240Z crank case evacuation system ideas.?

[bjhines]

I installed the crankcase evac kit that Mr gasket offers....there is a Moroso kit for twice the money. They are one way valves mounted on an angle cut tube welded into the header collector. They create vacume by venturi effect from exhaust gasses rushing through the collector pipe.

 

I got 2 of the check valves in the kit...I had to replace the first one mounted 3inches off the pipe after only a few thousand miles....I added thinwall tubing and some flare adaptors to place the check valve up high away from heat....The second valve has lasted for 5000 miles soo far and has no signs of quitting.

 

I am currently using the original "flow control valve" mounted on the left inner fender of my 240Z....this valve is a 2 stage relief valve for crankcase vacume.

 

I have the exhaust evac. tube pulling on the top valve cover vent. The PCV valve is connected as usual to the lower crankcase vent...I added one of the oil separators that came in the evac kit to the lower crankcase vent with a 90degree elbow soo that it sits level and drains back into the crankcase.

I am routing the small nipple on the lower crankcase vent to the "flow control valve" in the stock configuration.

 

The reason I am using the stock vent system is that it provides a vacume relief for the crankcase. It works in 2 stages...first it pulls vacume on the fuel tank...as vacume builds in the tank the second stage opens and draws air from the atmosphere.

 

Soo far I have no problems...except the darn thing pulls too much air....I am afraid It is going to cause fuel pump problems with anything but a brand new pump. I can hear and feel air rush IN the tank when I pull off the gas cap with the engine running at high idle.

 

The system worked fine with my old restrictive muffler....2.5" exhaust and the muffler had a 1.5" restrictor tube buried inside...I recently added a Dynomax "turbo" muffler with no restrictor. Now the crankcase vent system is really pulling a lot of air. In fact the "flow control valve" cannot flow that much air...at full throttle vacume builds slowly until you let off the pedal.

 

Keep in mind that none of this affects the Manifold vacume...only the crankcase side is affected.

I am considering adding a oil separator tank with baffles and a drainback system that combines the various vents and plumbing to one location.

I would like to provide a way to "flow" fresh filtered air through the crankcase while maintaining a slight vacume in the crankcase. The current system pulls on both ends of the block and only allows air from the outside through the highly restrictive "flow control valve" (into the lower crankcase vent).

I would also like to combine manifold and crankcase vacume(with check valves) in a resivoir to aid the brake booster servo...the cam I am using provides very poor vacume at idle...hard brakes can surprise me in slow traffic sometimes. The brake booster only stores enough for 2 or 3 pushes on the pedal. I would like more reserve.

 

Any ideas would be welcome.

[Sam280Z]

I put a crankcase evacuator together from scratch when I built the collector for my Clifford Research headers.

 

It has only been on there for a month. The valve is still good. I will keep an eye on it to make sure that it doesn't fail.

 

I just have it plumbed to the breather on the side of the block and a small K&N breather filter on the valve cover. I just wanted to replace the blowby with fresh air in the crankcase to keep the oil cleaner longer. Previously there was nothing there.

 

Mine is cobbled together. I don't get nearly the amonut of vacuum you are.

 

You might just get an electric vacuum pump from a turbo car or deisel for the brakes. Then use an fixed orafice to control vacuum in the crankcase, like a controlled leak.

 

That way there are seperate systems to fail and not impact each other.

[bjhines]

LOL! This was my first post here! and it comes up again.

 

Here is the original system on the L24 with DCOEs. you can see the top vent tube going down to where the exhaust check valve is located. The copper piping provides manifold vac to the brake booster and allows for venting the block through PCV.

 

 

 

 

I have done the same thing for my V8 powered Zcar. This time using 2 pulse tubes, and better check valves that can take the heat. I do not have the vacuum relief valve in place on this build and the V8 does not have a block breather like the original L24 engine.

 

PCV inline adapter

 

 

recovery canister

 

 

 

Exhaust pulse tube and check valve

 

 

 

...

