cant control boost

[droptopgst]

I just installed my tdo5 18g on a 98 gst and my POS boost controller (turbonetics) wont keep the boost down. No matter how far I turn the b/c the boost still shoots to 20+. I dont keep the gas down, as soon as I see it shoot above 15 I let off but why wont this control it. any suggestions? The pull of this turbo is unbelievable, unfortunately I cant use the real power till I get the pump in. It got dark so I have not put the fuel pump in yet, and need to take my car to school tomorrow. I am going to put the pump in after. Still need to figure how to keep this boost down. It worked fine for the T25. Is it posable that this turbo is to strong for this POS controler????

 

[peregrine]

so you put the bigger turbo on before the bigger fuel pump?

 

[99GSBBTurbo]

The MBC won't make the boost go any lower then the set waste gate spring on the turbo or your external wastegate. ( which ever you have ) I would check to see if your vacume lines are cramping under pressure also, or just check to see if your vacume lines are hooked up all the way and not leaking.

 

[Boosted98gsx]

I had the same exact problem with my car and MBC's. They will not hold boost as long as that bleeder hole is there. Get some epoxy or something and plug it up. [yoda]Then your boost will it be able to hold[/yoda]

 

[droptopgst]

bleeder hole? what one is that?

 

[Boosted98gsx]

Look at the pic uploaded, it should be somewhere around the nipple circled

 

[-=TWITCH=-]

why and the hell is the bleeder hole there in the first place?

 

[Boosted98gsx]

Here's the scenario:
You go, boost pressure builds to a point where your MBC is set to vent air to your wastegate actuator, actuator opens letting exhaust gas out, fans spin slower decreasing boost, you let off the gas, spring inside MBC closes the "intake" hole. Where does the boost go that's caught in between the wastegate and "intake" hole? That's where the bleeder hole comes into play, It's supposed to let out that extra air so your actuator won't stay open.

Personally i've never experienced any problems with covering my bleeder hole. I do not know why the hell this is, because all my other car buds need the bleeder whole and i can't seem to utilize it.

 

[droptopgst]

I have everything ported

I just disconnected the boost controler and hooked the hose from the BOV to the goldish waste gate thing, no clue what its called. So without the boost controler hooked up this is still doing this.

Come on guys keep throwing out pos. fixes to this. Sux that I cant get on the gas due to the 25 psi

 

[Boosted98gsx]

then i dont know. might be the spring in the wastegate actuator (goldish thing) then. Should run about 13 psi with a hose goin from the boost source nipple to the wasegate. Try this:

Run the "inlet" line to the MBC from the BOV hose. DONT CUT THE HOSE mind you, just put a tee on the end of that hose and run some extra hose to the BOV, then run the "inlet" hose from the T. Then run the "outlet" line from the MBC to the wastegate actuator.

If this still doesn't work, its either your wastegate actuator or the MBC itself. Try taking the MBC apart and make sure it's innerds haven't moved around any. the two ball bearings should sqeeze the spring together and the screw adjustment should tighten the spring using the top bearing forcing pressure on the bottom bearing which covers the "inlet" hole.

 

[droptopgst]

the place where i bought the turbo said that the problem is from not having enough fuel. He said that since my ex.manny, turbo, and O2 houseing is all ported then it is supplying too much air and not enough fuel. He said if I put in 660 injectors and afc then i would be able to control it. Does this sound right?

If so where is the best place to get injectors and an afc?

 

[asian312]

Nope, what it sounds like is a bunk wastegate (the goldish waste gate thing). When u hooked the line directly to the wastgate i should have opened at whatever psi it's designed for. So either:

1) it's toast

2) it's set to open at a higher boost.

Mine is designed to pop at 10 psi, but thanx to my trusty AVC-R I can hold at 15 dead on. I remember a technique used to get the wastegate to hold more boost and technically it should be the reverse to get it to release sooner. If your actuator arm is threaded, unscrew it a few turns to get it to open sooner. I'm not certain about this and maybe someone can verify.

I understand your thing with the pump. I've been there too. Last minute turbo decision leads to pump not big enough and injectors too small . Oh well can only imagine what she'll do when they go in.

 

[droptopgst]

I have the 255 fuel pump in and the guy said that that is big enough. Said the injectors are not. and the afc is a must with this big of a turbo

 

[Boosted98gsx]

Now that we've tried alternate boost sources, try messing with the wastegate control arm. unscrew it some and see if that helps any.

 

[droptopgst]

I called the tech. back again and he said the actuator is set to 12 psi. Which is what it spikes to at first. Then when the turbo gets spinning it keeps building real quick so I guess this is boost creep. He tried to explain the whole scenario to me and something about the air is spooling the turbo faster than the fuel can come in. therefore creating a huge increase in psi. he said with the injectors and AFC i can equal out the fuel and air mixture and this will stabilize my boost. No clue here buts sounds logical.

 

[Boosted98gsx]

whats going into your cylinders should have NOTHING to do with how much boost your turbo is making. That makes no sense to me.

 

[GSX24PSI]

had the same turbonetics mbc on my 91 laser...it did the same exact thing, that was made to be use with an externel waste gate(from what i have heard)...but right when i changed the mbc to a custom one(didnt even change the hook up tubes, it worked perfectly

 

[wastefuldreamer]

Is the controller hooked up right???

 

[droptopgst]

yes, and it still does it when i eliminate the boost controler.

 

[-=TWITCH=-]

I had the same prob with my T-25. You might want to see it the wastegate is opening all the way mine wasnt. I even just ran a hose from the boost soure to the wastegate acutator it still didnt help. My problem was that when I was messing around with the t-25 the bracket that hold the wastegate actuator on got bent! it was not letting the wastgate open all the way. You might have ment it on the install you might want to check that out! just a thought!

Chris

 

[doug]

Originally posted by -=TWITCH=-
I had the same prob with my T-25. You might want to see it the wastegate is opening all the way mine wasnt. I even just ran a hose from the boost soure to the wastegate acutator it still didnt help.

DSMtuners member Ricardo (and local guy to me so I've seen it first hand) had the same problem with his T-25. Boosted over 20 even with the hose running directly from compressor housing to wastegate. After replacing the turbo with a T-28, it's fine.

 

[Boosted98gsx]

well, it sounds like it's your turbo. That information that turbocahrgers.com gave you about the fuel supply doesn't seem to make sense. I'll call wade and talk to him for you and get back on here with what i acquire knowledge wise

 

[Something Rudy]

Are you still runnig the stock cheezy plastic upper IC pipe?? IF so you are also leaking pressure through your bov. This causes a little creep.

What kind of boost gauge are you running and where is it hooked to??

And you didn't up the fuel pressure and you were seeing at leat 15lbs and possibly even 20lbs??? I hope you have some cash for a rebuild becaue that will cause SERIOUS detonation.

Good luck

Poor

 

[Boosted98gsx]

If you looked at his mods on his user page you'd see that he has an upgraded UICP and BOV

 

[ASZRAEL1266]

If your car is creeping up like that from what i read i am guessing you have exhaust. My friend put a 3" turbo back on his 1G with a 14B and set the boost to 15 PSI his car hits 15PSI and then creeps to 17. Whats happening is the flow of exhaust is out flowing the amount that can leave through the waste gate. Other then port out the wastegate more all you can do is tune your car to run at a min of 20 PSI. The same friend whos talon creeps to 17 PSI, he also has an T2 rx-7 and had the $hit ported out of the wate gate but it still flowed to much and creep up. From what i have read like i said i think you are out flowing your waste gate.