Understanding th GDI Mini PCV systems and how to improve on it.
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2nd Gear
Joined: Jan 2015
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From: Florida
Understanding th GDI Mini PCV systems and how to improve on it.
It is never good to delete or defeat the PCV system, especially on a GDI engine and here is why:
All engines have a certain amount of blow-by. That blow-by consists of combustion byproducts consisting mainly of 70% water and acids (acids are formed during the combustion process and attack the metals internally. The main one being sulfuric. The oil additive that has properties to combat this is TBN), 23% raw unburnt fuel (that washes down the cylinder walls and dilutes the oil so it is barely protecting as a GDI engine introduces the fuel at 1,000-3,000 PSI vs the old port injection engines at 45-55 PSI, so it pushes 8-12 times the amount of fuel past the rings)., and 7% is oil saturated with abrasive particulate matter (mainly ash/soot/carbon). IF you delete or defeat any of the functions of the PCV system, these stay in the crankcase and settle mixing with the oil and accelerates wear and damage if they are not flushed and evacuated (sucked out) the foul/dirty side of the PCV system. Filtered fresh MAF metered air in one portion of the crankcase to flush and make up for the foul contaminant laden vapors being evacuated (sucked out) the opposite portion. The shortcoming on the Mini is no evacuation when in boost, and excessive oil vapors included in the combustion byproducts cause intake valve coking...the Mini, and BMW engines as a whole have more severe issues than many other automakers, but ALL GDI engines have all of these issues. And if you use a synthetic blend oil the petroleum based portion is a large part of what causes those formations to build. Run ONLY a full synthetic oil in a GDI engine. And to help counter the fuel dilution that reduces actual viscosity to far too thin. and that adds to wear and failure issues. Also, as the valves having no fuel contact as in the past, operate at far higher temps so the deposits bake into a hard crystallin structure that is extremely abrasive. Same consistency as sand. And that scores cylinder walls and piston skirts and rings if an engine running solvent based cleaning is done. They are only safe in the old port injection engines. Then with GDI engines we have a new phenonium known as LSPI (Low Speed Preignition). This is when the oil vapors and unburnt fuel get trapped behind the rings and if it ignites, breaks the piston at usually the top ring land. Far too often the land stays in place and oil consumption increases and the occasional misfire and is often missed in diagnosing. So, the PCV is far more than a pollution control system, it has several functions that are critical to engine life and other issues. So the solution is NEVER to vent or delete, bit to enhance the current functions. One way is to add a secondary evacuation suction source and a series of special checkvalves so the crankcase always has suction pulled. This prevents pressure from building in the first place, so the crankcase is always being flushed and evacuated of these compounds and substances leaving very little to settle in the crankcase. This helps maintain viscosity as well as greatly increases oil life. Here is an example of a tech testing just this with a twin turbo GDI engine that is modified and driven hard. Pay special attention to the Lab Techs comments:
Other benefits from an enhanced system? Less oil ingestion equals less KR pulling timing so power and fuel economy improve. Not allowing pressure to build also reduces the parasitic power loss of the pistons fighting crankcase pressure on each downstroke. It also reduces the incidence of "Ring Flutter" where with forced induction engines allowing pressure to build in the crankcase allows the rings to enter into a State of rapid vibration that increases blow-by and reduces power output. A vent or breather also introduces un metered air into the intake air charge so fuel trims go nuts trying to compensate. If we look back through history up until the mid 1960's, all engines vented through a "draft tube" and that released pressure, but did a very poor job of evacuating so engines wore rapidly. It was not until after the PCV system was mandated that engineers saw the same engines, with the same oils and oil change intervals were now lasting 2-3 times as long as prior. So after study they discovered what they could not see was responsible for much of the wear. Then we look at the racing industry. No form of Professional racing uses breathers unless the specific class forbids a crankcase evacuation system for all the reasons listed above and more. So we see far too many great tuner shops who do excellent builds completely ignore all of this. Why? It has been decades since any of this has been taught in Automotive Tech Schools and dealer training. So with no where to actually learn, most just make assumptions and as the damage done is gradual, few associate failures from deleting this system. Reading the threads on anything PCV and catchcan related it seems there is a ton of misunderstanding on this subject. Ask questions and willing to answer.
