NewFoundPower

I'm having problems with too much oil getting into my intake while on track, specifically on a long left hand high g and high throttle turn. This was at MSR Cresson (big bend) and has happened before, and I thought my catch cans would solve it but they obviously did not.

After this turn I had a long smoke screen coming out the exhaust on the straight, then another puff on the downshift into the following right hand turn. This would happen during each session with the catch cans emptied ahead of time. By the time I got back to my pit, there was so much oil in the intake that it would drip down the tube above the radiator shroud, out through the connection and drip out between the bumper and shroud and leave a sizable spot under the bumper. After getting black flagged and having a dozen people come tell me my car is smoking it gets pretty frustrating.

After researching this it seems common for left hand turns like this in the C5Z, and that the easiest way to definitely stop it is to block off the ports that let oil go back into the intake. My question is how do I do this while still providing a crankcase vent but without getting oil all over my engine bay? My catch cans are not vented, and you can see the leak point and PCV setup in the pics below.

Thanks for any advice.

Kingtal0n

Measure your crankcase pressure and go from there.

If the pressure is higher than 0PSI you have an issue with either a leaking gasket, or the air filter is too free flowing for the power you are making.

Look up Oil droplet experiment.




Pressure and gas density are related to oil droplet velocity (return to pan and wick from parts) and oil droplet radius.
When pressure rises you form large droplets of oil in the crankcase and they have trouble returning to the oil pan.
This in turn forms large oil droplet mist which is pulled into the intake system.

The goal of your performance PCV system is to reduce crankcase pressure to below atmospheric, somewhere between 0.75" Hg to 2.5" Hg is typical for wet sump operation.
Dry sump engines run deeper depressions.

You can measure crankcase pressure using a 1-bar map sensor. Here we did it with a dry sump Z06 engine.





I recommend eliminate the can. Cans and additional lines add friction which will reduce the kinetic energy component of crankcase gasses which causes higher pressure. It is working against your efforts to reduce crankcase pressure. This is why people will catch for more oil in the can than will normally exit the engine without the can.

Once you are able to maintain low crankcase pressure, if the problem persist, the engine has a baffle issue due to forces involved with racing. The Engine's internal separator can either be modified (cut open and modified by drilling holes for oil return, or adding screens and plates) or an additional separator can be added externally. External separators will have a oil return pathway to the oil pan to prevent stagnant oil from collecting in an external reservoir and interacting in the presence of water. You can set the crankcase pressure via monitoring to account for the additional lines and friction. The reason this is a last resort is because it will cost power to drive the kinetic energy of evacuation, therefore always measure and set the crankcase pressure without any external reservoirs first to see if that cures the issue.

Rzepka_r

One "silly" thing to check/understand is how much oil you are running.

I have a 2003 Z06 with a Dewitt's radiator oil cooler and didn't have any issues until the one day I decided to go a full quart above the top hole level, compared to my normal less than that full measured quart.

I ended up with your outcome - oil in my intake and running all through my air filter system AND a little smoke screen at various parts of the track too.

Did a lot of things this winter, one was changing the pan gasket, so I took this photo with a straight edge on the windage tray...



I don't have a good photo of the rod clearance to the windage tray, but in my case the quart extra was crank assembly swinging level and caused the issues.

I backed back down a little with my extra oil, after that day, and didn't have any re-occurring issues.

Thanks,
Rich

smitty2919

Are your can inlets on the top and exit out the side?

If so the can for the valley cover routing looks backwards. Your check valve line is feeding the side of the can.

On your PS VC can the routing is opposite.

I reference this:
https://www.eliteengineeringusa.com/...uctions_CC.pdf

fatbillybob

I like this post but I don't think I understand it. I think the cliff notes are get pressure at the PVC lines to read zero? At idle? Then if not baffle changes? inside the motor? and or external separator.

I have had perfect raced LS6 motors not need catch cans. I have raced new built LS6 from new parts making good power on dyno spit oil to the point I'm black flagged on track oiling the guys behind me. There was no catch can solution for this motor. I finally welded a bung on the dipstick tube and rant the valley line and the valvecover line into a single catchcan and a line out to the intake and a drain line off the can to the dipstick bung. This worked perfectly and I never have to empty a catch can. This method no one talks about is my go to method for these motors running the GM recommended +1 qt of oil for the track.