[Tony D]

Stock flow diverter valve can be removed and a small K&N filter placed on that vapor recovery line (or left on if you want to buy two K&N's...) In it's original configuration it let pressure built up in the tank relieve to the crankcase (gas fumes to be sucked up and burnt at startup-it was a one-way valve, while driving down the road it would revert to the Air Cleaner to allow for vacuum break action on the tank as the fuel level was lowered from driving.

 

Without it, and with properly sealed tank, you can suck the filler neck down FLAT and eventually get no fuel to the engine due to the high vacuum in the tank from loss of fuel through consumption.

 

If crankcase vacuum is applied to the fuel tank, the valve is broken, or hooked up improperly.

[bjhines]

I turns out that the flow control valve and blowby was enough to relieve high vac conditions. The pulse tubes could never generate more than -8"hg vac. They were the high flow rate vac source, beyond 6-8" vac the PCV was the only source capable of drawing higher vac. The PCV is a limited flow high vac source that is easily overcome by blowby before it can draw much more than 10-12"vac on a sealed crankcase. I suppose that without a properly functioning PCV valve, an open manifold source could quickly oil-can the fuel tank.

 

On my SBC, Holley 4150, highest manifold vac is off idle @ 2500RPM = 22"hg vac. I don't think the L24 ever made that much vac.

 

This SBC system is on a well sealed crankcase and breather system. It takes ~60 seconds for the crankcase to equalize to atmosphere from 11" of vac on shutdown.

 

On startup, The vacuum will build slowly(~30 secs) to ~11"hg at idle. Blipping the throttle will build vac to ~8"hg very quickly but it climbs slowly to 11" after that.

 

Driving on the highway gives good vac on all but long full throttle runs, even then, it is better than 2"hg vac.

Edited December 23, 2011 by bjhines

[bjhines]

In my search for info on this I have come across several other potential ways to deal with this problem.

 

Many cars come with a secondary AIR/smog pump. During the 1970s and 1980s these were usually mechanical pumps driven by the accessory belts. It appears that GM and Ford used similar designs that even incorporate the same pulley hubs. I found that the mid 1980s Ford truck smog pumps are $50 rebuilt. These pumps require some oil vapors to operate properly so they are usually plumbed first in the system and then on to a catch can and vent. The CFM depends on pulley speed, and they can pull 16" of vacuum. GZ motorsports offers upgraded pumps for use as crankcase evacuation pumps

 

 

There are a variety of electric pumps available as well. German makes offer the best quality pumps, but there are many GM/Delphi AIR pumps that will work as well. Racetronix offers a neat little wiring set up for these pumps.

[LanceVance]

There are a variety of electric pumps available as well. German makes offer the best quality pumps, but there are many GM/Delphi AIR pumps that will work as well. Racetronix offers a neat little wiring set up for these pumps.

 

I'm not sure of the exact details, or if it work for you but the newer Subaru STI's have an electric pump. Alot of people remove them while upgrading, so you might be able to get one for next to nothing.

[bjhines]

The Subaru pumps do not have an easy to use inlet connection. They appear to have a filter housing around the motor which would need to be modified. In addition the motor on these units appears to be very small.

 

The GM LT1, LT4, and LS1 secondary air pumps have large electric motors and easy to use hose connections.

[johnc]

Bilge blower fan.

 

http://www.hrpworld.com/index.cfm?tpc=Inline-Duct-Marine-Bilge-Blowers&form_prod_id=73&action=product

[z-ya]

From your original post, I guess I don't understand what the problem is. You just want to evacuate crankcase fumes through the engine? And this is your track car, right?

 

Why not just vent the valve cover and block to the atmosphere through a filter? Why evacuate at all?

 

This is what I did:

 

 

I have a drain petcock on the bottom of the can, and a K&N style filter on the top. Both the valve cover and crankcase tie into the can. Have not had any issues whatsoever with this setup.

 

Pete

[bjhines]

I tried vents, I even tied both vents to a catch can with vent on top. It always made a misty oily mess. My valve cover collected a lot of moisture around town. I wanted to positively ventillate the crankcase using whatever method worked best for weight and money spent. Obviously dry sump and racing vac pumps are tried and true but out of my budget. There are a lot of advantages to PCV systems, including longer oil life, cleaner engine, fewer external leaks, better ring seal, even pulling fumes out of the fuel tank if you use the tank vent line.

