Lsx Twincharged pcv and backfiring in search of help!
Thread Starter
On The Tree
Joined: Jan 2016
Posts: 100
Likes: 0
From: Colorado
Lsx Twincharged pcv and backfiring in search of help! I need some help with how to run the pcv hoses. I do not have a pcv valve or anything but need a good way to vent the crank case since it has already cause a valve cover gasket to start leaking and ever since I messed with the pcv hoses it starts backfiring once I hit 14psi of boost. Any ideas?
Step 1: locate all passages leading into and out of your engine's crank case.
Step 2: locate your engine's pcv valve (one way check valve)
step 3: the pcv valve routes to the intake manifold from the valve cover (usually), and should shut when boost is applied from the intake manifold side, I recommend you apply pressure from an air compressor to the pcv valve to make sure it remains air tight at whatever boost pressure you intent to run (blowing into it with your mouth only applies 1~psi and they can leak anywhere from 2->30psi without you knowing)
step 4: any other passages need to route to the pre-turbo (or pre compressor) inlet tube, after the air filter
In other words, during boost, the crankcase pcv is applied by the pre-compressor inlet. When off boost, the pcv is applied from the intake manifold vacuum. There should not be any catch cans or any excessive length of plumbing anywhere, extra hoses and extra volume to fill results with less pcv action. If you have an oil control issue you should deal with it directly i.e. fix the baffle or repair the toasted piston rings, catch cans are just temporary band-aids for people who don't want to tackle their engine's real problems. Its also just extra unnecessary **** to sell you.
Here is an image to help you, this is the OEM method for PCV on turbo cars, every turbo engine from every manufacturer across the globe uses something like this.
notice this is off-boost. During boost the pcv valve will shut and pcv action is supplied by the pre-turbo compressor inlet.
Step 2: locate your engine's pcv valve (one way check valve)
step 3: the pcv valve routes to the intake manifold from the valve cover (usually), and should shut when boost is applied from the intake manifold side, I recommend you apply pressure from an air compressor to the pcv valve to make sure it remains air tight at whatever boost pressure you intent to run (blowing into it with your mouth only applies 1~psi and they can leak anywhere from 2->30psi without you knowing)
step 4: any other passages need to route to the pre-turbo (or pre compressor) inlet tube, after the air filter
In other words, during boost, the crankcase pcv is applied by the pre-compressor inlet. When off boost, the pcv is applied from the intake manifold vacuum. There should not be any catch cans or any excessive length of plumbing anywhere, extra hoses and extra volume to fill results with less pcv action. If you have an oil control issue you should deal with it directly i.e. fix the baffle or repair the toasted piston rings, catch cans are just temporary band-aids for people who don't want to tackle their engine's real problems. Its also just extra unnecessary **** to sell you.
Here is an image to help you, this is the OEM method for PCV on turbo cars, every turbo engine from every manufacturer across the globe uses something like this.
notice this is off-boost. During boost the pcv valve will shut and pcv action is supplied by the pre-turbo compressor inlet.
Well yall seem to think it is alot of info and it really isn't that big of an idea. The principle is simple enough, we wish to maintain as much vacuum in the crankcase as possible at all times, off or on boost, and do whatever it takes to achieve that. Large displacement blower engines use belt driven vacuum pumps because it is worth 50-100 horsepower on a 1000-1500 horsepower engine. The engine builders who have been assembling these engines for 20-30 years know they need to seal the engines up very well (lest you suck in an oil seal) to run them like this.
We street/daily drivers do not run such pumps, which are expensive and require maintenance etc... so we do the best we can using the engine's natural breathing. A unique, elegant PCV system is a top requirement for a performance engine, not just for the performance benefit but also the cleaner oil / engine byproduct removal.
We street/daily drivers do not run such pumps, which are expensive and require maintenance etc... so we do the best we can using the engine's natural breathing. A unique, elegant PCV system is a top requirement for a performance engine, not just for the performance benefit but also the cleaner oil / engine byproduct removal.
Trending Topics
Launching!
Joined: May 2013
Posts: 270
Likes: 30
From: Detroit
Ok I'll bite. First, you may want to work on the drawing a little. Maybe do it in a power point and add some more info. Looks a little childish.
I don't think you are way off however, but a few questions:
Is point A before or after TB?
What is point B?
Underboost, where does the fresh air come into the crankcase if it is being evacuated by the line in front of turbo?
"There should not be any catch cans" Why would you say that? Who wants oil in the intake?
I don't think you are way off however, but a few questions:
Is point A before or after TB?
What is point B?
Underboost, where does the fresh air come into the crankcase if it is being evacuated by the line in front of turbo?
"There should not be any catch cans" Why would you say that? Who wants oil in the intake?
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
TECH Enthusiast
Joined: Apr 2009
Posts: 723
Likes: 4
Ok I'll bite. First, you may want to work on the drawing a little. Maybe do it in a power point and add some more info. Looks a little childish.
