Manual boost controller / T-25 question...

[ClassicalBor]

First, based on what ive accumilated the T-25 runs 10-15 psi from the factory is this correct?

Second, the previous owner of my car i know upped the boost to 16pounds, actually sometimes it appears to peak a tad near 17 pounds... But i thought that he upped his boost @ a speed shop on a tuning run. I am not sure if this is a manual boost controller or not.. certainly looks like one and the two tubes run to the oilfeed (i think isnt that the gold thing) and the other runs down below to the turbine side of the turbo, not sure where. If this is a manual boost controller is it a simple turn of the knob to release the amount of boost back towards stock settings?

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[cool_g_83]

First, based on what ive accumilated the T-25 runs 10-15 psi from the factory is this correct?

Yes, stock is ~10-12 depending on BOV

Second, the previous owner of my car i know upped the boost to 16pounds, actually sometimes it appears to peak a tad near 17 pounds... But i thought that he upped his boost @ a speed shop on a tuning run. I am not sure if this is a manual boost controller or not.. certainly looks like one and the two tubes run to the oilfeed (i think isnt that the gold thing) and the other runs down below to the turbine side of the turbo, not sure where. If this is a manual boost controller is it a simple turn of the knob to release the amount of boost back towards stock settings?

That appears to be a MBC. Yes you can turn it to lower your boost setting. Start off by turning it counterclockwise then take it for a spin to see if it lowered your boost.

 

[freshfabiotsi]

First, based on what ive accumilated the T-25 runs 10-15 psi from the factory is this correct?

Second, the previous owner of my car i know upped the boost to 16pounds, actually sometimes it appears to peak a tad near 17 pounds... But i thought that he upped his boost @ a speed shop on a tuning run. I am not sure if this is a manual boost controller or not.. certainly looks like one and the two tubes run to the oilfeed (i think isnt that the gold thing) and the other runs down below to the turbine side of the turbo, not sure where. If this is a manual boost controller is it a simple turn of the knob to release the amount of boost back towards stock settings?

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That gold thing is the wastegate, when a certain amount of boost goes into the wastgate the rod comming out of it gets jerked back and releases some boost into the 02 housing, thats why you do not run dangerous amounts of boost...And the boost controller that is hooked up to it through that piece of hose delays that signal, wich then allows you to run the right amount of boost you want. and that other hose below the turbine side goes into a nipple hooked up to the t-25.

 

[spyderturbo007]

Why do you want to turn down the boost? Running 16psi on the T-25 is completely safe.

 

[romeen]

That gold thing is the wastegate, when a certain amount of boost goes into the wastgate the rod comming out of it gets jerked back and releases some boost into the 02 housing, thats why you do not run dangerous amounts of boost...And the boost controller that is hooked up to it through that piece of hose delays that signal, wich then allows you to run the right amount of boost you want. and that other hose below the turbine side goes into a nipple hooked up to the t-25.

Not to be nit-picky, but the gold thing is the wastegate ACTUATOR which in turn controls the opening of the wastegate itself which is located in the turbine housing.

 

[ClassicalBor]

I want to turn down the boost a few pounds to see if it has any effect on my clutch slipping... i replaced my clutch about 4 weeks ago with a factory-sufficient placement from napa... coulda gone for a street clutch but i really do not have the time or money to put a lot of work into the car probably until late summer.. but when that comes around i will swap that clutch back out for an act2100 most likely. The replaced clutch seems to slip in gears 2-5 im sure it COULD do it in 1st but its just too fast to test, i first noticed it in 4th gear when i was on the highway accelerating at 75-80% throttle boost kicks it slips then it catches as soon as that boost drops back to approx 10 psi .. i tried other things such as reflushing the system for air pockets or adjusting my freeplay etc... nothing seems to be fixing this problem so im gonna lower the boost to see if maybe i got a sub-par clutch that cant handle the power. :/

 

[ClassicalBor]

I turned the mbc as far counterclock wise as i could.... before it fell out and tightened the holder nut thing so it wouldnt go any further... not sure if im seeing much of a difference my 1st gear seems like its getting less boost but all my other gears are still getting 15pounds... im not sure many people actually TRIED this but can it go any lower than 15 pounds? or does it "know" that the factory set its settings at 15psi stock?

If i turn it clock wise and just keep going will the boost just keep going up and potentially blow the turbo?

 

[cool_g_83]

You say it was installed 4 weeks ago...did you break your clutch in properly (not driving hard for a while)?

As stated before, stock boost is ~12psi. Have you done the BCS restrictor mod or upgraded your BOV?

Yes if your MBC is working properly (I am assuming it is), then if you keep turning clockwise, boost will rise to a point where it will wear/blow the turbo prematurely.

You should check to see if it is lowering you boost by boosting in a gear that isnt 1st gear(3rd-4th). If it's not lowering, report back here.

