boosting issue

[5150]

My mods are in my profile, so heres whats up. I was running just 12psi everything was going fine except for some boost leaks fixed those and after that the car doesn't boost at 12 it just goes up to 20 and jerks around. I tried a bunch of stuff like removing the mbc and running the wg to a vacumn source, nothing. so im really kind of stumped on why i cant get my boost to stay at 12? so please give me some ideas. Any info you need to know then let me know.

 

[CTP_MADDOG]

i assume you are running a stock internal wastegate. my guess would be boost creep.

does your boost spike to 20 psi and settle around 12 or does it hit 12 momentarily then gradually increase to 20 psi. internal wastegates are notorious for spiking and creeping especially if you have a restrictive o2 housing. are you sure your wg spring is 12 psi?

just a few things to consider. my suggestion would be to switch over to a external wastegate. they are much better at regulating lower boost levels.

 

[5150]

it is an internal style wg but its not stock i got the turbo from fp awhile ago its a 38mm wg, turbo has been ported and all that. It doesn't even stop at 12 it justs shoots to 20psi.

 

[xioca]

Hook up a pressure source and pump air into it and see if you wastegate actuator arm moves, it may be stuck or not working.

 

[5150]

basically like a boost test but just to see if the actuator arm moves at all?

 

[xioca]

Yes, just find a way to only pressurize the the Wastegate nipple and and see if it'll move at around 10 psi, or whatever the spring inside is set at.

 

[kenamond]

Or you could just disconnect the actuator arm from the lever on the turbine housing, check that you can move the lever with your fingers (with a cool motor!), then go for a full-boost drive. If it still boosts to 20, it's most likely boost creep (nothing is holding the flapper closed).

Part of the problem is that most actuators only have enough throw to open the WG flapper part way, so you either have to port the crap out of the turbine housing around the WG entrance, go to an external WG or one built into the O2 housing (removes the flapper altogether), or get supporting mods for 20psi and live with the creep.

Good luck!

 

[5150]

one thing i did do was about 2 weeks ago i noticed that my wastegate wasn't closing all the way so i put some washers between were the actuator mounts to the turbo, i put enough so the flapper would close and stay closed could this be and issue? cause it was fine until the other day.

 

[kenamond]

one thing i did do was about 2 weeks ago i noticed that my wastegate wasn't closing all the way so i put some washers between were the actuator mounts to the turbo, i put enough so the flapper would close and stay closed could this be and issue? cause it was fine until the other day.

That might decrease the amount the WGA can turn the lever, but I'm not sure.

If you have the equipment, try what was suggested by xioca and pressurize the WGA to 12-15psi and watch how much the lever on the housing turns; that's how much the lever with the flapper connected to it will turn, so you can get an idea if the WGA isn't opening the flapper enough.

Maybe you could play around with less washers or thinner washers and see if that gets rid of the creep and help hold it closed at low boost.

In one case - pre-boost - the WG is supposed to be closed so that all exhaust flow contributes to accelerating the turbine. In the other case - full-boost - the WG is open - and it's supposed to be - so that just enough exhaust goes to the turbine to get the boost you dialed in on your MBC. In between those two cases, the WG is opening more and more as the boost builds to the desired level.

It seems that you had a problem with the first case, and your turbo was maybe spooling a bit slower than it could with a tightly closed WG. You added shims to hold it closed, but you may have limited how far it could open, so at full boost, it can't open enough - creep.

Given a choice between slower spool-up and creep, I'd choose slower spool-up, but I'm not sure how bad it was before adding the spacers. Maybe thinner washers would leave a little bit of play during spool-up, but cure the creep - sort of a happy medium.

 

[5150]

Before i put the washers in the actuator would sit about 1/8 in. from the turbo when i bolted the actuator to the turbo it would force the flapper open at first i thought it was the actuator so i took the one of my 16g and put it on and it did the same thing so i dont know whats up cause i put the actuator from the 18g (the one on the car) on the 16g to see if it did the same thing and it didn't.

 

[RayPeters]

Before i put the washers in the actuator would sit about 1/8 in. from the turbo when i bolted the actuator to the turbo it would force the flapper open at first i thought it was the actuator so i took the one of my 16g and put it on and it did the same thing so i dont know whats up cause i put the actuator from the 18g (the one on the car) on the 16g to see if it did the same thing and it didn't.

I've had this happen on 2 cars, one a t-25 turboed, and the other a 1g of a friend, but both times the actuator didn't have the correct travel. It would stick open part way and not be consistant. Swap one from another car, or get a new one.

Be careful running with the wastgate locked closed, even a 14b will make 30psi at lower rpm.

 

[5150]

so your saying i should swap my actuator from the 16g with the one from my 18g?

 

[kenamond]

so your saying i should swap my actuator from the 16g with the one from my 18g?

I think he's saying get another actuator for an 18g. Maybe yours is damaged.

Can you close the flapper with your fingers all the way? If not, that's probably the problem. Easy to check.

 

[5150]

well i checked to make sure the wg was opening wich it was the one thing i wanted to make sure was if the flapper itself should open up the full 90deg. or the 45deg wich it opened?

 

[kenamond]

well i checked to make sure the wg was opening wich it was the one thing i wanted to make sure was if the flapper itself should open up the full 90deg. or the 45deg wich it opened?

The WGAs rarely open the flapper 90*. 45* is pretty typical. The WGA just doesn't have enough "throw" to open it farther. Is it closing all of the way when you disconnect the arm and close it with your fingers?

 

[romeen]

Try removing the washers that you placed between the WGA and the turbo to see if that fixes the problem. I believe the washers preload the diaphragm in the actuator causing increased pressure required to open the wastegate.

 

[5150]

i know for a fact that the washers are not preloading the diaphram, when the washers are out, the WGA sits about an 1/8in away from the turbo about the size of the washers.

 

[oldman]

Dude, no more talking about it until you come back with the result of the actuator test suggested several times above.

 

[5150]

well i checked to make sure the wg was opening wich it was the one thing i wanted to make sure was if the flapper itself should open up the full 90deg. or the 45deg wich it opened?

dude hey i already did

 

[oldman]

dude hey i already did

If you did, my apoligies. The statement you quoted wasn't very clear whether you actually applied pressure to the actuator fitting or just disconnected the actuator arm from the flapper. So at what psi did it start to open and fully opened.

 

[5150]

well maybe i should of been more clear on what i did.

What i did was i disconected the vacumn line from the wga and just presurized it with the air compressor and it opened right up, but now that i think about i guess it would open up with the compressor and 60 psi. So looks like im going to be redoing that test with the compressor set at a lower psi..

 

[oldman]

I hope you didn't use the same 60psi for your boost leak test.

 

[5150]

well when i do the boost leak test the system is not being presurized to 60 psi, i keep an eye one the boost gauge and usually stop about 15psi. I still havnt retested the actuator yet just been so bussy, hopefully tonight ill be able to get to it.

 

[oldman]

well when i do the boost leak test the system is not being presurized to 60 psi, i keep an eye one the boost gauge and usually stop about 15psi. I still havnt retested the actuator yet just been so bussy, hopefully tonight ill be able to get to it.

If that is the case, I would retest and set the regulator to no more than 20psi. What kind of man cheats on a boost leak test.