I understand how a manual boost controller can be used to raise boost by not letting the wastegate actuater see the full boost pressure, but how can a MBC bring your current boost level down? To lower the boost you are supposed to make the controller longer (Grainer/ball and spring type) which lessens the tension on the ball and allows air through at lower pressures. It seems that this could only take the boost level down to what it was without the controller (when all the air at any pressure was being let through.

Also which of the 3 vac. lines attached to the wastegate actuator should the MBC be installed in if I'm running non-seq?

Thanks for the help.

 

it lowers it by allowing more air to flow thru to the wastegate. you can adjust the mbc to be open all the time if you want or have very little tension. as for which line, its the one going to the wastegate from the turbo nipple

 

A MBC (needle valve type) lets you adjust the size of the opening in the wastegate line. From the factory, the wastegate line has a restrictor "pill" in it. It's a piece of metal with a hole in it that allows a certain amount of air to go thru it. As you modify the intake and exhaust, boost levels rise with the stock "pill". In order to reduce boost, more air must be allowed to pass through the opening. A manual boost controller allows you to open that line, and reduce boost.

 

The ball & spring type works by lowering the pressure to the wastegate actuator. The difference between the full boost pressure and what the actuator sees is the air pressure required to pass air by the ball. This differential pressure is controlled by the amount of spring compression.

If there is no restriction in the line, and the actuator sees full boost pressure, then the wastegate will open at ~7 psi of boost, the same as if the "pill" were removed, or a needle-valve type of boost controller were fully open.

 

edit:

I can't find a pill anywhere in my lines which I can understand since they have been replaced with silicon, but then why is my car boosting above the default 7psi? If I disconnect the boost signal line from the actuator and cap off the nipple, I should only get 7psi correct?


What is the second nipple on the actuator used for? Right now mine has a line connecting it to some solenoid under the intake manifold. Can I cap this nipple off and plumb my MBC in the line connecting to the other nipple?

 

First of all where exactly is the pill, since I will need to get rid of this in order to reduce boost.

its inside of the vaccum line going from the turbo outlet nipple to the wastegate!!!






Also my wastegate actuator has three nipples on it,one side by side pair and one lone one. Am I to cap off the pair and just run the MBC in the vacuum line that connects to the lone nipple?

oh god no!!! do not cap off anything! perhaps you should take your car to someone which knows what they are doing as you have no clue of what the f*ck you are doing and will end up with a popped engine haha.

seriously man, just leave it alone or pay someone to do it for you becuase at the rate your going, your gonna have to pay 2-3k for a new engine and then another couple hundred to a couple thousand for new turbos after your apexseals take them out on the way out as well as a few more hundred to a thousand+ for labor.

 

Go **** yourself. I'm confused about one simple issue and you suggest driving 4 hours to a rotary shop to have them install my MBC instead of helping out. I guess you didn't need help when you first got your FD. I like to learn about the car I am driving and putting money into rather than just paying someone else to do everything to it.

I am asking these questions before I do the modifications, so you can relax in knowing that I'm notrandomly modding my car.


Please take your holier than though attitude to another thread where you can get off telling those less experienced than you that they are unworhty of driving the car you drive.

 

Back to the topic:

Is the wastegate control solenoid needed if I use a ball and spring type MBC to set the boost? I'm running non-seq with a PFC. It isn't needed with an electroinic boost controller.

What is it's purpose? I I cap the nipple offon the actuator, and set my MBC to let air flow through at 10psi wouldn't I max out at 10psi all the time? I don't see the need for the WCS.

Also I can't find a restrictor in the vac. line going to the actuator, the line is not factory, it has been replaced with silicon. If there is in factno restricter,why is it that I can boost to 13/14psi? Will I be able to bring theboostdown to 10psi with a MBC? I don't see how since I won't be able to lessen the restriction.

 

OMG.....

Uggg ill help u....

DONT ******* CAP OFF THE LINE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
if u cap that damn thing off IT WILL NOT OPEN THE WASTEGATE!!!!!!!!!! u know what happens when it doesn't open?

boost will just keep going up untill u blow your ******* motor.

okay so your getting 14 to 15 psi?

what are your mods? full nonseq right, do u have a full exuast and an intake?

if so welcome to boost creap. your wastegate hasn't been ported then. if there is no reistor in the line and your still getting 13psi

to fix this u need to port your waste gate. that means taking your turbos off, something i would not recomend you to do....

is this your first car that u have modded or worked on?

or have u been working on car for many years like MANY people on the forum?

 

\???

P.S. i did mention that "as for which line, its the one going to the wastegate from the turbo nipple" there is only one line yet you keep on asking which line it is or if you should cap stuff off. im pretty sure im correct in saying that "its the one going to the wastegate actuator from the turbo outlet nipple" and im not sure if anyone can put it any more simply.

 

http://robrobinette.com/boost_controller.htm

 

The stock spring in the wastegate actuator opens at 7 psi (~0.5 Bar). There are two ways to install a manual boost controller to change the point at which the actuator opens...

1. In-line with a vacuum line going from a boost source to the wastegate actuator, in order to limit pressure to the actuator. Cap off the second vaccum line nipple on the wastegate actuator.

2. On a line going from the wastegate actuator to outside air, to bleed off pressure, again limiting pressure in the actuator. Connect an unrestricted vacuum line from a boost source to the second vacuum line nipple on the wastegate actuator.

Either way, you're limiting the pressure level the actuator "sees", but if someone happened to change the position of your controller's valve, or it became clogged (for whatever reason), the "bleed valve" (option 2, bleeding pressure away from the actuator) is the safest arrangement. If the valve is fully closed, the actuator will get full pressure and open at 7 psi. Fully open, boost will be limited to whatever restriction the valve itself provides. This is the way I controlled boost on my car.

You cannot limit boost to less than 7 psi without changing the internal spring so that the actuator opens at lower pressure.

 

So in either option you no longer use the wastegate control solenoid?

Also wouldn't option 1 result in quicker spooling since the wastegate is held closed until the desired boost is reached and then fully opened (when using a ball and spring device)?

and if this is true could two of these devices be used (one on each side) to produce the decreased spool time but still have the safety valve should the one controller get clogged?

Thanks Jim, your help is always very much appreciated.

 

Nope.

They're both going to open the wastegate gradually as pressure builds, so neither really has a benefit over the other in that regard. Only an electronic boost controller can leave the wastegate fully closed until boost pressure builds to a preset level.

 

thanks, oh and congrats on you're 9000th post, keep them coming

 

I'm glad this thread finally got some useful responses, thanks jimlab and davew.

Now for my question to see if I understand before I install a mbc, if both hoses were to pop-off the actuator so it was seeing zero boost, the wastegate would never open, and you'd have a meltdown right?

So even jimlabs second design isn't completely fail-safe?

 

If you weren't watching your boost gauge and kept your right foot planted, sure.

If you zip-tie the hoses, you're not going to have any problems. However, there are no guarantees even with the stock setup.

 

Understood. I just wanted to double-check that the system actually works the way I think it does...

 

I went with the second setup, 13/14psi with no creep, unported wastegate

works for me, thanks again.