Electronic boost control
 

I am using a gm ebc solenoid that i have attached to my car in a way so that i can run wg pressure (7psi), or flip a switch and run the ebc (11psi) program in the adaptronic.

I have it set so that as soon as it spools up to 11psi (roughly 3600rpm) it adjusts the EBC solenoid so that it holds within .5 psi of my target up till red-line.

My issue is that, if i stab the throttle at anything above 4500 rpm or flat-shift, the boost pressure spikes to 14psi (where my over-boost protection is at).

I am currently using open loop wastegate control since i can't see any difference when i activate any of the closed loop settings.

any idea how to remedy this spike? i already have a MBC connected in parallel with the EBC and it does not fix the spikes. If i set the MBC to a point where it reduces the spike to 11 psi, it vents pressure after that initial spike down to 8 or 9 psi.

If you have not done so already, set the EBC at 100% across the board, then adjust the MBC for the cutoff pressure you want. Then, go back and retune the EBC.

When I first installed the EBC/MBC hybrid it was doing some weird stuff like that. Once I tuned the MBC with the EBC closed (100%) and then retuned the EBC, everything was fine.

ok, i will try that again. Even with just the MBC i was getting a similar spike. any idea how to fix a spike from a MBC

Does your MBC have a small bleeder port on it? Where is your boost source for the wastegate?

Yeah good questions. I am assuming you installed and plumbed everything correctly. Post up some picts of your install, or describe in detail.

also you have the Solenoid hooked up like this on the right:

http://www.miatamx5.com/EBC.jpg

This works too; that is how I did it.
http://lh3.ggpht.com/_jh2HiMm4nKQ/Sg...C-MBC-ASSY.JPG

Read this, specifically post #25...
https://www.miataturbo.net/forum/t30067/#post372400

Brain that avatar is really... disturbing... :eek:

:) that's exactly the same as the diagram I posted.

yes the MBC does have a small bleeder hole in it. Should i enlarge it slightly?

My pressure source is on the compressor outlet.

My EBC and MBC are configured similarly to your first diagram (left side) Brain

i will post pics as soon as i get home.

Do I need to even say what I'm planning on suggesting? :brain:

wait till i get a picture to you before you suggest it

Brain, the way you have posted on the right doesn't make any sense at all. if 0% duty cycle sent all of the charge to the wastegate, 100% duty cycle would send absolutely no charge to the wastegate. none of it would be sent to the MBC or the wastegate.

At least not with the GM, ebc

why did you say you had the GM Solenoid?!

.... I would have posted this:

http://www.boostedmiata.com/gallery2...serialNumber=1

this is have i do mine and it works perfectly.

I cannot tell for sure from your picture but it looks like you have it hooked up the same way I use it. The EBC and MBC are in parallel. It works for me. But, we have two things that are different. The MBC (yours is DIY) and the EBC (but I believe it is functionally identical).

Are you sure everything with your MBC internals is fine? No leaks anywhere in any of the fittings? How big is your bleeder hole?

there are no leaks in the mbc, permatex on all threads. as for internal functionality, how would i check that? it is just a plain old ball and spring. i got it from a company on ebay called NXS

the bleeder hole is really tiny, 1/16"

DO IT LIKE I JUST FREaKIN POSTED AND PROFIT HARDCORE>....


http://www.boostedmiata.com/projects/ebc_mbc_combo.jpg


WHY Do YOU DOUBT GLORIOUS BRAIN!?!??! :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.

Because you are a damned terrorist that is trying to blow up his car!








:giggle:

The way he has it is functionally 'exactly' the same.

In his configuration, if the solenoid is off, the boost will bypass the mbc. If it's set to 100% DC, the boost will try to escape through the blocked port but have no place to go but back through the MBC. Instead of blocking the port I utilize it.

So I suggest lengthening the wastegate rod a touch, should help with the spike without noticeably affecting spool-up.

Yeah I know. It's all good. Not saying yours does not work, just being silly.

does the adaptronic have a DC% table as well? I bleed off boost when I'm part throttle to prevent spikes, i have no issues when WOT however.

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?

http://lh4.ggpht.com/_ScASycO1DOk/Sv.../Wastegate.jpg

This is what i have to work with on the Adaptronic.

I think the problem is the DC% targets are too high. I have a feeling it tries to target the DC% first then adjust from that.

it is running open loop. 100%DC means straight MBC right?

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.

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?

Oh, fuck, you are right. I am an idiot. I had it all backwards :facepalm:

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.

try lengthening the wastegate rod first. like two full rotations longer.

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)

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 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)

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.

any one know of a cheaper/ equally good MBC?

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.

On an mbc I made I drilled the bleeder hole (~3/32") through a threaded part to give an adjustable bleeder hole, worked for me.

do you have a pic of this?

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.

no worries, your description cleared it up for me.

That is the MBC that FM sells huh? since i have been having such poor luck with mine, i think that i should try one of those.

DIY autotune also sells them.

No, the MBC not the EBC, i have the gm ebc already

oh my bad. build your own.

boostcontrol

nice writeup, wish i had found that when i first started this project.

i followed the instructions in that link and had good results. i get absolutely no spike in high gear pulls, but i still get spikes when i shift, and the boost does drop off at high rpm.

I wish i had ordered this ceramic ball when i made my first purchase... McMaster-Carr

i think that it would help with response at high rpm

and i am sure that when i put anything other than the stock exhaust on the car, the boost drop issue will reverse it self and turn into creep.