High crankcase pressure normal at high output?
Apr 23, 2024, 04:47 PM
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High crankcase pressure normal at high output?
Posted this on the new members/faq thread but figured it's more fitting here. Sorry for the double post.
Hello all,This may seem like a dumb question but here goes nothing. There are tons of long forums regarding crankcase Pressure and the good ol' dipstick popping out issue.I've gone through most of the threads and I understand a broken or damaged ringland can cause the dipstick issue, but what I don't understand is if it's normal on a high output built motor?Essentially, the Evo 8 I'm looking at is on a precision 6466, built motor, and the owner has the dipstick spring installed. Car makes about 700hp on E85 and has the STM vented catch can with AN lines(the cylinder one by intake manifold not the box on trans).Should I be concerned about the dipstick spring being present and being a bandaid for a deeper issue or is the spring a normal thing on a high output scenario?Some forums mentioned the dipstick will pop out regardless of how good the crankcase venting is with high boost, is that accurate?Just trying to learn about this convoluted topic as much as I can, as the sight of the spring and catch can seemingly filling quickly concerned me.Thanks in advance.
Hello all,This may seem like a dumb question but here goes nothing. There are tons of long forums regarding crankcase Pressure and the good ol' dipstick popping out issue.I've gone through most of the threads and I understand a broken or damaged ringland can cause the dipstick issue, but what I don't understand is if it's normal on a high output built motor?Essentially, the Evo 8 I'm looking at is on a precision 6466, built motor, and the owner has the dipstick spring installed. Car makes about 700hp on E85 and has the STM vented catch can with AN lines(the cylinder one by intake manifold not the box on trans).Should I be concerned about the dipstick spring being present and being a bandaid for a deeper issue or is the spring a normal thing on a high output scenario?Some forums mentioned the dipstick will pop out regardless of how good the crankcase venting is with high boost, is that accurate?Just trying to learn about this convoluted topic as much as I can, as the sight of the spring and catch can seemingly filling quickly concerned me.Thanks in advance.
Apr 24, 2024, 01:00 PM
#2
Pretty normal for a built 4G63 to have a reasonable amount of blowby.
I wouldn't be overly concerned about the dipstick clamp, it certainly saves cleaning up oil from the engine bay and underneath the car.
Extra power, larger piston to wall clearance and ring gaps will all increase blowby.
Factory ring gaps are between 10-14 thou. Most aftermarket pistons recommend between 18-24 thou.
The blowby total flow increase causes the head to not drain effectively. This is because the blowby is going up the oil drains. So it suspends or restricts the oil drain function. This is why Mitsubishi put those "walls" around two of the drains, to promote breathing while the head has liquid oil in it.
When there is lots of oil in the head, they will block off the ports for the crankcase to vent. The block crankcase pressure will go up, while the head pressure will remain low. This will then pop out the dipstick as it's the next link in the chain. Personally I installed thicker O-Rings on the handle, that stopped it popping out as it's very snug in there now.
I wouldn't be overly concerned about the dipstick clamp, it certainly saves cleaning up oil from the engine bay and underneath the car.
Extra power, larger piston to wall clearance and ring gaps will all increase blowby.
Factory ring gaps are between 10-14 thou. Most aftermarket pistons recommend between 18-24 thou.
The blowby total flow increase causes the head to not drain effectively. This is because the blowby is going up the oil drains. So it suspends or restricts the oil drain function. This is why Mitsubishi put those "walls" around two of the drains, to promote breathing while the head has liquid oil in it.
When there is lots of oil in the head, they will block off the ports for the crankcase to vent. The block crankcase pressure will go up, while the head pressure will remain low. This will then pop out the dipstick as it's the next link in the chain. Personally I installed thicker O-Rings on the handle, that stopped it popping out as it's very snug in there now.
Apr 24, 2024, 01:19 PM
#3
I had 2 builds in 1 year, and both (<500hp)do not have CC pressure/oil catch issues. no spring on the dipstick. before that my similar buschur 2.0 had blowby/oil catch issue right off the bat
I'm sure its only a matter of time before i get some so I left my vented oil catch/return setup installed. i would have used the spring also if it was still there
I'm sure its only a matter of time before i get some so I left my vented oil catch/return setup installed. i would have used the spring also if it was still there
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