Hey guys how are you? Ever since I did this 1g 6bolt with a 14B install in my 2g I have been having really bad turbo lag problems. I checked both compressor cold/hot side and they were fine. When I am in 2nd gear and punch it, I hit full booost around 3000 rpm. However, lets say I punch it in 2nd redlining it, then shifting into 3rd then punch it again, the boost takes forever to build, it just slowly climbs. However, if I am in 3rd rolling at 3000 rpm, I get full boost pretty quickly, but then if I am boosting in 3rd than shift into 4th then punch it again, the boost takes forever again! Damn it, it is really annoying and severally killing my cars performance. I have done boost leak tests and the 1g BOV is leaking slightly but not a lot. It doesn't leak enough to make a significant boost lag problem. Alright guys help me out here, help me fix this annoying problem. I lost to an STi today and was pissed because this lag really dragged me back. My mods/setup:

1995 Eagle Talon TSi
1G 6 bolt engine (155 across the board)
14B turbo
walbro 255LPH /w AFPR
450cc injectors
DSMLINK
3 inch exhaust (turboback + high flow 3 inch cat).
MBC (TURBOSMART) set to : 15PSI (Goes to 16-17psi sometimes).

Maybe your clutch is slipping (or you're slipping it). Do you shift really slow? Not to be a smart ass or anything but if you're redlineing in, say, 2nd gear, clutch in, shift to 3rd, clutch out, your rpms at this point should still be quite high and well within boost. Unless of course you're taking a long time to shift or else riding your clutch.

I don't ride my clutch sorry, I shift pretty fast.

Clutch slipping shouldn't effect boost anyway. it is my boost thats laging. The boost after shifting from 2nd to 3rd at WOT goes up very slowly, the RPN's are over 4500 rpm and still takes up to 5200 RPM to get full boost in that gear.

Are you going by a stock or aftermarket boost gauge? I know its a dumb qustion but dont trust the stock one. I can run 20psi all day long and never see 14psi on my stock gauge. I guess if you say it feels kinda gutless, then it must be someting else. If you are reving up to 7000rpm it shouldnt feel fast. with a 14b they usually only make power to 6000 then fall on their face. especially in higher gears!! After 6000rpm your just making noise and going no where!! Hopefully this helps.

lol guys guys, I am not saying how fast it is at 7000 rpm, I am talking about the lag. I have an autometer 30-0-30 boost gauge, the stock gauge is a POS.

What is your base timing set to. Too much timing takes away from spool. Post a log or something, you have link, give us better information than My car goes vroom vroom

This is only a guess as i have never seen a 14b flow map but. Maybe when you are rolling your turbo is producing enough to pressurize the pipes and when you punch on it it has enough there already to give you little to no lag but when you shift your BOV lets most of the pressure out and your 14b isnt enough to fill your cooler and piping? Only guessed that because I know you are running a huge front mount

Yeah I am running a huge FMIC. Maybe I should put shims on my 14B actuator. It could be possible that it isn't closing all the way.

Try another mbc, maybe your current one isnt letting the wastegate flapper close fast enough during shifts.
Mbc usually have a little pin hole to let air out just for this reason.

Dave's got it. The wastegate isn't closing.

The WG opens to control boost, and will be quite far open at the top of any gear under boost. If it doesn't close (it should close instantly) when boost pressure drops such as when you shift, the gate will still be open when you step on it in the next gear, and it won't build boost.

Either the wastegate itself is sticking, or there's a problem with how you have it connected. I can't count the number of times i've seen boost controllers hooked up wrong.

My boost controller is "T" off to the BOV line while the other side is connected to the wastegate. On the turbosmart boost controller it says plug in wastegate vacuum line here. Thats what I did. If I connected the boost controller the other way in reverse, it would build unlimited boost.

Well, i can't say for sure if the boost controller is causing the gate to stay open based on that description, but i can certainly say that you don't have the controller hooked up right.

The controller should be using the intercooler pipe pressure as it's source, NOT the manifold.

There are a couple VFaq's with diagrams showing the MBC using a "T" to the BOV line that I have seen and I cannot figure out why. A lot of people are using these to hook up their MBC's and getting undesireable results. I recently looked at a guy's car and he had it hooked up that way with a bleeder style MBC, which in effect not only bled off pressure to the wastegate but also to his BOV and I suppose also created a vacuum leak.

I don't see why you would need vacuum for your MBC.

*edited for pic*

This was taken from the VFAQ.

Can anyone tell me why someone would hook up a MBC this way? I just run it from the compressor outlet to the MBC then the wastegate.

I run it that way, because I have no nipple on the compressor or IC piping. I havent really driven my car to give any feedback on it tho.

Chris thats how I run it too because I have no nipple on the IC piping.

