legacycentral bbs

Why can't you go out and get a pressure sensor from another car thats good for up to say 20psi, hook up a vacuum line to it, put the output to a simple logic circuit/relay, and controls a solenoid that opens a vacuum path to the wastegate?

So basically, when the pressure sensor reads a certain amount of resistance or above, it opens the solenoid 100%


Simple, cheap, partial gating free.


Am I missing something?

I wouldn't want to risk assembling it wrong or buying the wrong parts, which could result in some kind of really bad boost spike or something. I'd leave stuff that advanced to the pro's.

Not that you dont have a good idea, but some boost controllers do a lot more than just control boost around one parameter. Take my Blitz for example. It has 4 modes that you can preset to whatever boost limit you want, and you can also adjust the boost response. It also has a program called "scramble boost" where it adds on an additional Xpsi depending on throttle application. Its pretty crazy. Although, I dont use a lot of that crap thats on my controller...

A simple EBC could probably be made like you say. Why not try it?

Imprezive, you could design all of those features into a home-made EBC if you know how to program and such.

I don't understand the benefit of the "scramble boost" feature though. Why?

who knows what the point is, maybe just so you can have more boost when you really get on it. I wish I had a more simple boost controller to tell you the truth. There are too many goodies on this one that I dont need. meh...

I'm sure you could design and program your own controller if you had the know-how, I just wouldnt trust it.

Why not trust it? If something goes wrong, it's directly related to your right foot, so you just back-off and you don't risk damaging anything.

It's not like you could make full-boost at idle if you made a programming error.

Why not wire a resistor in place of the stock boost control solenoid, and then just control duty cycle through that? You could read the signal from the factory pressure sensor, or use a different one. You could just play with it a little and work out duty cycles on your own through a simple basic microprocessor, then just have it closed below a certain level of boost (keeping the wastegate shut) and when you reach desired boost, have the factory solenoid cycle to let however much air you want pass through.

Using the factory solenoid is a good idea, actually. Ill pull it out sometime soon and get a handle on how it works, and o the same with a pressure sensor. Ive got a local friend who designs logic circuits and microcontrollers so Ill ask him what he thinks he could rig up.

Unfortunately I dont think you can modify the stock setup for this safely, since the pressure sensor is only good for up to 14 psi or so. It depends on how the sensor and the solenoid relate to one another. I can image a situation where the ecu would freak out pretty quick using resistors to trick the solenoid into opening at higher pressures

Vikash, any thoughts?

Thoughts:

A very simple circuit will kinda sorta work but won't be effective at regulating boost without some intelligence and some semblence of PID control.

The stock solenoid is not intended to be run at 100% duty cycle ever; it's meant to be pulse width modulated.

PWM is better suited to this purpose than a nonlinear open/closed deal. The ideal steady state of this system involves the simulation of having the solenoid partially open.

You'll need to provide a path for pressurized air to escape the wastegate actuator (the stock solenoid I think has this built in; otherwise you could use a small bleed orifice or a check valve).

If you use the factory sensor or any other sensor reading from the intake manifold instead of from the compressor outlet, you risk PTFB-type issues.

I don't see how this is simpler than an MBC.

What is partial gating?

A microcontroller could be used to pulse width modulate the solenoid and do PID control. You're talking about designing an EBC here.

It wont be simpler than an MBC, but Im hoping to get better boost control.

Im having lots of problems maintaing proper boost right now, and Im trying to come up with a solution

What's partial gating?

If your wastegate is functioning properly, an MBC ought to be able to give you decent results.

You're currently using a homemade ball-and-spring MBC? How are you relieving pressure between the outlet and the wastegate actuator? How did you create a seal between the inlet and the ball? Does the spring neatly fit the ball? And not bind on the adjustment screw? And not bind when it's compressed to where you want it?