This solenoid came off a factory turbo Dodge vehicle.
It simply switches "open" to allow pressurized air to go through (to the turbo's wastegate).
I'm looking for a more progressive solenoid that can open at the range of 0 to 100%, instead of just snapping open or close.
For example, if I set a dial or switch to 50%, the solenoid will open 50%, allowing a smaller amount of air through.
It's for a different project (not controlling turbo boost). I'll post results here later but I just need the progressively opening solenoid first.
Does anyone know where I can find one?
Thanks,
Mark
The valve you seek does not exist, not for a reasonable amount of money anyway. The cost for a true analog variable pneumatic valve runs into the thousands of dollars. To achieve performance similar to a true analog valve with cheap and available parts, automakers generally use digital Pulse Width Modulation or PWM control. This scheme involves pulseing the valve at a steady frequency. The ratio of "on" time to "off" time of the constant frequency waveform is varied to vary the flow through the valve. This method is very effective, very reliable and, above all, very cheap. A quick search of the internet for pulse width modulation should give a few circuit examples. The valve you have is probably designed to operate in this fashion to modulate the boost pressure in the 2.2 dodge, it should be suitable.
Thank you for the great response. Now I know where to start searching.
I don't know what your application is, but pulse width modulation to a solenoid control valve is a common way to do this (as QuickTD pointed out).
VW used pulse width modulation to a solenoid valve to control the idle speed on CIS-E equipped cars (the ISV is a solenoid valve). Also, in the older CIS-Lambda system, the "frequency valve" is a solenoid fuel valve that is pulse width modulated to control mixture. And Digifant-II injectors are pulse width modulated to control flow, as are most other electronic fuel injectors in most electronically controlled systems. And pulse width modulated solenoid valves are used in many modern electronically controlled automatic transmissions to control pressure and operate the hydraulics in the transmission.
Sorry to jump in like this, but I'm having a little trouble grasping how the solenoid valve controls boost exactly. Hopefully someone can clarify for me.
The way I understand it, the boost line normally going from the compressor side of the turbo straight to the wastegate is hi-jacked and routed through the solenoid valve. Does the valve open and close rapidly to maintain the selected pressure? If so, does that not make for jerky turbo response?
I no little of electronic or mechanical engineering, but do understand turbine technology.
Hopefully these questions aren't to uninformed to recieve a reply.
Thanks all the same. :roll:
Does the valve open and close rapidly to maintain the selected pressure?
Yes. The valve is generally pulsed on/off several times a second. This switches the wastegate between manifold pressure (or in some cases, vacuum) and atmospheric pressure.
If so, does that not make for jerky turbo response?
Not at all. The valve usually has small orifices, therefore it takes some time to pressurize/depressurize the wastegate and the associated plumbing. Because of this dead volume and the orifices the wastegate is not able to respond to each pulse of the solenoid. The volume of the wastegate effectively integrates the pulses into a nice steady pressure.
I don't know why, but that makes me giddy. I love turbo diesels.