Anyone running a manual boost controller with their big turbo kit?

I was maxing at 15PSI and couldn't figure out why. I was then told I was dialing in the wrong direction lol. I have it set to ~20psi I think. I'm going to do some more runs tonight to see where I am with it. I think my boost response in 1st and 2nd gear is slower but I'm not sure.

I'm probably going to experiment with it as a standalone too. This thing is pretty simple but cool.

I was tweaking the settings but I wound up pulling back timing too much (10 degrees!).

I wanted to establish a "feel" for the boost. I think it spools more slowly with it in parallel.

Had it set to 20.. and boy did WOT feel great! :-D But, without running your N75 in parallel, the wastegate is either open or closed, so it's difficult to drive the car smoothly, plus even with a diode in the MAP sensor wire, you would still get throttle cut at lower RPMs with part throttle. (ECU: "Where'd this 1 bar of boost come from? I haven't requested it!")

I am trying to get a grasp on the effects.

My thoughts of having it in parallel was that partial throttle would allow the N75 to do it's thing. The MBC would be restrictive and most of the pressure would be directed through the N75.

At higher boost the MBC would open once the set PSI was hit and prevent spiking while the N75 hit it's max duty cycle.

I need to think about the effects of having it in series. I initially believe that the placement of the components (which one is closer to the wastegate) would matter in this case. All of this is just speculation of course. I know I should just try it but I also want to think about it a little before I "fix what ain't broke". ;-)

there are two differences in our setups though which may or may not make a big difference.

1) I'm a non-DBW (no throttle cut via MAP)

2) I'm running a T-28 vs. K-03.

running in series would be the same as running the MBC alone.. only difference being if you have your MBC set lower than your ECU requests boost, the N75 will be responsible for getting your max boost, and the MBC will just keep the wastegate closed below whatever it's set at.

When you run in parallel, you really should have a throttle cut circuit of some kind on the MAP sensor wire. What this does is allows you to get a maximum amount of boost without setting codes and/or getting throttle cut, but the N75 makes part throttle driving liveable with stock like control of the wastegate. In the parallel setup with throttle cut defender type circuit (diode), the MBC is only there to put a limit on the max boost made. If it wasn't there, the N75 would keep the wastegate closed because with TCD your ECU doesn't see more than x amount of boost (depending on diode used). This setup works well if the diode used reports a reading back to the ECU just lower than what it's requesting.

What happens when you get more boost than requested? For my DBW car, I get throttle cut.. do you just keep going?

I'd be a little scared turning up the boost on nDBW car without having some sort of control with the fueling in case it's needed. (for DBW cars, lemmiwinks sure comes in handy for this!) Just log and make sure your A/F isn't getting whacky! When you turn up the boost, do it in slow increments, clear codes, then log blocks 001.. and after driving for a while, check block 032 for ltft.

I believe it can keep going which we know is bad since it can lean out. I don't think that's the case (I hope).

I wanted it so I can turn the boost down.

Thanks for the VAG block recommendations. With the MBC in parallel and set to ~21psi (I can spike to ~23) my LTFT was around -7% IIRC.

Are you going to turn up the boost? with -7%, i'd think you have a little room without needing more fuel.

More boost or faster response or both?

In series w/MBC first:
set the MBC below the N75 boost value, this will quicken response, and the N75 will still control the boost. If the boost is strong in the mid range, but tapers off in the upper RPM, set the MBC higher to keep it from tapering off.

in series w/MBC second:
Blown motor?
The N75 is a bleed valve, so the pressure going into the MBC will not be enough to open the MBC. I think if you set the MBC to whatever the wastegate is set for, you can avoid "wastegate creep" (where the wastegate starts to slowly open before it's boost setpoint) for faster response, but it will have no affect on peak boost.

in parallel:
Under the MBC setpoint, the N75 will control boost, and over the MBC setpoint, the MBC will control the boost.
If the MBC is set below the N75 value, it will have absolutely no affect.
This might have the affect of controlling boost spikes, but response will be the same as just having an N75. The MBC should be set to your desired boost point, but you're still at the mercy of the ECU.

1) Eliminate boost spikes.

2) Achieve a faster response.