You need a small "vent", "pinhole", whatever you want to call it, between the actuator, and the MBC.

A "ball and spring" MBC acts as a one way valve.

If there's nowhere for the pressure to bleed off, the actuator will keep the wastegate open.

I have a TURBOSMART Boost controller the regular one.

So, does it have some way for the pressure to escape from between the wastegate actuator, and the controller?

I bet it doesn't.

Did it come with instructions? A plastic/metal "T" fitting?

It did come with instructions, however, this MBC is like 2 years old. In the 7 bolt motor I believed there was an extra nipple on the compressor housing. However, this 6 bolt motor, there was none. The "T" is a plastic one.

"So, does it have some way for the pressure to escape from between the wastegate actuator, and the controller?"

Dont MBC's have a pressure bleed off valve or similar?

I used the VFAQ method of hooking it up thats the bottomline, I thought the MBC automatically did the bleeding. The picture Scotty Mac posted is what I did. I am going to take the MBC and run it off the BC solenoid and see if that fixes it.

"I used the VFAQ method of hooking it up thats the bottomline,"

Actually, the bottom line is, if there ISN'T any way for the pressure to escape, you wil get results EXACTLY as you've described.

"I thought the MBC automatically did the bleeding"

Instead of "thinking" it does, why not find out?
The fix for this is way easier than removing the MBC and putting the solenoid back in. You just have to be willing to look at things, and think for yourself for a few minutes.

The reason you should (nay... MUST) connect the WG or boost controller to the IC pipe is that you're trying to control the pressure inside the IC pipe, so that the throttle will determine how much pressure mkaes it into the manifold. Set it to 15 psi, and you get 15psi at WOT. Half throttle will be about 7psi.

If you run the WG or controller off the intake manifold and it's set to 15psi then no matter what the throttle position is the boost controller and/or WG will be trying to make the manifold pressure 15psi. If you're at half throttle, you'll still get 15psi in the manifol,d, but about 30+ at the turbo outlet. This is bad for efficiency, and extremely bad for the turbo thrust bearing because it will have far more pressure on the compressor side than the turbine side. The driveability also sucks.

Trust me. I've seen MANY cars hooked up this way that had very poor boost modultion with the throttle, and i've seen MANY blown turbos as a result of this.

A VFAQ is just something someone took the time to make public. In most cases they're helpful, and have the right information. Not in all cases though.

Whoa, I had my old MBC hooked up off the manifold, I guess when I install my new MBC in the new car I will run the pressure source from the j-pipe than? Definitely good information to know. Learn something new everyday.

Nick
If the turbo has a port on the compressor housing going to the wastegate, that would be the best place for the MBC correct?

Alright, so if you don't have any pressure source from the j-pipe or compressor housing, how should you hook this thing up? I looked at the MBC and it looks like its fine. The bleeds holes are clear from dirt or anything else that could plug them.

The Turbosmart MBC (underhood type) has a bleed hole in the body. Look for the bleed hole midway up the body on the left side of this photo. The hole is just about at the tip of the needle valve in the picture.

The underhood type Turbosmart MBC has the check valve (ball and spring) integrated in the controller body, whereas the in-cabin type has the check valve in the special tee-fitting. Both controllers use a needle valve to allow adjustment.

The arrow on the body (or on the tee-fitting) must point towards the actuator.

I already had it installed with the wastegate vacuum hose is connected to the side where the arrow points. It is just I don't have a compressor housing nipple or intercooler pipe nipple.

Jesse, you can do a rough check of your MBC by doing this series of checks:

1) Blow through the ports in the direction of the arrow on the MBC body. As you apply more pressure in the direction of the arrow, air should flow out the other end, as well as from the bleed hole. If you turn the knob to increase boost, more air should come out of the bleed hole.

2) Blow through the port in the reverse direction of the arrow. Air should come out from the bleed hole, but no air should come out of the other port. As before, turning the knob to increase boost should cause more air to flow from the bleed hole.

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As for the actuator, you'll need to apply at least 11 psi to cause it to move, but you can pull on the rod to see if it is sticking. If I recall correctly, the actuator on my old T-25 only moved about .25 inch at about 17 psi on a lab bench.

Caveat: If the 14b is anything like the T-25, extending the actuator rod too far (1 inch?) will cause the flapper to jam. If this happens, disconnect the rod, then start the engine briefly to allow the flapper to free itself.

I think your MBC is connected correctly, and according to my sketches here for connecting to the BOV, the MBC ought to work fine. As you've mentioned, if the MBC were backwards, your boost would be uncontrollable.

As someone mentioned earlier, check your actuator. Make sure the rod is not binding on the bracket or heat shield, and that the actuator functions properly when pressurized.

