mrmees

I'm an MP62 heretic, but I don't think this is directly supercharger related so please know in advance that I wholeheartedly apologize for not going turbo. The supercharger was shiny and I wanted it.

Got everything up and running recently, no major issues. Have been getting idle and VE dialed in, was hoping to go get it tuned later this month. Drove it up into town and back the other day (total 75 miles) and lost enough oil to go from full to empty on the dipstick. Wasn't pushing it at all and rarely got up into boost (maybe 6-7 PSI, system should max at 12). By the time I got home the oil catch can had overflowed. Both valve cover vents are piped to the can can, then VTA. The PCV is still inline, mostly because I'm lazy and didn't want to get another barb.

Did a compression test and leakdown at cold and hot. All tools are Straight From The Freight. Double checked compression tool gauge and leakdown gauge vs compressor gauge, all gauges within 1-2% reading. Leakdown baseline pressure taken @ 90PSI:

Cold

• #1 - 16% loss / 140 PSI compression
• #2 - 13% loss / 130 PSI compression
• #3 - 11% loss / 135 PSI compression
• #4 - 17% loss / 140 PSI compression

Hot

• #1 - 3% loss / 145 PSI compression
• #2 - 7% loss / 135 PSI compression
• #3 - 6% loss / 138 PSI compression
• #4 - 4% loss / 142 PSI compression

During leakdown all cylinders could be heard expelling through the hose to the catch can, thus venting to the valve cover.

I figured the engine was toast, but the numbers don't look that terrible, other than compression being generally low. Did I do something drastically wrong with my venting or is it time to pull the motor?

Edit: Turns out I'm probably dumb for leaving that PCV in. I've got a spare cover so I'm going to drill it out and tap some larger lines to the can. Hopefully that fixes the issue.

curly

iTrader: (25)

I'm confused about the PCV, it's perfectly ok to keep it for boosted engines, you just want to protect it from boost, usually with a check valve (nvm, I re read and see that it's there, but VTA, which is also fine). More than likely all of your leak down losses are through the rings, the low compression confirms that theory. It's a little loose currently, with much worse leak down when cold than when warm. You're loosing a quart in 75 miles, I'd be concerned about that.

What kind of mileage is on the engine? Can you post your tune and a data log of full throttle from as low of RPM as possible to as high of RPM as possible, preferably in the 1:1 gear.

mrmees

From my (newer) understanding, blow-by should be at least moderately expected under boost and a significant driver of the oil loss during blow-by will be the velocity of the air. I was lazy and just tee-d the PCV and breather together with 3/8" hose and ran them to the catch can. Doing this now seems doubly dumb. I restricted the discharge by half (increasing velocity) and since the PCV acts as a restriction (however minimal) most of the air will be going out the breather. From the definitive thread it sounds like that side can already be problematic as far as oil puking. New plan is drill/tap and upsize fitting to 5/8 hose, then mount individual catch cans higher on the back firewall. I think the bigger (plus extra) hose and the upward slope will help to drop a lot of the oil out of the mist and back to the valves.

Around 225k miles. I got it at 165k and it's been solid since then, no unexplained oil loss. Three owners and none have abused it. If it's on the way out I'm fine with it - just trying to figure out if I should keep this engine in the car while I learn enough about engine building to put another one together or find a parted out engine to slap in while I get this one fixed. I attached the tune and the first half of the drive when the overflow occurred (also here)- I've had the MS3PNP in for at least a year but I wouldn't be surprised if I fat fingered something as I've been getting the SC figured out.

Thanks for any help!

Gee Emm

Read up on the 'tiny hole' modification. Bigger hose is not the solution to your problem.

Boost is not the source of blow-by, though it can make matters worse. Worn rings and valve guides are the issue, and only a rebuild is going to fix that. I have just added a 2860 and built my engine - zero coming out of the breather, the secret is the rings and VGs are in top condition.

Fireindc

iTrader: (13)

Personally, i did have some issues with my catch can filling on track with my built bp4w + gt2860 after only a few laps at my local track (CCW). After some reading on this forum, I found that my catch can routing was probably the issue, as I was venting both the PCV and "breather" sides to the can, and on the CCW road course oil was pushing out of the lesser baffled PCV (passanger) side.

I completely eliminated/capped off the PCV side, then enlarged the holes on the drivers side (added/enalrged the tiny holes within the baffles, as well as 2x 10AN hoses off the valve cover, from inside the baffles), and it fixed all my issues. The enlarged holes in the baffles are ugly, I know, but it increased the flow by about 4-5x compared to the single stock tiny hole.





Though OP's issue does sound like blow-by, I thought I'd chime in. I will say that the small diameter of the holes in the stock baffles + the tiny nipple/hose on the stock breather promotes a higher velocity of air if you have some blowby, which will carry more oil to the can. So on a tired engine you might have some luck enlarging the venting on that side to keep air velocity down.