The Forced Induction Crankcase Evac Thread
Drifting
Joined: May 2007
Posts: 1,879
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From: st. louis MO
Drifting
Joined: Apr 2008
Posts: 1,607
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From: TIRECRAFT RACING NJ
When building a purpose built race motor with low tension ring packs a vacuum pump / negative pressure in the crankcase is a must . This is where you can see 30 to 40 hp from the combination .
In a stock/ standard ring pack FI application the horse power is usually from removing the blow by in the crankcase , and allowing the rings to seal better against the bore. We have seen the more blow by in an engine the more HP you can pick up when utilizing a vacuum pump . Also with having negative pressure in the crankcase the pistons are not fighting pressure on the downward stroke allowing the engine to spin more freely
That being said most of the Forced Induction engines will benefit from a vacuum pump or a Good 5 stage roots style dry sump system that will keep the crank case pressures in the negative . This is my opinion .
In a stock/ standard ring pack FI application the horse power is usually from removing the blow by in the crankcase , and allowing the rings to seal better against the bore. We have seen the more blow by in an engine the more HP you can pick up when utilizing a vacuum pump . Also with having negative pressure in the crankcase the pistons are not fighting pressure on the downward stroke allowing the engine to spin more freely
That being said most of the Forced Induction engines will benefit from a vacuum pump or a Good 5 stage roots style dry sump system that will keep the crank case pressures in the negative . This is my opinion .
Le Mans Master
Joined: Jan 2009
Posts: 7,767
Likes: 19
From: East Texas
When building a purpose built race motor with low tension ring packs a vacuum pump / negative pressure in the crankcase is a must . This is where you can see 30 to 40 hp from the combination .
In a stock/ standard ring pack FI application the horse power is usually from removing the blow by in the crankcase , and allowing the rings to seal better against the bore. We have seen the more blow by in an engine the more HP you can pick up when utilizing a vacuum pump . Also with having negative pressure in the crankcase the pistons are not fighting pressure on the downward stroke allowing the engine to spin more freely
That being said most of the Forced Induction engines will benefit from a vacuum pump or a Good 5 stage roots style dry sump system that will keep the crank case pressures in the negative . This is my opinion .
In a stock/ standard ring pack FI application the horse power is usually from removing the blow by in the crankcase , and allowing the rings to seal better against the bore. We have seen the more blow by in an engine the more HP you can pick up when utilizing a vacuum pump . Also with having negative pressure in the crankcase the pistons are not fighting pressure on the downward stroke allowing the engine to spin more freely
That being said most of the Forced Induction engines will benefit from a vacuum pump or a Good 5 stage roots style dry sump system that will keep the crank case pressures in the negative . This is my opinion .
Thread Starter
ISIS SUCKS FAT CHOAD
Joined: Oct 2008
Posts: 8,124
Likes: 53
From: Earth, United States
The flow through a oil separating can must be regulated. On the OEM setup GM assumes the same CI and cylinder fill, etc. so they use a sized PCV valve or in the case of the vallet cover, a fixed orfice that controls the amount of flow through & out of the crankcase. When you veture outside of that parameter then the flow must be matched to the engine build and FI or NA and the amount of boost run if FI. The RX system has matched flow control checkvalves to ensure this and do not use the valley cover vent as it is far to restrictive if it is a big cube or FI application. On a stock cube NA motor the valley can still be used but it does not allow the entire crankcase to be properly flushed since the entire drivers side bank is left stagnant. The drivers side valve cover has a nipple on the rear of the valve cover that can be uncapped and used allowing the integrated checkvalves to work properly.
