Is venting your crankcase bad for your tune?
#1
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Is venting your crankcase bad for your tune?
I just read a post where someone recommeded _not_ venting your crankcase to the atmosphere.
I followed one of the How-To's here - more specifically MalibuJacks home made catch can.
Is it detrimental because of the fact it allows unmetered air into the system?
I followed one of the How-To's here - more specifically MalibuJacks home made catch can.
Is it detrimental because of the fact it allows unmetered air into the system?
#2
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Which line are you talking about. The PCV valve side of the breather side going to the intake.
You can vent the one going to the intake without problems, but not the PCV side. Even though many people will say they have done it for many years without problems....its just like all of the people with their boost gauge tapped into the FP regulator line that have never had problems.....dosent make it right or safe
Just keep the PCV valve hooked up, and you can either run the othe rline to the ground and let it drip, or put a breather filter on it...
You can vent the one going to the intake without problems, but not the PCV side. Even though many people will say they have done it for many years without problems....its just like all of the people with their boost gauge tapped into the FP regulator line that have never had problems.....dosent make it right or safe
Just keep the PCV valve hooked up, and you can either run the othe rline to the ground and let it drip, or put a breather filter on it...
#3
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This is probably one of the most overlooked problems because some people don't understand the operation of the PCV system or because they buy intake pipes from vendors like Buschur that tune mostly with speed density and don't use a MAF.
You should NOT vent your valve cover with a MAF based system. Let me explain why. I know I have explained this a few times in the past, but since this thread is dedicated to that, maybe it will be good for the archives.
Your valve cover has a PCV valve going to the intake manifold and a breather hose (straight through fitting) that connects to the intake pipe after the MAF.
Under conditions of vacuum in the intake manifold, like idle and cruise (anytime your boost gauge shows vacuum), the PCV valve opens. The vacuum from the intake manifold is used to scavenge excess cranckcase pressure, moisture, and gases to be burned back in the cylinders. The breather hose on the other side of the valve cover is there to provide clean, fresh, metered air after the MAF to mix with this mixture of moisture, crankcase pressure, gases, etc.
So, you can think of the path like this:
(1)Air comes in through your air filter, (2)through and counted by MAF, (3)through the breather hose, (4)into breather fitting, (5)through and under valve cover to mix with gases, (5)out of valve cover through PCV valve, (6)and then into intake manifold and finally cylinder to get burned.
The problem is that when you disconnect this breather hose and vent the valve cover from this fitting is that the air is now not metered. You are bypassing steps (1) and (2). So now your MAF has no idea of that extra air being consumed by your engine. So, you fueling will be lean. The front o2 notices this and corrects by making your fuel trims positive. How much positive depends on how much air is actually being drawn into your valve cover uncounted.
This is what messes up your fuel trims and why you shouldn't vent your valve cover with a MAF based system. You can still use a catch can in line with your breather hose, but the hose should be connected after the MAF to your intake pipe still.
Eric
You should NOT vent your valve cover with a MAF based system. Let me explain why. I know I have explained this a few times in the past, but since this thread is dedicated to that, maybe it will be good for the archives.
Your valve cover has a PCV valve going to the intake manifold and a breather hose (straight through fitting) that connects to the intake pipe after the MAF.
Under conditions of vacuum in the intake manifold, like idle and cruise (anytime your boost gauge shows vacuum), the PCV valve opens. The vacuum from the intake manifold is used to scavenge excess cranckcase pressure, moisture, and gases to be burned back in the cylinders. The breather hose on the other side of the valve cover is there to provide clean, fresh, metered air after the MAF to mix with this mixture of moisture, crankcase pressure, gases, etc.
So, you can think of the path like this:
(1)Air comes in through your air filter, (2)through and counted by MAF, (3)through the breather hose, (4)into breather fitting, (5)through and under valve cover to mix with gases, (5)out of valve cover through PCV valve, (6)and then into intake manifold and finally cylinder to get burned.
The problem is that when you disconnect this breather hose and vent the valve cover from this fitting is that the air is now not metered. You are bypassing steps (1) and (2). So now your MAF has no idea of that extra air being consumed by your engine. So, you fueling will be lean. The front o2 notices this and corrects by making your fuel trims positive. How much positive depends on how much air is actually being drawn into your valve cover uncounted.
This is what messes up your fuel trims and why you shouldn't vent your valve cover with a MAF based system. You can still use a catch can in line with your breather hose, but the hose should be connected after the MAF to your intake pipe still.
Eric
#5
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This is probably one of the most overlooked problems because some people don't understand the operation of the PCV system or because they buy intake pipes from vendors like Buschur that tune mostly with speed density and don't use a MAF.
You should NOT vent your valve cover with a MAF based system. Let me explain why. I know I have explained this a few times in the past, but since this thread is dedicated to that, maybe it will be good for the archives.
Your valve cover has a PCV valve going to the intake manifold and a breather hose (straight through fitting) that connects to the intake pipe after the MAF.
