Compression And Boost Leak Test Results(please Look)

[fwdeclipse]

ok I have been having a problem and its starting to upset me.I cannot seem to hold my boost all the way to redline.Im running 24psi of boost and by 6k it drops to 19psi.Its driving me crazy.The only boost leak I have is leaking into the crankcase.I plugged the pcv and it still does it.I put it on the licp and it still does it.I did a compression test and it came out to 142 across the board.That seems really low to me,but the car runs strong as hell it just wont hold 24psi to redline.What should I do now,should I do a leakdown and find out how the boost is getting in there.One more thing It does not blow an ounce of smoke.Any suggestions would be greatly appreciated as im stumped.

 

[Boost95]

What turbo are you running 24 psi?

 

[napkinthief]

Sounds to me like your turbo is just running out of steam past 6k rpms. Get something bigger

 

[fwdeclipse]

Im running an evo316g and I have heard of alot of people holding 24psi to redline.THis turbo does not run out of steam at that psi.

 

[andymoraitis]

Chris,

Do you have the 34mm flapper or the standard 31mm? The reason I ask is that the 34mm will somewhat limit maximum boost that you can hold since the orifice is larger. If you do have the 34mm installed, you can try installing a couple of washers in between the wastegate and the turbine to make the gate hold longer. Be careful when testing this, but it's what I used to do on the Big16G to get it to hold more boost since the cams went in.

FYI, 142 compression isn't very good on a 2G since perfect compression is 180. Before I lost the rod bearings on the 2.0 this week, I measured compression at 160 across with Comp 200's. Without the cams, I was at 175 across. Make sure the motor is hot when you do the test (drive it around for 5 minutes beforehand) and if the readings are still low, drop a few tablespoons of oil into each cylinder and re-test it to see if compression goes up. If it does, it likely means that your rings aren't sealing properly. This would explain why you've been able to run as much as 24psi on pump with plenty of timing and no knock.

Let me know,

Andy

 

[fwdeclipse]

No I dont have the 34mm gate,I wish I did cause it would be an easier fix to my problem.Sorry to hear you blew the motor that kinda sucks but then again now you can build it.I will try the oil in the cylinders and see what I find.This is really weird cause I does not blow any smoke or anything.I am pretty sure its either piston rings of valve seals because of the boost leaking into crankcase,It just doesnt make sense cause it runs strong and does not smoke at all.Plus theres only 60k on the clock.

 

[fwdeclipse]

Well I went ahead and did another compression test.This time with a brand new tester and came up with the following160-160-158-154. That seems alot better to me.So where else can boost get into the crankcase from?

 

[fwdeclipse]

So I guess no one has a clue?

 

[Enraged78]

So I guess no one has a clue?

DON'T plug your PCV. Bore out your PCV, and route it to a catchcan along with your valve cover breather, and run that into your intake. Make sure to cap the nipple on your intake manifold with a proper cap and clamp.

The PCV is designed to let crankcase pressure out of the engine due to blowby gasses. If you plug your PCV, the only way out they have is through the valve cover breather, which in most cases is not enough, especially when you're running high boost. A good test to see how much blowby you're getting is to warm the motor up, and pull off your oil cap. Use your hand to put pressure on the filler hole, then pull it off. You'll find that pressure builds under your hand. Now cover the filler cap, and check the air coming out of the valve cover breather. Not as much as what was coming out of the filler cap, is it? Now, run a bored PCV and your breather into a T fitting, and that into a single vacuum line. Check the amount of air coming out of it. It's a lot more, isn't it? Now imagine that your engine is at full bore pushing 24PSI, and you'll understand why plugging a PCV is bad and why having as much ventilation you can is a good thing.

One more thing. Don't run a vented catchcan. Run it to a non-vented can, and plumb that back into your intake line. The theory here is that the intake line is always in a vacuum, especially under boost. That vacuum will help draw blowby gasses from your crankcase back into the intake, and help decrease crankcase pressure. It will also help with engine efficency and fuel mileage, as a crank in a vacuum doesn't have to work against pressurized air. It will also keep oil from backing up your oil drain line from your turbo, and keep the turbo from leaking oil out of it's seals. Turbines don't like to sling oil at 150,000 RPM. This may also expalin why you're turbo isn't making the boost it should. When crankcase pressure has nowhere to go, it goes to the past of least resistance. In most cases, this includes the gravity drain on your turbo. Ask me why I know all this....

