[RESOLVED] BOV cause over boosting?

[spicoli619]

so i have a HKS SSQV blow off valve on my 1996 talon TSI. (well was on my car)
when i had it on my car it was WAY over boosting like 20psi at 4k rpm. so i took it off and put the stock one back on. For 2 reasons, to see if it would fix the over boosting and i also had to smog my car. it passed smog and now its not over boosting at all.
im new to turbos and such and have searched the forums but with no luck. i am wondering why it was over boosting. it didnt have the Recirculation Kit on it so mabe that might be it. but im not sure.
how would i fix this problem? i do have a MBC that is going to be put on. but what im wondering is will that fix it? or will the Recirculation Kit fix the over boost problem?
please and thank you for all your advice.

 

[DSM4me44]

Your stock bov leaks, so you will notice a psi decrease for sure.

If you haven't installed any form of boost management yet and you are running more then stock boost, I would take a guess and say something is wrong with your wastegate. It could be that your WGA is not opening the flap.

 

[the_mork]

Your wastegate actuator might be the problem but I would think it is more likely that you have a damaged vacuum hose connected to the wastegate actuator. Start at the turbo, there should be two lines, one from the compressor housing and one from the wastegate actuator (gold can). Follow these lines and any lines that connect to them and check for tears, holes, or disconnections.

Also try a boost leak test, you should do one no matter what, it will be the cheapest and easiest horsepower gain possible. Just use the search button to find instructions.

 

[usdrew]

if its the wastegate, you can often buy aftermarket wastegates that have a higher boost setting. for exmple, the hks wastegates don't open until 14psi.

 

[DSM4me44]

if its the wastegate, you can often buy aftermarket wastegates that have a higher boost setting. for exmple, the hks wastegates don't open until 14psi.

The thing is, he shouldn't need an aftermarket wastegate on a stock turbo.

 

[akasoldats]

Your wastegate actuator might be the problem but I would think it is more likely that you have a damaged vacuum hose connected to the wastegate actuator. Start at the turbo, there should be two lines, one from the compressor housing and one from the wastegate actuator (gold can). Follow these lines and any lines that connect to them and check for tears, holes, or disconnections.

Also try a boost leak test, you should do one no matter what, it will be the cheapest and easiest horsepower gain possible. Just use the search button to find instructions.

I'd start with a boost leak test. The stock BOV is a leaky whore. When I put my 1g crushed on I put a manual boost controller on for the exact same problem you are having now. Their not that expensive and can give you more control over your boost pressures. I recommend you pick one up bro.

 

[Alexvance]

I'd start with a boost leak test. The stock BOV is a leaky whore. When I put my 1g crushed on I put a manual boost controller on for the exact same problem you are having now. Their not that expensive and can give you more control over your boost pressures. I recommend you pick one up bro.

I thought the MBC was more for turning the boost up? (I could be wrong though) if so, that doesn't really help when he's trying to tone it down.

As said before boosting too much probably isn't your bov, it's much more likely to be a wastegate-not-opening-when-you-want-it problem.

 

[juanpac0]

I thought the MBC was more for turning the boost up? (I could be wrong though) if so, that doesn't really help when he's trying to tone it down.

As said before boosting too much probably isn't your bov, it's much more likely to be a wastegate-not-opening-when-you-want-it problem.

This is correct, the MBC can't lower boost, the boost the wastegate opens at is the lowest boost that can be run.

 

[usdrew]

The thing is, he shouldn't need an aftermarket wastegate on a stock turbo.

they also sell aftermarket wastegate actuators. theyre pretty cheap too.

 

[spicoli619]

awsome thanks for all the help. my buddy told me the MBC would fix it. cause i guess it can put a cap on how much the turbo will bost.
ive tried searching the forums on boost leak test instructions but couldnt find anything. just stuff about results. is it a kit i have to make or buy?
either way i will do it.
once again thank you for all your help

 

[the_mork]

That wont help you, there is an actual problem with your car and you need to fix it. Perform a boost leak test and find out why vacuum/boost signal isn't making it to your wastegate actuator.