By the way, is your BOV adjusted properly? You can check it by removing it and applying vacuum (18 mm Hg approx.) to make sure it's not sticking between shifts. Alternatively, you can simply push on the piston to make sure it doesn't stick.

If you've been rolling along at any boost for some time, your BOV is likely closed, so if you punch the gas, you'd make boost. However, if your BOV sticks between shifts, it would take some time for the valve to close and for your boost to come back up.

That's a good place for it. At the throttle body elbow or somewhere on the upper pipe is good too. Each has their benefits, and drawbacks.

At the compressor outlet, there will be the minimum delay between the turbo making more boost and the controller reacting to it. The downside is that it won't be accounting for pressure drops across the IC and pipes.

On the upper pipe or TB elbow, the system will be compensating for the drops in the IC and pipes, but with the time delay between more boost coming from the turbo and the controller seeing the change, there's a chance for oscillations.

Certain combinations of controllers, gates and turbos can be sensitive to oscillations. I used to have a B16G, and the controller ran from the TB elbow. It was a simple ball-spring device, and everything worked well. Now I have a 38mm Tial with a 57trim T04E running off a custom manifold. For boost control i'm using a pressure regulator to the top port and pipe pressure to the bottom port. When i ran with the source connected at the Tb elbow, there was TERRIBLE oscillations in the boost because of the time delay in the control loop. When i moved the source to the lower pipe just after the compressor outlet, the oscillations went away.

If there's no nipple or port on the turbo outlet, then add one, somewhere.

I think one of the reasons that most people think the controller should go to the manifold is that quite a bit of the simple 'development' work many many years ago by the early tuners of turbo cars were running turbo dodges. They ran the wastegate from the manifold, and through a WG solenoid. The computer controlled the solenoid using readings from the MAP sensor. This may look like the same scenario as having a mechanical controller connected to the manifold, except that the computer in the turbo dodge took the TPA into account, and reduced the target boost pressure to a function of the TPS. The pressure in the pipes stayed nearly constant. It was cheaper to do it that way since all the sensors were already in place, rather than ading a new MAP to the pipes.

Alright, I will drill a hole on the J-pipe on the top area and put a nipple there. Will my MBC run fine than?

It doesn't sound like the only problem is the boost source, so i'd have to say no, that won't make the difference.

with complete good intentions, I must say you are approaching this problem, like a few others, not the right way.


running WG off the manifold is totally wrong as explained. However if you run it right off the J-pipe, you shouldn't expect a HUGE improvement.

I took out the MBC and unhooked the wastegate vacuum. I get unlimited boost and I get it really fast. The wastegate is closing properly. In addition, I have a brand new 14B actuator because my old one was bent. I blew through the MBC in both directions and no air is coming out even when I turn the MBC all the way to the plus sign. Amin, I would you like me to hook up my MBC then? Nick is telling me to hook it on the J-pipe, Amin is saying I shouldn't expect much of a difference. Alright guys so how should I hook it up then?

OK, so your actuator ought to be good.

I'm pretty sure your MBC is also working fine, since it was able to control boost to 15 psi. You will need to blow reasonably hard to open the check valve (one-way valve).

I'd say to concentrate on fixing your original problem before looking at changing how your MBC is hooked up.

How did the BOV test go?

By the way, are you in Brampton or Scarborough?

My BOV is actually opening fine. Originally when I had it hooked up, it would flutter a lot. I believe the original owner of the BOV had it sitting for a while and got gummed up, and usually a fluttering noise means compressor surge or bov not opening properly. However, I cleaned it out and now it doesn't make that flutter noise. It really doesn't make any kind of noise just a quiet whoosh sound. I am from brampton when I don't have school and scarborough when I am in school.

FWIW, the signal which feeds the wastegate should be tapped AS CLOSE TO THE TURBO AS POSSIBLE.

The BOV should be tapped from the inntake manifold somewhere before the head and after the throttle body.

Make sure these things are connected as such before continuing anything despite what anyone else in here says. Just do it. Then thats out of the picture and we can move on.

Continuing with Steves point, it is a possibility that the waste gate ISNT closing BECAUSE of the MBC. Picture it, the mbc needs to bleed in order to maintain a constant signal feed to the wastegate. At the same time, ths very bleed is what lets the waste gate close again when there is no pressure signal to open it, otherwise if there wasnt a bleed from the signal line, the gate would remain open due to the pressure still inside the line on that side of the MBC, hence causing severe boosting issues..........So what am I getting at? Clean the mbc with break cleaner and compressed air. Its worth a shot.

My last suggestion comes from Jesse saying that boost came on imediatly and hard when the WGA was dissconnected from any boost source. Im guessing the flapper and actuator are fine, and connection/mbc issues are the culprit.