Boost leak dilema

[kenamond]

Okay, so I fixed all of the boost leaks I could find (insulators, TB gaskets, leaky UICP pipe weld, and PCV), but I still leak out the VC breather (I'll do a compression test when I get some time). It drops a bit less than 1psi/second. I see no other bubbles no matter where I look, but...

How do I know I got em all since I'm losing pressure from the valves and/or rings?

I hear statements like "must hold 20psi for 30 seconds" but I don't see how that'll happen, atleast on my car. If you have 178psi compression, how much would you leak in a 20psi boost leak test? How about 150psi compression?

Thanks!

 

[44pirate]

Have you tried blocking off the VC breather? I'm not trying to sound like a dick.

 

[kenamond]

Have you tried blocking off the VC breather? I'm not trying to sound like a dick.

I thought about it and even suggested it to others in this same situation until it was pointed out that you don't want to pressurize your crank case to 20psi, or you risk blowing all of the seals.

 

[skinnykenny84]

are you still running a stock pcv system?

 

[kenamond]

are you still running a stock pcv system?

Yes. The PCV is brand new OEM and doesn't leak. I pulled the PCV out of the VC (still on the vac line), pressurized, and got no leaking air out of it at 20psi. So the VC breather air has to be coming from blowby or intake valve stem seals into the crank case. I have a fuel filter on the VC breather line which still runs to the intake pipe, but that has nothing to do with this (more of an FYI).

But my question is how do I know I got all of the boost leaks given that I can't hold pressure due to blowby or valve stem seal leaks?

Also, I did my boost leak test with a cold motor (hate it when I put my hand on the VC when the motor is hot), so I could warm it up, do a compression test, then follow up with a boost leak test while still warm. I know that the rings will seal better warm, but do the valve stems seal better warm, too? If so, I might get a better idea of how well my intake is sealed. Even if I have good compression, I may add oil to each cylinder like a wet test just to help seal it, put the plugs back in, then do the boost leak test with extra help for blowby. My motor only has 78k on it, so I'm expecting good compression.

 

[matt97gst]

are you testing at the throttle body elbow?

 

[skinnykenny84]

alright oldman, where ya at?

 

[kenamond]

are you testing at the throttle body elbow?

I have a Dejon UICP which replaces the TB elbow (the UICP bolts straight to the TB), so I can't test there. I'd have to pull the 1st UICP off in order to get a tester on the 2nd UICP intake. Nevertheless, it's still pressurizing the cylinders which will leak, so where I test has nothing to do with my question. About all I could do to test sections of the intake without pressurizing the cylinders as well would be to separate the two UICPs and put a cap on the end of the first one and pressurize at the compressor inlet, but I already checked all of the LICP, IC, UICP, BOV couplers and gaskets for leaks, and there were none. My only question is the underside of the IM/head gasket which I can't reach to spray soap on nor see if it bubbles. Thanks, though.

 

[skinnykenny84]

My only question is the underside of the IM/head gasket which I can't reach to spray soap on nor see if it bubbles. Thanks, though.

Well the only way that I know of to check in this area is by hearing a leak, but it would have to be a pretty bad leak to be able to hear it huh?

I noticed that I have a lil air coming from my catch can last time I did a boost leak test. I have the fuel filter catch can mod and its not routed back into the intake. I assumed that it was normal but I guess thats what I get for ass uming!

 

[kenamond]

Well the only way that I know of to check in this area is by hearing a leak, but it would have to be a pretty bad leak to be able to hear it huh?

I noticed that I have a lil air coming from my catch can last time I did a boost leak test. I have the fuel filter catch can mod and its not routed back into the intake. I assumed that it was normal but I guess thats what I get for ass uming!

I don't hear any leaks from the IM, but that doesn't mean it has none. And I can't think of a way to tell.

Sounds like you get the same leak that I get from blowby or intake valve stem seals. I don't know what "normal" is in that regard, and that's my whole question.

I wonder if I could tell anything from LTFTs or something on my logger. If I'm running rich, wouldn't that show up in the LTFTs?

 

[skinnykenny84]

Sounds like we both need some help.