 

[DSM4me44]

they also sell aftermarket wastegate actuators. theyre pretty cheap too.

I'm not saying that they don't sell aftermarket wastegate actuators. Refer to this post...

The thing is, he shouldn't need an aftermarket wastegate on a stock turbo.

That wont help you, there is an actual problem with your car and you need to fix it. Perform a boost leak test and find out why vacuum/boost signal isn't making it to your wastegate actuator.

Exactly. You don't want to band aid or get around the problem because the problem you have will still exist. It would be like creaking a boost leak to fix an overboosting problem. Reguardless what your boost gauge tells you, your turbo is still spinning that fast.

 

[spicoli619]

so ive been doing research on boost leak tests and am going to make a tester today and do a test. but what ive been noticing is that people are saying boost leaks can cause no boost or over boost. i dont understand how a leak can cause an over boost. especially 10 psi. also on the BOV there is a screw in the back that seems to be adjustable. would doing anything with that mabe fix my problem.
the car is only over boosting when i have the HKS BOV on but its not over boosting when i have the stock one on. that is what is really confusing me

 

[DSM4me44]

I wouldn't adjust the screw. In fact, the new HKS SSQV doesn't include one because they didn't want people touching that.

Your over boosting with your HKS becaue your stock bov leaks boost. It is a known fact.

 

[the_mork]

so ive been doing research on boost leak tests and am going to make a tester today and do a test. but what ive been noticing is that people are saying boost leaks can cause no boost or over boost. i dont understand how a leak can cause an over boost. especially 10 psi. also on the BOV there is a screw in the back that seems to be adjustable. would doing anything with that mabe fix my problem.
the car is only over boosting when i have the HKS BOV on but its not over boosting when i have the stock one on. that is what is really confusing me

Here is a quick explanation of how boost control works in most cars (and why a boost leak can cause too much boost).

To start with we need to understand that a turbo uses exhaust gases in order to spin the turbine side of the turbo which is connected to the compressor side which also spins, this should be pretty common knowledge. Now when the turbo is spinning fast enough that it pushes more air than we desire (usually measure as boost (psi) on an individual car or as flow lbs/min if we are comparing different setups or vehicles) then we need to slow the turbo down. The way that we do this is to use a wastegate, it is simply a passage that opens up and allow the exhaust to move around the turbine instead of over it. Again this should be pretty common knowledge for most people who have done some work with turbo cars and I'm just stating it so that we can be sure that you have enough background to understand the next part.

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This is a picture of two 16g turbos that I borrowed from the RRE website. The gold cans on them are called wastegate actuators and they are simply a diaphragm with a vacuum nipple and a spring. To control boost the reigning philosophy has been KISS (keep it simple, stupid), what better way to regulate boost than to use boost to manage the system. In the case of a 16g turbo generally the spring on the actuator can handle about 8-10 pounds per square inch of pressure. Simply put if you hook a vacuum line to this can when the pressure in the vacuum line reaches 10psi the diaphragm has enough force to overcome the resistance of the spring and the wastegate actuator arm moves outward (the arm at the very bottom fo the picture).

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This is a picture of a wastegate flapper, it appears to be damaged but it shows you what the wastegate actuator arm is pushing open. The green arrow can be ignored but it does point at the wastegate flapper linkage which the wastegate actuator arm attaches to, I found this on Google imaged but I believe it is from a user here by the name of Jusmx141 by the title and the fact that it was linked to from dsmtuners.

