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#801 |
Scooby Newbie
Member#: 356436
Join Date: May 2013
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![]() I'm only going to be 350whp but it's a really good midrange power setup for track. You're right I will probably not need to lower boost in any gear though at my power level just still trying to understand the full concept of this a little & wanted to make sure because I had a potential buyer for my MBC but didn't wanna keep it I it wouldn't work with my EMS controlling per gear and stuff. I guess this is why I'm not a tuner though haha I am trying to understand without getting lost in all of these concepts
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#802 |
Scooby Guru
Member#: 32792
Join Date: Feb 2003
Chapter/Region:
NESIC
Location: lincoln, ri
Vehicle:2003 GGA MBP 12.9 / 105+ |
![]() Actually, I do plan to pull a little boost (ie get off the mbc) in 5th gear when I get around to enabling per gear compensations.
Not so much for preventing wheelspin though... ![]() |
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#803 |
Scooby Newbie
Member#: 356436
Join Date: May 2013
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![]() So you're saying if you do want to pull boost in any gear you need to get rid of the MBC? Because it controls the peak over the EBCS every time?... Just curious why are you pulling boost in 5th? Do you have a 6speed & want to save your 5th gear (I heard those are the weakest gears in USDM 6 speed)?
I'm a little confused on how the MBC takes full control of the boost at WOT & how the EBCS takes full control while in part throttle, can anybody give a simple explanation so I can understand this? I see 1/2 the boost going to each so I am just not fully understanding how each unit takes full control of the boost in the separate scenarios |
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#804 |
Scooby Guru
Member#: 48219
Join Date: Nov 2003
Chapter/Region:
MAIC
Location: Pittsburgh, PA
Vehicle:. Always drive the race line . |
![]() With the ROM he's running, he has Per Gear boost control. He's going to reduce boost in 5th vs other gears to save his engine.
The way the MBC takes control is by limiting the max boost no matter what you do with the EBCS. He currently has setup his boost targets and WGDC to go to 'infinite' above a certain TPS%. So the MBC sets the 'ceiling' in that case. So if he tunes his EBCS to target a boost level below what the MBC is set to, the engine will run at the LESSER of the two values. His BCs are in parallel. One is blissfully ignorant of the other until the threshold of either is met. But in general, think of this setup as two separate entities entirely. The engine will run whatever is the LESSER of the two setups at any given RPM and TPS value. HTH |
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#805 |
Scooby Guru
Member#: 32792
Join Date: Feb 2003
Chapter/Region:
NESIC
Location: lincoln, ri
Vehicle:2003 GGA MBP 12.9 / 105+ |
![]() what shek said.
if i go wot in 5th I'm going to have my foot in it for a while. ![]() mbc boost for me is right where the map sensor pegs... |
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#806 |
Scooby Newbie
Member#: 53603
Join Date: Jan 2004
Location: NORCAL AND SOCAL
Vehicle:2004 EJ207 WRX PSM |
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#807 |
Scooby Newbie
Member#: 356436
Join Date: May 2013
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![]() Ok, thank you for the explanation, so then I ask how does the parallel set up increase the boost speed (I know that the mbc has a quicker/smoother response)... why does it choose to take the route of the mbc for building boost quicker? Is there an explanation of why it does not choose the ebcs route instead when it comes to this? sorry if these are stupid questions. I just like to try and learn about how something works before I do it so I'm not some idiot "I got parallel boost setup"... "why"... "cuz it's better" haha
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#808 |
Scooby Specialist
Member#: 73932
Join Date: Nov 2004
Chapter/Region:
RMIC
Location: Denver
Vehicle:2005 STi EFR 6758 04 S2000 EFR 7064 |
![]() 100% WGDC closes the path off from anything passing through and forces the only route from the turbo to the wastegate through the MBC.