 

[Turbo Monk3y]

Well when I do a boost leak test On my GT35R it is a PITA because I don't have 4.5" T-bolt clamps to hold the blockoff piece on... So everytime I do a boost leak test I get to 10 Psi and I get air coming out of the PCV and breather area as I have them routed to a catch can... I had this head rebuilt with brand new seals and ported not but a few months ago so I highly doubt its the seals... I also did a compression test and I got 140Psi across all 4 cylinders with the FP2 cams(stock 7.8:1 compression 1g motor). I've actually always wondered how people say they pressure test up to 30psi and it holds I don't see how the hell it would.... Mine goes up to 10psi and slowly falls back to 3-4 and then really just sits at 1 psi then to 0, it does this all within 10-15 seconds.... I've run many low 11s with it doing this so I really don't know how else to get a good boost leak test done...

 

[matt97gst]

Mine goes up to 10psi and slowly falls back to 3-4 and then really just sits at 1 psi then to 0, it does this all within 10-15 seconds.... I've run many low 11s with it doing this so I really don't know how else to get a good boost leak test done...

Maybe the classic story that it needs to hold steady for 30 seconds or whatever isn't true if you're running low 11s with test results like that.

 

[kenamond]

Maybe the classic story that it needs to hold steady for 30 seconds or whatever isn't true if you're running low 11s with test results like that.

Well, I'm in doubt of that story right now until I can either see it on a car for myself or until someone I trust reports that it's possible. It surely wouldn't suprise me if someone said it once (and was full of it) and it turned into urban legend.

So should I worry about it? I was getting 8mpg before I fixed my TB gaskets, insulator, and PCV boost leaks, then 20mpg after I fixed them but still had the UICP weld leak, and haven't remeasured mpg after replacing the UICP with an air-tight unit, but it should be the same or better. It looks like I'm most definitely not running pig rich anymore. Maybe I got enough of the leaks?

Damnit, I'm supposed to ask questions and have them answered correctly around here!!

Nice to hear I'm not alone and that a car in the 11's is seeing the same thing.

Thanks guys!

 

[LessIsMore]

Air escapes past the the turbo oil seals, through the oil return pipe into the oil pan. From there it makes its way through the piston rings and then up through the valve seals into and out the crackcase vent.

All of these components seal properly while parts are moving, up to temp and supplied with proper oil pressure. When cold and stationary blow by will likely happen.

One thing you can try is doing a boost leak test while the engine is still hot.

 

[skinnykenny84]

HHHmmmmm

 

[44pirate]

Well I have to block off my VC breather or I can't boostleak past 20psi. I've had to do this with all the motors I've run. I've never blown any seals in my VC. If your VC seals leak, then I suggest replace them. I don't have a PCV, I run that to the catch can.

 

[kenamond]

Well I have to block off my VC breather or I can't boostleak past 20psi. I've had to do this with all the motors I've run. I've never blown any seals in my VC. If your VC seals leak, then I suggest replace them. I don't have a PCV, I run that to the catch can.

It's not the VC seals you should be worrying about. The crankcase isn't supposed to hold 20psi. Blocking the VC breather pressurizes the entire crankcase, not just the VC.

And I assume that you realize what you're doing to your motor by not using the PCV system.

One thing you can try is doing a boost leak test while the engine is still hot.

Thanks. I was wondering about that. I guess it's definitely worth a try. Can't hurt anything (well maybe I'll burn myself ). I also thought about doing a compression test at the same time and adding oil to the cylinders just to help the boost leak test seal better before I put the plugs back in. Might as well check my plug gaps while I'm at it.

 

[44pirate]

<It's not the VC seals you should be worrying about. The crankcase isn't supposed to hold 20psi. Blocking the VC breather pressurizes the entire crankcase, not just the VC.

And I assume that you realize what you're doing to your motor by not using the PCV system.>

Can you elaborate on the what in the crankcase I should be worried about?
I have all my pollution vac lines off and EGR blocked off. So what am I doing to my motor by not using the PCV system?
I ask in wanting to know, not in trying to be an asshole.

 

[kenamond]

<It's not the VC seals you should be worrying about. The crankcase isn't supposed to hold 20psi. Blocking the VC breather pressurizes the entire crankcase, not just the VC.

