rflow306

Victor the best way is to run a vacuum pump which is to much work for our cars. Venting out of each valve cover to atmosphere is the second best thing but has its drawbacks. One being a constat oil smell in the engine compartment and sometimes oil residue. The pcv valve only works under vacuum so under boost it is not venting. The reason they use a pcv valve is for emissions and enviromental reasons only so you don't drip oil all over the road. So in summary your way is the best way to go to avoid these drawbacks. One other thing we could try is to go with the old school method which involves a vent from the valve cover to the exhaust to create suction drawback to that would be having to add oil occasionally. I have tried all the above on different FI cars just not on the E yet.

Grumpy666

Be careful here - old school isn't always compatible with newer technologies. Most petroleum-based oils are high in ash content. Oil ash will contaminate the O2 sensor and severely shorten its lifetime. If you use a synthetic oil, you should be OK, since most synthetics have a very low ash content. The best compromise for his setup is probably a check valve between the catch can and intake tract.

vrus

rflow306,

I think I'll install it normally for now and do some "testing" with it to see how it works out.. The check valve is the only thing that was puzzling me.


Grumpy,

That's exactly what I keep getting told. Why do I need a check valve between the catch can and intake tract? What do I buy to accomplish this?

rflow306

Yes you are correct, even with synthetic oil the lifespan of the o2 is shortened. It was not a problem for me because they were way cheaper vehicles. It also came with the price of running torko or c16 quite often. I can only imagine how much the stealer wants for an E55 o2 sensor.

Victor is definitely doing a great service to anyone with a benz. Thanks Vic.

rflow306

Victor if you remove the factory pcv valve then a check valve is a must. If you do it in line after the factory pcv you should be alright. I don't see why you would need two check valves, the factory pcv is a check valve basically. Anyone else have any input on this?.

Grumpy666

Two reasons: you don't want to pressurize the crankcase when you're in boost, and when you are in boost, w/o a check valve, you will bleed off boost into the crankcase - reduced power.

eclou

As long as the "suction" line of the vent is plumbed into the intake tract upstream of the compressor you will not be pushing air back into the crank, and no check valve will be needed. The only situation you might experience back flow back into the crankcase would be if you were to experience a backfire - unlikely to see that unless you start playing with NOS.

Grumpy666

I think you meant to say Torco.

I'm not familiar with C16. Is that a fish-based or vegetable-based oil?

eclou

Only if you plumb somewhere downstream of the compressor and there would be no reason to do that anyway. The only place to plumb the line is upstream of the compressor. Downstream of the compressor is ALWAYS under positive pressure so you would NEVER get any vacuum to scavenge the piston blow by.

I don't believe the E55 has any diverter valve or "blow off valve" to dump excess boost back into the intake tract the way a turbo does, thus upstream of the compressor never gets any blow-off pressure to require a check valve either.

vrus

Thanks guys for all the advice and input!

I really appreciate it.. Catch can has left TX and should be entering Canada tomorrow if I am lucky.. Was hoping to do the install on Saturday..

If it doesnt show up then I will do the install on Monday or Tuesday night.

Pics will follow.

Grumpy666

There are two problems to running the line upstream of the compressor:

1) That area is under positive pressure, and the venturi effect from the air flow is not as effective as the vacuum in the intake tract to pull the fumes through the can/filters and small line. And there is not enough pressure in the crankcase to push it through.

2) You do not want to introduce oil fumes and combustion contaminates into the compressor. I would not rely on the catch can to capture all of them, even with additional filters. The tolerances of the screws to each other and the housing are very tight. I would worry about compressor lifetime.

E55AMG99

Are we missing something here? Didn't Vic already say he was going to put the can in line with the original PCV system? If so, it would seem that no additional work/check valves are necessary nor is there any debate about where to plumb the return. Both above and below the compressor have advantages and disadvantages but I've got to believe that under makes more sense here. Where is it now?

