Technical PTE oil restrictor before/after

veer90

Captain
Nov 16, 2016
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I did some quick and dirty data comparison after installing a 0.035" oil restrictor on my gen2 PTE 6266 ball bearing turbo. I went with a restrictor because after double checking the drain and PCV setup, the turbo still burned oil with occasional smoke on hard pulls when hitting high rpms. On the dyno it burned 1/2 a quart in 2 hours over 20+ pulls which was very unexpected.

Purpose of these tests was to verify the restrictor wasn't too small - starving the turbo of oil.

Test 1: Spin time after hot shutdown at idle
For this test I let the engine idle for ~30 seconds prior to shutting it off with the oil warm. I love that ball bearing turbos keep spinning for a while after hot shutdown.

RestrictorOil Temp (F)Spin Time (s)
NO22055
NO17243
YES22052
YES21652
YES208~51
YES17241
[TBODY] [/TBODY]
Test 2: Boost response
I compiled some logs where I started a WOT pull in 3rd gear around 3000 rpm, and graphed the rate at which boost built up. Since they were done in different maps the boost target was different. I had to check the response during spool up instead of rpm where target was met.

spool.PNG


w/ restrictor: 0.0299 psi/RPM
No restrictor: 0.0272 psi/RPM (average of 3)

Based on the slopes of each trend line I'd say no difference to a marginal improvement in boost response. Ideally there would be 2 more pulls with the restrictor so I could do an average, like with the "no restrictor" data.

In conclusion: I think it's safe to say a 0.035 restrictor is not starving the turbo. Time will tell if it fixes my oil consumption problem, I have a hunch it will.

Input / thoughts / comments welcome
 

suspenceful

700 HP Club (N54)
Aug 1, 2017
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Doesn't the ball-bearing 6266 already come with a restrictor from Precision? I believe mine has one... not sure of the size.
 

veer90

Captain
Nov 16, 2016
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Doesn't the ball-bearing 6266 already come with a restrictor from Precision? I believe mine has one... not sure of the size.

I emailed precision about running a restrictor and got their blanket reply "we recommend -4AN feed with no restriction, -10AN drain, and that your smoking issue is drain/pcv related". Told them it was a ball bearing turbo. So most likely no.
 
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The Convert

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Jun 4, 2017
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I'm starting to wonder if my Xona doesn't need a smaller restrictor than what it came with due to our higher than normal oil pressure. I sent my turbo back to have it inspected after I blew oil out of my bov, since the only place it could have come from was my high load pcv line, which was bone dry, or the front shaft seal on the turbo. They said everything was in spec. So, curious to see how this goes for you OP.
 

veer90

Captain
Nov 16, 2016
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West Nyack, NY
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e90 335i 6MT
I'm starting to wonder if my Xona doesn't need a smaller restrictor than what it came with due to our higher than normal oil pressure. I sent my turbo back to have it inspected after I blew oil out of my bov, since the only place it could have come from was my high load pcv line, which was bone dry, or the front shaft seal on the turbo. They said everything was in spec. So, curious to see how this goes for you OP.

what size restrictor did the Xona come with?
 

veer90

Captain
Nov 16, 2016
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West Nyack, NY
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e90 335i 6MT
restrictor graph v2.PNG


An update...

Logged some more pulls with the restrictor. Average of the slopes was 0.0251 psi/rpm with restrictor and 0.0264 psi/rpm without. It's worth noting that the numbers with the restrictor are more consistent on paper, but behind the wheel obviously I can't tell a difference.

Car still burns oil on pulls though... 0.5L/1000mi :sweat::sweat::sweat::sweat:
 

noorj

Corporal
Jul 12, 2017
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Good testing veer. I would recommend one thing though; an industry standard turbo response test called a transient tip-in. Start at designated engine speed above the boost pressure threshold/gear with 0% pedal, stomp the pedal and look at the time from the WOT stomp to the time where boost target is reached, or 90% of the steady-state boost pressure value. You can then compare this time much more universally to different calibrations/setups and even vehicles.