How to steady the boost?

L

Logan

Member
I hope my thread name isn't too misleading.

I'm looking for thoughts/ideas/opinions on how to get steady boost from my MSP.
It peaks around 9psi at 4000rpm, and then slowly declines to around 6.5 or 7 at redline. This is with a Joe P MBC.
(It had the same pattern, just lower numbers without the MBC)
I would like to know what sort of boost characterisitics people like Braden (turboge) are getting with new BOVs, is that the solution to this "problem"??
 
Logan said:
I hope my thread name isn't too misleading.

I'm looking for thoughts/ideas/opinions on how to get steady boost from my MSP.
It peaks around 9psi at 4000rpm, and then slowly declines to around 6.5 or 7 at redline. This is with a Joe P MBC.
(It had the same pattern, just lower numbers without the MBC)
I would like to know what sort of boost characterisitics people like Braden (turboge) are getting with new BOVs, is that the solution to this "problem"??
Click to expand...

Referencing my earlier post on page 2:Turboge's reasoning for pressure drop

He believes that it is the effeciency of the turbo and intercooler, or lack thereof. The BOV is not the problem, and did not fix this issue when he replaced his.
 
With all 6 "shims" in my BOV I get the same problem. I took them all out and the car runs better but still has the same boost characteristics. The only thing that swapping the BOV fixed was the nasty kick when you let off slightly under boost. Still sounds the same as well.
 
just cap the BOV and totally remove it. I did that and it halled ass! leaky ass BOV. Ask the 2nd Gen Eclipse guys about this one. They have the same BOV as us.
 
just cause the boost peaks somewhere doesn't mean that is where it's set at. keep slowly adjusting the boost until in 4th or 5th the boost maintains a desired level, MBC's take more tune and drive trys than you might think. if the boost initially goes to 10 then drops back to factory you don't have the boost up enough to maintain a solid boost level, raise the boost until it stays where you want it. I am going back to the factory bypass set up cause the car runs too ritch when the car is producing vac. I have driven a stock MSP and compared it to my 10 psi w/BOV and found that the stock pulls from vac to boost more efficently. The car adds to much fuel in vac, and when it transitions to boost the car stays fat until about 5000 rpm, then it runs a better A/F ratio.
 
I leaky Bypass valve doesn't mean s*** if you are controoling boost, as long as the MAP (manifold pressure) is where you want it
 
With the electronic controllers out there it is easier to tune a solid boost level throughout the rpm band if the turbo/wastegate are willing to work with you.

My experience with the Joe P MBC hasn't been all too great, it seems to have an "on/off" quality and not really a "1 turn 1 psi" type of method. Theres maybe 1/4-1/2 a turn of true adjustment and the rest is either full bore or stock boost.

In order to maintain a higher boost level over stock past 5000rpm the MBC has to be turned up so high you get boost spiking to 12+. With the MBC all the way out my roomates WRX would spike to 18psi in 1st and 2nd gear. It works somewhat but I haven't been able to get anything consistant or fairly adjustable.
 
The Joe P seems to be doing what I want it to.
I wanted to get about 3psi more than stock, and once I had the knob set to the right spot, that's what I get across the board.
I would like to get even boost at say, 9psi all the way to redline though.
Braden, what does stephs car do with the intake? same characteristics?
 
Don't know, last time I drove it I felt a lot of flat spots and stumbling. We're both waiting on the new design injen to see if it fixes it. It seems to be nearly gone on Jack's car.
 
Just a quick mention / question re: boost conditions and BOV's

There is a boost sensor in our (MSP) vacuum diagram, has it occured to anyone, that this may be bleeding off boost through the BOV at 6.5-6.9 PSI's?

I was thinking of adjusting the boost manually and noticed the Boost sensor in the diagram, and thought It would be better to go with an electronic Boost controller. 'cause I think it doesn't matter how much I turn up the boost manually it will be dumped by the BOV if I boost over 6.9 Psi??????????

Anyone!?
 
Hey turboge- the MBC is pretty sensitive, but that was done so the guys running 25 + psi can use the same MBC as the guys running 10 :).. A lot of others still require a blled or something after a certain level to run high boost. If the adjustment is too sensitive, I have lighter springs here that will make it a lot easier to adjust, it just won't hold high boost. All you had to do was ask :).. Let me know if you want me to send you one.

The issue of the boost dropping off is likely not the BOV. It is NOT THE SAME as a 2G eclipse. Although it is plastic, it is a SLIDE style (similar to a motorcycle carb) and it totally blocks the airflow until vacuum sucks it open.. Boost CANNOT blow it open like a standard BOV..

Also, I had brought this issue up with my turbo guy a week or so ago- without knowing the exact specs on the turbo yet, we can only assume, but we feel it is the weak wastegate spring allowing the gate to open up at higher RPM's/exhaust pressure due to the spring not being able to hold the flapper closed with all the back pressure of the stock exhaust. Mine got a bit better when I gutted my cats, but it still does it. It may even go away completely with a bigger, free flowing exhaust. We are also trying to find a heavier actuator for me to throw on my car and see if it still does it, I will keep you guys posted. He honestly doesn't feel it is the turbo because even the smallest of the GT25R's will hold 16-18 psi on a 2 liter. And, for those of you who still think it is the same as a regular T-25- that one will hold 14-16 psi with no problem also- so it *shouldn't* be the turbo..

As for the IC, it is not the best, but it is not that restrictive that it would not let the turbo sustain 50% of it's capable boost levels :)..

Trust me, the car is in the right hands to get to the bottom of all the *mis*information out there :).. I will have the boost dropping issue taken care of soon enough.
Joe
 
Cool, I'll need about 4 of those springs, 1 for me, 1 for my 2nd MBC, 1 for my roomates WRX and 1 for Jack.

I turned it all the way down and was still hitting 9psi, so if that new spring helps I'll be sure to use it.
 
All the way down, you are not using the spring at all.. What was your boost at stock? Did you have a gauge on it? Even wide open, the MBC is a slight restriction in the line and it has a small bleed hole in it, so it is normal for boost to be about 1-2 psi above wastegate psi even with it open. My car was only 5 psi stock, so I can run as low as about 6-6.5 psi.. If you had the 6.9psi that the car is advertised as, then it is entirely possible the 9psi will be the lowest. Pretty much any MBC will cause that, some more than others and some will respond differently on different cars. The idea is to raise the boost, not run stock :)..

As for needing one for the WRX, I have sold over 300 to the WRX community so far with 0 issues brought to my attention. If it is just an issue with it being too sensitive, that is the way it was designed- it was the only way I can make one MBC handle cars that run as low as 6 psi and as high as 30+ psi :).. The sensitivity is usually only an issue with low boost cars.

Shoot me an email during the week sometime at kwiktsi@nycap.rr.com and give me your address so I can send the springs when I get back from vacation.

I don't mind sending you a few, but the MBC was designed the way it was for a reason, I don't want to send a bunch of replacement springs out that no one else ever requested :).. If I see more demand (so far in over 2000 sold, I haven't :) ), maybe I will make two versions to offer- the standard one and one for low boost applications where the sensitivity is tough to tune with.

Thanks.
Joe
 
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