Under conditions of vacuum in the intake manifold, like idle and cruise (anytime your boost gauge shows vacuum), the PCV valve opens. The vacuum from the intake manifold is used to scavenge excess cranckcase pressure, moisture, and gases to be burned back in the cylinders. The breather hose on the other side of the valve cover is there to provide clean, fresh, metered air after the MAF to mix with this mixture of moisture, crankcase pressure, gases, etc.
So, you can think of the path like this:
(1)Air comes in through your air filter, (2)through and counted by MAF, (3)through the breather hose, (4)into breather fitting, (5)through and under valve cover to mix with gases, (5)out of valve cover through PCV valve, (6)and then into intake manifold and finally cylinder to get burned.
The problem is that when you disconnect this breather hose and vent the valve cover from this fitting is that the air is now not metered. You are bypassing steps (1) and (2). So now your MAF has no idea of that extra air being consumed by your engine. So, you fueling will be lean. The front o2 notices this and corrects by making your fuel trims positive. How much positive depends on how much air is actually being drawn into your valve cover uncounted.
This is what messes up your fuel trims and why you shouldn't vent your valve cover with a MAF based system. You can still use a catch can in line with your breather hose, but the hose should be connected after the MAF to your intake pipe still.
Eric
You should NOT vent your valve cover with a MAF based system. Let me explain why. I know I have explained this a few times in the past, but since this thread is dedicated to that, maybe it will be good for the archives.
Your valve cover has a PCV valve going to the intake manifold and a breather hose (straight through fitting) that connects to the intake pipe after the MAF.
Under conditions of vacuum in the intake manifold, like idle and cruise (anytime your boost gauge shows vacuum), the PCV valve opens. The vacuum from the intake manifold is used to scavenge excess cranckcase pressure, moisture, and gases to be burned back in the cylinders. The breather hose on the other side of the valve cover is there to provide clean, fresh, metered air after the MAF to mix with this mixture of moisture, crankcase pressure, gases, etc.
So, you can think of the path like this:
(1)Air comes in through your air filter, (2)through and counted by MAF, (3)through the breather hose, (4)into breather fitting, (5)through and under valve cover to mix with gases, (5)out of valve cover through PCV valve, (6)and then into intake manifold and finally cylinder to get burned.
The problem is that when you disconnect this breather hose and vent the valve cover from this fitting is that the air is now not metered. You are bypassing steps (1) and (2). So now your MAF has no idea of that extra air being consumed by your engine. So, you fueling will be lean. The front o2 notices this and corrects by making your fuel trims positive. How much positive depends on how much air is actually being drawn into your valve cover uncounted.
This is what messes up your fuel trims and why you shouldn't vent your valve cover with a MAF based system. You can still use a catch can in line with your breather hose, but the hose should be connected after the MAF to your intake pipe still.
Eric
#6
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It has no effect when you are in boost as the PCV valve is closed. It only affects, basically, closed loop fueling. I welded a breather hose bung onto the intake pipe that AMS includes with the 35R.
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well, there is no problem doing that. it is just the emission device. Best way to do that is to remove the pcv and breather side all together and VTA . Removing just breather side will change the maf readings bit but that is when you are crusing and idling not when you step on the gas. also, stock ECU will compensate it pretty well for the cruse and idle. you don't have much control over closed loop operation anyway...
However, I didn't see any performance gain from it. Again, it only affects when you don't have any boost, Theoretically, removing those emission device will improve the power but there is too little to gain and your car becomes not street leagal. Also, under hood smell is awful .
However, I didn't see any performance gain from it. Again, it only affects when you don't have any boost, Theoretically, removing those emission device will improve the power but there is too little to gain and your car becomes not street leagal. Also, under hood smell is awful .
#11
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I read a similiar thread somewhere and so I tried running the breather back into the intake after the maf. But it leaned out the afr and made it inconsistent so I put it back to venting to the atmosphere. It's my opinoin that on my car it is mostly venting air and not sucking in unmetered air this is also supported by the oil on the end of the breather hose filter. I'm not saying it doesn't suck in any air I just think that on my car it doesn't suck in much at all.
#14
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Well, if your fuel trims aren't maxed out because of this, then your AF would go unchanged. When you are under vacuum, you are most likely under close-loop fueling. So, you aren't using your open-loop fuel maps. You are using O2 feedback with fuel trim correction.
The problem is that your fuel trims will get out of whack, along with the transition to open loop fueling. Your transitional AF ratios will be affected, but not likely your closed loop idle and cruise AFRs. Those will still be 14.7, unless you are maxing out your fuel trims.
Eric
#15
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Well, if your fuel trims aren't maxed out because of this, then your AF would go unchanged. When you are under vacuum, you are most likely under close-loop fueling. So, you aren't using your open-loop fuel maps. You are using O2 feedback with fuel trim correction.
The problem is that your fuel trims will get out of whack, along with the transition to open loop fueling. Your transitional AF ratios will be affected, but not likely your closed loop idle and cruise AFRs. Those will still be 14.7, unless you are maxing out your fuel trims.
Eric
The problem is that your fuel trims will get out of whack, along with the transition to open loop fueling. Your transitional AF ratios will be affected, but not likely your closed loop idle and cruise AFRs. Those will still be 14.7, unless you are maxing out your fuel trims.
Eric