Grumpy666

I doubt that this is true. During normal driving conditions, the intake manifold is under vacuum. Boost is generated when the engine is put into a load condition. This is accomplished by controlling the engagement of the compressor clutch. MB chose to utilize a clutch instead of a bypass valve to avoid the parasitic losses incurred by turning the compressor when the bypass valve is open. Run a vacuum line into the drivers compartment and attach a gauge to it - you'll see.

rflow306

Yes torco thanks. I am sorry I didn't make my self clear I used their leaded race fuels not torco synthetic race oil , which I have heard is very good stuff. The c16 is a race fuel made by VP racing fuels. I mostly used amsoil and royal purple synthetic oil.

Mind you none of these vehicles had catalytic converters but the combination of oil and lead was killer on the O2's, which is what I meant to convey. All I was interested in was making more power ie lots of boost and timing. .

eclou

This is absolutely correct. The engine is still going to be under vacuum in the intake tract when there is no load. But that is not when the crank pressure is going to increase anyway, and therefore that is not when crank ventilation is critical. The blowby occurs under boost, and that is when you need to vent the pressure. By definition when you are under boost there is no more vacuum condition downstream/past the compressor. Period.

By plumbing as if this was a PCV you are following the conventions of a naturally aspirated motor. The motor is the airpump and there is almost always vacuum or neutral/atmospheric pressure in the intake, never positive pressure. On an FI motor the intake tract(downstream from the compressor) goes from a vacuum environment to positive pressure as soon as the compressor builds boost. On our twin screw system that occurs almost off idle. On my 944 turbo the boost won't hit until 2700 rpms or so. Therefore you will build pressure in the crankcase and you won't be able to relieve any of the crankcase pressure until you let off the gas or coast.

That is not a very effective system. Not only will you experience peak pressures in the crankcase, but when the check valves open a huge surge of gas/oil vapor will get regurgitated/surge into the intake. The downside of the upstream plumbing as you mentioned is the possibility of oil film on the vanes/rotors of whatever compressor type you are using, and even more detrimental the film buildup on the intercooler exchanger. But, that's the whole reason to use the catch can.

eclou

A more readily available but dangerous octane booster is toluene which is at any home depot or paint supplier. I will dig up a link for a witches' brew if anyone is interested.

rflow306

Victor you were right from the begining the catch can should be installed before the rubber throttle body hose and will not require a check valve. The factory pcv valve will do the job. I took apart the filter covers for a better view of the hose and it routes to the valve cover. Since the hose is pre-throttle body right after the filters it will not change the factory design. It should however catch unwanted oil. I think we all overthought this one.

vrus

I thought it was too simple so I figured I would ask for input just in case... It's funny because I was in the garage tonight doing the same thing you just did.

I figured it was worth another look just to be sure.

My car is dropping 1ltr of oil every 2,000km so I figure the catch can will prevent alot of that from being injested by the motor now.

Grumpy666

Only if the clutch is engaged. Clutch engagement occurs when the ECU senses a rapid drop in vacuum and the TPS is past a predefined setting. You can be cruising down the road at 55mph, using perhaps 20HP. The engine will be pulling vacuum and the clutch will not be engaged. Now, floor it to pass another car. The ECU will sense the drop in vacuum and the TPS position and then engage the clutch. Now you have boost. No load on the engine - no boost. That's the way it works.

eclou

No argument there, but no load=no boost=no blowby=no crankcase pressure problem. Under those conditions you will have active crank ventilation thru your pcv plumbed into the post compressor intake path, the check valve will open. Now address what happens when the boost builds. See my point?

The other advantage of having a constantly functional active crankcase ventilation is that a vacuum draw in the crankcase can free up HP by reducing internal power loss (the piston is not having to push against positive pressure on the downstroke)and also help reduce blowby by seating the rings. The Escort Cosworth rallye motors (400 hp) pick up about 25 hp from active ventilation. In my old rodding days we used to rig up venturi systems at the tailpipe to vent the crank actively.

vrus

Update...

