This was originally posted in my 50 Trim install thread, but I wanted to post it here because not many poeple venture to the How-To section and for search exposure
I added a dual stage boost controller. Its a TurboXS dual stage manual boost controller. I did this so that whenever I'm not at WOT, the turbo will only boost what the wastegate spring is (10 PSI in my case). Then when I floor it, the turbo will spool up to the boost level I have set (18 PSI right now).
I did this so I wouldn't have to worry about partial throttle full boost (PTB). It takes about 50% throttle to get 50 trim to start spooling, but the car has plenty of power at 60-80% for just casual lane changes. The problem I was having was that as the turbo started to get up around 12-15 PSI in partial throttle, the car would like surge, like it was cutting ignition back and I would have to let off. With this setup the turbo hits 10 PSI and stays there. Considering that the DTEC is doing about -25% correction at that point, the PCM only thinks its running about 4-5 PSI, so its happy. The car still pulls pretty good for lane changes. I actually floor it less often now, because I know it will do what I need.
You could do this with any turbo, even the stock unit. The minimum amount of boost is going to be whatever the wastegate spring is. The default AGP kit comes with a 10# and 12# (?? I think). Though you could just as easily put in a 7# and use that, or put in a 7# and use the first stage of the boost controller and set it to 9 PSI.
To tell the boost controller its time to switch to the second stage, it needs a 12V signal. The entire time it gets that 12V it will stay on the second stage. The kit comes with a red "missle arming" switch that you mount in the dash. That obviously is not going to help when I'm flooring it and steering and shifting. So I opted to use a snap-action microswitch, much like what nitrous kits use.
There are a number of sources for these. I bought mine at Fry's Electronics in the parts section (with resistors and stuff like), it was like $2. I'd say the arm on the switch was about 2.5" long.
Summit Racing (little more expensive and I made the bracket)
Digi-Key
Mouser Electronics
Heres the exact model I bought. Its the
VS10N03 on the page.
Heres the DSBC and microswitch.
The boost controller comes with the relay harness and the metal tab. The tab is supposed to be used for mounting the boost controller, but I used something else for that and used the tab to mount the microswitch as it worked perfectly with some modification.
The way this works is that when you push the pedal, it pulls the throttle cable, which rotates the throttle body butterfly thingy which I shall call the TB lever for the time being. Well there is a tab on TB lever that you use to manually rev the engine. We want to mount the switch and bend the metal arm in such a way that when the lever rotates around it pushes the switch at the desired amount of throttle.
There are two bolts that hold the throttle cable to throttle body. I used the outside one to hold the mounting bracket for the switch. This way doesn't hide the switch as well, but it makes the installation straight forward. Heres how I modified the metal bracket and attached the switch. I opened up one of the holes for the throttle cable bolt (in the picture) and had to drill an additional hole for the switch mount points. I then cut off the excess length of the bracket so that it would not interfere with the second bolt on the cable linkage. You can also how I bent the arm to actuate it when I want it to. It just took some trial error of rotating the TB lever and bending the arm to contact it.
To mount the boost controller itself I used a computer PCI slot cover. I mounted it where the battery tray normally mounts. But since I have the battery in the trunk it gives me a couple extra mount points in the engine back. The two small holes fit the bolt pattern on the back of the DSBC, and then I bent it at a 90* angle near the single hole so it sticks up. I cut off the excess lip afterwards with a dremel cut-off wheel.
To make it a little easier to count the revolutions as I "turn up" the boost. I used the Dremel cut-off wheel and made some divits in the BC, so that I would have a reference to count the turns. Its kind of hard to see, but there are actually indentions in the base underneath the knob.
Heres the harness I made up. I soldered a 10A fuse inline just incase. Its not very practical should the fuse ever actually blow, but power will only flow when you floor it (or rather activate the relay), so even if it did short out, as soon as you lift the throttle it will cut the power. For the 12V signal I just connected to the unused post inside the fuse box thats under the hood. The red wire coming into the fuse box connects to one post and there is a second one next to it that is not used, but does have 12V.
The way the switch works is that you have COM, NC & NO. They stand for
COMMON,
Normally Closed, and
Normally Open. COM is like your input, whatever signal is there can go to either of the other two. NC is the path the switch has when its not pressed in. Meaning that whenever your
not pushing to button the signal will always travel from COM to NC. NO means that normally there is no contact between it and COM, but when you press the button you change the path so that COM and NO are now connected. So we want to connect the trigger for the dual stage so that it only activates when the throttle lever hits the button, thus we use COM and NO.
You can see in the first picture there is an inset of the the switch in detail. You see that it has the internal layout embossed on the switch surface. Many relays and switches have something similar on their body. You can see that the line connects COM and NC, and NO is just sitting there. This is to let you know that the switch inside can only connect one or the other and that by default it connects NC.
Heres the switch mounted on the throttle body as well as it connected to the harness. I put a piece of plastic convuluted tubing over it just to keep it clean and dry.
The boost controller hooks up like a regular single stage boost controller. You have one input and one output. Because I wanted to keep the first stage of boost at what the wastegate spring is, I turn the first knob all the way down which should be (10PSI + 0 PSI = 10 PSI), for the second stage I wanted 17-18 PSI, so I turned it 7 turns for (10 PSI + 7 PSI = 17 PSI). Now its probably not going to be spot on, as the wastegate will have some play and the boost controller will some play, but it practice its very close. The stock SRT-4 boost guage shows about 11-12 PSI, and its known to be a tad off. I should look at the DTEC and see what actual MAP voltage is coming in.
Heres a WMV video of the actual switch actuation.
There you go, another way to get around partial throttle boost (PTB) on our cars.
Use a dual stage boost controller (dsbc) to control partial throttle boost (ptb)
vs the crap with the hobbs switch that didn't do much except give me a cel code. Now if you could come up with one that will vary boost by gear so bigger turbo people like us can get some traction in 1st and 2nd. My DAB shit don't work so I'm looking for alternatives.
Linear Mode