All engines have a certain amount of blow-by. That blow-by consists of combustion byproducts consisting mainly of 70% water and acids (acids are formed during the combustion process and attack the metals internally. The main one being sulfuric. The oil additive that has properties to combat this is TBN), 23% raw unburnt fuel (that washes down the cylinder walls and dilutes the oil so it is barely protecting as a GDI engine introduces the fuel at 1,000-3,000 PSI vs the old port injection engines at 45-55 PSI, so it pushes 8-12 times the amount of fuel past the rings)., and 7% is oil saturated with abrasive particulate matter (mainly ash/soot/carbon). IF you delete or defeat any of the functions of the PCV system, these stay in the crankcase and settle mixing with the oil and accelerates wear and damage if they are not flushed and evacuated (sucked out) the foul/dirty side of the PCV system. Filtered fresh MAF metered air in one portion of the crankcase to flush and make up for the foul contaminant laden vapors being evacuated (sucked out) the opposite portion. The shortcoming on the Mini is no evacuation when in boost, and excessive oil vapors included in the combustion byproducts cause intake valve coking...the Mini, and BMW engines as a whole have more severe issues than many other automakers, but ALL GDI engines have all of these issues. And if you use a synthetic blend oil the petroleum based portion is a large part of what causes those formations to build. Run ONLY a full synthetic oil in a GDI engine. And to help counter the fuel dilution that reduces actual viscosity to far too thin. and that adds to wear and failure issues. Also, as the valves having no fuel contact as in the past, operate at far higher temps so the deposits bake into a hard crystallin structure that is extremely abrasive. Same consistency as sand. And that scores cylinder walls and piston skirts and rings if an engine running solvent based cleaning is done. They are only safe in the old port injection engines. Then with GDI engines we have a new phenonium known as LSPI (Low Speed Preignition). This is when the oil vapors and unburnt fuel get trapped behind the rings and if it ignites, breaks the piston at usually the top ring land. Far too often the land stays in place and oil consumption increases and the occasional misfire and is often missed in diagnosing. So, the PCV is far more than a pollution control system, it has several functions that are critical to engine life and other issues. So the solution is NEVER to vent or delete, bit to enhance the current functions. One way is to add a secondary evacuation suction source and a series of special checkvalves so the crankcase always has suction pulled. This prevents pressure from building in the first place, so the crankcase is always being flushed and evacuated of these compounds and substances leaving very little to settle in the crankcase. This helps maintain viscosity as well as greatly increases oil life. Here is an example of a tech testing just this with a twin turbo GDI engine that is modified and driven hard. Pay special attention to the Lab Techs comments:
Other benefits from an enhanced system? Less oil ingestion equals less KR pulling timing so power and fuel economy improve. Not allowing pressure to build also reduces the parasitic power loss of the pistons fighting crankcase pressure on each downstroke. It also reduces the incidence of "Ring Flutter" where with forced induction engines allowing pressure to build in the crankcase allows the rings to enter into a State of rapid vibration that increases blow-by and reduces power output. A vent or breather also introduces un metered air into the intake air charge so fuel trims go nuts trying to compensate. If we look back through history up until the mid 1960's, all engines vented through a "draft tube" and that released pressure, but did a very poor job of evacuating so engines wore rapidly. It was not until after the PCV system was mandated that engineers saw the same engines, with the same oils and oil change intervals were now lasting 2-3 times as long as prior. So after study they discovered what they could not see was responsible for much of the wear. Then we look at the racing industry. No form of Professional racing uses breathers unless the specific class forbids a crankcase evacuation system for all the reasons listed above and more. So we see far too many great tuner shops who do excellent builds completely ignore all of this. Why? It has been decades since any of this has been taught in Automotive Tech Schools and dealer training. So with no where to actually learn, most just make assumptions and as the damage done is gradual, few associate failures from deleting this system. Reading the threads on anything PCV and catchcan related it seems there is a ton of misunderstanding on this subject. Ask questions and willing to answer.
