[RESOLVED] crank case venting to exhaust

[govproperty]

One of my friends asked me why dsm use breather tanks or catch cans, while Supras run the crackcase vent straight to the exhaust. He thinks that the supra way is far superior. I really didn't know what to tell him since using the exhaust to carry away the fumes sounded like a good idea. I believe some chevys used to do that also. Is a breather system with catch cans any better or worse than running two lines that connect some where after the catalytic converter?

 

[crimsondragon]

I wouldn't want exhaust fumes in my crankcase.

 

[govproperty]

That's a good point, but I guess you could install a couple check valves in there to keep it going one way.

 

[DougR]

The lines running to the Cat is called Air injection, Its used to help thin the noxious gasses exiting the exhaust. A lame attempt to please the EPA, Most early vehicals would do this directly at the exhaust manifold, costing a Ton in manufacturing. so the engineers decided just to dump the fresh air into the cat, reducing costs and materials, which ended up being a catch 22.
Dumping cool air into the cat reduces the cats temps thus reducing its effectiveness at converting bad gaases to good gasses and water vapor (cats need to be Extremly hot to work properly). Its old school and requires a Huge a$$ air pump driven via your accesory belt. for power.
And NO its not superior!.

A working PCV system and properly installed catch can (and a tight ring seal) Is the superior way to vent crank case gasses. Some will go as far as installing a electric vacume pump to put a slight vacume in the crankcase to inshure ring sealing and to positivly evacuate unburt fuel and vaporized oil.
But thats Excessive and is used for ultra high end racing of all types. Not daily driven vehicals.

As far as breather tanks thats for the weekend warrior, who does NOT drive on the street (altho alot of guys do). As this setup allows harmfull gasses to exit the engine to atmosphere, hence Illeagal..
And in my opinion is NOT the best way to vent a crankcase for a Daily driven vehical (This allows dirt and bad sheet to enter the system, Altho very very small amounts, some ppl are alil more anal then others).

Leave your PCV system intact and install a properly built can or bought Catch can.
If anything install larger hoses through out the entire PCV system to increase the flow throughout the system. This is Garunted to clear the crankcase while being street legal and dramaticly reducing the amount of oily sheet in the intake and head reducing carbon buildup and mainting optimum power levels.

As far as venting the crank case directly to the exhaust, This is used by the BIG boys, who are making in excess of 1k HP, Where Street ability and Epa is not a concern. Mainly due to the Extreme compression and or boost they are running, That they cannot control or use the unburnt vapors. Or just simply dont care to, Because they are running sub 6 sec quarters. Aka Top fuel cars etc...

There are Numerous threads here at DsmTuners about this exact topic... Im shure with alil research you will come to the same conclusion as me and 70% of the rest of the guys here. Leave the PCV alone and install a good catch can.

ok, time for another beer.

 

[luv2rallye]

ok, time for another beer.

Wow after all that you deserve one.

 

[govproperty]

I agree you deserve another two or three for all that. You certainly answered my question. I actually just bought a new oem pcv and I am glad I did now. I had been considering doing the 10an to breather thing but your comments about the epa were dead on. Now I'm going to go do some trash talking to the guy that said that supras had a better way. Thanks.

 

[redtsi252]

...I never said supra's way was better...I just said it sounded like it made sense......dont put word in my mouth

 

[dsm-onster]

Being that exhaust gases move at high speeds like intake charge, I fail to see the effective difference in how much is vented when on boost between the setups. I know a supra has a pcv valve, so off boost the system is just like a dsm. The good thing about such an exhaust venting setup is no gunky build up in your intake-- no need for a vent can.

 

[MidShipCivic]

As far as venting the crank case directly to the exhaust, This is used by the BIG boys, who are making in excess of 1k HP, Where Street ability and Epa is not a concern. Mainly due to the Extreme compression and or boost they are running, That they cannot control or use the unburnt vapors. Or just simply dont care to, Because they are running sub 6 sec quarters. Aka Top fuel cars etc...

There are Numerous threads here at DsmTuners about this exact topic... Im shure with alil research you will come to the same conclusion as me and 70% of the rest of the guys here. Leave the PCV alone and install a good catch can.

ok, time for another beer.

Not really it allows you to use lower tension rings and reduce blow by but this setup is known to put oil out on the track/road/w/e in some cases suck all the oil out of your valve cover.


A member has tried all types of setups.

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Exhaust slashcut evacuation
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This is based upon the same Bernoulli effect mentioned before but uses exhaust gasses to draw out crankcase gasses instead.

Their are 2 ways of doing this:

1) Weld a slashcut tube in your waste-gate dump-tube
2) Weld a slashcut tube in your exhaust



In the first test I connected my Dewyer Magnehelic Pressure Gauge to the slashcut in my wastgate to measure the vacuum draw. As expected I only saw maximum vacuum drawn when the wastgate was open after reaching my maximum boost pressure set on my boost controller. The amount of vacuum went up from 0.25psi(0.5") to 0.4(0.8") vacuum. The numbers shown here were very similar to those shown with the Intake slashcut with the exception of being present when the wastgate started to open.


I chose to connect my valve cover breather and top port (oem- not modified plugs) on my block to the waste-gate slashcut tube. Check valves aren't really needed here but you can use one if it make you feel better.


For my second test I welding in a slashcut tube in my downpipe(12" from turbo). At first I had problems melting my high temp tubing with the heat from the downpipe and exhaust so I soldered together some copper pipe to solve this problem. I placed a check valve in-line on the top 6 inches of hose and wrapped it in reflective heat wrap as you can see.



At Idle the Dewyer Magnehelic Pressure Gauge showed 0.1-0.2psi of vacuum. Driving around town was more unpredictable. The gauge would oscillate between positive pressure(when i tested without the check valve) to 0.5 psi (1") to 1.1 psi ((2.2"). It rarely displayed positive pressure but I could find no simple pattern either rpm or load dependent. Typically it would bounce around 0.6psi to 1psi.



Here is a picture of the hose connected to the valve cover port without being tested. You definitely want to run a one way check valve in-line here.

I purchased the check valve for 1 dollar at a local junkyard. You can find the check valve in-line on the brake booster line on any honda.

Another source for a check valves and slashcut tubes(In case you don't feel like cutting your own is Moroso:


Bottom Line


Cost: 20-80 dollars (dependent upon if you have it welded or not)
Performance: Great.
Reliability: Great.
Environment: Poor.

The Official Crankcase Evacuation thread for Turbo Hondas / PCV / Catchcan / - Honda-Tech


There are pumps for 4g63's if you'd like to pay up.

Mitshubishi 4G63T Vacuum Pump Kit Galant, Eclipse, Eagle Talon, Plymouth Laser

 

[govproperty]

...I never said supra's way was better...I just said it sounded like it made sense......dont put word in my mouth

I wasn't trying to throw out any names just find out some info. There was another guy with a first gen supra who brought up the same thing. But he also thought supras were gods gift to man. I had considered this for the dsm since my cat had a fitting for it. I ended up using two check valves and two catch cans with a pcv and connected it back to the intake.

 

[govproperty]

That vacuum pump is expensive but if your at the level where you need something like that I guess $600 is nothing. I do like the slash cut point he mentioned. I may do that to my intake recirculation tube. Also, if this is poor for the environment would it have any adverse effect on the cat like clogging.

 

[MidShipCivic]

Be sure to read the others he mentioned you're wanting to look for '' of vacuum pulled.

 

[dsm-onster]

I'd like to add that an exhaust mounted ventilation system should have the connection oriented after the o2 sensor for the sake of letting unused oxygen into the exhaust stream and scewing the o2 reading.