M20 Turbo Oil Drain Advice

[zwill23]

Hey there R3v,

I've been chipping away installing a turbo setup on the car and I have some concerns with the bung tilt for my turbo oil drain.

I had a bung welded on perpendicular to the pan, but I'm realizing I didn't account for the engine tilt. Has anyone had success with a similar drain setup? I was thinking of testing the drain with some clear tubing to verify drainage, maybe the static head will be enough to overcome the tilt and provide proper drainage?

Here are some pics to show what I'm working with:

[varg]

My setup is similar. No issues. My fitting is a little higher up and the fin was ground off in that area so that it would fit between the pan bolts with plenty of clearance.

[zwill23]

My setup is similar. No issues. My fitting is a little higher up and the fin was ground off in that area so that it would fit between the pan bolts with plenty of clearance.

Good to know, I had the bung welded up there based on advice you gave me a while back. Wasn't sure if you angled the bung a bit though to compensate for the tilt.

I think I'll just double check drainage with some clear tubing and run with it, if it becomes an issue I'll pick up another pan and try again.

Thanks!

[TobyB]

The potential issue is if the drain airlocks- there's some air possible in the turbo oil, so if that slows return flow too much, it can
(potentially) block liquid flow. One thing you can do is to channel away the lower edge of the inside hole to provide as low a
'ridge' as possible, and then use a forged, not tube, A-N fitting. All you're trying to do is not create a liquid lock like
a trap in a sink or toilet.

I say 'potential' because Varg's works, and I've seen others done that way too, with no problems.
I suspect it's only a problem with marginally- sized drains, but all the books freeq out about it...

fwiw. I bet it works.

t

[varg]

It's definitely not ideal to have it angled like that but that is how the vast majority of M20 turbo setups are and you don't see people having issues with that it. What it all boils down to with the oil drain where it is in this case is that if the line is big enough and not kinked you won't ever have an issue. The volume of oil flow through an oil cooled journal bearing turbo is really quite small. When flowing through a straight 5/8" line with good angled fitting at the end (not cheap necked down ebay crap) you're nowhere near the flow capacity of the drain line and unless you're experiencing oil froth or something you'll never know the difference between ideal and angled just a bit. When I had mine done I just had John (forcedfirebird) put it where he usually does on turbo M20s, much bigger sample size than one. It's much more important to have a proper drain fitting on the CHRA and a gasket that doesn't protrude into its opening than to worry about whether the drain ends above or below the oil level. If everything is working ok and the fitting in the pan isn't undersized the oil level will be the same inside the line as inside the pan.

The ideal setup is to have it go through the block above the oil level but that's a lot of effort when the standard hole in the pan method works fine.

[zwill23]

The potential issue is if the drain airlocks- there's some air possible in the turbo oil, so if that slows return flow too much, it can
(potentially) block liquid flow. One thing you can do is to channel away the lower edge of the inside hole to provide as low a
'ridge' as possible, and then use a forged, not tube, A-N fitting. All you're trying to do is not create a liquid lock like
a trap in a sink or toilet.

I say 'potential' because Varg's works, and I've seen others done that way too, with no problems.
I suspect it's only a problem with marginally- sized drains, but all the books freeq out about it...

fwiw. I bet it works.

t

It's definitely not ideal to have it angled like that but that is how the vast majority of M20 turbo setups are and you don't see people having issues with that it. What it all boils down to with the oil drain where it is in this case is that if the line is big enough and not kinked you won't ever have an issue. The volume of oil flow through an oil cooled journal bearing turbo is really quite small. When flowing through a straight 5/8" line with good angled fitting at the end (not cheap necked down ebay crap) you're nowhere near the flow capacity of the drain line and unless you're experiencing oil froth or something you'll never know the difference between ideal and angled just a bit. When I had mine done I just had John (forcedfirebird) put it where he usually does on turbo M20s, much bigger sample size than one. It's much more important to have a proper drain fitting on the CHRA and a gasket that doesn't protrude into its opening than to worry about whether the drain ends above or below the oil level. If everything is working ok and the fitting in the pan isn't undersized the oil level will be the same inside the line as inside the pan.

The ideal setup is to have it go through the block above the oil level but that's a lot of effort when the standard hole in the pan method works fine.

Thanks for all the feedback guys, the fitting is -10AN so the drain size should be sufficient. Good to know John sets the drain up similarly at his shop, I won't lose sleep over the fitting angle then.