And I assume that you realize what you're doing to your motor by not using the PCV system.>

Can you elaborate on the what in the crankcase I should be worried about?
I have all my pollution vac lines off and EGR blocked off. So what am I doing to my motor by not using the PCV system?
I ask in wanting to know, not in trying to be an asshole.

Aside from emissions, the PCV system ventilates the crank case at idle when the IM is under vaccuum. Normally, the PCV valve opens in this condition, and air enters the VC breather, and the crank case fumes are swept out the PCV valve into the IM to be reburned. If you don't do this, fuel fumes will blow by your rings and pollute your oil. This degrades the oil and increases wear on your internals.

The other role of your PCV is to provide a vent so that you don't build pressure in the crank case under load. With a catch can setup, you're still letting it vent.

Just keep in mind that the PCV system includes the PCV valve and VC breather. The VC breather alone is the exit point under load in the stock configuration (the PCV valve closes when the IM is pressurized). At idle, the VC breather is the source of fresh (but metered) air to replace the fumes being purged from the crankcase. So the VC breather is 2-way, but the PCV valve is one-way.

So your setup is only serving half the job.

Nobody has reported any study of the affect of fuel in the oil, but it's possible to set up your motor with a PCV valve and catch can to serve the normal PCV function and to keep oil out of the intake (in addition to the common fuel filter on the VC breather hose). The trick is to set it up so that you don't boost your catch can . I think you just need to add a catch can (2 nipple, no vent) with a check valve between it and the IM to keep from boosting your catch can. The stock PCV is still in its normal place.

 

[GSTdude06]

If you pour a bit of motor oil into each cylinder then compression test it, if the numbers jump up then your rings are bad, then just turn the car on in watch it smoke away the oil.

 

[kenamond]

If you pour a bit of motor oil into each cylinder then compression test it, if the numbers jump up then your rings are bad, then just turn the car on in watch it smoke away the oil.

Yes. I was going to do a compression test (expecting good compression). Even if my compression was good, I was going to add some oil just to help seal the rings for another boost leak test. Then I'd reinstall the plugs and repeat the boost leak test with a warm motor and oil helping seal the rings just so I could get a better idea of how tight my intake is.

 

[44pirate]

Aside from emissions, the PCV system ventilates the crank case at idle when the IM is under vaccuum. Normally, the PCV valve opens in this condition, and air enters the VC breather, and the crank case fumes are swept out the PCV valve into the IM to be reburned. If you don't do this, fuel fumes will blow by your rings and pollute your oil. This degrades the oil and increases wear on your internals.

The other role of your PCV is to provide a vent so that you don't build pressure in the crank case under load. With a catch can setup, you're still letting it vent.

Just keep in mind that the PCV system includes the PCV valve and VC breather. The VC breather alone is the exit point under load in the stock configuration (the PCV valve closes when the IM is pressurized). At idle, the VC breather is the source of fresh (but metered) air to replace the fumes being purged from the crankcase. So the VC breather is 2-way, but the PCV valve is one-way.

So your setup is only serving half the job.

Nobody has reported any study of the affect of fuel in the oil, but it's possible to set up your motor with a PCV valve and catch can to serve the normal PCV function and to keep oil out of the intake (in addition to the common fuel filter on the VC breather hose). The trick is to set it up so that you don't boost your catch can . I think you just need to add a catch can (2 nipple, no vent) with a check valve between it and the IM to keep from boosting your catch can. The stock PCV is still in its normal place.

So having both vents to a catchcan is no good. Well I've been running my DSM's for 4 yrs this way and no problems. I've been using MAFT and now I use MAFPRO Speed Density. PCV just all have to do with passing emissions. I don't have emissions here in Fl so I don't worry about it and I change my oil every 3000 miles.

 

[joe]

its fine as long as they are able to breathe freely

 

[kenamond]

its fine as long as they are able to breathe freely

How do you know this? The PCV isn't just to vent crank case pressure or to pass emissions. What do you think the "V" in PCV stands for?

I've been running my car for 10 years with the stock PCV without any problem.

Unless you know this for a fact, don't say it'll be fine.

Just realize that there is more to it than you think. Bypass at your own risk.

Because you upgraded your MAS, you don't have to recirc your VC breather to the intake pipe, but you're still not ventilating your crank case which has nothing to do with emissions.

There is a way to set your PCV system up so that you get all the good and none of the bad.