bcdavis

I'd like to know what the supercharged folks came up with as their answer to the issue of excessive crankcase pressures, as well as not wanting any oil in their intakes...

What was the plumbing?
Just a tube to a breather?

Z

That's the setup with Tim Murphy's supercharger kit. The current configuration uses a crimped hose assembly instead of the metal tubing pictured above, but is the same otherwise. At full throttle through the RPM range a crankcase pressure of .5psi or less was measured with the above configuration.

PorKen

Z - I can't make out the air/oil separator. What's it from/who makes it?

The electric pump above is not in town, but I found a price of $126.95 + $20 core at my local Carquest (used Cardone number). Just have to wait a week unless I pay for shipping. Hmmm...

Z

It's a non-automotive part that's apparently used in different industrial and agricultural applications. I'm not sure where Tim is getting them from now, but the initial ones were coming from a local agricultural supply store.

You might want to check on a Ford Motorsports crankcase evacuation pump too. Summit lists them at $159.95. The Summit part number for it is FMS-M-9486-A460. I'd think that one of the mechanical pumps like that should be more effective than one of the electric ones that was designed to just provide better vacuum for braking, but I've never experimented with one of the electric ones.

PorKen

After further thought (and a look at my bank balance ) I've decided to make an exhaust evac system first. After I fix my seals I'll consider a pump.

Hopefully the exhaust evac will at least cut down on the oil leakage. With the existing leaks, with higher vacuum, unfiltered air would be pulled in, and the vacuum will be hard to maintain.

Looks to be easy, just some 1/2" plumbing pipe cut with a 45 degree angle, and a cheap air injection one-way valve.

Z

Don't forget about a pretty good air/oil separator of some kind. Without it your first full throttle test drive will be pretty memorable for you and and all of the cars behind you. Keep an eye on the oil level in the crankcase and in any catch can if you have a system using one until you get things working satisfactorily.

John..

Ahh yes, the tasty topic of the 928's nasty crankcase breather system. Even with the Devek baffle installed, the Bastard still gets blow-by. As of today, I have the Devak baffle, and a piece of sheet matal wrapped around 3/4 of the screen in the filler port. My vent tube is routed to an aluminum catch tank with a vent to atmosphere. While this works, I can still smell those nasty fumes at idle. Routing the hose to the intake was a big no-no because of oil induced detonation as well as oiling my new hot wire conversion. I also got tired of looking at what I called my "paper K&N air filter". Routing hoses on the 928 is a royal PITA, there just isn't room to do 1/4 what you want to do. It is a miracle I was able to keep the stock air filter system and install a 3.5" MAF system in the car....tight and trick.

I had considered a seperator like is pictured above, but never pursued it. This setup is similar to what Carl uses on his blown 928s, without the oil seperator. There is some cool seperation equipment out there for industrial use, so that will probably be the route I take as well.

It is amazing to see the actual amount of oil a boosted 928 will blow by the crankcase breather hose on boost. You would swear the bottom end was garbage, but it is and continues to be a nasty issue with the 928. Maybe it stems from the fact that the freakin' crank rotates 2" from the breather port? Ya think? Couple this with some boosted blowby and you have a very efficient oil misting system. They should call it the "928 air oiler system"

This method of dropping oil back in through the cam housing seems to have merit and is probably what I will end up doing long term.

For now, I have the SOB running well and I walk down the aisle the 6th of December, so this will have to wait until next year.

John..

I do have one last trick I might try to eliminate that oil. I have a oil scavenging pump that pulls oil out of the turbos after they drain into a small catch can. That catch can has a breather tube that vents to the air box on top of the engine.

Last week, I noticed that that little nipple fitting to the catch tank has a slight vacuum even at idle, so what I may do is route the breather hoe to its normal position, then pass a hose through the air box and out to this breather hose from the catch can....instant pumping of the breather vapors....I may have to rethink this a bit, but I think it can work. The think I don't think would be good would be returning gasoline vapors back into the crankcase, so I am not totally sold on this idea just yet.

PorKen

I have to put all the emission equipment back on this month for a DEQ trip...

Afterwards I might try making something like this with the air pump output, and see how much vacuum it pulls:


Create suction with compressed airflow.

The combined air and crank gases would exit via the exhaust pipe.

BC

But Porken, Zs point is valid, and it should be heeded - if you do it that way, you will have great vaccum - vac enough to do a james bond type of smoke screen when that vac pulls all the out out of suspension and into your hot exhaust.

GlenL

COOL!

If the crank case is sealed then it shouldn't be too bad.

Z

That's what I initially thought too. It didn't take long at all to find out I was wrong.