Boost problems(Long)

[koho2731]

Boost seems like its now starting to spike and creep. My friend has a 93 DSM AWD Turbo auto with 14B turbo, Evo 3 housing, 2g ported exhaust mani, man. BC, M/T ECU, 3inch turbo back exhaust, tubular O2 housing, 440cc injectors, Supra TT Fuel pump, ect. Boost was set at 17psi when first bought and ran great. After messing with the BC(tunning boost up/down) it won't hold consitant boost levels. We set it to 15psi, and it spikes to 19ish in 1st, then on highway runs it goes to 16ish and creeps to 20ish. This doesn't happen all the time, but seems to be happening more and more.
Right now we're looking for boost leaks and such... and we've found that the breather line is only hooked up to the valve cover, the other end is just hanging somewhere. Any idea where this is suppost to be hooked up to? Also a small vaccum line thats off of the TB is just hanging off... not sure about that either.
Any idea's would be great, thanks.

 

[koho2731]

Please help, we're kind of stuck here.

 

[oldman]

1. You're right on the boarder line of creep/not creep. I would suspect if you turn the mbc up to 17-18 psi, you should see no creep. the lower you set the boost level the more chance of boost creep.

2.The breather valve is just hanging there to vent the crank case pressure, this is ok as long as the return nipple on the intake pipe is pluged.

3. Too many vacumm hoses comes off the TB, be more specific.

 

[koho2731]

Is the breather hose suppose to connect back to the intake though? I'll give more info about the vaccum line in a bit. Also, it seems that the creep/spike occures mostly when its cold outside. Thanks so much for responding.

 

[oldman]

Is the breather hose suppose to connect back to the intake though? I'll give more info about the vaccum line in a bit. Also, it seems that the creep/spike occures mostly when its cold outside. Thanks so much for responding.

The breather hose does route back to the intake in the stock form. Problem with that is it dirties up your intake with oil blow by. Some people just drops the hose and plug up the hole on the intake and let vent to atmosphere, some route it to a oil catch can. The colder the denser the air which increases air flow.

 

[koho2731]

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Here is some pics of the TB. Sorry it is kinda hard to get to a good pic of the TB. The lines are on the bottom side of the TB. The line had two clamps on it but was just hanging there. The line is a little short to make it to the actuator. Thanks for any help.

 

[oldman]

Looks like the previous own had removed the vac lines. Where does the other end go? Follow the diagram here, I'm sure you can figure it out.

http://www.taboospeedshop.com/emissions.htm

 

[koho2731]

Thanks man the dig will help alot and the line stars on the foward bottom side of the TB

 

[oldman]

You're welcome, might as well remove the vac lines following the article if it's not already done.

 

[koho2731]

The vac lines on the top of the TB are capped except for port p wich is going to the boost gauge. I didn't see the ones on the bootom side of the TB on the Dig. Also with the car runnig and reved to about 3000RPM the line on the bottom side of the TB has no pressure coming out of it.

 

[oldman]

Are you talking about the EGR maybe?

 

[koho2731]

Sure it could be I was kinda thinking that because the car runs fine with out it being hooked up. The boost thing seems to have gone away. I retorqued the BOV lines and played with the BC some more. Now it only spikes to 20psi then holds ant 15-16 psi, but it runs at lot stronger. Thanks again for the help

 

[koho2731]

Well, I took the BC off to see what would happen. Up until around 5000 rpm or so, it would hold at 10 psi, then it would go up to 15-17 psi! It doesn't seem to lose any power when this happens though(like when creep usually occurs). I don't know what else to do... I wish I could be 100% sure that it was the BC so I could just buy a new one.

 

[oldman]

Well, I took the BC off to see what would happen. Up until around 5000 rpm or so, it would hold at 10 psi, then it would go up to 15-17 psi! It doesn't seem to lose any power when this happens though(like when creep usually occurs). I don't know what else to do... I wish I could be 100% sure that it was the BC so I could just buy a new one.

What type and brand BC (mbc or ebc)? If it spikes to 20psi with the bc, holds at 10 psi without spiking then creeps to 16-17 psi without the bc, I would think a good mbc set at 16psi would solve both your spiking and creeping problem.

 

[koho2731]

It's a Joe P. I'm being told by people that its wastgate related(needs to be ported or bigger flapper)... but that doesn't make sense considering it was perfectly fine 1 month ago. I hope its the BC, so I'm liking what your saying. Thanks for the quick response.

 

[oldman]

It's a Joe P. I'm being told by people that its wastgate related(needs to be ported or bigger flapper)... but that doesn't make sense considering it was perfectly fine 1 month ago. I hope its the BC, so I'm liking what your saying. Thanks for the quick response.

Joe P are known to be very reliable but not impossible to have a used go bad. I'm guessing the mbc because of the information you have provided, so let's go over them again just to be sure. On your third to last post you claim that it was holding at 16psi but it was spiking to 20 psi first. My understanding is that this spiking issue is what led you to test without the the mbc and the result, as per your second to last post, hold 10psi to 5k then creeps to 17psi without the initial spike to 20 psi. If this is true, I think some how the mbc is delaying the pressure to reach the actuator causing the initial spike.

What other people have told you about porting your wastegate area is true because you do have boost creep, however, a very miner one. Since you will be running 16psi anyway, this miner creep has become a none issue FOR NOW. You may have to revisit the boost creep issue later as you add more mods to the car.