When peforming boost leak test, warm up your motor first. Rings and pistons expand when your motor is at normal operating temp, and will show you what the car is really doing when you're running it. It will also minimize leaks through the rings while your running your test. I run a forged bottom end, and the difference leak testing it while cold vs. hot is night and day.

Matt.

 

[fwdeclipse]

DON'T plug your PCV. Bore out your PCV, and route it to a catchcan along with your valve cover breather, and run that into your intake. Make sure to cap the nipple on your intake manifold with a proper cap and clamp.

The PCV is designed to let crankcase pressure out of the engine due to blowby gasses. If you plug your PCV, the only way out they have is through the valve cover breather, which in most cases is not enough, especially when you're running high boost. A good test to see how much blowby you're getting is to warm the motor up, and pull off your oil cap. Use your hand to put pressure on the filler hole, then pull it off. You'll find that pressure builds under your hand. Now cover the filler cap, and check the air coming out of the valve cover breather. Not as much as what was coming out of the filler cap, is it? Now, run a bored PCV and your breather into a T fitting, and that into a single vacuum line. Check the amount of air coming out of it. It's a lot more, isn't it? Now imagine that your engine is at full bore pushing 24PSI, and you'll understand why plugging a PCV is bad and why having as much ventilation you can is a good thing.

One more thing. Don't run a vented catchcan. Run it to a non-vented can, and plumb that back into your intake line. The theory here is that the intake line is always in a vacuum, especially under boost. That vacuum will help draw blowby gasses from your crankcase back into the intake, and help decrease crankcase pressure. It will also help with engine efficency and fuel mileage, as a crank in a vacuum doesn't have to work against pressurized air. It will also keep oil from backing up your oil drain line from your turbo, and keep the turbo from leaking oil out of it's seals. Turbines don't like to sling oil at 150,000 RPM. This may also expalin why you're turbo isn't making the boost it should. When crankcase pressure has nowhere to go, it goes to the past of least resistance. In most cases, this includes the gravity drain on your turbo. Ask me why I know all this....

When peforming boost leak test, warm up your motor first. Rings and pistons expand when your motor is at normal operating temp, and will show you what the car is really doing when you're running it. It will also minimize leaks through the rings while your running your test. I run a forged bottom end, and the difference leak testing it while cold vs. hot is night and day.

Matt.

Ok I did not have the pcv blocked while driving,just when I was doing a boost leak test.So should I take the pcv and hollow it out and then run that and the valve cover breather into a catchcan,did I get that right.You think this may be why im losing my boost up top.Where can I buy a catch can from?

 

[andymoraitis]

Well I went ahead and did another compression test.This time with a brand new tester and came up with the following160-160-158-154. That seems alot better to me.So where else can boost get into the crankcase from?

That's better than the previous test, but did you also try a wet test? That's the best way to see if the rings are allowing blow by.

 

[fwdeclipse]

No I did not I figured it was better test I did not do it.But Im going to do that to see if thats where its goin.

 

[Enraged78]

Ok I did not have the pcv blocked while driving,just when I was doing a boost leak test.So should I take the pcv and hollow it out and then run that and the valve cover breather into a catchcan,did I get that right.You think this may be why im losing my boost up top.Where can I buy a catch can from?

RRE has a few. This is a link to the vented one with the lines routed the way I spoke of:

http://www.roadraceengineering.com/instructions/catchcaninstructions.htm

This is a non-vented can. You can route the lines like in the first one I posted, but the price is crazy. $100.00 for a catch can is nuts.

http://www.roadraceengineering.com/instructions/greddycatchcan.htm

There are other vendors that sell things like this. Or, you can make your own using a jar and some fittings from home depot. I made mine for $5.00. It's a jiffy peanut butter jar sealed with RTV, so it looks a little ghetto, but works perfectly. There's a link to another here on tuners:

http://www.dsmtuners.com/forums/showthread.php?t=212235&highlight=pvc+catch+can

You can make this without the breather, which I would recommend.

Matt.

 

[No_Skillz]

You can also buy the RRE catchcan, take off the filter on top and cap it. That's what I did.