Have I hit a boost limit?

[Joe's_GSX]

Ok first off I hope there are no other posts like this, if there is please send me the link! I don't post unless I think I need to.

OK I have done the following to my car:
removed cat
put in dynomax race ultra bullet muffler
all service work, timing belt, water pump, etc.
A/F and boost guage
hacked air filter
K&N filter
replaced almost all the hoses
stock 14b
good compression 135 all cylinders
doesn't run lean, although it may need a new 02 sensor, after 128k?
crushed BOV

maybe a few other minor things. I turned the MBC I got up and no matter what I do I'm limited to 12lbs. I was able to get the boost to decrease with the MBC, and currently I left it at 12lbs.

When I hooked up the MBC I removed all the hoses to the canister. I also took out the hose that goes from the wastegate to the intercooler pipe. I have all unused hoses capped off.

I want to believe that I really need the 3" exhasut, although with the basic open exhaust I have now I read on other posts I should be able to run 15lbs with my setup.

ANY replies appreciated!

Joe

 

[Rob]

maybe your blow off vavle is no good ...bleeding off your boost at 12psi
other wise you have all the right mods to turn it up and should hold.

 

[candela]

Through my experience, Im willing to bet you hae a jacked up turbo!
Its probably your turbinr housing is leaking past the flapper port cause they tend to crack after a while. I had the same prob and no matter how high I turned the boost it wouldnt go past 11psi...
BTW 135 psi isnt good compression. It may say its within spec (very low spec) but thats about time for a rebuild bro...good luck

 

[CH152]

Yeah 135 compression is horrible. i am not the one to brag on this but mine was 175, 169,169,169 now the car has 76,547 miles

 

[rdrkt]

Originally posted by CH152
Yeah 135 compression is horrible. i am not the one to brag on this but mine was 175, 169,169,169 now the car has 76,547 miles

2nd gen motors have 8:5:1 compression as opposed to 7:8:1 in a 1g.

 

[Kevin Jewer]

In a 1g you're looking for roughly 150 psi. I get 155,155,150,145 left to right... 123k miles. I believe on 2Gs you want closer to 180.

 

[Joe's_GSX]

The 135 compresison was on my girlfriends 1991 Geo Storm!

My compression ran out around 160 on the 4G63T. Duh! I should have read (my own) that first!

As far as the turbo is there any way I can check that easily without taking the whole thing apart. There is little shaft play, although my car is waiting on a 16G I have in the garage, I would like to see what this turbo can do.

The BOV was on a 2G and he boosted around 18 with it daily. I have the dump tube back to the intake pluged, and the BOV is venting in the atmosphere. I think the only reason I did this is for the sound. So I could care less If I have to hook that pipe back up.

Let me know!
Joe

 

[candela]

hook it up.....

 

[Violater101]

Don't vent to atmosphere unless you have a VPC/GCC type combo working imo. I would definately hook that back up. If your into the sound, then I can't help you. If you hook that back up and you still can't run more than 12lbs, then you have some sort of problem. Have you checked for boost leaks?

 

[CH152]

1991 Geo storm. Hey rdrkt didn't know that my bad. Yeah well 160 i guess is ok i reckon.

 

[Joe's_GSX]

I will hook the dump back up and keep you guys posted about the difference it makes with upping the boost. Do you guys feel this could be my problem?

What about moving to a 3" exhaust, do you guys feel that this is holding the boost back, or should I be able to get 15lbs off a stock exhaust as described above?

Let me know!

Thanks.

Joe

 

[Violater101]

If you have done the free mod's and have the MBC hooked up correctly, then you should be able to run 15psi without the exhaust. The exhaust will open things up though and you should feel a difference in power.

 

[Silent2g]

you have a leak somewhere
check for em

also the exhaust really has nothing to do with how much boost you can run perse'

i ran 18 psi on stock exhaust, stock dp and stock 167k mile cat.

sounded like a fat woman with asthma actually

 

[GreenGVR4]

3in is definatly not needed....

