Electronic boost control
11-08-2009, 07:07 PM
#22
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ok, so i tried to match brain's setup, but it functioned identically to my previous setup. so i don't think that is the issue. With the DC% values set to 100% (just to set the MBC) i get spikes up to 13-14 psi as soon as it spools. Then a second later it will settle to between 11.5 and 10psi depending on rpm.
On high gear pulls it settles to 11psi after the initial spike, then when it reaches high rpm (6000-7000) it will decrease to 9.5-10psi. This is using the MBC only.
Could more wastegate porting help with the spikes? Would a better exhaust (currently stock) help with this?
On high gear pulls it settles to 11psi after the initial spike, then when it reaches high rpm (6000-7000) it will decrease to 9.5-10psi. This is using the MBC only.
Could more wastegate porting help with the spikes? Would a better exhaust (currently stock) help with this?
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11-08-2009, 09:17 PM
#26
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Yes that is correct. You are essentially just running on the MBC. All of your PID settings are zeroed so the Target MAP (second column) does not come into play.
I would try drilling out the bleeder hole on the MBC first. Here is what I am thinking...
In the lower gears everything is happening faster. So your spike is higher because the MBC does not have enough time to vent off the excess signal to the wastegate, and vent the wastegate itself. So the boost spikes (wastegate is not opening fast enough) while it is trying to bleed down. In the higher gears it is better since there is more time for venting to keep your turbo from spooling to a higher boost level.
The drop off at higher RPM is normal, especially if you do not have a huge exhaust, or you have a small A/R turbine. If your wastegate was not properly ported you would get boost creep at higher RPM; The boost would continue to climb. I think BEGI ports all the wastegates on their bigger turbos by default. Are you sure it is not ported?
Anyway, I think you should try drilling out the vent hole on the MBC a tiny bit, like the next size bit, and try it again without changing anything else and see if it helps. That is a lot easier than changing exhausts, or pulling the turbo to check for porting.
I would try drilling out the bleeder hole on the MBC first. Here is what I am thinking...
In the lower gears everything is happening faster. So your spike is higher because the MBC does not have enough time to vent off the excess signal to the wastegate, and vent the wastegate itself. So the boost spikes (wastegate is not opening fast enough) while it is trying to bleed down. In the higher gears it is better since there is more time for venting to keep your turbo from spooling to a higher boost level.
The drop off at higher RPM is normal, especially if you do not have a huge exhaust, or you have a small A/R turbine. If your wastegate was not properly ported you would get boost creep at higher RPM; The boost would continue to climb. I think BEGI ports all the wastegates on their bigger turbos by default. Are you sure it is not ported?
Anyway, I think you should try drilling out the vent hole on the MBC a tiny bit, like the next size bit, and try it again without changing anything else and see if it helps. That is a lot easier than changing exhausts, or pulling the turbo to check for porting.
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11-08-2009, 09:52 PM
#27
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the only porting on the wastegate is from me taking a dremel to smooth out the rough casting.
I will try the slightly larger bleeder hole on the MBC and let you know how it works. Although the logic seems a little backwards. If i wanted the wastegate to open quicker, wouldn't i want less of the pressure to bleed off?
I will try the slightly larger bleeder hole on the MBC and let you know how it works. Although the logic seems a little backwards. If i wanted the wastegate to open quicker, wouldn't i want less of the pressure to bleed off?
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11-08-2009, 09:54 PM
#28
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Oh, ****, you are right. I am an idiot. I had it all backwards 
What about trying a different MBC if you can get one? Seems like that one is not reacting fast enough. Mine does not overshoot at all IIRC when on 100% DC. I have a TurboXS I bought used off of ebay. Nice little unit.
I seem to remember reading some discussion about the homebrew plumbing fitting style MBCs and how about using a different ball made it work better. Not sure I remember that right.
What about trying a different MBC if you can get one? Seems like that one is not reacting fast enough. Mine does not overshoot at all IIRC when on 100% DC. I have a TurboXS I bought used off of ebay. Nice little unit.
