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Old 09-11-2013, 01:46 AM   #1
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Default TurboSmart In Cabin MBC

So I feel that i have search quite a bit, and have yet to find anything about this in cabin boost controller (bleeder/tee type) not being able to hold more than about 11psi. I have started it out at fully closed like they suggest, and it makes just more than wastegate pressure (6psi). However, when i begin to turn it up, i make about 10 psi after about 3 full turns, but then the next 20 turns or so make no difference. What am i missing? I had EBC working well on open loop, but got sick of the +/- 4psi based on ambient temps, so i went this route. The EBC was running great holding the 17psi that i am after, so i dont think it has anything to do with my wastegate or any other internals. Thoughts?
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Old 09-11-2013, 09:48 AM   #2
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well if it was hitting your target with the ebc, nothing changed, and doesn't with the garbage bleed-type mbc, then the problem is obvious.

get a ball and spring mbc. I like hallman pro but the cheap ones work too. just not as well
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Old 09-11-2013, 09:52 AM   #3
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Put the EBC back in and tune it correctly. If open loop EBC gets you a +/-4psi swing based on temp the MBC will as well since open loop EBC is basically electronic emulation of an MBC with better part throttle properties.
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Old 09-11-2013, 10:12 AM   #4
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Quote:
Originally Posted by Leafy View Post
Put the EBC back in and tune it correctly. If open loop EBC gets you a +/-4psi swing based on temp the MBC will as well since open loop EBC is basically electronic emulation of an MBC with better part throttle properties.
huh?
no its not.
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Old 09-11-2013, 10:15 AM   #5
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huh?
no its not.
Abstractly it is. Though I guess it depends on the ECU's control strategy of the valve. Either way, open loop EBC and MBC are not closed loop so boost with vary with intake air temp and altitude.
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Old 09-11-2013, 11:24 AM   #6
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Nope. Stop being a fgt and just admit that its not, orrrrr actually give me a valid response on why I'm wrong and you're right.

Open loop gives the valve a set voltage at a preset place on the map. It will do exactly as its told by the ecu at all times, regardless of altitude or temp or whatever. Its always action, never reaction.

Mbc has a preset pressure that its always trying to hit no matter what. wot, part throttle, doesn't matter, if you set it at 17 and temp or barometric changes make the car hit more boost, it will start closing and therefore lowering boost. Problem is it only references pressure and not temp or anything else, so its more of a reaction then action, since its target or "duty cycles" never change.

Closed loop is obviously awesome sauce and everyone needs it.

If I'm completely off about something I'm all ears on how I'm wrong, but don't lump mbc with open loop ebc.
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Old 09-11-2013, 11:31 AM   #7
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Open loop specifies a pulse width for the ebcs, not a voltage, so the valve opens and closes rapidly, just like the mbc will. The MBC is supposed to achieve the same pressure differential between the boost reference and the atmospheric reference, so if barometric pressure goes down, boost drops too but the PR stays the same. I dont have an explanation of why MBCs vary with temps but all I see is subaru people complaining they have to turn their MBC down in the winter and turn it back up in the summer and fiddle with it throughout the day in the spring/fall. And the MBC duty cycle does change, that how it works, its just a mechanical duty cycle controlled by the spring, mass and pressure of the system.
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Old 09-11-2013, 11:36 AM   #8
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Quote:
Originally Posted by Leafy View Post
Open loop specifies a pulse width for the ebcs, not a voltage, so the valve opens and closes rapidly, just like the mbc will. The MBC is supposed to achieve the same pressure differential between the boost reference and the atmospheric reference, so if barometric pressure goes down, boost drops too but the PR stays the same. I dont have an explanation of why MBCs vary with temps but all I see is subaru people complaining they have to turn their MBC down in the winter and turn it back up in the summer and fiddle with it throughout the day in the spring/fall. And the MBC duty cycle does change, that how it works, its just a mechanical duty cycle controlled by the spring, mass and pressure of the system.
You obviously don't know how it works then.

MBC does not pulsate. At all. Bleed type bleeds it off, and ball-spring also bleeds it off, just differently.

Some subaru's have to turn down their mbc's in the winter because undersized turbos and undersized wastegate ports and oversized engines.

Its target never changes. It always wants to hit the pressure its set for. Sure the ball goes up and down to bleed off excess, but it doesn't target differently.

You know ILU but you also know I'm gonna call you out every time you BS about something, which you love to do. Just stop.

*edit: I've used an mbc on at least a handful of turbo miata's year round. How many do you have experience with?
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Old 09-11-2013, 04:31 PM   #9
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Hate to say it, but i believe Leafy is right. Simply put, MBC is a mechanically set pressure based on the ball and spring. It will oscillate when it has allowed too much through and the wastegate is open for too long, then the wastegate closes and the spring builds up enough pressure to open the wastegate again. This happens quickly and cannot really be "felt", but acts as a gradient for both sides of the MBC. EBC does the same thing, only the "mechanical" pressure setting is done via a solenoid. This solenoid, based on duty cycle (in open loop), is given a duty cycle percentage based on its TPS vs. KPA map that correlates to an allowed pressure to hold; much like the MBC. So in both cases, they will fluctuate with ambient temps and baro. Feel free to correct me if i am wrong, but i am not
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Old 09-11-2013, 04:34 PM   #10
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Quote:
Originally Posted by wolfram View Post
Hate to say it, but i believe Leafy is right. Simply put, MBC is a mechanically set pressure based on the ball and spring. It will oscillate when it has allowed too much through and the wastegate is open for too long, then the wastegate closes and the spring builds up enough pressure to open the wastegate again. This happens quickly and cannot really be "felt", but acts as a gradient for both sides of the MBC. EBC does the same thing, only the "mechanical" pressure setting is done via a solenoid. This solenoid, based on duty cycle (in open loop), is given a duty cycle percentage based on its TPS vs. KPA map that correlates to an allowed pressure to hold; much like the MBC. So in both cases, they will fluctuate with ambient temps and baro. Feel free to correct me if i am wrong, but i am not
At the very least that has the halman style works. I'm not familiar with the bleed type I assumed it was the same as the halman put with less ports but if its more like a needle valve then we're off the mark.
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Old 09-11-2013, 04:45 PM   #11
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Yeah, I was just chiming in on the heated debate on how open loop EBC is essentially MBC (ball and spring type).

The one i have is a bleeder T-Fitting (needle) type. Ultimately here is my situation:

For whatever reason, closed loop EBC can get close, but i still have some oscillations. I can get my target fine, but just sick of screwing with it, and went back to open loop. I live in Denver, where my drive to work might be 30degF and the ride home could be 80degF. That being said, my open loop duty cycles produce anywhere from 13 to 17psi depending on the temp. What i had envisioned was an "In-Cabin" dial where i could adjust it on the fly without whipping out the laptop and changing the map every time. I had some serious issues with this TurboSmart yesterday where i could only get to 12psi no matter what the dial settings.

Went back to open loop and for now have 100% TP set to about 18psi on a warm day, and have 97% throttle set to about 18psi on a colder day. So i just have to peg it when its warm, vs staying a little back when its cool outside. Sucks too, cause i have tried other cheap "in-cabin" types (~$12 off ebay) and the were crap, so i heard the TurboSmart was pretty good and splurged for the $130 one. Now its sitting on the shelf.
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