 

I saw a lot of folks on track dumping oil, smoking in turns and braking zones, etc. I figured this was a common problem, but I was surprised at how little was ever done to solve the problems.

[zbloke]

I run a similar set-up to z-ya on my track Z and as yet have had no issues

 

 

 

[bjhines]

I like the catch can. I assume it has a "road draft" tube that dumps the vapors near the ground like cars of the 1950s. How about moisture buildup around town? My oil fill cap would always have a slimy milky coating on it from moisture buildup.

 

My MLS head gaskets seep oil. I have them on the SBC V8 as well as one on the L24. The sides of the engine would get oily until I got a proper vac pulled on the crankcase. The vent system eliminated the moisture/vapor problems entirely.

[zbloke]

I like the catch can. I assume it has a "road draft" tube that dumps the vapors near the ground like cars of the 1950s. How about moisture buildup around town? My oil fill cap would always have a slimy milky coating on it from moisture buildup.

 

I've not got round to fitting a dump tube to the outlet of the catch can, there is another threaded fitting directly behind the one with the 90 degree elbow on it that is currently open to the elements you can just see the top of it in the second pic, I don't smell any oily/fuely fumes in the car so may just go with a breather type cap/cover for it

 

One thing I'd really like to do though is, get the car on a dyno and pull a vac on the outlet of the catch can......see if running an open vent/non vac system is loosing me any significant HP

 

TBH I've never noticed a milky buildup on the underside of the oil filler cap yet

[blairjj]

BJ,

 

I have been saving this link for years:

 

Turbo Bricks LT-1 Smog pump

 

I can't vouch for the info, but some of the guys seemed to really like the solution.

 

Jay

[bjhines]

I found an LS1 GM smog pump to play with. The pump alone weighs 2.25 lbs.

These things are a lot like 12v shop-vacs. They have an extremely high RPM rotor that moves a whole lot of air. The motor will run free flow for 10 minutes before it even gets warm. The housing gets hot very quickly when airflow is blocked and the motor draws nearly twice the current. I think most of the heat is coming from the impeller not the motor.

 

 

The free flow current draw is ~11A.

 

 

 

 

Restricted flow current draw goes up to almost 20A. Pressure side restriction at 2 psi.

 

 

 

 

The pump pulls the highest vacuum with some small amount of flow at 17A. Vacuum is 4"hg at 17A.

 

 

 

 

It looks like the Turbo guys are using these intermittently; only when boosting above a certain level. The original duty for these things was only for a short time after startup. I would set it up to work only under full throttle for a track car. A microswitch or a vacuum switch would do fine to operate a relay to switch this thing on only when needed. PCV could do the rest at idle and part throttle.

Edited December 29, 2011 by bjhines

[bjhines]

So... The pump pulls excessive current at +4"hg vacuum. I should limit it's operation to below 3" vac or so.

 

1. A 3" vac switch hooked into the crankcase or recovery canister should do the trick. The pump would cut off when crankcase vac approaches 3" and we are good. PCV valve should do the trick at idle and part throttle.

 

2. A 10" vac switch in the intake would cut the pump off whenever the intake vac is greater than 10". This would indirectly control the pump when PCV valve is capable of providing flow. The pump would only turn on when the throttle is mid to WOT.

 

3. A micro switch on the throttle would cut the pump on at mid to WOT. This would ensure that the pump only works when the PCV cannot. This is another indirect approach but it would work.

 

4. A relief valve that would open to atmosphere to allow free airflow for the pump under high crankcase vac conditions. The LS1 A.I.R. system came with a large 5/8" port tee that opens when 10" vac is applied to the diaphragm port. I could indirectly plumb this to intake vacuum to open up the port on the tee when PCV can do the work. This would allow me to run the pump all the time and simply relieve the load on the pump.

 

5. I could combine several switches into a logic controller that could do many things under different conditions.

 

I would like any help finding a vacuum switch for this purpose. Does anyone know what to look up when searching for an automotive Hobbs switch that is not $100 or more?

Edited December 29, 2011 by bjhines