 

[lambertvr4]

You should do a pressure test of your intake track to fix any leaks. I've done tons of these and have yet to find a car that didn't have a leak somewhere. Usually small, but yours may be bigger.

Here's some instructions on how to build a pressure tester. If you use straight 2" everywhere you can do it even cheaper (<$10). Use a bicycle pump or an air supply w/ a regulator to pressurize the intake. Easy. Well, except for fixing your leaks.

http://john.lambert.tripod.com/Pictures/psitester/psitester.html


If you don't have any intake leaks, then I'd say your WG is hung open or that the housing is severely cracked around the WG flapper. The actuator arm may be bent too. I had a turbo w/ this problem and I finally just unhooked the hose to the actuator and went for a drive. The boost lagged horribly still, so I knew the problem was w/ the turbo instead of the controller or intake track. Have to be careful w/ that approach tho b/c the wastegate has no signal to tell it to ever open. When boost comes on, it keeps on coming. I just went to 12psi and let off so that the 14B didn't try to puke in an attempt at 25psi or something.

 

[Joe's_GSX]

I hooked the BOV back-up with no difference in Boost. I have done all of the free mods. A little diappointed, although a vaccum test will work wonders. The boost guage stays at the same level, and doesn't variate a lot, when there is boost it displays boost, and when there is vaccuum it shows vacuum so the problem isn't reaching the boost guage. I Tee'd in the boost guage at the fuel pressure line by the firewall on the drivers side.

I will build that tester, i hope that have all that stuff at Home Depot! I don't have a Lowe's around here. As far as testing I will get a bike pump with a guage. Please explain to me exactly what I'm testing for and what typical results I should plan to expect with this test. I also will use an extra vacuum hose to probe areas where air could leak.

Now if the wastegate is bad, should I buy a new one? What is the best fix for that? I get pretty bad turbo lag in 1st and 2nd gear, although in third I get the 12PSI-13PSI reading. The whole time I'm running 1 bar under rich, so I must not be detonationg. Also if I disconnected all cacuum lines to the BCS, as instruched in a FAQ do I need to plug these or can I disconnect the BCS and eliminate it completly? If there are no lines going to it then I must not need it, although I dont understand the electrical use of the BCS, and how it works with the ECU so disconnecting may hurt my situation.

This is a lot to read...WOW

Thanks.
Joe

 

[BatmanGSX]

First, make sure the MBC is hooked up right, here is a diagram I made:

You must be logged in to view this image or video.

Lastly, and maybe I am not giving you enough credit, but, screwing the screw in makes the boost go up.

 

[KenTSIII]

Definately check for boost leaks. I'd highly recomend that you use an air compressor instead of the bike pump.. as it sounds like you have a serious leak & you won't be able to create pressure fast enough before it all leaks out. Once you get it hooked up.. listen for leaks & trace them down...

MBC hooked up incorrectly is another very good possibility.

 

[lambertvr4]

Holy testicular fortitude Batman!

Hilarious!

You'll want to hook up the pressure tester to the inlet of the turbo and pressurize the intake track w/ the bicycle pump, regulated air compressor, or maybe somehow use your #@%#@%#@%#@%&balls in a unique fashion. The compressed air will simulate boost from the turbo. If there is a leak then you will hear it hissing. If it's big, then you may not be able to pump it up w/ the bicycle pump.

It sounds like you have a bent actuator arm or a crack near the wg flapper on the turbine side of the turbo. If you disconnect the vacuum line to the actuator and make a run w/ no change in the lag or boost level then the problem is at the WG. Be careful tho b/c the turbo will want to boost to the moon. Just run up to 10-15psi. If it's still the same then you need to check that the actuator arm isn't bent or loose. It's held to the flapper arm w/ a carter pin. If it's straight and completely retracted under vacuum then you've probably got a cracked housing. That shouldn't be too hard to replace. A good used one shouldn't be too outrageous. I have never seen a Mitsu turbine housing that didn't have big cracks in it, so don't get freaked out if you buy a used one and see cracks inside. If they go all the way thru or if there's a really bad one by the WG flapper then I'd recommend more shopping.

