum, will set the wastegate duty cycle to zero and make a ramp run to see what the turbo will do for boost without the manipulation of the wastegate. I can see how you can get an idea of boost targets from this but I can imagine the danger you put the motor and the turbo in by doing this as you are effectively throwing the entire boost control system in the trash. Any insight into this?

I would say to size your wastegate spring for the maximum boost you expect to be able to support. It makes no sense to have a higher value than the engine components can support.

It should be OK to make a ramp run on just the wastegate, boost control is all about lowering the boost to improve driveability.

That makes sense, that is what I will do! I really appreciate your insight!