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For my turbo project, I'm thinking that I'd like to switch between 2 different boost settings(for gas mileage and for fun). A TurboXS mbc has this function. Think it's worth it?

I seem to recall there being a few discussions at one point about trying to do a dual stage MBC, I think the conclusion was that it is doable but a little harder and wouldn't be able to just flip a switch at your convience like with an EBC. I personally like the idea of having two settings though, lets you keep a low one for tooling around town and another for when you want to go out and play. Being an NA guy though, I'm probably not too much help.

well, i dont know about the turboxs ones but i have a turbosmart 2 stage and its wonderful. holds boost like none other. none of that pesky creep or spike or whatever you want to call it. maybe a psi or 2 in 4th goin 120mph but thats about it.

afik the turboxs ones are simple ball and spring which is why i didnt get one. teh turbosmart seemed a little more tecnologicaly advanced.

there is one catch though. the high boost setting is directly related to the low boost setting. turn the lower up and the high one goes with it. gfb (go fast bits) has one that is completly independent of each other. the aussi guys were talking about it when someone brought up the same question.

with mine i put the swich next to my gauge in the din void that occured after i got a new stero. if you want to be cool you can not use the togle swich it comes with and get a hand heald push button or a nos style button on your steering wheel then you can tell your passengers you have nos, when you push the button they can feel the power. it might not be as good if you want to autox with it on high boost but for me if i have high boost on while autox'ing my spinout rate doubles. i get going fast enough but stock brakes arent enough to slow me before teh turns. time for fhi 4pots

I don't think it would be hard at all.

Connect two ball-and-spring MBCs in parallel (using vacuum tees) but put a solenoid valve in series with the one with the lower setting.

When the valve is open, you'll get the lower boost level. When it's closed, you'll get the higher boost level.

Depending on the particular solenoid, it'll either be open when you apply 12v to it and closed when you don't, or the other way around. Either way, it's easy to wire to a switch in the dash.

You can make each MBC easily and cheaply; I and others have described how in other threads.

You could use an OEM pressure exchange solenoid or purge control solenoid, or just go to any pick-a-part and pull any old random solenoid out of the engine bay of pretty much any car made in the past couple of decades.

im having trouble pictureing what your trying to say V. if you put them in series the second one is the end boost you would have.


if you put them paralell than the lower one would always be the one youd be boosting unless you put 2 electric valves on each side so that you could close one and open the other.

azn2nr wrote:im having trouble pictureing what your trying to say V. if you put them in series the second one is the end boost you would have.


if you put them paralell than the lower one would always be the one youd be boosting unless you put 2 electric valves on each side so that you could close one and open the other.

You don't need two valves to change boost, just use the solenoid valve to block off the one set to the lower boost level.

Since you don't usually hit full boost while tooling around town, why would you get any mpg savings? Seems like mpg savings would be much better if you have the fuel system tuned to run at one higher boost.

2nr- vik is saying to plumb 2 parallel mbc's (one set high, one set low), and then have a diverter valve to choose which setting.

I hit full boost around town more often than I do on the freeway.

I guess I get on boost getting on the freeway, and passing cars, but usually I'm just cruising on the freeway.

I guess it also depends on the town. When I was in washington in a small town, I barely ever got full boost, and never in town. Speed limits were set at 35.

I hit nearly full boost in my neighborhood.

Here's a link... The first blue one on the page is the one i'm likely going to get(cheaper on ebay)
http://www.turboxs.com/shop_prod.php?what_category=1

Jason - Yes; if the two MBCs are in parallel you just get the lower boost level. But if the solenoid in series with that lower-level MBC is closed, you effectively eliminate the lower-level MBC from the picture, so you just run the higher level of boost.

Scott - With an MBC set higher, you get hotter air even at part throttle, because compressor outlet pressure is higher.

And no, I'm not saying to use a diverter valve. You could if you wanted to, but a plain old open-or-closed valve would work.

Laurel - Are you seriously gonna pay more than $150 for this?! Let me build you one for half that.

Laurel, i just installed my turboxs dsbc (used) if you can wait a day or i'll give you a better idea of it's performance.

I'm still trying to work out if it's broken or if i did something wrong.

I'll start another thread with my problem.

Autospeed the Australian online mag has a "Independent
electronic boost controller". This has two programable boost
curves---high and low. These relate to the duty cycle of the
injectors such that only at WOT do you get full boost. At about $60, its available in kit form.

When its soldered up and installed I'll pass on some comments.Then my Profec B will be for sale.

Ok, sorry about the delay, the TurboXS DSBC runs great.
I have stage 1 set to 8psi and stage 2 set to 11psi. It's not a big difference i know, but the plan is after the intercooler, push it up to 13 or 14.

Installing the FCD today and hopefully will be running the intercooler by next weekend.

Too bad i couldn't get it done sooner.

the club up here has arranged for a dyno day. I would have loved to have seen if any of the mods made a big difference.

scottzg wrote:Since you don't usually hit full boost while tooling around town...

Maybe you don't...but I sure do!!!

You could buy a nice EBC that you could have preset levels and be able to adjust boost levels on the fly at the touch of a button.

that's what the turboxs one does.

The other night it was raining and the temp was 45* F.
Profec B set at 12#---lots of front wheel spin.

The low set was at 8#-- no spin.

Tonight same old rain but at 55*--no spin at 8 or 12.

Either setting at the push of a button.