Kingtal0n

Crankcase pressure is like tire pressure, fuel pressure boost pressure etc... you have to measure it, then set it properly.
If you install a set of tires or a fuel regulator then neglect to set the fuel or tire pressure, bad things happen.

Same with crankcase pressure.

You can review some details here on SupraForums where I discuss PCV measurement and involvement
https://www.supraforums.com/threads/.../post-13980010

The smaller the engine displacement, the more power it makes (power: displacement) the more important PCV becomes in a performance sense.
So 3L Toyota Supra engines for example making 1000rwhp are much more sensitive to crankcase pressure than say a 5 or 7L Engine in theory.
However design also plays a role.

This should help with the concept some more,





For Factory Wet sump engines the published crankcase pressure target is near 0.5" to 1.0" Hg for all engines in the world



For performance engines, the target can be lower, near 3" Hg for wet sump stock style engines. With a vacuum pump the target could be 8" to 12" Hg for some engines.
The vacuum is set to reduce crankcase gas density which will prevent oil droplet forming in PCV gasses. This allows the engine to pull a powerful suction on the crankcase during Wide Open Throttle which prevents oil from being sucked out, this will
1. Keep engine oil clean
2. Prevent deposits which lead to wear and eventual failure
3. Prevent oil leaks
4. Protect piston rings from accumulating sticky carbon deposits which cause them to eventually seize and score the cylinders
5. Extend the life of the engine

Thus PCV is the most important and overlooked aspect of performance engine tuning.

High crankcase pressure is a sign of something wrong. It could be a broken piston, for example. Or a wrongly configured line as somebody suggested. This is why measurement of crankcase pressure is both preventative and informative, crankcase pressure monitoring is a window into the health of an engine's bottom end seals (piston rings and ring function). You can tell by crankcase pressure whether the engine is healthy or not, and it allows us to diagnose issues related to engine health, sealing, oil system, and so forth.

NewFoundPower

Is this a test that can be done in a garage or on the street? This only happens at one track and in one, sometimes two turns, so it will be difficult to duplicate without being there.

NewFoundPower

When on track I generally run about 1/4" above the top hole, which corresponds with about 1/2 qt. I only have this problem at one track so that indicates to me that the problem isn't related to the oil level, or at least that isn't the singular cause. Does that make sense?

Were you having the issue in multiple areas on track? Or more than one track?

NewFoundPower

Yes, inlets on top and outlets on the side. The outside can has valve cover inlet and throttle body outlet. The inside can has valley cover inlet and intake manifold front port outlet, through the PCV valve.

Looking at the top figure on sheet 7 from your link, it looks correct to me. However figure 1 on sheet 2 shows the opposite. Then figure 3 on page 3 again shows the same as sheet 7, can outlet through the PCV valve to the intake manifold.

Does that look the same to you? It looks like 2 of 3 figures show the way I have it routed now.

smitty2919

Ahh, OK I see it now.

Jfryjfry

it could be just me and/or that I’m looking at this on my phone vs a computer but your images are coming up small and low-res and unreadable. I’d like to see what you’re posting so I’ll try my computer later!

I can read one of them and it says that you can have pressure that’s too low in the crankcase. I’m assuming they mean negative pressure (vacuum).

and you mentioned a powerful suction while wide open but full throttle generates the least vacuum.

NewFoundPower

Do you have any pictures of this, or further instructions? Particularly the bung and welding - how did you modify the dipstick tube while maintaining the same length to be sure you measure the correct level?

I'm not a welder so I'd have to take it somewhere capable. What about material compatibility and welding rod material and procedure?

I assume this eliminated the smoking problem too, correct?

Kingtal0n

If pressure goes too low, depending on the engine, around 8" to 12" Hg for most engines, it will wick the engine oil from piston wrist pins and cause friction due to lack of splash lubrication. This is generally only possible when using a vacuum pump. please read the post in supra forums.

At wide open throttle the pressure drop is achieved between the air filter and compressor inlet or throttle valve. You can have as much vacuum as you want at WOT with enough air filtering.

Here is a video of my measuring the WOT crankcase pressure on my 5.3L Turbo free scrapyard 600rwhp demonstration vehicle

Kingtal0n

Some more searches for other people who do this for decades

Here somebody has a gauge for theirs, and a electric vacuum pump to provide the kinetic energy for evacuation
https://www.evolutionm.net/forums/ev...l#post11930508


Here somebody explains how they used a gauge and where they set the pressure to in the 30 years ago
https://www.evoxforums.com/threads/m...6/post-1527554

Its not a new thing. Only a lost art.