If you have a monster FI build then there is another model with -8 outlets, and app 30% more capacity and the flow controlling checkvalves are a greater flow and are moved inline allowing the amount of evac needed. But, what we see far to often is there is a piston/ring/cylinder damage/sealing issue allowing more blow-by than any system, belt driven vacuum pumps included so if your blowing the dipstick out or oil seals you may still have a motor ecent power, but your blow-by issue can only be addressed by tearing down and replacing the damaged pistons and correcting the bore where there will be metal transfer & scouring. Doubt this? Ask any reputable engine builder if they see this in other builders engines they tear down (most wont say they have issues just as most tuners that cause the damage during dyno tuning by going to aggressive w/Air Fuel and/or timing) and you will se how common this is. Even the best forged pistons will suffer from detonation in a few short seconds. The most common is the top ringlands soften enough to pinch the compression ring and then the seal is compromised.....#8 is usually the cuplrit as it runs leaner than the rest in the LS based engines with 5 & 7 also subjet.
That is why we see so many come in with the evac system deleted and huge lines running to vented cans or just open lines. That will release the pressure, but the underlying problem causing this amount of blow-by is damage and it wont go away.
Keep the questions comming. This is back on track thanks to the mods.
ANYthing you don't fully understand, and the oil analysis is still what I will go back to for any that want proof as to the amount of harmfull compounds contaminating the oil due to not having proper evacuation, not just venting. And again, if you change your oil after every outing/track event to avoid this and can get away with just venting.
:thumbsup:
If you have a monster FI build then there is another model with -8 outlets, and app 30% more capacity and the flow controlling checkvalves are a greater flow and are moved inline allowing the amount of evac needed. But, what we see far to often is there is a piston/ring/cylinder damage/sealing issue allowing more blow-by than any system, belt driven vacuum pumps included so if your blowing the dipstick out or oil seals you may still have a motor ecent power, but your blow-by issue can only be addressed by tearing down and replacing the damaged pistons and correcting the bore where there will be metal transfer & scouring. Doubt this? Ask any reputable engine builder if they see this in other builders engines they tear down (most wont say they have issues just as most tuners that cause the damage during dyno tuning by going to aggressive w/Air Fuel and/or timing) and you will se how common this is. Even the best forged pistons will suffer from detonation in a few short seconds. The most common is the top ringlands soften enough to pinch the compression ring and then the seal is compromised.....#8 is usually the cuplrit as it runs leaner than the rest in the LS based engines with 5 & 7 also subjet.
That is why we see so many come in with the evac system deleted and huge lines running to vented cans or just open lines. That will release the pressure, but the underlying problem causing this amount of blow-by is damage and it wont go away.
Keep the questions comming. This is back on track thanks to the mods.
ANYthing you don't fully understand, and the oil analysis is still what I will go back to for any that want proof as to the amount of harmfull compounds contaminating the oil due to not having proper evacuation, not just venting. And again, if you change your oil after every outing/track event to avoid this and can get away with just venting.
:thumbsup:
heres the thread that I was looking at when I made the purchase.
http://forums.corvetteforum.com/c5-p...ch-cans-6.html
I guess I dont know what I have and I didnt know that there was differen models nor was it specified. a little confused.
Pro
Joined: Jan 2011
Posts: 633
Likes: 6
Hi great thread
i´m installing a GZ motorsport vacuum pump kit "belt driven" and it has vacuum control valve included, the pump is susposed to draw atleast 15" and the contol valve is adjustable from 12"-19"
but when do you know when to much vacuum is to much vacuum for the engine. ?
i was thinking of installing a vacuum gauge in car so i can monitor the vacuum , can i log it threw my HPT if i get for example auto meter gauge?
i have a 404ci LS2 NA engine built whith nitrous in mind whith whith wider ring gap .
thanks
Baezi
i´m installing a GZ motorsport vacuum pump kit "belt driven" and it has vacuum control valve included, the pump is susposed to draw atleast 15" and the contol valve is adjustable from 12"-19"
but when do you know when to much vacuum is to much vacuum for the engine. ?
i was thinking of installing a vacuum gauge in car so i can monitor the vacuum , can i log it threw my HPT if i get for example auto meter gauge?
i have a 404ci LS2 NA engine built whith nitrous in mind whith whith wider ring gap .