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#809 |
Scooby Guru
Member#: 32792
Join Date: Feb 2003
Chapter/Region:
NESIC
Location: lincoln, ri
Vehicle:2003 GGA MBP 12.9 / 105+ |
![]() it's "faster" because it is extraordinarily difficult (if not impossible) to run a true 100% duty cycle in a pure EBC scenario WITHOUT overshoot/boost spike/ringing.
in any feedback controlled circuit (ie, an EBC), there is an inherent tradeoff between responsiveness and stability. you can increase one, but only at the expense of the other. |
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#810 |
Scooby Newbie
Member#: 187965
Join Date: Aug 2008
Chapter/Region:
MWSOC
Location: NE
Vehicle:2003 WRX Wagon AW |
![]() Woohoo
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#811 |
Scooby Newbie
Member#: 356436
Join Date: May 2013
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![]() Ok thanks guy
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#812 |
Scooby Specialist
Member#: 172698
Join Date: Feb 2008
Chapter/Region:
MWSOC
Location: Des Moines, IA
Vehicle:11 STi BW 8374 E85 02 v8 Spec C E85 |
![]() I want to talk through a boost control failure I had while tuning a car with a hybrid boost control setup to see what others think. I've always recommended and often insisted on 3 port EBCS control only for the cars I tune but I had a customer who really wanted to use hybrid control so I agreed but it did not go well and ended in over boost and exceeding the limits of a rod which snapped at the small end. I want to make sure this doesn't happen for anyone else using hybrid boost control.
Target boost was set at 22 psi, fuel cut was set at 25 psi. On the initial runs, WGDC was set to 0% and boost was solid at 17 psi which was the wastegate spring pressure. Fueling was dialed in at 17 psi and we were moving to 19 psi. WGDC was set to 100% to give full control to the MBC and it was plumbed correctly with no leaks as verified by the pulls done at wastegate pressure. The MBC was set at the 19-20 psi mark. We did a pull and when I saw boost exceed the target I had the customer let off which was also right as the ECU cut fuel and WGDC to bring the boost under control. His turbo being what it is (GT35r), was able to go from 22 psi up to 37 psi in a little less than one second which was enough time to make the torque it did which snapped the rod at the small end. A smaller turbo would have been limited by its efficiency so it wouldn't have been able to spike so high so quickly. The fail safes did kick in but it was too late and the limit of the rod has already been exceeded. So, why was boost not limited to where the MBC was set? I don't know. Perhaps it was faulty or stuck. It was a Grimmspeed MBC for those who care. I can understand the benefit of hybrid boost control and I understand the fail safes. On a smaller turbo that cannot make so much power so quickly, I have no doubt the fail safes can get boost under control quickly enough to prevent an issue in most cases. On a setup like this where there is a turbo that can get way out of control quickly, I'm not sure if hybrid boost control is a good choice. Working with an EBCS alone and a small window of WGDC gives a lot more control for overboost situations aside from something impossible to control such as vacuum hose coming off. If that happens, you are at the mercy of fuel cut and the limits of your internals. |
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#813 | |
Scooby Specialist
Member#: 73932
Join Date: Nov 2004
Chapter/Region:
RMIC
Location: Denver
Vehicle:2005 STi EFR 6758 04 S2000 EFR 7064 |
![]() Quote:
- Was 100% WGDC tested with it turned all the way down to ensure you still achieved the same 17 PSI via the WG? Then ramp up the MBC accordingly? - Do you have a diagram of exactly how it was hooked up? - Was the WG or spring ever changed in between the two points the hybrid method was used? Last edited by yamahaSHO; 03-11-2014 at 05:27 PM. |
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#814 | |
Scooby Specialist
Member#: 172698
Join Date: Feb 2008
Chapter/Region:
MWSOC
Location: Des Moines, IA
Vehicle:11 STi BW 8374 E85 02 v8 Spec C E85 |
![]() Quote:
It was hooked up the way Grimmspeed says to do it which is also the way you said was best from your testing. I checked it several times and checked to make sure there wasn't an apparent vacuum hose issue that led to the overboost. Everything was very well secured. All lines where tight and secured with zip ties. The line to the EXT-WG was even covered with a heat tubing jacket. |
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#815 |
Scooby Guru
Member#: 32792
Join Date: Feb 2003
Chapter/Region:
NESIC
Location: lincoln, ri
Vehicle:2003 GGA MBP 12.9 / 105+ |
![]() how did you ever test that the mbc was set to 19psi?
