Oil feed restrictor

[Reinhoud]

Gents,

 

I could find anything with the search thingy..

 

Um, rollerbearing crank and ball bearing turbo, I made myself a banjo bolt to connect the oil feed to the turbo, I drilled a 0.8mm hole in it, is that sufficient?

I understand from what I read here on the forum that the restrictors are pretty small with ball bearing turbo's..

 

Thanks.

Edited February 13, 2020 by Reinhoud

[Gixer1460]

Maybe ok but mostly restrictors apply to oil cooled motors where the oil pressure is waaaaay to high! With a GSX / GS you have the opposite problem - not enough OP! As it has roller / open bearings elsewhere, personally I wouldn't bother with a restrictor - 20psi is hardly going to be an issue.

[Arttu]

Yes, I would ask why you want to use a restrictor?

As general rule the turbos are designed to work without any restrictors if the oil pressure is within normal range. And normal pressure means about 2-5 bars as far as I know. So if you are going to use some restrictor you should really know what you are doing. Otherwise you may risk reliability of the turbo. So unless you know that you have unusual high oil pressure or you have noticed oil leak problems I would forget the restrictor.

I have to admit that I often get a bit annoyed when someone asks what size restrictor to use with some turbo without any idea about supply pressure. And usually there are plenty of professionals telling to use size xx or yy without any better knowledge

It's true that there are cases when a restrictor is useful or even necessary. With ball bearing turbos too high oil pressure will increase drag of the bearings and slow down spooling. Additionally you may get oil leaks to compressor or turbine side regardless how good oil return you have. With ball bearing turbos experimenting is also somewhat safer since they aren't too strict about minimum pressure. So if you use too small restrictor the turbo probably won't blow up right away. With journal bearings it's more critical to maintain sufficient pressure.

In real life I have had few cases where it has been useful to limit oil pressure to the turbo. On my air cooled GSX I had a slight unbalance in oil supply system and the turbo got about 6-7 bar pressure. When I enlarged the restrictors to the rest of the engine to get pressure down to 2-3 bar I noticed that turbo was spooling up faster than before. Then on some race bikes that can have even over 10 bar pressure due to high volume pump and harder relief valve it has been necessary to use 0.5-1.0mm restrictors for the turbo to stop smoking.

[Reinhoud]

The reason I ask is because I don't know what is ok.

I know what oil pressure a car has, I also know what oil pressure my bike has, bugger all, if I don't put a restrictor in the feed line I loose the little bit of pressure I have.

I know a ball bearing turbo doesn't need much oil, but what would be the minimum?

That's why this makes it difficult.

 

I had hoped I can lose the oil feed pump I made and connect it to oil gallery behind the cylinders, but may be I should keep it like it was.

[Gixer1460]

7 hours ago, Reinhoud said:

The reason I ask is because I don't know what is ok.

I know what oil pressure a car has, I also know what oil pressure my bike has, bugger all, if I don't put a restrictor in the feed line I lose the little bit of pressure I have.

I know a ball bearing turbo doesn't need much oil, but what would be the minimum?

Cars have an easier time a) they generally don't use roller bearings, b) gearboxes are seperated, c) their oil pumps produce copious pressure and flow. 

Whilst a BB turbo doesn't need much pressure it does require flow through its bearings to take heat away from the bearing cages which tend to be plastic and deform if overheated. In this regard the GSX / GS engines usually have good flow / poor pressure ! I'd concentrate on improving oil pressure to the head with its plain bearings and just feed the turbo what is available. 

[Arttu]

8 hours ago, Reinhoud said:

The reason I ask is because I don't know what is ok.

I know what oil pressure a car has, I also know what oil pressure my bike has, bugger all, if I don't put a restrictor in the feed line I loose the little bit of pressure I have.

I know a ball bearing turbo doesn't need much oil, but what would be the minimum?

At least Garrett specifies minimum 2 bar oil pressure for their ball bearing turbos. I assume others have similar requirements too. But I have understood that this requirement isn't actually for lubrication but to ensure enough cooling for the bearings. So you may get away with lower pressure but naturally there isn't any quarantee.

Oil flow through the turbo should be so low that you don't need to worry about robbing that from the engine. And definitely I wouldn't use any addtional restrictor for turbo when feeding from roller bearing GS/GSX engine.

What I have done with my GSX is adding restrictor(s) on oil channel feeding the crank and head and taking oil to the turbo before the restrictor. This way I can get more pressure to the turbo. Oil pump speed is also increased by GS750 gears so the engine still gets at least as much oil than in stock form. But this should work fine even with stock pump gears. At least if you don't have some extreme cams that need more oil to survive.

[Reinhoud]

Thanks guys, I think I keep the oil pump I made before.

 

I have a bit of a bit of a restrictor to the gearbox bearings, I also have 750 oil pump gears and a main oil pump what is 50% wider.