thanks
Baezi
I know when I ordered my RX catch can(it arrived on june 10th 2011 it was via this thread and I specified that I had a blower and a 402 in the notes when i ordered. However I'm a little confused still on different catch cans based on engine size and fi vs non fi. With that said how do I know if I have the right one for my new set up?
heres the thread that I was looking at when I made the purchase.
http://forums.corvetteforum.com/c5-p...ch-cans-6.html
I guess I dont know what I have and I didnt know that there was differen models nor was it specified. a little confused.
heres the thread that I was looking at when I made the purchase.
http://forums.corvetteforum.com/c5-p...ch-cans-6.html
I guess I dont know what I have and I didnt know that there was differen models nor was it specified. a little confused.
There are two different models for the type of FI. I can also help walk you through direct via phone if you need. PM for the #.
Tirecraft....you are a breath of fresh air man!!!!! Another builder that understands!!!! Are you doing any oil analysis as well?
Yes, we build with low tension rings and the vac is crucial to sealing. The better sealing and the elimination of crankcase pressure (parasitic loss from the pistons pushing against the pressure on the down strokes).
On a conventional ring tension build we still se some HP gains.
Yes, the DZ pump has worked for some I've read.....just had not tried it so can't vouch for it.
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Drifting
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From: TIRECRAFT RACING NJ
Thread Starter
ISIS SUCKS FAT CHOAD
Joined: Oct 2008
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From: Earth, United States
Team Owner
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From: cookeville tennessee
Pro
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Need more details? Just ask and we can guide you through it.
Safety Car
Joined: Jul 2007
Posts: 4,456
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From: Wichita Falls Texas
Yes. You are mixing the "clean"& the "dirty" side of the crankcase evac system rendering it inoperative. You are venting excess pressure to the air....but no evacuation or flushing is occurring and unless you have a SD tune you have fuel trims hunting for stoic.
Need more details? Just ask and we can guide you through it.
Need more details? Just ask and we can guide you through it.
what else do you need to know
Pro
Joined: Jan 2011
Posts: 633
Likes: 6
You have no cross flow evacuatio by what we see.....the clean and dirty sides need to be separate so you are purging or flushing the harmfull compounds out of the crankcase. Changing the oil often helps alot and w/a SD tune your not dealing with the fuel trim/tune issues so thats a plus.
Safety Car
Joined: Jul 2007
Posts: 4,456
Likes: 29
From: Wichita Falls Texas
You have no cross flow evacuatio by what we see.....the clean and dirty sides need to be separate so you are purging or flushing the harmfull compounds out of the crankcase. Changing the oil often helps alot and w/a SD tune your not dealing with the fuel trim/tune issues so thats a plus.
Melting Slicks
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From: Nathalie VA
St. Jude Donor '15-'16-'17-'18
Le Mans Master
Joined: Jan 2009
Posts: 7,767
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From: East Texas
You need fresh air pulling through the motor from the left side valve cover and out the right side valve cover. Right now your just letting the blow by breath so you don't push oil out the front and rear seals, your motor needs to be aired out with fresh air to get the contaminated gases out! Its like your home filled with smoke and only 1 window open! but if you open 2 windows one on each side of the home it will get the cross air flow and blow the smoke out faster 
Correct me if I'm wrong just trying to help 
Correct me if I'm wrong just trying to help
Team Owner
Joined: Jan 2007
Posts: 29,063
Likes: 1,839
From: cookeville tennessee
You need fresh air pulling through the motor from the left side valve cover and out the right side valve cover. Right now your just letting the blow by breath so you don't push oil out the front and rear seals, your motor needs to be aired out with fresh air to get the contaminated gases out! Its like your home filled with smoke and only 1 window open! but if you open 2 windows one on each side of the home it will get the cross air flow and blow the smoke out faster Correct me if I'm wrong just trying to help
Correct me if I'm wrong just trying to help I am with him, scott if someone dont understand that there is no help for them..