Forrest Gump 9

Hello all

Is it possible to run the car with the PCV capped off?

I'm thinking about running this set up. From the engine block will run to an oil catch can with filter. The PCV will still attached to the intake manifold but will be capped off.

Anyone run this set up? Any adverse affect? Just trying to keep the damn intake manifold clean.

Alex.currie44

Why do this? All the PCV valve does is vent the crankcase of blow by gases that all IC engines have to some degree. What do you gain?
You might also run afoul of the emissions testing gurus.

Celicasaur

Still attached to the manifold but capped off....I'm confused.....

Do you mean, you're going to DIY mod a catch can and cut the PCV to run through it before routing back to the manifold, ie like the Weistec one?

Or do you mean you're going to cap it off in the literal sense and block it's path from venting pressure back into the intake manifold?

BLKROKT

The vented pressure has to go somewhere. Unless you're trying to create a bubbly mess in your catch can, just route it back to the intake.

Phil_T

I know what you mean as I had something similar in my last Audi S3 without a catch can, It was like the below.

https://www.forgemotorsport.co.uk/VA...uct--1361.html

Celicasaur

Interesting ^

Learn something new everyday....I always understood that not having a PCV meant that...well....yeah. Spooky.

I remember back in the ricer days it was commonplace to vent the PCV to atmosphere via one of those cute little cone filters, but then that's not an entirely great idea because it doesn't allow crankcase pressure to get 'sucked' from the block....

The benefit of this is purely to keep oil out of the inlet and then being burnt > marginally affecting the tune?

Personally I'd just run a catch can, but then I don't know what the benefits of blocking off the PCV are.

Jasonoff

Yes, you can vent a catch can to atmosphere and plug the PCV inlet if you want. There's nothing special with this motor.

I wouldn't vent it in the engine bay though. Run a tube somewhere to the back so you don't get the fumes in the cabin.

But, like others said, why bother?

Forrest Gump 9

Well, to simply put, I can't leave well enough alone.

It started sometime last week that I want to change the air filters. I ended have the whole intake manifold off and in pieces. Cleaned the intake manifold and decided to upgrade to 82mm throttle bodies (have couples spare back in my E55 days). Got everything done and buttoned up but don't have my catch can yet (already modified the PCV for that). Went out for a test drive and it just screamed. Got home popped the hood with the engine running, everything looked good and then oil started to spray out of the sensor in front of the passenger valve cover.

Of course I freaked out, but after some thinking I came to the conclusion that the pcv was modified and the hose got kinked so that's caused the oil to spray. Now I have to tear everything out and do the valve cover gasket. While at it may as well do headbolts and lifters, lol

Celicasaur

Blimey

deadlyvt

The vacuum from the sucking of the motor helps the crankcase vent the blow by gases and even helps with ring seal unless you are running crazy boost where you are getting lots of blowby at high rpms and needing more flow than the pcv can provide you really aren't helping the system any. In saying that you can definitely do it... it's just you are basically doing a mod with no real benefit

Alex.currie44

Some of you is too young to remember the days that the oil filler cap was like a derby hat without the brim. As I recall the idea was blow by gases would come up the push rods or some other opening from the block up into the valve covers and the cap was lined with a mesh wool to prevent oil coming out and the gases vented to atmosphere. With the advent of emission controls the idea is to take those gases and return them to the combustion chamber to be reburnt and exit the tail pipe thus running a cleaner engine. That is still what this system does so I don't see what the gain is. Most things I read say there is nothing to be gained except in the tiny minds of those who think there is. I have yet to find an dyno test that says there is even 1 hp gain. Keep in mind the big bruha in F1 these days is who is mixing oil with fuel to enhance engine performance. So eliminating the PCV may make it worse.

Forrest Gump 9

My goal is to have a clean intake manifold not performance gain. But the oil vapor mixing in the combustion chamber can't be good. Iirc the oil vapor actually lower the octane level.

Alex.currie44

Much ado about nothing.

Alex.currie44

Then again if you follow F1 there has been considerable conversation this season and warnings from the FIA - some think directed at MB - about adding oil to fuel to boost output particularly in qualifying where on a number of occassion Hamilton has put in times that astound people leaving them asking "where did that time come from?'

roadtalontsi

sounds like you need a weistec catch can or fab up your own to go in between the intake and crankcase. I can tell you straight up if you try to do what you're talking about you will have issues. Even something so silly as the dipstick not being all the way in not allowing it to seal properly can and will turn the check engine light on. Dont do stupid crap to this engine, It's a master piece and work of art. There is nothing to gain by doing this. The suction created helps keep the crankcase pressure from getting too high which will cause seals to blow out and leak prematurely. If it didnt do anything and wasnt necessary they wouldnt waste all the time and money to engineer all the hoses, fittings, valve and other components for the system to function correctly. It would be like deleting secondary air injection claiming that it hurts performance.

Jasonoff

He was going to vent a catch can to atmosphere and plug the pcv inlet, not plug the system.

Recirculating vent gasses back into the engine is not necessary.

Alex.currie44

Ya but your car which is coming up on a requirement for a Drive Clean test being 7 yr old would not pass with it disconnected and it's irresponsible to do this. It is part of the pollution control system and there is nothing to be gained by doing it other than add to the crap in the air.

Jasonoff

Correct, but that's not why I replied. Although pointless, it will NOT harm the engine doing it.

roadtalontsi

You need suction on the system this isn't some crappy 8:1 compression motor 4 cylinder terd engine. It will blow seals out.

you know what just go ahead and do it. You'll get all sorts of oil leaks, which will cause more issues and either screw the car up trying to fix it yourself or waste tons of money paying someone to fix it. not my bread.

Jasonoff

He's NOT removing the PCV, just venting to atmosphere instead...