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#816 |
Scooby Specialist
Member#: 172698
Join Date: Feb 2008
Chapter/Region:
MWSOC
Location: Des Moines, IA
Vehicle:11 STi BW 8374 E85 02 v8 Spec C E85 |
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#817 | ||
Scooby Specialist
Member#: 73932
Join Date: Nov 2004
Chapter/Region:
RMIC
Location: Denver
Vehicle:2005 STi EFR 6758 04 S2000 EFR 7064 |
![]() Quote:
The MBC was hitting 19 PSI on it's own prior to this? Either check solely with the MBC or 100% WGDC and post comp at 100% on the hybrid? This was with the exact same WG and spring setup prior? 3rd port was capped? No cracked (plastic?) fittings/T's? When you said you checked the lines, did that involve a boost leak test? That is about the only way I find the small leaks that lead to hard-to-track-down issues. Did you visually inspect the line that was covered with heat tubing/sleeve? When approaching something like this, it is much better to start with the MBC turned all the way down, then work your way up. Quote:
Also, "as instructed by Grimmspeed"... In trying to be very clear, what does that mean? PSI will vary based off the wastegate setup, so are you saying you got a "19 PSI" instruction by Grimmspeed? Last edited by yamahaSHO; 03-11-2014 at 05:59 PM. |
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#818 | |
Scooby Specialist
Member#: 172698
Join Date: Feb 2008
Chapter/Region:
MWSOC
Location: Des Moines, IA
Vehicle:11 STi BW 8374 E85 02 v8 Spec C E85 |
![]() Quote:
The 0% WGDC pull was intended to check that the WG would open at WG spring pressure which it did. You are right that it would have been better to start with the MBC all the way out. There are a lot of things we would have done/checked if we'd simply hit fuel cut and the rod has not let go. A boost leak test would have been one of them and the customer is going to have it checked now to see if that was the point of failure or not. The MBC itself is also going to be pressure tested. Its even possible the wastegate failed somehow. That will be checked as well. The GS MBC is a ball and spring type so when you exceed the pressure needed to move the ball, it sends the pressure signal to the WG which opens it. This is different than a bleed style MBC which hides some of the pressure. That's why the GS is a lot better. You set it for the boost you want and when that boost is reached, it opens the WG so long as that pressure is higher than the WG spring. On a very similar setup, a customer set his GS MBC to the 24 psi mark on a 35r, external WG with a 19 psi spring and it held 24 psi perfectly. On that setup the customer tried capping and un-capping the 3rd port on the EBCS and it made no difference in boost control. This customer had followed GS's instructions so the 3rd port was capped. I know there has been a lot of debate about capped vs un-capped and I think capped is better personally but it doesn't seem to make a difference from the experience from other people in this thread. Have you ever tried un-capped to see if it makes a difference on your own car? I am by no means blaming the MBC or this style of setup for directly causing the failure. It could have easily been something else like the wastegate itself or a small leak in the vacuum lines that opened up during the pull. Many others have used it with success and I've got other customer cars running it with success as well. Myself and the customer accept that something failed and I provided the details here as to how it happened. My objective was to get opinions as to what could have happened but equally important, I wanted to bring up the point: What IF a MBC fails? What IF a ball sticks in it's seat? I don't care if its in a hybrid setup or an MBC only setup. If you are on a turbo that can exceed the limits of your internals before fuel cut kicks in, you are in trouble. With an EBCS, they SHOULD fail closed generally, limiting you to WG boost pressure only. Last edited by WRXt4cy; 03-11-2014 at 06:45 PM. |
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#819 | |||||
Scooby Specialist
Member#: 73932
Join Date: Nov 2004
Chapter/Region:
RMIC
Location: Denver
Vehicle:2005 STi EFR 6758 04 S2000 EFR 7064 |
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#820 |
Scooby Specialist
Member#: 172698
Join Date: Feb 2008
Chapter/Region:
MWSOC
Location: Des Moines, IA
Vehicle:11 STi BW 8374 E85 02 v8 Spec C E85 |
![]() The car was checked over before and had no issues. All things will be checked again to see if an issue developed.
