Quick question: T28 oil restriction

[SHIFT_*grind*]

I know the BB S14/15 T28s need a .03 oil feed restrictor, while non-BB T25/28s need an unrestricted .06 fitting. I'm looking at trading my GTiR T28 (journal bearing) for another member's BB S14 T28. He has stock lines, I have Takas. I thought we could just trade oil inlet fittings, but apparently that's not how S14s are set up.

I just read that the stock banjo bolt (oil line --> block) is the restrictor on S14 motors. This is what he has, I have a blacktop S13 SR. Could we just trade off oil feed banjo bolts, and everything would work fine?

Thanks =D

[oneviaman]

i believe that the stock s13 sr banjo is also a restrictor.

[SHIFT_*grind*]

But wouldn't it be...less restrictive? Since the T25 isn't ball bearing? I.e. S14 banjo bolt = 0.03 restrictor, S13 banjo bolt = 0.06?

[golfer17]

There is no visible restriction on the stock s14 sr banjo bolts for a ball-bearing turbo (I've looked). However, there is a restriction of about the .03-.04 recommended size in the inlet of the s14 t28 (gt2560r-1), so I'm assuming nissan had garrett include the correct restriction in this turbo so they would not have to include it in their oil lines. There is also a restriction of approximately the same size in the bolt-in replacement gt2871r (p/n 472560-15), so I assume that this feature carried over for this turbo as well since it is a direct replacement. However, I would bet the other garrett turbos including the other gt2871r do not have this small of a built-in restriction and thus require the .035 restrictor (you can buy one from atp here
http://www.atpturbo.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=tp&Product_Code=ATP-OIL-036&Category_Code=GTBB). If anyone has any information to the contrary though, I'd love to see it.

So look at the turbo first, it might not need a restrictor (though you can put another one on there anyways if you want to).

also, to clear up any confusion about the reasons why a restrictor is required, here is what garrett says about the need for one

"Does my turbo require an oil restrictor?
Oil requirements depend on the turbo's bearing system type. Garrett has two types of bearing systems; traditional journal bearing; and ball bearing.

The journal bearing system in a turbo functions very similarly to the rod or crank bearings in an engine. These bearings require enough oil pressure to keep the components separated by a hydrodynamic film. If the oil pressure is too low, the metal components will come in contact causing premature wear and ultimately failure. If the oil pressure is too high, leakage may occur from the turbocharger seals. With that as background, an oil restrictor is generally not needed for a journal-bearing turbocharger except for those applications with oil-pressure-induced seal leakage. Remember to address all other potential causes of leakage first (e.g., inadequate/improper oil drain out of the turbocharger, excessive crankcase pressure, turbocharger past its useful service life, etc.) and use a restrictor as a last resort. Garrett distributors can tell you the recommended range of acceptable oil pressures for your particular turbo. Restrictor size will always depend on how much oil pressure your engine is generating-there is no single restrictor size suited for all engines.

Ball-bearing turbochargers can benefit from the addition of an oil restrictor, as most engines deliver more pressure than a ball bearing turbo requires. The benefit is seen in improved boost response due to less windage of oil in the bearing. In addition, lower oil flow further reduces the risk of oil leakage compared to journal-bearing turbochargers. Oil pressure entering a ball-bearing turbocharger needs to be between 40 psi and 45 psi at the maximum engine operating speed. For many common passenger vehicle engines, this generally translates into a restrictor with a minimum of 0.040" diameter orifice upstream of the oil inlet on the turbocharger center section. Again, it is imperative that the restrictor be sized according to the oil pressure characteristics of the engine to which the turbo is attached. Always verify that the appropriate oil pressure is reaching the turbo.

The use of an oil restrictor can (but not always) help ensure that you have the proper oil flow/pressure entering the turbocharger, as well as extract the maximum performance. "

source: http://www.turbobygarrett.com/turbobygarrett/tech_center/faqs.html

[SHIFT_*grind*]

Interesting...does anyone know for sure if the S13 and S14 banjo bolts on the oil feed are different?

[Def]

S13 banjo bolts definitely have a restriction built into them. 0.060" is fine for a BB CHRA even if it is a bit over Garrett's recommended orifice diameter.

Honestly, I wonder if they've done an instrumented test on their 0.030" claim. That will SEVERELY drop the pressure going to the CHRA, such that I doubt it ever gets anywhere remotely close to their maximum seal pressure of 20-25 psi. Maybe the operating range is lower, which would make sense, but in my "day job" I've seen lots of engineers just do a quick little CFD on their desktop and it's about as close as trying to piss 30 ft into the wind.

[golfer17]

S13 banjo bolts definitely have a restriction built into them. 0.060" is fine for a BB CHRA even if it is a bit over Garrett's recommended orifice diameter.

Honestly, I wonder if they've done an instrumented test on their 0.030" claim. That will SEVERELY drop the pressure going to the CHRA, such that I doubt it ever gets anywhere remotely close to their maximum seal pressure of 20-25 psi. Maybe the operating range is lower, which would make sense, but in my "day job" I've seen lots of engineers just do a quick little CFD on their desktop and it's about as close as trying to piss 30 ft into the wind.

lol, I think I know exactly what you're talking about (hell, I do the same thing sometimes myself with the little CosmosExpress add-in for FEA in SolidWorks).