I don't think you are way off however, but a few questions:
Is point A before or after TB?
What is point B?
Underboost, where does the fresh air come into the crankcase if it is being evacuated by the line in front of turbo?
"There should not be any catch cans" Why would you say that? Who wants oil in the intake?
I don't think you are way off however, but a few questions:
Is point A before or after TB?
What is point B?
Underboost, where does the fresh air come into the crankcase if it is being evacuated by the line in front of turbo?
"There should not be any catch cans" Why would you say that? Who wants oil in the intake?
https://ls1tech.com/forums/forced-in...-question.html
Thread Starter
On The Tree
Joined: Jan 2016
Posts: 100
Likes: 0
From: Colorado
Ok I'll bite. First, you may want to work on the drawing a little. Maybe do it in a power point and add some more info. Looks a little childish.
I don't think you are way off however, but a few questions:
Is point A before or after TB?
What is point B?
Underboost, where does the fresh air come into the crankcase if it is being evacuated by the line in front of turbo?
"There should not be any catch cans" Why would you say that? Who wants oil in the intake?
I don't think you are way off however, but a few questions:
Is point A before or after TB?
What is point B?
Underboost, where does the fresh air come into the crankcase if it is being evacuated by the line in front of turbo?
"There should not be any catch cans" Why would you say that? Who wants oil in the intake?
Thanks for the questions
The picture is used in many posts on many forums with great success, its "childish" nature helps those new to engines understand what is happening. Traditional pictures of PCV systems often neglect to show novices where the crankcase gasses are mixing, that they are truly mixing into and coming out of the oil at all times due to diffusion, and that we are burning them and sending them right into the exhaust system.
Points A and B:
I recommend for the non-emissions vehicles that we move the point A to point B (using proper exhaust scavenging parts), in order to bypass the "re-burning" of combustion gasses and oil vaporization product, to help keep valves/chamber clear from hardened carbon product which accumulates over time. Anyone that would have said "but why would I put oil vapor into my exhaust system" can also clearly see that it will be getting there anyways, after it makes a pass at your engines internals.
Underboost, where does the fresh air come into the crankcase if it is being evacuated by the line in front of turbo?
Finally catch cans are band-aids that help us keep oil from causing trouble, as it leaves the engine in some way while we drive our vehicle. They are additional crankcase volume, which has a negative impact on PCV. There is no reason to use a catch can on a healthy engine with properly designed PCV system and properly machined parts / selected internal parts. I have provided similar, and more info, here
https://ls1tech.com/forums/general-m...l#post19100870
For what it's worth, I'm running a -10 line from the valve cover to a breather can and have had no issues. Sure, you get some vapor coming out of it, but nothing that can't be fixed with a sweat band..
The previous owner of my car ran 8.60's@157mph with a breather setup as well. Is there hp left on the table with a breather setup? I wouldn't doubt it, but that's why we have turbo cars...just raise the boost.
The previous owner of my car ran 8.60's@157mph with a breather setup as well. Is there hp left on the table with a breather setup? I wouldn't doubt it, but that's why we have turbo cars...just raise the boost.
Thread Starter
On The Tree
Joined: Jan 2016
Posts: 100
Likes: 0
From: Colorado
Oh okay sweet thanks guys! Do you think that it could have messed with my tune since I changed the pcv system? Cause ever since I changed t I can't go over 10psi of boost without it backfiring and falling on its face
I read your other post as well...not sure if you stated what your current pcv setup is or not.
I would think that if you're getting a **** ton of oil vapor coming in through the intake, that could certainly cause the motor to pull timing and run like crap.
I wouldn't think that changing the pcv routing would change the tune..unless you have unmetered air coming in from some place...of course, if you're running a speed density tune, I suppose it wouldn't matter either way.
I would think that if you're getting a **** ton of oil vapor coming in through the intake, that could certainly cause the motor to pull timing and run like crap.
I wouldn't think that changing the pcv routing would change the tune..unless you have unmetered air coming in from some place...of course, if you're running a speed density tune, I suppose it wouldn't matter either way.
Last edited by 98Zheadsncam; Jan 7, 2016 at 01:36 PM.
Launching!
Joined: May 2013
Posts: 270
Likes: 30
From: Detroit
That brings me to the next point. I understand during boost you may/will draw air from the crankcase. (not ideal either for same reason oil vapors). You still need a clean air source to replace the air you are extracting. I don't see that in your drawing.
Lastly as I mentioned, oil vapors due exist even in tight motors. There is no such thing as 100% sealed. Therefore, because I don't want oil going through my turbo, IC, intake valves etc, and my mufflers, or car to smoke, I think it's a good practice to use a catch can. Dont agree its a bandaid, although it could be used that way too. The volume of the can is negligible relative to the crankcase in my mind.