TT Oil Feed Check Valve Question?

[911TT33]

Hey guys,

Just want to clarify, the ball bearing for the turbos oil feed “double AN4 banjo” fitting sits at the bottom of the fitting right, underneath the spring? Not at the top where the oil pressure light switch screws into?



What’s the purpose of this ball bearing anyway? Stops oil flowing back down into the motor when the engine is off, so oil is really available to the turbos at next startup?

[911TT33]

Sorry here’s a better picture:



The ball bearing won’t restrict the flow of oil required for the two turbos, right?

[Ollies930]

No, it is designed as a backflow prevention device so that the oil does not drain out of the lines after sitting for a period of time.

[911TT33]

Originally Posted by Ollies930

No, it is designed as a backflow prevention device so that the oil does not drain out of the lines after sitting for a period of time.

Right OK. But it definitely goes in the bottom, right?

[Ollies930]

Absolutely. Oil comes up from the bottom and pushes the ball out of the way when oil pressure present, when pressure is off it falls/pushes down and blocks the flow.

[911TT33]

Originally Posted by Ollies930

Absolutely. Oil comes up from the bottom and pushes the ball out of the way when oil pressure present, when pressure is off it falls/pushes down and blocks the flow.

Excellent! Thanks for confirming 👍🏼

[911TT33]

What type of thread sealant are you guys using on your threaded AN oil feed and oil drain lines?

Would vibrations and heat cycles make them work loose over time?

I’m thinking Loctite 592 High Temp sealant should do the trick?

[kamaro]

Originally Posted by 911TT33

What type of thread sealant are you guys using on your threaded AN oil feed and oil drain lines?

Would vibrations and heat cycles make them work loose over time?

I’m thinking Loctite 592 High Temp sealant should do the trick?

Never use any sealant on any AN type fitting, they just seal as they are and never come lose if you tight them reasonably, I just lube the two mating surfaces a little bit and that's it.

[911TT33]

Originally Posted by kamaro

Never use any sealant on any AN type fitting, they just seal as they are and never come lose if you tight them reasonably, I just lube the two mating surfaces a little bit and that's it.

Cool, thanks 👍🏼

[RarlyL8]

I've got a similar setup for a twin turbo system but will not be using it until I get some data on the oil volume for each turbo with the split banjo.
You're feeding two turbos with the same volume that used to feed one, which doesn't sound like a good idea. The check ball not only prevents back flow but it also restricts pressurized flow. Remove the ball and see what happens; it ain't good. I would measure the oil feed you get from the twin banjo and compare it to the oil spec for your turbos and adjust as needed.

[911TT33]

Originally Posted by RarlyL8

I've got a similar setup for a twin turbo system but will not be using it until I get some data on the oil volume for each turbo with the split banjo.
You're feeding two turbos with the same volume that used to feed one, which doesn't sound like a good idea. The check ball not only prevents back flow but it also restricts pressurized flow. Remove the ball and see what happens; it ain't good. I would measure the oil feed you get from the twin banjo and compare it to the oil spec for your turbos and adjust as needed.

You make a good point. When I consulted Borg & Warner about the 993TT K16 oil feed, they advise 3AN is sufficient for oiling, but I'm running 4AN to be safe.

Should I perhaps use a twin banjo bolt instead, like others have done here, and tap the top of it for the oil pressure light switch?

[RarlyL8]

I'm also using modified K16 993 twin turbos. The plan is to use two banjos as you suggest but I haven't tested the flow with the ball bearing check valve in place. Removing it may still flood the turbos and blow out the seals. I'm using catch cans on the turbos with a common small reservoir and two exit lines, one to the oil pump and one to the engine sump. The common reservoir will be vented to atmosphere. I also have a turbo oil pump that has been modified for use with twin turbos.

[jonesb930]

Im following this thread as I too will be using a pair of K16's (996) and planned to use a double banjo bolt. I am not sure about the 993 K16's but my K16 off the 996 have check valves at the turbos to prevent the oil line from draining. I was thinking of removing the check ball at the banjo to increase flow for the two turbos. I will also be running a custom oil catch system with a Clewett scavenge pump in the OE location.

I would be interested in others experience with oiling a pair of K16's.

Bill

[911TT33]

Hmmmm… I recall speaking to Turbokraft about this a while ago and he said as long as the banjo is 14mm, it’ll work. He advised coming off the Banjo should be a short AN4 line going to a T-piece, then two AN4 lines going to the turbos. I opted for the banjo solution pictured above for simplicity and reducing the need for extra lines and a T piece.

I’ve shot an email across to Borg Warner asking about the oiling requirements for these K16’s. I’ll share what I get back.

BTW, mine are K16s with the updated Mitsubishi 16G compressors and high pressure, 1bar wastegates.

[Ollies930]

Be careful not to overwhelm the factory scavenge pump if you modify the oil flow to the turbos. If there is too much flow (i.e. not enough restriction), you can also drop oil pressure in the system and/or add too much aeration into the oil. Ask me how I know, LOL

[911TT33]

Originally Posted by Ollies930

Be careful not to overwhelm the factory scavenge pump if you modify the oil flow to the turbos. If there is too much flow (i.e. not enough restriction), you can also drop oil pressure in the system and/or add too much aeration into the oil. Ask me how I know, LOL

LOL, thanks for tuning in. My car is actually a turbocharged Carrera (with 930 internals), so it never actually had a turbo scavenge pump. I’m using a TurboWerx electric scavenge pump. 👍🏼

[flightlead404]

Originally Posted by RarlyL8

You're feeding two turbos with the same volume that used to feed one

hang on a sec, are you feeding them with the same volume, or the same pressure?

same pressure at a larger cross section is higher volume.

or am I thinking about wrong?

[Ollies930]

You are correct. And if there is very little restriction (i.e. low pressure) on the turbo side, then the oil feed line becomes the restriction. On a 930 the volume of oil getting pumped through under those conditions, can far exceed the amount of oil the factory scavenge pump can remove even at idle. Easy test is to drain the oil out of the turbo into a bucket and have the scavenge pump pull from the bucket. You will see the oil level rise at an alarming rate at idle and worse when you increase rpm.

[911TT33]

So, if Borg Warner recommends AN3 oil feeds (AN4 also acceptable) for their K16’s then I should be OK using the 14mm double Banjo with the two AN4 lines coming off it, right?

[911TT33]

So, I’ve completed all the oil plumbing and GT3 style TT exhaust for my conversion… finally.

Anyway, when I crank the engine, oil was pissing out from the M14 seal/washer underneath banjo bolt.

I figured it must be a bad crush washer, so I replaced both M14 crush washers for the banjo bolt, and torqued it down to 25Nm.

Next attempt to crank the motor, oil now started pissing out from underneath the M18/M14 crankcase adapter.

Tomorrow I’ll replace the M18 crush washer and see how that goes.

Any ideas if I keep getting oil leaks at this junction?

I’m basically running a TurboKraft oil feed banjo bolt with the spring loaded check valve / ball bearing. I also have a AN4 T fitting off the AN4 banjo, with AN4 oil feed lines to my K16/16G hybrids.

Both turbos were pre-lubed with KLM pre-lube treatment to ensure they’re appropriately lubricated in a new install.

Here’s a pic of the fitting configuration, but now uses the Turbokraft Banjo bolt/check valve:


Couple pics of the new TT exhaust: