# VRT Exhaust Slash cut method for crankcase evacuation / Venturi



## MaxwellMoulton (Jul 26, 2006)

Hey guys, been running an open crankcase breather now for some time, and have started to get concerned about all of the fumes/ oil fire risk in the engine bay, not to mention the smell/residue problem. I have been weighing my options for crankcase evacuation and all seem to have their drawbacks(i refuse to use a stock pcv system). However, other than emissions, the exhaust slashcut method seems to work well, but I am concerned that a vr6 does not have enough displacement for the Venturi effect to create enough vacuum to even bother with it. 
So the question is, has anyone with a VRT done this method, and were your results good enough to bother? In other words was there constant vacuum through all rpms, with no risk of pressurising the crank case? I know some have done this with the FSI, so I am concerened really with vrt owners.

Other info:
I am currently catless and know i would have to run it post cat.
42lb injectors with c2 software etc.
Thanks for your time. http://****************.com/smile/emthup.gif 
Max.


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## TBT-Syncro (Apr 28, 2001)

*Re: VRT Exhaust Slash cut method for crankcase evacuation / Venturi (MaxwellMoulton)*

a lot easier to just buy a proper catch can.


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## PapioGXL (Jun 3, 2008)

*FV-QR*

You should use a check valve with it, available at summit and most parts stores. If you need a part number I can grab one from work tomorrow.


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## MaxwellMoulton (Jul 26, 2006)

*Re: FV-QR (PapioGXL)*

have a catch can, but dont want to use it since it will never be one hundred percent effective and some oil/vapors will eventually get in there anyways...
papio, i was thinking of using the set up from summit, im just curious though, and maybe you can answer this, if the check valve needs to close from positive pressure from the exhaust, doesnt that mean that the crankcase with become positively pressurized anyways since the blow by will build up? or is the logic that the pressure built by the blow by is somewhat negligable in relation to the exhaust gasses.
thanks,
max.
ps, still looking for vrt guys who have used this method and had success.


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## TBT-Syncro (Apr 28, 2001)

*Re: FV-QR (MaxwellMoulton)*


_Quote, originally posted by *MaxwellMoulton* »_have a catch can, but dont want to use it since it will never be one hundred percent effective and some oil/vapors will eventually get in there anyways...


if you have a proper catch can, and vapor is still a problem. then the motor needs a rebuild.


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## MaxwellMoulton (Jul 26, 2006)

*Re: FV-QR (TBT-Syncro)*

hmm i did not know there was a perfect catch can...how much does it cost and how huge is it? working with a somewhat tight confinement as im sure you know.


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## TBT-Syncro (Apr 28, 2001)

*Re: FV-QR (MaxwellMoulton)*


_Quote, originally posted by *MaxwellMoulton* »_hmm i did not know there was a perfect catch can...how much does it cost and how huge is it? working with a somewhat tight confinement as im sure you know.

the best ones will have two inner chambers, with the upper one being full of stainless steel wool or similar, and of course it should have a drain on the bottom.


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## MaxwellMoulton (Jul 26, 2006)

*Re: FV-QR (TBT-Syncro)*

hmm, yea mine does not have two chambers how crucial is that? im thinking about running the catch inline with the exhaust evac set up so it doesnt look like i drive a diesel when i get on it...


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## Rocco R16V (Oct 7, 2008)

*Re: FV-QR (MaxwellMoulton)*


_Quote, originally posted by *MaxwellMoulton* »_ the exhaust slashcut method seems to work well, but I am concerned that a vr6 does not have enough displacement for the Venturi effect to create enough vacuum to even bother with it. 

If there is flow there can be a venturi effect, the shape and angle of the “slashcut” create the effect. Note the angle 









_Quote »_have a catch can, but dont want to use it since it will never be one hundred percent effective and some oil/vapors will eventually get in there anyways... 

You should still keep your catch can with the exhaust scavenge system. 

_Quote »_i was thinking of using the set up from summit, link if the check valve needs to close from positive pressure from the exhaust, doesnt that mean that the crankcase with become positively pressurized anyways since the blow by will build up? 

No, the check valve only allows air to flow in one direction preventing pressurizing the crank case. It will draw fumes into the exhaust.

_Quote »_thanks,
max.
ps, still looking for vrt guys who have used this method and had success.

don’t need to, it will work.











_Modified by Rocco R16V at 9:43 PM 12-30-2009_


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## MaxwellMoulton (Jul 26, 2006)

*Re: FV-QR (Rocco R16V)*

wow very elaborate response dude i appreciate it... ive heard that its best to have the slash cuts on a part of the exhaust that is parallel to the ground, but it would be easier for me to put it on the down pipe after my O2 ports. Would this work as well, or should i put it farther down on the parallel to the ground tube? Also, would it be wise to put two slash cuts to create more vacuum or is it not necessary (really asking because the kit i bought is made for headers of v8s and such and comes with two of everything). Thanks for the info man!!


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## Rocco R16V (Oct 7, 2008)

*Re: FV-QR (MaxwellMoulton)*

On the down pipe will work, dont think you would need 2, one will be fine.


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## MaxwellMoulton (Jul 26, 2006)

*Re: FV-QR (Rocco R16V)*

cool man, your info is much appreciated.


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## Dubrunner (Nov 8, 2000)

*Re: FV-QR (Rocco R16V)*


_Quote, originally posted by *Rocco R16V* »_
If there is flow there can be a venturi effect, the shape and angle of the “slashcut” create the effect. Note the angle 








You should still keep your catch can with the exhaust scavenge system. 
No, the check valve only allows air to flow in one direction preventing pressurizing the crank case. It will draw fumes into the exhaust.
don’t need to, it will work.


*Damn, I never thought of this!* 
Rocco, do you use a sealed catch can (meaning, no open filter) - running a line from the crankcase breather to the catchcan and then running another line to the one way valve in the downpipe? I have been looking at trying to eliminate the damn fumes and oily residue on my pretty motor.











_Modified by Dubrunner at 1:08 PM 12-31-2009_


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## billyVR6 (May 8, 2000)

*Re: FV-QR (Rocco R16V)*









Interesting to see this run with a full exhaust system in place. There are those who deem this open headers only and I still have a set in my rollaway from years ago; I never got a straight answer and forgot about it. It's a bit odd that the effort is there for the evac yet they still opted for a crush bent exhaust system.


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## MaxwellMoulton (Jul 26, 2006)

*Re: FV-QR (billyVR6)*

Rocco will know more, but ive been told you use a sealed catch can with the top port attached to your crankcase vent, and the side port attached to the downpipe/exhaust.
I had a feeling others were wondering about this method though since its been used on muscle cars and some nascar for years.


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## Rocco R16V (Oct 7, 2008)

*Re: FV-QR (billyVR6)*


_Quote, originally posted by *billyVR6* »_Interesting to see this run with a full exhaust system in place. There are those who deem this open headers only and I still have a set in my rollaway from years ago; I never got a straight answer and forgot about it. It's a bit odd that the effort is there for the evac yet they still opted for a crush bent exhaust system.









Just a photo I grabbed off the net, crush tube








Don’t need open headers, but if your muffler is too restrictive it won’t work well. I’ve heard right after collector is best on N/A. I haven’t done it on a turbo, worked great on my truck. 

_Quote, originally posted by *Dubrunner* »_
*Damn, I never thought of this!* 
Rocco, do you use a sealed catch can (meaning, no open filter) - running a line from the crankcase breather to the catchcan and then running another line to the one way valve in the downpipe? I have been looking at trying to eliminate the damn fumes and oily residue on my pretty motor.








_Modified by Dubrunner at 1:08 PM 12-31-2009_


_Quote, originally posted by *MaxwellMoulton* »_Rocco will know more, but ive been told you use a sealed catch can with the top port attached to your crankcase vent, and the side port attached to the downpipe/exhaust. 

Yes sealed, the cc goes to the catch can which separates the oil from the fumes and the catch can vent (was a filter) is routed to the exhaust system, this helps draw a vacuum in the cc for better ring sealing and provides a place to dump the blow by that happens at wot without making a mess.
Usually the side vent is the inlet, this spins the air to remove oil and the top is the outlet. 
If your motor is worn out and there is too much blow by, this will not fix it, the catch can, will fill up too fast and you’ll have a smoke screen exhaust. 
http://****************.com/smile/emgift.gif 

_Modified by Rocco R16V at 4:37 PM 12-31-2009_


_Modified by Rocco R16V at 2:00 AM 1-1-2010_


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## MaxwellMoulton (Jul 26, 2006)

*Re: FV-QR (Rocco R16V)*

For all who care, i have ordered the necessary parts, and will be performing this evacuation method on my vrt within two weeks and will post results. I will not do a dyno test anytime soon, but i will test the vacuum produced by this method and let you know how it works out.
max.


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## EL DRIFTO (Jul 11, 2004)

*Re: FV-QR (Rocco R16V)*


_Quote, originally posted by *Rocco R16V* »_
sealed, this helps draw a vacuum in the cc for better ring sealing 
http://****************.com/smile/emgift.gif 



never seen this
great idea http://****************.com/smile/emthup.gif


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## Rocco R16V (Oct 7, 2008)

*Re: FV-QR (EL DRIFTO)*


_Quote, originally posted by *EL DRIFTO* »_
never seen this
great idea http://****************.com/smile/emthup.gif 

the exhaust check valve probably wont have enough flow to actually create a vacuum but it will have less pressure.
People who build high $, big boost motors will run a vacuum pump driven by a belt off the crank to create a real vacuum and help ring sealing.


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## EL DRIFTO (Jul 11, 2004)

*Re: FV-QR (Rocco R16V)*


_Quote, originally posted by *Rocco R16V* »_
the exhaust check valve probably wont have enough flow to actually create a vacuum but it will have less pressure.
People who build high $, big boost motors will run a vacuum pump driven by a belt off the crank to create a real vacuum and help ring sealing.










i have seen the vac pump, but have heard horror stories of using an electric pump, oe on taurus or something, & it being too much vac @ idle & destroying the rings instantly
that's why nascar's is crank driven
the whole exaust idea would be proportionate vac http://****************.com/smile/emthup.gif 
pcv plaques up the intake, i wonder if it would plague the exaust somehow


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## billyVR6 (May 8, 2000)

*Re: FV-QR (EL DRIFTO)*


_Quote, originally posted by *Rocco R16V* »_Don’t need open headers, but if your muffler is too restrictive it won’t work well. I’ve heard right after collector is best on N/A. I haven’t done it on a turbo, worked great on my truck.

I had these set up on a larger displacement small block but that car was always open headers. I wanted to try them on a full exhaust system but I couldn't find any real solid information, everything was vague. I thought about this years later with the VR6 but again it was the same deal and I never really bothered.


_Quote, originally posted by *MaxwellMoulton* »_For all who care, i have ordered the necessary parts, and will be performing this evacuation method on my vrt within two weeks and will post results. I will not do a dyno test anytime soon, but i will test the vacuum produced by this method and let you know how it works out.

There is a very long and details topic on Honda-Tech with results posted. It will be interesting to see what kind of vacuum draw you get from your test and how they compare. I still have interest in all of this mainly because it could be effective and it's inexpensive to set up; vacuum pumps/scavenging systems are big bucks.


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## Yareka (Mar 5, 2002)

*Re: FV-QR (billyVR6)*

I've been toying with this idea for the past year after reading a bit on it, have the moroso evac parts just ready to go in. Most of the points have already been hit here, but it seems like there are so many variables in making it work(mufflers/angle/check valve) that you should definitely hook up a vacuum gauge to the system to make sure you dont pressurize the crankcase anywhere through the powerband.


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## groupracer (Apr 15, 2002)

*Re: FV-QR (MaxwellMoulton)*


_Quote, originally posted by *MaxwellMoulton* »_hmm i did not know there was a perfect catch can...

try one of these...
http://www.42draftdesigns.com/....html


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## billyVR6 (May 8, 2000)

*Re: FV-QR (MaxwellMoulton)*


_Quote, originally posted by *MaxwellMoulton* »_For all who care, i have ordered the necessary parts, and will be performing this evacuation method on my vrt within two weeks and will post results. I will not do a dyno test anytime soon, but i will test the vacuum produced by this method and let you know how it works out.

Just checking, did anything happened with this?


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## MaxwellMoulton (Jul 26, 2006)

*Re: FV-QR (billyVR6)*

my local welding guy dicked me around for a month so he still has the parts...this weekend im going to give him a call and probably bring the pipe elsewhere..


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## billyVR6 (May 8, 2000)

*Re: FV-QR (MaxwellMoulton)*

Still interested to see if this went anywhere...


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## MaxwellMoulton (Jul 26, 2006)

*Re: FV-QR (billyVR6)*

hey man..will let you know hopefully this upcoming week.. ive been away at school and havent had a chance to get the pipe back...ill keep you posted.


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## Crispy222 (Mar 10, 2008)

*Re: FV-QR (MaxwellMoulton)*

Subscribed: This is the thread I've been looking for. I want to do this on my 1.8T. I'm working on my second design for a catch can, this time it will be a box. I'm sick of oil vapors in the bay and dripping off my subframe on the driveway. Atleast the subframe won't rust like this, but its full of road grim. I'll post once I get my BT installed and start playing with the exhaust vacuum port.


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## CDJetta (May 11, 2004)

*Re: FV-QR (Crispy222)*

I'm making a VR6 test stand. I could rig this up easily to it but I won't have a full exhaust. Just a partial. Stock headers to stock downpipe to a small amount of exhaust tube to get it to the ground or near.


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## mk1vw (Oct 17, 2007)

not debating the engine driven vacuum pump works, but i wonder how much power it draws at high rpm?


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## CDJetta (May 11, 2004)

*Re: (mk1vw)*

MK3 and I'm sure MK4 TDI's come with vacuum, engine driven systems. The N75 valve even let's you control how much vacuum. It'd be cool to adapt that over.


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## MaxwellMoulton (Jul 26, 2006)

*Re: (CDJetta)*

for those who care, just got the downpipe back from the welder...as long as it still fits, it should be hooked up within a day..ill let you know what kind of vacuum the slash cut creates, it any.


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## MaxwellMoulton (Jul 26, 2006)

*Re: (MaxwellMoulton)*

installed...few tweeks i have to make before i start the engine, but might have results as soon as tomorrow.


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## Crispy222 (Mar 10, 2008)

photos of the piping?


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## Yareka (Mar 5, 2002)

*Re: (Crispy222)*

Glad you kept this going, and photos of the angles and placement would definitely help http://****************.com/smile/emthup.gif


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## turbodub (Jul 6, 2000)

*FV-QR*

from what i have heard using this method with forced induction is a big no no! something about having all the pressure from the turbo pulling the oil in the motor right out of the oil pan.


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## billyVR6 (May 8, 2000)

*Re: FV-QR (turbodub)*


_Quote, originally posted by *Yareka* »_Glad you kept this going, and photos of the angles and placement would definitely help http://****************.com/smile/emthup.gif 

Yareka, most of the basic kits come with the weld-in tube pre-cut for the angle.
(I think that is what is being tested here)

_Quote, originally posted by *turbodub* »_from what i have heard using this method with forced induction is a big no no! something about having all the pressure from the turbo pulling the oil in the motor right out of the oil pan.

Could be, here is the link from HT that I mentioned previously...
http://www.honda-tech.com/showthread.php?t=1199935
This goes above and beyond the basic exhaust slashcut kit. The answer to what you just mentioned might be in here. I honestly don't remember, I read this some time ago and some things that are boost specific didn't get my full attention.


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## MaxwellMoulton (Jul 26, 2006)

*Re: FV-QR (billyVR6)*

cars running well..the results of the slashcut are somewhat negligable. there is a vacuum being created, i can feel it, but to small to be noticed on my gauge (hooked it up to my boost gauge for a little bit, if i get a better gauge i iwll let you know... as for pics, not yet.. plan on doing a video at some point.


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## PeOpLeG60T (Jul 5, 2004)

what rpms ? faster rpm will create more vacc
and you would hardly see psi i guess vacc is hard to get without a pump in an enclosed area , all you need is a flow , it is just fumes you are not trying to suck molasses from the block.
for a better test i would put a breather on the block somewhere and wrap some loose cloth around it , run the car a few days and look if the cloth gets oily dirty . would probably tell you quite easily if the slash cut is working properly no oily residue will tell you the thing is sucking enough to get rid of the fumes


_Modified by PeOpLeG60T at 3:12 AM 3-17-2010_


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## MaxwellMoulton (Jul 26, 2006)

*Re: (PeOpLeG60T)*

vacuum or not, all that nasty sht is going out my tailpipe and not into my engine bay now, so even without vacuum assisted ring sealing im happy.
as for the rpms... i didnt check at higher rpms under load becuase the car is not registered so i can only do 1-2 passes using my fathers assistance with his dealer plate...the car we had following behind said he couldn't notice any black soot coming out of the tail pipe so i don't think the turbo is sucking any oil out of the pan either...plus im using an in-line oil catch as well to lessen the emissions, so if it were sucking up oil that would fill fast and be readily noticeable.