I'll admit that too much faith was put into the MBC doing what it is supposed to do. I wouldn't have been surprised by a small amount of over boost or even under boost and we had a pretty large margin to handle some overboost, but such a gross overboost should not have happened with where the MBC was set and how things were plumbed based on the information in this thread, other threads, other people's experiences and findings and my own experience and findings. In my other example rather than "un-capped" it was actually routed back to the intake. Yes, this does let some of the boost signal escape back to the inlet but from my (and other people in this thread's) testing, it doesn't seem to be enough of a "leak" to cause the wastegate to not see the pressure it needs to open. I will agree with you that capped is the better way to go and from your testing it sounds like un-capped was enough to affect your boost control so that makes a case for the capped party. WGDC was 100% in my testing. That is the only way to give full control the MBC as we all agree on. Since there is no benefit that anyone has even seen to routing back on the inlet, I think most everyone can agree that going with the capped port method, as Grimmspeed even suggests is the best choice. We can leave this point alone I think. So were still left with the situation at hand. Something failed and let boost go out of control to the point where fuel cut had to cut the power. The fail safes kicked in like we all agree they can do but it was too late. So, that leaves my question. What if a MBC sticks closed and there isn't enough time to get boost under control before an internal component limit is exceeded? I guess you just have to include this in with other possible points of failure such as a vacuum line coming off or a wastegate failing to open. |
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#821 | |||
Scooby Specialist
Member#: 73932
Join Date: Nov 2004
Chapter/Region:
RMIC
Location: Denver
Vehicle:2005 STi EFR 6758 04 S2000 EFR 7064 |
![]() Quote:
Quote:
If not actually commanding 100% by choice or forgetting to set the post comp max (OEM setting is 80%), you can work around a leak, but it's still a leak. Meaning, you can't actually achieve 100% WGDC. Quote:
Lower boost limiter delay. |
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#822 |
Scooby Guru
Member#: 36033
Join Date: Apr 2003
Chapter/Region:
SCIC
Location: Tuning Lab
Vehicle:CEO PhatBottiTuning 2006 STi GTX3582 + Meth |
![]() Take the mbc off and put it on your car....test it.
Take the ebcs off and put it on your car....test it. Take the wg off and apply pressure and make sure its not stuck shut. Then hook it up in the hybrid fashion...test it. Doing that will rule out mechanical failure of each unit and also verify the installation method. I would suspect from the boost level achieved that the ebcs was controlling the boost or a vacuum line blew off (but I imagine you would have mentioned that). The only way the mbc was controlling the boost is if you guys had cranked it down 6-7 full turns. Or if the previous hybrid tune on the car didn't have the wgdc set to 100% and was thus requiring the MBC to be cranked down quite a bit more....so essentially his "19psi" mark was actually 37psi with 100% wgdc. |
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#823 | |
Scooby Specialist
Member#: 73932
Join Date: Nov 2004
Chapter/Region:
RMIC
Location: Denver
Vehicle:2005 STi EFR 6758 04 S2000 EFR 7064 |
![]() Quote:
Exactly one of my thoughts. Last edited by yamahaSHO; 03-11-2014 at 10:15 PM. |
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#824 |
Scooby Guru
Member#: 36033
Join Date: Apr 2003
Chapter/Region:
SCIC
Location: Tuning Lab
Vehicle:CEO PhatBottiTuning 2006 STi GTX3582 + Meth |
![]() Do you remember at this point how much the mbc was turned? Or can you look at it and see where the mark is?
To increase 2 psi it should have been 8clicks or half a turn. So if the mbc was tightened more than that...then you probably have the answer. |
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#825 |
Scooby Specialist
Member#: 73932
Join Date: Nov 2004
Chapter/Region:
RMIC
Location: Denver
Vehicle:2005 STi EFR 6758 04 S2000 EFR 7064 |
![]() You'd have to first determine where the WG spring matches up and then you can could count up from there, and those clicks are just a rough estimate.
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