Manual Boost Controllers and You

[Backlash2032]

So I've recently installed a MBC to my car and the results piss me off. It hits 10-11 psi all day long. By red line (well. By 4k) it's bled to stock boost already. It's a ball and spring type MBC, and it has the relief hole. Is there anyway to fix this? Or is that just an MBC thing?

 

[IndigoMKII]

Just a MBC thing. In order for it to hold til redline, you'd need more pressure on top of the spring but that will also cause increased pressure. Easiest is to get a EBC and let the solenoid work its magic.

 

[Backlash2032]

Is there anyway to reduce it? I hate losing to stock cars when I know if I held 10 pounds till red line I'd be cars in front of them lol

 

[IndigoMKII]

Well, the biggest problem is that with the pressure raised, the stock turbine housing and wheel can't flow enough to maintain the pressure in the plenum. In other words, the turbo isn't producing the CFMs. Even with my profec b spec 2, I still go from 16 PSI at 3.5 to 13-14 PSI by 6k.

IIRC, getting the turbine wheel clipped will help the ct pull to redline better. So between your MBC and the inefficiency of the turbine wheel, I doubt this can be remedied.

 

[Backlash2032]

Alright.. I'll just deal with it until I get my 57 trim with a clipped exhaust wheel rebuilt... Lol

 

[jake8790]

Still on the stock downpipe? My car used to do the same thing, until I put on a bellmouth 3" downpipe and straight 3" exhaust. The CT wastegate is small, but so is the turbine wheel. So with a free flowing exhaust it will creep to 11-12 psi with no boost controller, but raising it much past that will cause it to lose boost at high rpms like IndigoMkii's car. Mine did the same thing.

 

[Backlash2032]

It's got full 3 inch turbo back exhaust and hard pipes and a front mount

 

[IndigoMKII]

It's got full 3 inch turbo back exhaust and hard pipes and a front mount

Basically my mods minus 57 trim and supporting mods. Its such a fun car in this state for such little money invested.

 

[Backlash2032]

Yeah I wish. I lost to a stock VR6 by a car, WRX with exhaust, STI with intake and exhaust, and an SRT4 with quite a few mods. All these were in the quarter. The SRT4 was funny.. I pulled 2 cars on him through the 1/8th, then he blew past me right before the finish lol

 

[black89t]

from my experience with the ct26 the stock waste gate spring is the issue. for best results put two washers between the waste gate and compressor housing. then use a boost controller from there. doesn't matter what boost controller you use when the waste gate is getting blow open. at one point i had a pile of stock waste gate actuators so for fun my and my buddy cut two open and put the springs from the two into one and welded it back up. doing that made it hold 12psi to redline just off the waste gate

 

[Backlash2032]

I guess I see why it's just a "MBC" thing... As boost raises, exhaust pressure raises... So now that pressure is pushing on the wastegate, also acting on the wastegate actuator.. it's weird thinking that there's more like 14 psi of spring pressure in the waste gate haha. For 7

 

[TurboStreetCar]

Not really a mbc thing. My mbc holds 20psi perfect. Only problem I ran into is pressure drop across my ~24x12x4 intercooler over around 19psi at high rpm. I Routed the mbc pressure line to just before the throttle body and it was back to solid. Now the mbc regulates the turbo to keep the throttle body inlet at proper boost rather then the compressor housing. So if it drops 2psi across the intercooler it'll automatically compensate by raising boost at the turbo because it will sense the drop.

It also had dropped from 25psi to 23psi but I only have 12psi of spring in the wastegate so I think I need more spring to hold back the exhaust pressure when i go to turn it up.

I have a really old "Joe P" brand mbc. Also running a 6466 but mbc's hold just as steady as electronic if your setup is right.

 

[Backlash2032]

Well I need to get in there and shim the wastegate lol

 

[TurboStreetCar]

I think when i had the 7m and CT26 in my car two washers under the wastegate got me 10psi.

 

[Skeezix]

How exactly did you run the pressure line for the MBC just before the throttle body? Did you add a small nipple to your piping?

 

[Trent]

Get a good quality MBC and you won't have a problem. I've got the Hallman and it works perfectly and holds whatever boost level you want with no overboosting or pressure falling off. Granted I don't have a CT26, but the Hallman is shown to hold better than some EBC's when you get into higher boost situations as well.

My pressure source has always been the compressor housing of the turbo so I can't speak to how much more accurate it would be if you used a pressure source near the TB. It has always worked fine for me at the compressor.

 

[TurboStreetCar]

How exactly did you run the pressure line for the MBC just before the throttle body? Did you add a small nipple to your piping?

Yep.

 

[Backlash2032]

Well I shimmed it with 2 washers and it yielded 8 psi with the boost controller turned down. Turning it back up to 10 and it now only drops 1 psi

 

[7M4EVR]

Granted I don't have a CT26.

That may be the issue though. I really think it's just the stock turbo not being able to flow enough to keep from dropping. I had it happen to me with 2 boost controllers. Didnt help if I shimmed the gate. All that did was raise the boost, it still dropped off. Then I had Albert upgrade my CT to a 60-1 and it dramatically helped.

 

[Backlash2032]

I just cant wait for my lex afm, afr Gage and to get my clipped 57 trim rebuilt. Gonna be a beast