6th Gear
Joined: Nov 2018
Posts: 1,561
Likes: 331
From: Cali
Hmmm....
it is never good to delete or defeat the pcv system, especially on a gdi engine and here is why:
all engines have a certain amount of blow-by. That blow-by consists of combustion byproducts consisting mainly of 70% water and acids (acids are formed during the combustion process and attack the metals internally. The main one being sulfuric. The oil additive that has properties to combat this is tbn, 23% raw unburnt fuel (that washes down the cylinder walls and dilutes the oil so it is barely protecting as a gdi engine introduces the fuel at 1,000-3,000 psi vs the old port injection engines at 45-55 psi, so it pushes 8-12 times the amount of fuel past the rings)., and 7% is oil saturated with abrasive particulate matter (mainly ash/soot/carbon).
If you delete or defeat any of the functions of the pcv system, these stay in the crankcase and settle mixing with the oil and accelerates wear and damage if they are not flushed and evacuated (sucked out) the foul/dirty side of the pcv system.
Filtered fresh maf metered air in one portion of the crankcase to flush and make up for the foul contaminant laden vapors being evacuated (sucked out) the opposite portion.
The shortcoming on the mini is no evacuation when in boost, and excessive oil vapors included in the combustion byproducts cause intake valve coking...the mini, and bmw engines as a whole have more severe issues than many other automakers, but all gdi engines have all of these issues.
And if you use a synthetic blend oil the petroleum based portion is a large part of what causes those formations to build.
Run only a full synthetic oil in a gdi engine. And to help counter the fuel dilution that reduces actual viscosity to far too thin. And that adds to wear and failure issues. Also, as the valves having no fuel contact as in the past, operate at far higher temps so the deposits bake into a hard crystallin structure that is extremely abrasive. Same consistency as sand. And that scores cylinder walls and piston skirts and rings if an engine running solvent based cleaning is done.
They are only safe in the old port injection engines.
Then with gdi engines we have a new phenonium known as lspi (low speed preignition). This is when the oil vapors and unburnt fuel get trapped behind the rings and if it ignites, breaks the piston at usually the top ring land. Far too often the land stays in place and oil consumption increases and the occasional misfire and is often missed in diagnosing.
So, the pcv is far more than a pollution control system, it has several functions that are critical to engine life and other issues.
So the solution is never to vent or delete, bit to enhance the current functions. One way is to add a secondary evacuation suction source and a series of special checkvalves so the crankcase always has suction pulled.
This prevents pressure from building in the first place, so the crankcase is always being flushed and evacuated of these compounds and substances leaving very little to settle in the crankcase. This helps maintain viscosity as well as greatly increases oil life.
Here is an example of a tech testing just this with a twin turbo gdi engine that is modified and driven hard. Pay special attention to the lab techs comments:
other benefits from an enhanced system?
Less oil ingestion equals less kr pulling timing so power and fuel economy improve.
Not allowing pressure to build also reduces the parasitic power loss of the pistons fighting crankcase pressure on each downstroke.
It also reduces the incidence of "ring flutter" where with forced induction engines allowing pressure to build in the crankcase allows the rings to enter into a state of rapid vibration that increases blow-by and reduces power output.
A vent or breather also introduces un metered air into the intake air charge so fuel trims go nuts trying to compensate. If we look back through history up until the mid 1960's, all engines vented through a "draft tube" and that released pressure, but did a very poor job of evacuating so engines wore rapidly.
It was not until after the pcv system was mandated that engineers saw the same engines, with the same oils and oil change intervals were now lasting 2-3 times as long as prior. So after study they discovered what they could not see was responsible for much of the wear.
Then we look at the racing industry. No form of professional racing uses breathers unless the specific class forbids a crankcase evacuation system for all the reasons listed above and more.
So we see far too many great tuner shops who do excellent builds completely ignore all of this.
Why? It has been decades since any of this has been taught in automotive tech schools and dealer training. So with no where to actually learn, most just make assumptions and as the damage done is gradual, few associate failures from deleting this system.
