Fnschlaud4620 wrote:I think you would have to manually monitor shaft speed or it becomes a 3D map.
I think you would have to watch shaft speed and run the engine on a dyno at various RPM and LOAD and if it is too slow shaft speed you input a number that closes the housing, too fast and you enter a number that opens it.
I agree shaft speed alone would be ideal but it is along the same lines as using a boost actuator.
I don't think there will be any type of exhaust breaking without over speeding the shaft and breaking the turbo.
Running with your insistence-on-a-graph idea...
Instead of using engine RPM in your RPM/ TPS map, use the turbo shaft RPM.
If the shaft is spinning above 120,000 RPM, increase the housing size.
If the shaft is spinning below 120,000 RPM and exhaust brake is "on", reduce housing size.
If the shaft is spinning below 120,000 RPM and exhaust brake is "off", do not reduce housing size until throttle is pressed.
You want the output of the graph to control the size of the turbo. So you probably want it to output a 0-5 voltage that can go to a PWM that can go to an electric servo.
If the shaft RPM is 121,000, then increase the housing size a little. If it is 123,000 RPM, increase it a lot. If it is 129,000 RPM increase it as much as possible.
If the shaft RPM is 100,000 RPM, decrease the size of the housing a little. If it is 50,000 RPM, decrease the size of the housing a lot. If it's 20,000 RPM, decrease it even more.
If the "Exhaust Brake Off" switch is turned on, the housing will not decrease in size no matter what the shaft RPM is. If the throttle is pressed, the "Exhaust Brake Off" switch will turn off automatically.
The TPS/ "Exhaust Brake Off" circuit will just interrupt the map's input to the turbocharger, so it isn't going to impact the values on the map at all. I don't see a reason for the TPS or switch position to be separate dimensions on the map.
The million dollar question is how to get the shaft speed value imported into your graph.
Depending on what the shaft speed signal is, it might even be possible to not play around with variable opening and shutting
rates and just use an analog circuit that either opens or shuts at a constant rate. Or one that has a dynamic rate that increases automatically the faster the shaft is spinning over a predefined speed.
1990 D-250 Regular Cab: Tweaked injection pump, built transmission, a cataclysmic charlie foxtrot of electronics, the most intense street-ran water injection system in the country, and some more unique stuff.