_Modified by MaxwellMoulton at 7:49 PM 3-16-2010_


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## Yareka (Mar 5, 2002)

*Re: (MaxwellMoulton)*

So you dont see any measurable vacuum being pulled on your boost/vacuum gauge even at lower rpms? Doubt this would create enough vacuum to acually pull oil from the pan.


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## PeOpLeG60T (Jul 5, 2004)

maybe at fullthrottle it could be able to suck some liquid but not if the port is not in the oil...
just monitor your oil level to keep your confidence lol


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## GTijoejoe (Oct 6, 2001)

*Re: (Yareka)*

This is pretty interesting.....curious the results.


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## O2VW1.8T (Jul 9, 2003)

*Re: (GTijoejoe)*

I did this a while back and it worked fine. But when i was running E85 i think it ate up the checkvalve head and caused pressure to go in my engine. I blew all the oil out of my valve cover. After that i just dumped it on the ground.


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## PeOpLeG60T (Jul 5, 2004)

E85 ?? , the valve deteriorated ?


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## O2VW1.8T (Jul 9, 2003)

*Re: (PeOpLeG60T)*


_Quote, originally posted by *PeOpLeG60T* »_E85 ?? , the valve deteriorated ?

Thats what i think happened. I never had problems on pump gas i ran it like this for 5-8k miles then when i started using E85 for a couple tanks it failed.


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## 04VDubGLI (May 20, 2005)

O2VW1.8T said:


> _Quote, originally posted by *PeOpLeG60T* »_E85 ?? , the valve deteriorated ?
> 
> Thats what i think happened. I never had problems on pump gas i ran it like this for 5-8k miles then when i started using E85 for a couple tanks it failed.



It's actually because of E85 that I'm trying to research how to get a really solid vac source on the CC. I've heard/read that E85 vapors that get trapped will distill. Makes some sense from what I can figure. 

Anyhow, seems like I've read a fair amount about those check valves failing on the Moroso kits. Does anyone have any alternative check valves? Curious to see if anyone has any more info to add months later as well :thumbup:


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## therealvrt (Jul 21, 2004)

i am doing this on my car with vibrantpowers evac kit and a custom made catchcan fed via 2 -10an lines attached to my modded aluminium vr6 valve cover


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## 04VDubGLI (May 20, 2005)

I run a 1.8t, I just stumbled across this thread... so I'm trying to recall what a VRs pcv looks like from the factory. On the 1.8t there's a vent right on top of the oil filter housing and then the VC. I've been trying to figure out if it makes sense to plumb the one from the OFH to the exhaust venturi and the VC one to catch can/atmo or something? As mentioned I'm planning on going to E85, I just want to make sure I have this setup perfectly. I don't so much care if oil vapor gets burned up in my exhaust - I have a high flow cat anyhow... so hypothetically just plumb straight to exhaust with the provided check valves and it'd work?


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## MKII16v (Oct 23, 1999)

A Challenger with a big block was at my shop with a pair of the Vibrant fittings installed at the end of the headers where it met up with the rest of the exhaust. I pulled the upper hoses off the valve covers. It had enough suction at idle to suck and hold a full piece of paper against the hose.


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## elRey (May 15, 2001)

If I were to do this, I would use an OEM PRV between the exhaust side check valve and can. This is the same 'hockey puck' found on the 1.8T intake TIP boot. It 'regulates' the crankcase pressure/vacuum against the slight vacuum in the TIP during high load.

Also, it's one thing to have vacuum to suck vapor out. It's a totally different thing to have enough flow to evacuate all the fumes. If you're pulling vacuum thru a 3/8" hose, that might not allow enough flow at WOT. my 2 cents.


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