Oil restrictor required?

[R33-East]

I am in the process of installing a pair of GT-SS turbos on my R33 GTR and don't know if I need to install an oil restrictor and if so what size? I have searched and found various answers, basically what I get is that being a ball bearing turbo it requires less oil, and could receive a damaging amount when installed without the proper restrictor. I should also note that I am swapping the stock lines out for steel braided.

I did read that some turbos have a built in restrictor but couldn't find out if this was true for the GT-SS. I have messaged Garrett about this and will post their answer once they get back to me. If anyone has actual experience with this and could give me some helpful information please chime in!

[bobbo]

A restrictor is required if your converting from a bushing type turbo (oem r32 and "I think" R33 turbos) to a ball bearing turbo (anything worth buying).
Hope that helps a bit.

[R33-East]

Yes that seems to be what I am coming up with. It's just a matter of selecting the right size restrictor then, but I first need to confirm whether or not these turbos have one built in? I will have to keep searching.

[Skym]

From what I understand, smaller turbo's with ballbearing CHRA = smaller oil orifice inside the CHRA thus a smaller oil restrictor is needed. Bigger turbo's with a ballbearing CHRA run a slightly bigger oil restrictor.

Try this turbo supplier, as they mention, sell the different oil feeds with built in oil restrictors based on turbo -

http://www.atpturbo.com/mm5/merchant.mvc?Screen=CTGY&Store_Code=tp&Category_Code=GRT

Just need to match the turbo size, click on selected turbo link and look at the accessories at the bottom of the window (oil feed with built in restrictor).

If have HKS turbo's, HKS sell the correct oil feed / oil restrictor for the turbo (look on HKS website for turbo repair parts or similar).

Best advice if not sure what size oil restrictor to use, is to contact a local turbo rebuilder / expert -

http://www.cherryturbos.com/

[R33-East]

Thanks for the info! Also found this...

Ball Bearing Turbo

An oil restrictor is recommended for optimal performance with ball bearing turbochargers. Oil pressure of 40 - 45 psi at maximum engine speed is recommended to prevent damage to the turbocharger's internals. In order to achieve this pressure, a restrictor with a 0.040" orifice will normally suffice, but you should always verify the oil pressure entering the turbo after the restrictor in insure that the components are functioning properly.
Recommended oil feed is -3AN or -4AN line or hose/tubing with a similar ID. As always, use an oil filter that meets or exceeds the OEM specifications.

[R33-East]

I am getting close, also found this....

Hi Chris,

In reference to our conversation today about the gt3076r restrictor, here is the information from turbodynamics.

The confirmed answer:

No bother at all, this is a question I get asked a lot and there is no simple answer (feel free to paste this on the board if you like).

All Garrett ball bearing turbos feature a 1mm restrictor within the cartridge locking pin. On most applications this is sufficient to restrict the quantity of oil entering the turbo to a level it is happy with. However on some applications this restrictor is not enough and a second restrictor has to be introduced. This is normally introduced through modifying or replacing the adapter between turbo and oil feed line with a new restricted fitting.

40-45psi when warm on idle is normally around the tipping point but this is not true on all vehicles for instance other things such as exhaust backpressure and oil drain pipe play a key factor – you can have high oil pressure but a decent amount of backpressure and all may be ok, likewise you can have low backpressure and low oil pressure but still see some leakage. If an additional restrictor is required then you will notice the car smoking as you drive and there may an unusual amount of oil within the inlet system. If this is true then a secondary restrictor (also with a 1mm hole) should be added to see if this cures the problem (this may take a few miles to show as the leaked oil will need to blow through). I normally recommend people who are unsure to try running without the restrictor but keep an eye on things, the minute smoke starts appearing or the inlets get a bit oily introduce the restrictor. This will normally show on the turbos first outing and a small amount of leakage like this is very unlikely to damage the turbo. The reason we don’t supply these secondary restrictors with all turbos sold is if we did people would fit them regardless meaning they could potentially starve their new turbo of oil (if the secondary restrictor was not required)!

Easy rule – new BB turbo that smokes as driven, try a restrictor. New BB turbo that doesn’t smoke and produces no leakage then no restrictor is required.

Usually the cars that smoke have high pressure oil pumps etc fitted. And Subarus. Subarus always seem to need the restrictors for some reason.

p.s. Garrett most likely put that on their website to cover themselves, every car is different and what works for some doesn’t for others.

Kind Regards

Matt Waterman

Turbo Dynamics Limited
20-21 Somerford Business Park, Wilverley Road, Christchurch, Dorset, BH23 3RU. United Kingdom

[R33-East]

Ok pulled the bolt out of the oil feed line and sure enough the hole was 1mm. These turbos are supposed to be drop in so it makes sense that they come restricted, having bought them used I had my doubts, better safe then sorry! I think an additional restrictor might be required if you had an aftermarket oil pump which would create higher oil pressure.