Now that you have a basic idea of everything that is going on lets assume that you have a tear in the hose that goes to your wastegate actuator like I did when my transmission rubbed on my lower intercooler pipe and rubbed a hole right through my vacuum line. In this case the "signal" for the wastegate actuator is shooting out into the atmosphere and making my car run crappy, it is also not reaching my wastegate actuator so my wastegate never opens and my turbo suddenly begins boosting to 24psi, because my car feels so fast I don't notice that it is running like crap and I feel good until I look at my boost gauge and realize that I'm significantly overboosting. Great, I've realized my problem and now I can find a solution, in this case I just needed to reposition my lower intercooler pipe and get some new vacuum hose.

Now lets do this on a car that has a stock 2g bov, for some reason the vacuum signal isn't reaching your wastegate and your turbo is overboosting, but because of the 2g bov which is sufficient for stock but no more the pressure from the overboosting is being bled off back into your intake tube and causing undue stress on your turbo but honestly probably saving your motor. Yay for a 2g bov which by accident is acting as a safeguard. Now lets switch the bov to an SSQV or other high end BOV and you end up with my previous situation but probably on a car with fewer fuel mods and more danger. Now the turbo just keeps spooling and the air goes straight into you engine, it probably feels great. But remember just because it feels good doesn't mean that it isn't bad or immoral, ask Elliot Spitzer or John Edwards.

The second situation sounds like it might be your car, the symptoms fit but it could still be something else. Honestly this is the most likely situation and the only one that I can think of off the top of my head.

 

[Evilimports]

Simply put, bov controls compressor surge, waste gate controls boost. If your overboosting, you start with what controls boost.

 

[spicoli619]

i checked the vacuum hoses and they dont have any tears and they are in good condition. the only thing is that the ones that attatched to the compresser is a little loose fitting. it has a small clamp on it. its not loose enough to just slide off but when i pulled on it to get it off it came off easier then i expected. might be normal but i dont know. so then from what you are saying the problem is probly my WGA.
im more of a hands on kind of guy so just wondering how much work is it to replace that? like difficulty and in hours possibly (remember im new to turbos)
depending on how long it should take will let me know if i have to take a whole day.
once again thank you all for your answers they have been soo helpful. im learning alot... slowly but i am learning

 

[DSM4me44]

Changing the waste gate actuator is easy, about an hour for time. It may help if you jack up the car depending on what angle you wanna go at it.

1. Remove the clip (pin) holding the arm on the flapper door.

2. Remove the 2 bolts holding it to the turbo.

Install is the reverse of this. I think you have to remove your intake to get to a bolt but im not 100% sure.

 

[spicoli619]

ok cool sounds easy enough. if the actualy wastegates isnt bad but the little flap thing that it opens is bad, would that be much more work?

 

[the_mork]

It would but that is less common. start by grabbing a vicegrips and pulling on the wastegate actuator arm to make sure that it moves, it should move towards the drivers side if you pull it but it will also be quite stiff. If you can't move it then the next step is to take the arm off the wastegate flapper and see if the wastegate flapper is moveable. It will probably help to remove the heatshields from your exhaust manifold and downpipe but first disconnect the negative side of your battery. The lower heat shield is right near your alternator and you can hurt yourself or blow fuses if you accidentally touch it with a wrench or the heat shield.

Assuming that the flapper doesn't move you will probably have to remove the turbo but that is a battler that we can get to if we have to go there. Really it is not something to be scared of because it is all just nuts and bolts, my first time replacing my turbo took about 10 hours work but I was moving to an entirely different turbo setup, I could do the same install now in a couple of hours.

That is the beast of it, once you've tested your wastegate actuator, your wastegate flapper, and the vacuum signal then that is all that there is to boost control. Here is the kicker though, checking those vacuum lines is a huge step in the right direction and it tells us a lot more about your problem but without a proper boost leak test we can't know for sure.

