flash7210 wrote:
This is a relatively simple mod that will allow you to dial-in the max boost from your turbo.
What you will need:
1. An actual boost gauge, mechanical type is preferred
2. A 10K ohm variable resistor
3. TorquePro or other application that will allow you to read the MAP sensor
4. A soldering iron
The variable resistor gets spliced into the signal wire from the MAP sensor.
There are four wires going into the sensor. When standing in front of the engine, the signal wire is the one closest to you.
I mounted the resistor on the dash and ran its wires through the firewall.
The variable resistor is wired in as a voltage divider. That is, the splice from the sensor goes to one end of the resistor. The other end of the resistor goes to ground. And the center wiper goes to the splice back to the ECU.
Increasing the resistance lowers the sensed pressure at the MAP sensor.
Sensing lower boost, the ECU will allow the turbo to boost up to a higher pressure.
This is why you need an actual boost gauge. This mod fools with the MAP sensor reading.
To dial it in I used my TorquePro app to get a view of the MAP sensor reading.
With the key on and engine off, I adjusted the resistor till the reading showed between 2-3 vacuum.
Before doing this mod I could inly get 21-22 psi with a stock tune. As viewed by the gauge.
Now I can easily get 24-25 psi and dial in even more if needed.
However, there are some limitations.
I think 25-26 psi is the highest you would want to go under heavy acceleration. Dont want to blow a head gasket.
Too much resistance in this circuit can throw a turbo underboost code and may cause some drivability problems.
Too much boost can put the turbo into an overspeed condition which could destroy the turbo.
More boost does not automatically mean more power. With a diesel engine, more power comes from injecting more fuel.
Let me know if you need more details.
Do you also get more boost at idle or does that pretty much stay the same because of exhaust flow?
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