Reading the threads on anything pcv and catchcan related it seems there is a ton of misunderstanding on this subject.
Ask questions and willing to answer.
all engines have a certain amount of blow-by. That blow-by consists of combustion byproducts consisting mainly of 70% water and acids (acids are formed during the combustion process and attack the metals internally. The main one being sulfuric. The oil additive that has properties to combat this is tbn, 23% raw unburnt fuel (that washes down the cylinder walls and dilutes the oil so it is barely protecting as a gdi engine introduces the fuel at 1,000-3,000 psi vs the old port injection engines at 45-55 psi, so it pushes 8-12 times the amount of fuel past the rings)., and 7% is oil saturated with abrasive particulate matter (mainly ash/soot/carbon).
If you delete or defeat any of the functions of the pcv system, these stay in the crankcase and settle mixing with the oil and accelerates wear and damage if they are not flushed and evacuated (sucked out) the foul/dirty side of the pcv system.
Filtered fresh maf metered air in one portion of the crankcase to flush and make up for the foul contaminant laden vapors being evacuated (sucked out) the opposite portion.
The shortcoming on the mini is no evacuation when in boost, and excessive oil vapors included in the combustion byproducts cause intake valve coking...the mini, and bmw engines as a whole have more severe issues than many other automakers, but all gdi engines have all of these issues.
And if you use a synthetic blend oil the petroleum based portion is a large part of what causes those formations to build.
Run only a full synthetic oil in a gdi engine. And to help counter the fuel dilution that reduces actual viscosity to far too thin. And that adds to wear and failure issues. Also, as the valves having no fuel contact as in the past, operate at far higher temps so the deposits bake into a hard crystallin structure that is extremely abrasive. Same consistency as sand. And that scores cylinder walls and piston skirts and rings if an engine running solvent based cleaning is done.
They are only safe in the old port injection engines.
Then with gdi engines we have a new phenonium known as lspi (low speed preignition). This is when the oil vapors and unburnt fuel get trapped behind the rings and if it ignites, breaks the piston at usually the top ring land. Far too often the land stays in place and oil consumption increases and the occasional misfire and is often missed in diagnosing.
So, the pcv is far more than a pollution control system, it has several functions that are critical to engine life and other issues.
So the solution is never to vent or delete, bit to enhance the current functions. One way is to add a secondary evacuation suction source and a series of special checkvalves so the crankcase always has suction pulled.
This prevents pressure from building in the first place, so the crankcase is always being flushed and evacuated of these compounds and substances leaving very little to settle in the crankcase. This helps maintain viscosity as well as greatly increases oil life.
Here is an example of a tech testing just this with a twin turbo gdi engine that is modified and driven hard. Pay special attention to the lab techs comments:
other benefits from an enhanced system?
Less oil ingestion equals less kr pulling timing so power and fuel economy improve.
Not allowing pressure to build also reduces the parasitic power loss of the pistons fighting crankcase pressure on each downstroke.
It also reduces the incidence of "ring flutter" where with forced induction engines allowing pressure to build in the crankcase allows the rings to enter into a state of rapid vibration that increases blow-by and reduces power output.
A vent or breather also introduces un metered air into the intake air charge so fuel trims go nuts trying to compensate. If we look back through history up until the mid 1960's, all engines vented through a "draft tube" and that released pressure, but did a very poor job of evacuating so engines wore rapidly.
It was not until after the pcv system was mandated that engineers saw the same engines, with the same oils and oil change intervals were now lasting 2-3 times as long as prior. So after study they discovered what they could not see was responsible for much of the wear.
Then we look at the racing industry. No form of professional racing uses breathers unless the specific class forbids a crankcase evacuation system for all the reasons listed above and more.
So we see far too many great tuner shops who do excellent builds completely ignore all of this.
Why? It has been decades since any of this has been taught in automotive tech schools and dealer training. So with no where to actually learn, most just make assumptions and as the damage done is gradual, few associate failures from deleting this system.
Reading the threads on anything pcv and catchcan related it seems there is a ton of misunderstanding on this subject.
Ask questions and willing to answer.
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