I seem to remember reading some discussion about the homebrew plumbing fitting style MBCs and how about using a different ball made it work better. Not sure I remember that right.
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11-08-2009, 10:55 PM
#30
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alright, i will try lengthening the rod first.
i will also start looking for a different MBC tomorrow. (i will see if i can find any friends that will let me try theirs out)
i will also start looking for a different MBC tomorrow. (i will see if i can find any friends that will let me try theirs out)
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11-11-2009, 09:34 AM
#31
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well, lengthening the rod reduced the initial spike in a high gear pull. but if i try a flat shift or stab the throttle at high rpm (5k<) it still spikes to 13 or 14 psi.
i am thinking of taking the MBC out of the equation and just trying the EBC out to see if the MBC bleeder hole is the problem.
i am thinking of taking the MBC out of the equation and just trying the EBC out to see if the MBC bleeder hole is the problem.
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11-17-2009, 12:01 AM
#32
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i found the spike problem. It is the MBC bleeder hole. it is bleeding off too much pressure and causing the wastegate to open too slowly.
the bleeder hole is currently 1/16 inch. I either need to solder closed the current hole and re-drill it to a smaller size or i need to bet a different MBC.
What size is your bleeder hole?
What MBC would you recommend? (this one is from NXS)
the bleeder hole is currently 1/16 inch. I either need to solder closed the current hole and re-drill it to a smaller size or i need to bet a different MBC.
What size is your bleeder hole?
What MBC would you recommend? (this one is from NXS)
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11-17-2009, 12:09 AM
#33
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I have the TurboXS "High Perfomance Boost Controller (BC-HPBC)" as shown here, second from the top:
Turbo XS - WRX, STi, EVO SRT4, Subaru, Mitsubishi, Turbo, Turbocharged
Works great but not cheap. They are about $100 on ebay. I bought this one used.
Seems like others here have had good luck with cheaper MBCs though.
Turbo XS - WRX, STi, EVO SRT4, Subaru, Mitsubishi, Turbo, Turbocharged
Works great but not cheap. They are about $100 on ebay. I bought this one used.
Seems like others here have had good luck with cheaper MBCs though.
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11-17-2009, 04:36 PM
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well, i filled the 1/16 bleeder hole in the mbc with solder. i then drilled the solder out with a #60 drill bit. The boost spike is better, but is still there. i will try the same process again with a smaller drill when they come in later this week.
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11-20-2009, 11:44 AM
#38
No I don't have a pic but it was made using a T and threaded barbs. Where the output (to wastegate) barb was threaded in I drilled the part of the T where it was threaded on the inside and through the already threaded in barb. When tightened (super tight) the hole shrunk when put back to normal tight (with teflon tape) the hole was at max size.
I have a bmp diagram that won't upload but I could email it, too lazy for photobucket.
I have a bmp diagram that won't upload but I could email it, too lazy for photobucket.
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11-20-2009, 04:16 PM
#39
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No I don't have a pic but it was made using a T and threaded barbs. Where the output (to wastegate) barb was threaded in I drilled the part of the T where it was threaded on the inside and through the already threaded in barb. When tightened (super tight) the hole shrunk when put back to normal tight (with teflon tape) the hole was at max size.
I have a bmp diagram that won't upload but I could email it, too lazy for photobucket.
I have a bmp diagram that won't upload but I could email it, too lazy for photobucket.
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12-05-2009, 08:28 PM
#40
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DO IT LIKE I JUST FREaKIN POSTED AND PROFIT HARDCORE>....
WHY Do YOU DOUBT GLORIOUS BRAIN!?!??!
although it makes perfectly good sense that it will work in your configuration....You can always try to lengthen the wastegate rod something like 2 turns. so the same boost levels will crack it open ever so slightly more.
WHY Do YOU DOUBT GLORIOUS BRAIN!?!??!
although it makes perfectly good sense that it will work in your configuration....You can always try to lengthen the wastegate rod something like 2 turns. so the same boost levels will crack it open ever so slightly more.
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