UPS just delivered the catch can.. WOW! This thing is of even higher quality than I was expecting. It is a true masterpiece in construction. I mean, I know its just a catch can, but now I understand why everyone keeps telling me these things are the best on the market.

I ordered the black anodized version to help blend in to the engine compartment better.

Attention to detail is amazing.. I will post some high detail shots when I get home tonight as well as some install pics.

Grumpy666

Agree except for the no load=no boost=no blowby. Blowby is a fact of life for internal combustion engines, boosted or otherwise. Look at the oil that comes out at change time. The almost-black color and somewhat gritty texture is due to contaminates from blowby.

Before someone runs out and installs a vacuum pump on their engine to gain 25 HP, this needs to be clarified. The HP gain is a little more complex than just sucking air out of the crankcase. While 25HP is achievable, it's only applicable to racing engines. It typically requires a large, fairly expensive pump, since the crankcase actually needs to be in a vacuum state. And it only occurs at excessive RPM levels - well over 6000 RPM. Most crankcase-evacuated engines use narrower piston rings with lighter-than-normal spring tension. The HP gain is mostly from the reduction of drag friction from the piston rings. The evacuation/vacuum is needed to allow the lighter rings to work properly. Without it, they would flutter, which causes sealing problems, power loss, and eventual failure. If I'm not mistaken, I believe most NASCAR teams do this to their engines. And those 750+ HP engines run in the RPM stratosphere - and they do it for hours at a time - simply amazing.

vrus

Here is the pic of the catch can.. I was too tired to install it tonight so I will be doing it early tomorrow morning as well as some additional heat wrapping (I've become a heat wrap freak now).

The main canister is on the left. The wing nut on the bottom is used if you want to hook up a return drip line to the oil pan or some other spot to drain caught oil. It is closed in our case..

The cylinder that is standing with the metal plate that has the holes in it is the piece that screws into the top of the main canister. Below the metal plate with the holes in it is a ball of stainless steel mesh. This helps trap the oil and allows it to drip to the bottom of the canister.

The oil enters from the top, drips through the stainless steel mesh, through the metal plate with the holes in it, and then collects at the bottom of the main canister.

You can't tell from the photos but the quality is amazing. Everything is CNC cut and fits perfectly!

Will take some install photos tomorrow.

BTW, I didn't take pictures, but along with the kit comes all the hardware and enough hose to install it. Everything is in the box.

eclou

Yes, "=no blowby" is an exaggeration. But compared to what happens under >1 bar boost it would be minimal.


Well an easy test power gain/loss would be to run the car on the dyno with the crank ventilation line open to the active vacuum source vs the line clamped shut.

I would venture to guess that the HP gain may be lower on a forced induction car than on a naturally aspirated simply because as you mention the range of rpm is going to be typically higher on the NA motor, where parasitic losses can double as the rpms climb.

Race engines not only have "lighter" rings but much looser tolerances just because of metallurgic expansion with the sustained heat of sustained operations.

I have been puzzled as to why our motors would plumb the vent line back into the compressed side of the intake with a check valve ( I am assuming that the others' observations of the stock system are correct ). I would postulate that it may be that AMG has managed to coat and micro-hone the cylinder walls and run tight enough pistons and rings to make blow-by under boost a trivial matter. One possible test would be to run the motor under load on the dyno with the oil filler cap open and observe how much pressure is coming out. On my 944 turbo 18# of boost would push my oil dipstick right out of the tube until I doubled the size of the crank vent port

rflow306

You could go one step further by trying a GM electric vacuum pump.These are the part numbers GM part # 22062562 bracket part # 25534015. Very easy hook up just to test and relatively cheap. While not as strong as a mechanical pump it will pull up to 7" of vacuum under boost. On a mustang with 20 lbs of boost it was worth about 12 rwhp.

Also on a mechanical pump you can control the spinning of the pump with different pulley diameters. What I mean is you set-up the pump depending on your shift rpm. Like Grumpy mentioned vacuum pumps tend to work better on motors with racing rings which are usually made from tool steel to create a better seal.