I figure I can't have both without some compromise. I wanted to see which consequence I can deal with more.

I pull back up to 8 or 9 degrees with just the N75. With the boost controller set at that PSI range I was retarding at 10 degrees. This is with 93 in the tank and 60 degree weather.

I want to dial down the boost and see what effect it would have on the timing retard.

I'm planning on trying it that way tonight. How is part throttle?

Felt the same as Wills car and he's running his N75. Are you DBW or nDBW??..might be different on DBW cars. Try it. turn teh boost up carefully..don't wanna over boost that thing.

But since I'm a T-28er, I'd like to see how it responds. I remember Will mentioning that there was little to no difference.

in these temps it must have been a lot.

I'm going to try one more attempt to trap 100+ or hit 13's tommorow night. I am throwing the tolulene in tonight and driving to work and to the track with the car on 100 prog and hoping for the best. I'll probably keep the subs and spare in unless I have a friend there to store stuff with.

I don't notice part throttle jerkiness which is good. I'm not exactly sure where the MBC is set but I think it is ~18psi. It was about 50 degrees this evening. I did see 2nd gear spike to about 20 psi though. I'm pretty much holding at ~18 psi in 4th too. I guess I'll have to drive it tomorrow in the afternoon when it's warmer to find out. BTW, I found out I'm missing a nut on one of the turbine-side housing bolt-to-cat adapter. I think that's where some of that exhaust smell I was noticing the last month is coming from.

As for timing, it's weird. In my middle (3rd gear) runs, I pulled back as much as 11 deg. but then in later (3rd gear) runs, I pulled back 6-8 deg. Not sure why it pulled back less in later runs.

I think part of it is the 93. I usually run 94 (haha not sure what 1 octane can do) but I'm going to fill up on some 100 tomorrow if I can get to one of the stations that carry it and then do some more runs to see what happens.


Good luck tomorrow! I am supposed to go dragging but I think want to take care of that missing nut.

If the Red Sox can win a WS, then you can get into the 13s tomorrow! ;-)

I have a full tank of "100" right now. 5 gallons of tolulene and the rest is 93. It's nice and cold out so the car felt great on the commute. I'll try to be down to half a tank or so by the time I get to epping. I was going to throw on my 16" winters, but I figure I have some recent times on the 18's so I'll keep them on for comparsion. I probably won't be able to ditch my subs/laptop until my buddy arrives later in the evening with his car. I brought my motorcycle helmet....just in case :>P

not sure if we can really compare the engines/turbos because his turbo is smaller in relation to his engine (stock 14G) than ours to our engines, but his boost seems to spike with his standalone MBC. Stever or Will, did you guys see any spiking with the MBC?

So Alex, do you hit full boost in 1st and 2nd gear with the MBC?

I also noticed that I did hit full boost (with spike)even with the N75. I just never looked long enough.

Oh, I lucked out with the nut. I bought replacement studs and nuts for the manifild to turbo just in case a few months ago. It turns out that the same nut fit...phew. I put it on this morning but took the SE-R to work this morning. I hope it solves the exhaust leak I was getting.

Now I gotta figure out what the deal is with my timing retard. Part of me thinks the retard is almost the same with the just the N75 in there.

to totally eliminate boost spikes, you need to slow the response down, but that's no fun :)

If you increase the response too much, then you get big boost spikes.

IMHO, the ECU/N75 can't react fast enough to control big boost spikes, I think the MBC is the best compromise between fast response and less boost spikes.

Never seen it spike at all.

I have to agree. I see a faster response but I still get a boost spike. The strange thing is that I don't feel that abrupt partial throttle feel. Maybe it's because of th T28 slower spoolup when compared to the APR GT28R/GT25?

I just bought one, so I can tune the boost levels...
Not sure how to fit my hands in there...

T-28 setup. I can take pics sometime this week if you want. I'm running it as a standalone right now.

maybe try and see how much timing as well. alone these number dont tell the whole story.

What voltages should I be expecting at the high RPM range? I did some logging of those before the MBC and they were usually below 20 but a few spikes to 29V.

you are pinging... if you hit 29volts on accel you are knocking... oh and if let off and see a 29v spike that is not a big deal...