As an example, I just installed a new intake manifold on my car, I started it and it ran great but it wasn't until I did a boost leak test that I realized I had massive air leaks. Using my compressor I could not pressurize the manifold at all because of a leak at the throttle body because I had my gasket off by 90 degrees (poor workmanship on my part). Once I had that fixed I realized that I still couldn't pressurize the manifold, one of my new injectors hadn't seated well and was just blowing the all the pressure in my face. I would have never known without a boost leak test because the car idled and drove just fine (up the block and back with no boost). After I had those fixed I found a couple more very minor leaks from worn hoses that didn't like being pulled off and put back on. I had meticulously gone over every connection at the manifold but I still had to do a boost leak test to know that there was a problem.

 

[rEclipserGST]

How much would a BRAND NEW 2g stock bov cost? The stop i took my car too, broke off the recircluating nipple and my car is HELLA sluggish and wont go over 5 lbs of boost... im guessing because the HUGE boost leak. They stuck a ####ing screw in the tube to stock the air

Help me please. I want to charm then as much as possible for the broken part.

 

[the_mork]

Much cheaper and much better for your would be to get an adapter for a 1g bov and buy one of those or buy a whole new upper intercooler pipe.

I would suggest a new upper intercooler pipe personally but then you have to get a cone air filter. A cone air filter and a pipe would be a huge performance increase though and the 1g bovs can handle up to about 20psi. To purchase an upper intercooler pipe you can look at pipes from roadraceengineering.com or dejontool.com. You can purchase a cone filter adapter from Vibrant or many other vendors and a cone filter from K&N or from your local parts store. If you want to spend some money buy a K&N FIPK (it is what I have) but it isn't necessary and just about any cone filter setup will be as good.

PM me if you decide to go the route of the upper intercooler pipe and the 1g bov, I have some parts that I'm not using that I would sell. I also have a stock pipe and bov that you could charge whatever you want for.

 

[rEclipserGST]

Much cheaper and much better for your would be to get an adapter for a 1g bov and buy one of those or buy a whole new upper intercooler pipe.

I would suggest a new upper intercooler pipe personally but then you have to get a cone air filter. A cone air filter and a pipe would be a huge performance increase though and the 1g bovs can handle up to about 20psi. To purchase an upper intercooler pipe you can look at pipes from roadraceengineering.com or dejontool.com. You can purchase a cone filter adapter from Vibrant or many other vendors and a cone filter from K&N or from your local parts store. If you want to spend some money buy a K&N FIPK (it is what I have) but it isn't necessary and just about any cone filter setup will be as good.

PM me if you decide to go the route of the upper intercooler pipe and the 1g bov, I have some parts that I'm not using that I would sell. I also have a stock pipe and bov that you could charge whatever you want for.

I agree with everything you said. I already have a 1g bov sitting in my garage, BUT i want the shop to PAY for the broken part... to fund the conversion

Im thinking it should be atleast over $100 correct?

 

[spicoli619]

its hard to get shops to pay for things like that. especially if it isnt the same day that they did it. i just smogged my car today and the idiot didnt latch the hood (my fault for not checking) so when iwas on the highway the hood flew up and destroyed my windshield and smashed my carbonfiber hood. i luckily have a very large and aggresive big brother who helps influince people. so the shop payed for my windshield and is going to pay a pretty penny for my new hood ($550) haha.
but i did get something good out of all this. i found a turbo specific shop down here that can help me with my car and im getting a BRAND new hood haha.

 

[rEclipserGST]

its hard to get shops to pay for things like that. especially if it isnt the same day that they did it. i just smogged my car today and the idiot didnt latch the hood (my fault for not checking) so when iwas on the highway the hood flew up and destroyed my windshield and smashed my carbonfiber hood. i luckily have a very large and aggresive big brother who helps influince people. so the shop payed for my windshield and is going to pay a pretty penny for my new hood ($550) haha.
but i did get something good out of all this. i found a turbo specific shop down here that can help me with my car and im getting a BRAND new hood haha.

Yea your not lying. I called them today and they said that "you cant prove it & were not paying for it". I also have a big brother... BUT they sell rims and tires... you catch me drift

Either way, I threatened them with the Better Business Buruea and they didnt care. So i think something else will work