ImprovedRacing

Are both of your catch cans full when you start getting oil in your intake / smoking?
​

NewFoundPower

Only the one from the valve cover. The one from the valley cover hardly has any oil in it.

ImprovedRacing

Gotcha, and they are the stock valve covers, right?

So what is happening is basically obvious from the symptoms you described. On long, sweeping turns, the valve covers are filling up with oil (they will hold over 1 quart of oil inside of them when cornering at 1 G). Since you're also at high RPM's, there is little to no intake manifold vacuum in this instance and the crankcase is venting airflow in the opposite direction thank usual, with air flowing from the valve cover to the port just in front of the throttle body.

This is actually a pretty common problem with these engines. It's more common when running an aftermarket valve cover that has no baffling to help keep oil out of the vent port. This problem is very common if you overfill the oil level on the Z06's dry sump system as well.

You may want to make sure your baffles are still there inside the valve cover. You may also very likely be able to resolve the issue simply by routing the lines differently. Currently, you have a single vent line connected to the passenger side valve cover. You could instead try using a tee fitting to pull air from both the driver's side and passenger side valve covers. That way when you're on a hard left corner, and the passenger side valve cover is full of oil, it will pull air from the driver's side valve cover instead, which will not be full of oil. It's going to suck air from wherever you have the least resistance to flow. If you're only sucking air from the valve cover that's full of oil, it has not choice but to suck up a bunch of oil with it. So this should dramatically decrease the amount of going getting sucked into the can. It may not 100% solve the problem, but hopefully it will be good enough to prevent your can from filling up as long as you empty it out between sessions.

I'm not sure how your catch can is designed internally, but it might also help to reverse the lines and connect that top port on your catch can to the throttle body.

This exact problem is also why some newer Gen V small blocks come with a catch can from the factory, on the vent line only. These OEM catch cans have a drain port with a check valve and they drain directly into the oil pan. You could set up something similar by simply adding a drain line to your catch can and running it to your oil pan. Someone else mentioned plumbing it to the dip stick tube, but that doesn't seem very practical. You could simply connect it to the drain plug hole on the oil pan.

A check valve with a very low cracking pressure could be used just to make sure no air (or oil) is sucked up through the oil pan, but if the line is connected below the oil level in the pan, that shouldn't happen anyway. If you do want to add a check valve, our FCV-12 series valves would work great for this. We also have a smaller -6AN size valve coming out in about a month.

If you need a catch can with a drain port you could also check out the can we offer: https://www.improvedracing.com/ccs-h...an-7-oz-1.html

We also have all of the accessories you'd need.

Rockitansky775

Man I have a 2002 Z track car with 383 stroker and have had all kinds of oiling issues. I finally put an improved windage tray and hoping that will help. I got catch cans too. I would look into 2004 valley cover and the later years drivers side valve cover as they both offer better oil control. Seems like some motors, you can only mitigate the oiling issues, like mine, but as long as you make it through a full session, just keep draining cans like me. Oh I do have cans veted to atmosphere via the cans and a water bottle at the ind to catch any oil mist.

Kingtal0n

The higher the crankcase pressure, the more oil blows out of an engine. The more oil is forced into the pcv system, larger oil droplets, more oil in the head.

Breathers force pressure over atmospheric which causes oil leaks, increased blow-by, oil contamination, ring occlusion (oil creep into ring packs leads to stuck rings and worn cylinder), deposits, increased wear and eventual failure.

Never use a breather its the worst thing you can do for an engine.

NewFoundPower

I have an OBDII bluetooth reader that I can use to record data outputs with the Track Addict Pro app. I took the car out last weekend and at WOT the MAP sensor reading (labeled Intake Manifold Pressure) is around 14.7 to 14.94 psi. The intake pressure reading was slightly above the atmospheric pressure reading, which seems strange to me. For example, at one point the readings are:

Barometric Pressure: 14.76 psi
Intake Manifold Pressure: 14.93 psi
Pressure Altitude: -119 ft
Engine Speed: 1441 rpm
Throttle Position: 99.98%
Intake Air Temp: 89.6 F
Calculated Load: 19.49%
Accelerator Pedal: 145.455%

This was taken at low speed in 4th since I didn't have a lot of room to go very fast, I assume the main variable needed to be WOT to get the data in that condition. Is that correct? Does this data tell you anything? The load and pedal numbers seem weird too.