I'm trying to piece together a better understanding of how the factory boost control works. I think I've found most of what I was looking for but I still have a few questions. My goal is to reduce the factory boost taper without using a MBC. Essentially I would like to mimic what Works does with their P2 flash using ECUFlash and modifying the factory boost hose.

So far this is my understanding of how the factory boost control is laid out.



My questions are:

- Where exactly are these restrictor pills and what do they look like? I'm assuming they're inside one of the boost lines. How can they be removed? Pictures would be appreciated. I've looked under the hood, but it's hard to decipher what's what.

- What is the root cause of the boost taper? My understanding is that at high load/RPM the boost solenoid will be at 100% duty cycle trying to increase boost, but the restrictor pills prevent the solenoid from venting the air fast enough to reduce the pressure in the waste gate actuator, thereby preventing the wastegate from closing. Is this right?

- How is the Works boost line different from stock? Are the pills smaller to allow solenoid to vent more pressure from the actuator?

 

1) That pic doesn't look right to me. Unless I just don't understand the diagram, it's off a bit. The BCS has 2 hoses coming off of it - one to the underside of the MAF pipe (as pictured) and one going a long way down below the intake to a tee (as pictured), one hose goes to the WGA nipple (pictured) and the other goes to the turbo nipple (not pictured). You have the intake manifold in there, but it's not part of the stock boost system. There is a nipple on the compressor outlet pipe that is used as the stock pressure source.

2) One pill is in the long hose coming off the BCS, and it is located right at the end of the hose just before the BCS nipple. The 2nd pill is in the short hose going to the turbo nipple. It is closest to the tee.

3) The taper is not a function of the pills - the pills regulate the boost levels overall, but the taper is in the ECU. You can tune it out partly, but not fully unless you have an EBC.

4) Dunno, haven't seen exactly how they do it.

In the end, you have MUCH more consistent and full boost control with a boost controller (hence the name).

 

Thanks for your help. Is this better?



Using ECUFlash I already tuned the taper out of the software, which helped some, but it's still noticable.

You've probably read the Works sales pitch on boost control and their P2 flash. It sounds great, but it's $$$. Something about using the factory electronic boost control appeals to me more than using a MBC.

If this doesn't work, I might just try a MBC or just live with a little taper.

 

Plenty of people prefer to use the ECU to "control" boost, so it's definitely a viable and useful method. It's just that you can't CHANGE boost easily or at all unless you know how and where to put (or remove) pills. It's not like going and turning the knob a few times. There's typically less taper with an MBC/EBC than when utilizing the ECU, ESPECIALLY on IXs. Yeah, I mainly see Works customers claim that they have the coolest flash with 0 taper, but in reality I've never seen a MAP sensor log proving that the boost is flat, and most of them say "It hits 20 and holds steady!" Well, holding 20psi is much easier than holding say 22-23psi, and most people go by their boost gauge, which really doesn't tell the story anyway.

For you, if you've already removed most of the boost taper through EcuFlash, then the pill manipulation is mainly for raising boost. There should always be some taper - it's just natural for the stock turbo to taper at higher rpm where the head outflows the turbo.

 

Thanks again for your input. I think I will leave the pills alone since the results from just the tune were pretty good. I should probably get a TBE before trying to get more boost up top anyway.

 

isnt it safer to run a modified stock boost control system compared to a MBC? Using an MBC doesn't let the ECU go into limp mode if something goes wrong because it overrides factory failsafes, isn't this correct?

 

^anyone have a comment on this?

 

looks about right. I use the factory EBC and spike to 23 or 24 then it tapers to 19 or 20 by redline.

 

How often do people go into limp mode for a real reason? It's incredibly rare and is usually caused when there ISN'T A problem. Regardless, it can still go into limp mode and detune but it just can't lower the boost. That's certainly not a reason to not get an MBC.

 

The stock ecu will lower boost even when not in limp mode. If you are in a low octane mode the ecu will lower boost. Limp mode is when the ECU sees something bad throws a check engine light but runs the car uber safe so you can get it home. So unless you are getting a CEL you are not in limp mode.

Also it has boost cut , and boost timer limit functions that prevent boosting to high or for to long. This can be helpful if you are on the track and your map is too lean.

 

So how do you get the car out of limp mode? i think that is the problem right now.

 

Maybe this will help.

 

Hi,would anybody know the rating(how many psi/bar) of the stock actuator?

Some recommend to change the actuator to hold boost better.

Thanks.