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Anybody build a circuit to drive the stock boost solenoid?
Posted: Sat Dec 08, 2007 12:20 am
by All_talk
Has anybody designed an electronic circuit to drive the stock boost control solenoid? All you should need is a PWM output at something close to the stock frequency. You might even be able to use an IC as simple as a 555 timer with a FET for the output. I really like the idea of just tweaking a pot to adjust boost.
You would probably have to rig up a load (resistive/inductive) to put into the stock circuit so the ECU wouldn’t throw a code.
Just a thought.
Gary
Posted: Sat Dec 08, 2007 6:00 am
by vrg3
Yeah, I did that once. I did use a 555, a comparator, and a power transistor (it was a Darlington BJT rather than a FET, but same difference). It was basically the electronic equivalent of a bleed-type manual boost controller; instead of turning the knob on the MBC, you'd turn the knob on the potentiometer.
You can pacify the ECU with a 470-ohm 1/2-watt resistor.
Give it a shot!
Posted: Sun Dec 09, 2007 12:26 am
by Arctic Assassian
^ghetto tech at its most basic... But awesome!
I like the homemade FCD the best.
Posted: Mon Dec 10, 2007 7:08 pm
by Legacy777
Quick question, what would you have to tap into to let the circuit know what your manifold pressure is? Where's your input/sensing signal coming from?
Posted: Mon Dec 10, 2007 7:11 pm
by vrg3
The circuit I'm describing has no sensing signal. It just runs the solenoid at a fixed duty cycle (chosen by the position of a knob) to bleed off a certain amount of pressure from the wastegate actuator's diaphragm.
Posted: Mon Dec 10, 2007 7:15 pm
by Legacy777
With that setup, spool time should actually increase since the wastegate actuator will be seeing more boost before the desired opening time, when compared to the stock setup, or a MBC.
Posted: Mon Dec 10, 2007 7:42 pm
by vrg3
It is the equivalent of a bleed-type manual boost controller, like the standard TurboXS MBC.
So, yes, spoolup will not be as snappy as with an EBC (like the stock boost control) or a ball-and-spring MBC. On the other hand, it is easier to dial in and is much less likely to cause boost spiking.
Posted: Mon Dec 10, 2007 9:46 pm
by All_talk
You could add a pressure switch set just below wastegate boost to turn the circuit on. that would give you normal spool up and the solenoid wouldn't have to run all the time.
Gary
Posted: Mon Dec 10, 2007 9:50 pm
by vrg3
You'd probably get some boost spiking with that approach, but you might like the results better, yes.