 

[ClassicalBor]

yeah i broke it on softly i havent launched it or even drawn out any of the gears very much, (until recently doing some tests AFTER i noticed it)... since i was breaking it in soft i didnt notice it till i took it on the highway for the first time maybe 10days later and was accelerating in 4th.. (62mph @ 3krpm .... then 70% throttle to speed up led to slip and rpm jump to 4k then softly back down to 3.5k where it caught and went on fine from there)

I dont know what the BCS restricter mod is so i can safely say i havent done that.. gears other than first seem to still push 15psi. /shrug

 

[oldman]

Not to be nit-picky, but the gold thing is the wastegate ACTUATOR which in turn controls the opening of the wastegate itself which is located in the turbine housing.

Not to be nit-picky, but an internal wastegate consists of two parts, wastegate actuator and wastegate flapper, much like an external wastegate with both parts built into one.

That gold thing is the wastegate, when a certain amount of boost goes into the wastgate the rod comming out of it gets jerked back and releases some boost into the 02 housing

Not to be nit-picky, but that would be "forward" and "exhaust".

 

[romeen]

Not to be nit-picky, but an internal wastegate consists of two parts, wastegate actuator and wastegate flapper, much like an external wastegate with both parts built into one.


Not to be nit-picky, but that would be "forward" and "exhaust".

Bruce, since when did you start being so nit-picky?!

 

[ClassicalBor]

BCS restricter mod?

 

[ClassicalBor]

n/m i understand now what the bcs restrictor mod is, i got a MBC so had to be done, my question is why when i adjust my mbc the boost is stay at 16-17psi and i cant lower it anymore... Im trying to get it back down to about 13-14psi, anything else that i can do?

 

[elfroggo]

I skimmed through the rest but are you still routing the lines to the bcs? I would bypass it completely, just hook up your boost signal to mbc to wastegate. Or if you want to run wastegate boost then just hook up the boost signal straight to the wastegate

 

[kenamond]

o The BCS is the stock equivalent to your MBC, and it looks like you aren't using it, so don't worry about the BCS mod stuff.

o The lowest boost you can run is dictated by the WGA (wastegate actuator) which is the gold "can" bolted to your turbo. On a T25, that's around 8-9psi. The MBC or BCS "hides" some of the boost so that the WGA sees less than what is actually produced. The MBC can be adjusted to hide more or less from the WGA to raise or lower the boost, respectively.

o Usually, the MBC is connected to two things: nipple on the turbo compressor outlet (that's the source of the boost "signal") and the nipple on the WGA (that's what receives the boost signal and uses it to divert exhaust gas around the turbo's turbine wheel, thus limiting the boost that gets generated). The MBC has an inlet and outlet on it, and if it's connected backward, it won't function properly.

o To get minimum boost, try removing the MBC from the system. Just run a piece of 3/16 fuel line (Autozone, carquest, etc. or maybe you can use one of the lines connected to your MBC) straight from the compressor nipple to the WGA nipple. Then, nothing is "hiding" boost from the WGA. In this case, you should run about 9psi boost.

o "Boost spike" is almost unavoidable with a MBC. This is a delay in the response of the WGA/turbine to the boost signal. The boost level will settle at one pressure, but usually, it overshoots this pressure a bit as boost first hits (your boost will rise up from vaccuum to something like 14psi and then settle back down at 11psi). That's boost spike. If you are trying to dial in your boost to a certain pressure, pay attention to where it settles, but also take note of how high the spike is.

o The stock BCS (boost control solenoid) is controlled by the ECU. It may still be bolted to your car, but with the vaccuum lines disconnected. If you pull out your coolant reservoir/overflow bottle by your filter box and intake pipe (white bottle), you may see it (if it's still there) bolted to the driver's side of the passenger side frame rail with one bolt. It has two nipples pointing toward the driver's side and has a plug on the bottom. The vaccuum lines connect to the WGA, compressor nipple, and the bottom of the intake pipe (a "T" fitting is required). I forget the exact wiring of the vaccuum lines (ask and ye shall receive), but if you still have the BCS, you might consider temporarily using this, as it will limit boost to about 11psi. This will be higher than running a vaccuum line straight from the compressor to the WGA, but might be low enough that the clutch problem goes away.

Hope that helps.

 

[luvmygst]

Any one thought about trying to fix the problem instead of making it go away. When you had the clutch put in did you/they adjust clutch pedal freeplay? I would do a clutch adjustment, that could hopefully fix the problem. After that the boost issue would not be a big problem. Most any clutch will hold the power of a T-25 at 15-16 psi. Try the clutch adjustment and go from there. Just my.02

 

[ClassicalBor]

yes ive had the mechanic reflush the gear fluids as well as adjusting the freeplay, after a few adjustments it didnt really solve any problems, its adjusted back to where its supposed to be. I'm beginning to just think the clutch is faulty or something. It is under warrenty so tomorrow im going to get the product code of the clutch they put in and check it on napa to make sure they didnt give me some shitty one, because they did offer hi-performance clutches stage 1-4 for my make.

 

[spyderturbo007]

Did you check the clutch master and slave cylinder for leakage?