If I understand these ball and spring controllers right there is a spring that pushes a ball into the feed line to the wastegate and keeps pressure on the intake side until the intake pressure overcomes the spring pressure. Once this happens the ball moves and the high boost hits the wastegate and then the wastegate slams open.

Once boost starts to decrease bellow the spring pressue the ball falls back into place and the wastegate still sees the high boost because the pressure is trapped between the wastegate and the ball. As the boost slowly seeps out of the bleed hole the wastegate starts to close. I'm not sure how slowly it really is. Once boost builds back up the process starts all over again.

Does this seem right?

The reason that I'm asking is that this seems to be a pretty much like a switch. If it is I could use a solenoid as the switch and controll it electronically. I could make myself my own electronic boost controller pretty easily.


Well, I looked into my DFI software and there is an optional out put for, the this, VTEC. The great thing about this is that the output can be controlled by TPS, RPM, and/or MAP%. All you have to do is check the box that you want it to look at. And there is a turn on and turn off value for each. The MAP% also has a reverse function that I can tell it to turn on below a value and turn off over a certain level.

So if I tell it to Turn on when MAP% is below 15psi. It not let boost to the wastegate until it sees 15psi, and then it will switch. It will stay like this until the boost goes below the preset value of what ever, 14psi lets say. Then it cuts the boost off to the wastegate again.

This sounds great until I stop at the end of my run and the map sensor see's vaccume and the boost from the pipe gets cut off to the wastegate. Having a BOV should take care of this, but you still want the wastegate to open up to slow the turbo as much as possible. So you throw in the other constraint that the TPS is over 60%(50% off).

So basically it drives at low boost levels when you are normally driving, like you see real boost then anyways. Once you slam on the gas the solenoid cuts off the boost going to the boost gauge since the tps was over 60% and the boost was less than 15psi. Once it goes over 15psi it opens and bleeds off boost until you get to 14psi and then it closes off the boost again. And anytime you let off of the gas it will also open the boost to the wastegate.

The other nice thing about using the map sensor as the refrence is that you are regulating the exact boost going into the engine, not reading boost before the restrictions of the piping, intercooler, and maybe even throttle body.

 

Seems logical to me. Since you all ready dropped the cash for DFI, a $300 electornic boost controller kinda seems un-necessary if the DFI system will actuate a solenoid based on MAP and TPS%.

What DFI system are you using?

 

I'm running an Accel DFI Gen 7. The only thing that I'm worried about is that it might have to be regulated by something other than just an on or off. From what I've read there is a duty cycle for electronic boost controllers, but I think I can simulate that with the values that I put into the enable and disable. It's only about $30 worth of parts so I think I'll try it. As long as I'm carefully watching the boost the first time I do it, it should give me a good idea of what will happen.

 

Well, I just got off the phone with the Accel Tech line and they said that people do this and it works fine. They also told me that I should try using the nitrous output instead of the Vtec output because it is done in actual kpa instead of %map. Once the engine gets put back togther and on the dyno I'll try it out.

 

All the ones I have ever worked with are PW modulated. Be careful in your solenoid selection that they are rated for 100% duty cycle.
The main advantage of having a boost controller (other than be able to change boost from the driver's seat) Is that one can keep the wastegate shut longer and provide a quiker spool-up. That's what the duty cycle adjustment is used for, controlling overboost. or boost spikes.
Another effective way of doing this is set your main bleed (in the pressure line) for your desired boost. Use your solenoid (along with a check valve to let air back in) to prevent outflow of the vac. side of your wastegate. This will prevent movement of the wastegate until justbefore max boost (you will have to play with Kpa setting of switch) and allow the lowest time till max boost. If you wanted say a low/high boost setting you would need an addtional 12v solenoid and air bleed in the pressure line. Remember the wastegate begins to open at half of your desired boost pressure. This bleeds off alot of much needed impetus!

 

I was planning on using the GM boost solenoid that they use on the Typhoon trucks. Part number 1997152. I'm not sure how I could tell the recommended duty cycle for this part but it will be at 100% for given times.

I'm not exactly sure what the problem that you see is. If I'm the low boost setting it would act as if I didn't run a boost controller. But the high boost setting should keep the wastegate closed until it hits max boost. The DFI will be programmed to supply a high output for anything less than the desired kpa. Keeping the boost refrence cut off from the waste until max boost is hit(solenoid in the ON position). Once max boost is hit the solenoid switches to the OFF position and waits for the boost to come back down before it goes to the ON position again to build boost back up.

 

Not true, your wastegate will begin to open @50% of your max boost. This is due to the fact that the wastegate is seeing signal long before max boost is achived. A spring has a rate, it's not a switch. holding it shut until a few psi before max boost will greatly improve boost response by making all energy available to the turbine during spool up.
The way you have drawn will work fine (however Im not sure the gm solenoid is rated for what you want to do as factory I believe it's a PW modulated input) But you could use the same components to make a much more responsive system (albeit with a single boost setting) and only have the solenoid in the on position during the boost event instead of all the time other than a boost event.
However if the solenoid should fail for any reason the wastegate will not open and you might want to install a hobbs switch to kill the ignition.
your illustrated method does not suffer from this danger.

 

Ahhh, I understand what you are saying now. I half did the slow response for the low boost setting on purpose. When I'm on the street I don't want that big surge in first gear, a slower ramp would be much nicer. I'm very worried about keeping traction on the street. I'll probably use the switch for second and thrid gear.

So when you say PW(Pulse Width) modulation input you are talking about what? I'm not sure exactly how these are used in the stock application. Are you saying that they flicker the solenoid to get a proper mixture to the wastegate input. ie so many milliseconds of boost referecne to so many milliseconds of atmosphereic refrence to get the wastegate to sit where they need it to?

I can go to napa and get a heavy duty solenoid that they use on semi's but that's $60, the GM one was $30 for it and the wiring connector. I'm not sure the semi one would have the switching speed I would need either.

Well, I've now got a nitrous kit that I'm not using anymore, which comes with two very nice solenoids. The nitrous solenoid is a 3-way(line in, purge port, to nozzel) that I could use and it would be perfect for this application.


One of my big reasons for doing this is that I should be getting some engine dyno time when it's all put back together and I don't want to be wasting time figuring out how many turn it takes to get my boost controller to a certain boost. Its so much easier to just set a number and watch it work.





Here's another interesting idea I found on the web. The solenoid should allow air to flow through it until it gets the cut off signal. Then you essentially trap a new "atmospheric" signal at the wastegate. So if you wanted 15 psi on a 5psi spring you could tell the solenoid to work at 10psi giving the wastegate a new refrence for the 5psi spring to work off of. This would still leave the need for a quicker spool as discussed earlier in this thread.

 

pw modulated means pulses like an injector. Becareful using nitrous solenoids they reccomend not having them on for more than 30 seconds at a time. Does the gen 7Dfi have a pw modulatd output at all? then you could do it all with one setup.

 

From what I can find there's not pw output. As far as the Nitrous solenoid goes it won't work how I invisioned it, but it will work as you descriped earlier and that should get me by for my dyno time. The problem is that the purge port is always hooked up to the input so half the time it acts like a line from the input to the purge and when it's on it acts like a "T" between the input, purge and output.

So what I'm going to do is hook up a bleeder valve(nitrous jet #18) to the purge and the input to the turbo, and the intake to the output of the solenoid.

The solenoid is then only on when there is more boost than the preset amount. This only allows one boost level, but should be ok for the dyno. I may keep this setup and add a three way valve infront of it.


Well, I had a nice picture to illistrate everything, but my bandwidth is out again........This sucks I need to find a new place to host my pics!