WYSIWYG

so why have it and have another controller for the actuator?

xr4tic

A boost controller bleeds off the boost signal to the wastegate, this is how you get more boost than what the wastegate spring is set for (usually between 5-7psi)

If in parallel:
The boost controller will see that it's hit it's targeted boost, and stop bleeding off air, and try to open the wastegate, however, the N75 valve will still be open, bleeding off air, and overboosting.

If in series:
Same thing.

As long as the N75 valve is bleeding off the boost signal, you'll overboost.

Now, this would be a nice setup if you thought the chip was too conservative, and backing off boost for smoothness, the boost controller could let it the boost come on faster, and the N75 valve could control it at the peak.

Sounds to me like the N75 valve just isn't fast enough to control boost adequately on a larger turbo.

Is there a faster acting solenoid out there?

What happens if you run with just the boost controller, and leave the N75 valve plugged in, but not hooked up?

WYSIWYG

so in parallel, the more conservative controller (ECU/N75) will supply enough psi to have FULL control of the boost (given nothing is routed back to the BC in reverse flow)
in series, BC then N75, the BC will have control what psi the N75 can work with.

xr4tic

Or at least, isn't supplying it fast enough.

By adding a BC in parallel, when it starts supplying full pressure to the wastegate, and the N75 is still open, the pressure will not go to the wastegate, it will go back up to the N75 valve, and bleed off.

In series, almost the same thing, the N75 valve will still not react fast enough, and not send full pressure to the wastegate, causing an overboost problem.

I also have a feeling that since the two controllers aren't talking to each other, that you'll have more problems than you started with. Without the feedback, the controllers might start fighting with each other.

xr4tic

just curious.

If you plot requested vs. actual vs. N75 freq, what does it look like? I'm curious if it's a valve problem or chip problem (or DBW problem)

CharlieGSanD

usually if im cruising in 2nd & under vac & punch it, boost will jump to 1.8bar & then slowly taper off to about 1.3 over about 4-5 seconds or until i hit redline (usually the same amount of time)

other times it will jump up to 1.8 & hold

& then sometimes it barely makes it over 1 bar

when i talked with Garret last week i told him that it was boosting 1.45 bar & his response was "thats normal, but if it was any higher id be worried" so i assume the chip is programed for 1.45 bar

CharlieGSanD

the interaction between the B/C & the N-75 was my main concern...

WYSIWYG

the i get jerking ('light switch'?) when i tried an MBC(spring&ball type) with my k04, but only at 4/5th gears. charlie might want to try a bleeder or a ball/spring+bleeder type MBC - my suspision is the wastegate is not closing right with the pressure being trapped in the actuator lines

xr4tic

get a vacuum line coupler, and drill a very small hole in it.

Any of the ball/spring type mechanical BC already have this to relieve the pressure on the wastegate when the BC closes.

CharlieGSanD

so when the N-75 closes to let the boost build, any pressure trapped in the line wont keep the W/G from shutting completly?


IIRC the ECU has adaptation valus for how the N-75 & its duty cycle affect boost, i wonder how this will affect them?.....