Why might I want a turbo boost gauge?

Nov 11, 2003 22 Replies

Do you know whether the solinoid is an "on-off" digital type output or is it an analog out-put opening the wastgate gradually?? I have a 97 legacy with sequencial turbos and I can't quite get my head around how they work together, If they are syncronized using the ECU then I assume that my next upgrade ( a new ECU) will give me greater control over this aspect

the boost controller will not fix the problem. it may increase boost slightly but the charge will be warmer as well due to a loss of efficiency.

in a nutshell, turbos work on pressure ratios, not absolutes. if the ambient air pressure is lower, then the manifold pressure will be lower as well.

the only thing you can really do is put a turbo capable of larger pressure ratios on so that it will run at a higher manifold pressure and still be efficient.

ken

the wastegate system works by adjusting the duty cycle of the solenoid. iirc, the wastegate solenoid cycles at 14Hz, and its "on time" is adjusted by the ECU.

when the solenoid is closed, the air makes a direct route from compressor to wastegate actuator and "wastegate boost" levels are achieved. this is an output pressure equal to the spring tension of the wastegate actuator.

the solenoid bleeds some of the fed-back air (which is routed from the compressor housing back to the wastegate actuator) from the system. when the solenoid is open, this air is bled off, and the end result is a higher compressor output pressure due to the wastegate not opening and bypassing the exhaust turbine.

hth ken

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