 

[Joe's_GSX]

I disconnected the vacuum line from the wastagte to the BC and I noticed no incrase in Boost. Does this mean I need a new wastegate?

Should i still hookup the pressure tester, or should I just get another wastegate? I know the MBC and BOV are working fine. I have visually inspected all clamps and hoses to intake, and the intercooler. Everything checks out good.

I was wonderinf if I should be able to move the wastagate arm. Mine doesn't move, and I'm not sure it is the wastegate that is defective or if it is the internal flapper.

Please advise.

Thanks.

Joe

 

[onegee]

i seem to have a similar problem but im not upping the boost...most of the time my car will boost 10psi at WOT in 5th gear...only twice has it reached 13psi at WOT in 5th gear...now only upgrade i have a dave brode UICP and HKS ssqbov ...my k&n filter is kinda jacked up and sometimes doesnt stay fully flush with mas cause the clamps dont keep it closed...could the dirty k&n affect boost? plz reply ....VERY stumped...

 

[greyforestgst]

Originally posted by Joe's_GSX
I disconnected the vacuum line from the wastagte to the BC and I noticed no incrase in Boost. Does this mean I need a new wastegate?

Should i still hookup the pressure tester, or should I just get another wastegate? I know the MBC and BOV are working fine. I have visually inspected all clamps and hoses to intake, and the intercooler. Everything checks out good.

I was wonderinf if I should be able to move the wastagate arm. Mine doesn't move, and I'm not sure it is the wastegate that is defective or if it is the internal flapper.

Please advise.

Thanks.

Joe

if your wastegate is broken, you should be overspooling and trashing your car
thank whatever giant boost leak you have right now, because if you had no leaks in the intake track, your engine would be a smouldering hunk of metal right now.

wastegates are there to keep the turbo from putting too much air into the engine. once the intake mani pressure hits a certain pressure, it pushes past the little ball and spring in your mbc, goes through the tube and runs past the erect penis, and then opens the wastegate. the wastegate is basically a pressure switch that swings open that arm, which opens the door on the hot side of the turbo, letting exhaust gasses take the path of least resistance out to your exhaust and stop the turbine from spinning so fast. the wastegate SHOULD be the only component in your car that limits boost from building to extremely high numbers. the only other thigns that would limit you would be a blow off valve leaking, or some place along your ic plumbing letting air out.

 

[BatmanGSX]

Originally posted by greyforestgst
if your wastegate is broken, you should be overspooling and trashing your car thank whatever giant boost leak you have right now, because if you had no leaks in the intake track, your engine would be a smouldering hunk of metal right now.

Not necessarily true with a 14B. The 14B generally isn't big enough to destroy anything. If you are running max boost the 14B will hold and trying to top out 5th gear you might have a problem but an occaisional trip to 24psi on a 14B isn't going to harm anything, even on a stock fuel system. I know. I've done it (by accident).

I think this guy's turbo is toast or he has a boost leak. Looking at the couplers isn't enough. Test it.

If you have a boost leak big enough to only hold 12lbs with no boost control then you are overspinning your turbo. Fix the leak before your turbine wheel explodes.

 

[Joe's_GSX]

I will build the pressure tester. Then I will let you all know what is going on.

Also the MBC is able to turn the boost down, do you recommend that I do this so I do't have problems with the turbine?

I may need to replace the wastegate, although I will replace the turbo once I have that off. I have a 16G ready for it, I will have to hook the wastegate up to that.

Also if anyone can point to a good poerting FAQ for the exhasut manifold and O2 housing, I have never ported anything before so consider mu dumb in the subject. Therefore I realy need a good post about it.

Thanks.

Joe