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TECHNICAL ISSUES => Renault 5 GT Turbo => Topic started by: DeanGT5 on 18:54, Fri 02 December 2011

Title: Oil restrictor needed for T28?
Post by: DeanGT5 on 18:54, Fri 02 December 2011
Does anyone run a 1/16 oil restrictor or similar for there turbo? reason I ask is I had my engine rebuilt and thought the turbo was ok. I ran the engine in for 300 miles with no boost (didnt go over 3k anyway) until one day on tickover the turbo started smoking. I had the turbo rebuilt and fitted it. primed the turbo prior to start up, fired the car up and within minutes I had plumes of smoke from the exhaust. Took the turbo off and the exhaust housing was covered in oil (also a little behind the comp wheel) .

Ive had the turbo stripped again, checked cleaned and rebuilt and all is good. Im thinking that the engine is pushing to much oil through the turbo causing the leaks. I fitted a oil pressure gauge and once warm it reads 60psi on tickover and 80psi when you rev it.

All oil breather and drain pipes have been cleaned out, there was a bit of gunk in the oil breather filter.
Title: Re: Oil restrictor needed for T28?
Post by: DeanGT5 on 13:02, Sat 03 December 2011
Anyone?
Title: Re: Oil restrictor needed for T28?
Post by: Ash-Lee on 14:39, Sat 03 December 2011
I'm not entirely sure but wouldn't an restriction in the oil supply actually increase the pressure?

What temperature does your oil reach? A quick mental arithmetic shows you have about 4-5BAR worth of pressure when the oil is hot, is that at idle?
Title: Re: Oil restrictor needed for T28?
Post by: DeanGT5 on 15:53, Sat 03 December 2011
Ive done a bit of searching on the net and its not so much the pressure its the volume. Reducing the inlet lets the flow drain from the turbo a bit like when you fill the sink it takes time to empty (Andy b) analigy lol
Title: Re: Oil restrictor needed for T28?
Post by: markey mark (bd) on 09:52, Sun 04 December 2011
Just looking your oil pressure is little high mate, has it always been like that or have you never measured it before? I don't think ever did anything to the oil pump, strange for an oil pump to produce too much pressure.

Did you refit the one way valve you removed? Worth trying that and seeing what pressure is like again
Title: Re: Oil restrictor needed for T28?
Post by: DeanGT5 on 15:24, Sun 04 December 2011
Mark - It did read high with the old engine spec but that was on the original gauge. Yes thats with two inline as I have the T2 bolted on at the mo and the pipes a little short. I remember James said he had packed the pump.

It did drop to 40psi when the fan kicked in but I thought that was just Renault electrics  :lol:
Title: Re: Oil restrictor needed for T28?
Post by: fishead on 15:55, Sun 04 December 2011
did it jus start smokin by itself, i mean is there any story there at all ? like i fitted x y or z or i changed the oil or anything ?

was it 1st start of the day, jus back from a journey ?
Title: Re: Oil restrictor needed for T28?
Post by: DeanGT5 on 16:52, Sun 04 December 2011
I blew my engine a while back, had it rebuilt and thought the turbo was ok. I ran the engine in with no boost and didnt take it over 3k so it wouldnt of kicked in anyway. The turbo seemed fine for 200mile until I started the car back up after doing about 3 miles where it just started smoking on idle. Had the turbo to bits and the shaft was scored. Had the shaft polished and check and the turbo rebuilt. fitted it, started the car up and within minutes it was smoking.
Title: Re: Oil restrictor needed for T28?
Post by: danielmk323 on 20:32, Sun 04 December 2011
Quote from: "Ash-Lee"
I'm not entirely sure but wouldn't an restriction in the oil supply actually increase the pressure?

What temperature does your oil reach? A quick mental arithmetic shows you have about 4-5BAR worth of pressure when the oil is hot, is that at idle?
but is int 4-5 bar to many on idle and hot oil it should be  like 2 bar maybe a bit more if im not wrong
Title: Re: Oil restrictor needed for T28?
Post by: robx1r on 20:48, Sun 04 December 2011
i've a gt28 r and i dont see any restrictor on it but i can take pictures if you like mate!
Title: Re: Oil restrictor needed for T28?
Post by: DeanGT5 on 08:24, Mon 05 December 2011
If you could mate, it will probably be the connector that goes in the turbo core.

Any thoughts on the oil pressure?
Title: Re: Oil restrictor needed for T28?
Post by: fishead on 20:47, Mon 05 December 2011
so at no point have you changed the oil and filter ?

how much oil is in it ?  [i know you will read this, an yeah i was thinkin of you !]  :D  :D  :D

the turbo has been buillt by someone proper hasnt it, or is it an ebay diy kit ?

off top of my head thats some good oil pressure, i have tried a few things an i dont think im anywhere near that. if i remember i'll have a look in my notes but i recon there maybe something there

i have used restrictors in oil lines, for a journal bearing turbo i dont advise it
Title: Re: Oil restrictor needed for T28?
Post by: fishead on 20:50, Mon 05 December 2011
it is definatly the turbo an not the engine ?
Title: Re: Oil restrictor needed for T28?
Post by: DeanGT5 on 21:40, Mon 05 December 2011
Changed oil and filter when i fitted the turbo (after doing 300 miles on the engine) oil level is correct and turbo was built by my mate who works at Graham Goode racing. I sent the shaft off to Turbo Rebuild who polished, checked and cleaned it before sending it back. Rebuild kit was also from them. Definately to do with the turbo as I have a T2 fitted which seems fine apart from it did start boosting later just before i removed it?

Im wondering if it was a bit of sludge in the breather system as ive clean them out now. I dont really want to bolt it on and pump oil through it again.
Title: Re: Oil restrictor needed for T28?
Post by: fishead on 09:25, Tue 06 December 2011
does sound an odd one for sure.
i did have sorta similar thing once, but mine chucked oil out back all the time regardless of what turbo, it gave me oil pressure readings similar to yours
turned out to be an issue with the oil filter, i now will only use genuine o/e filters.
for the cost recon id be changin oil an filter an recheckin pressures before putting nice shiney turbo back on
Title: Re: Oil restrictor needed for T28?
Post by: DeanGT5 on 11:35, Tue 06 December 2011
Cheers, Ill try a new filter and see what the readings are, I love changing them anyway :lol:

I was wondering if the T2 was so clogged up it wouldnt leak if a 100psi was going through it lol
Title: Re: Oil restrictor needed for T28?
Post by: DeanGT5 on 11:39, Tue 06 December 2011
Found this on a 200sx site,

Turbocharger oil seals will handle just about any amount of oil pressure you can throw at them. Apparently turbochargers have more trouble with air getting into the oil than oil leaking past the seals. I know this goes against what you've heard. Turbo oil seals are mainly designed to keep intake boost pressure and exhaust pressure out of the oil system. They are not designed to keep oil in, they are designed to keep air out. That's not to say that they don't keep oil in, it's just the way the seals are designed. It is much easier for the seals to hold the oil pressure in, so they actually have a much harder problem to deal with, which is keeping the pressurized intake charge or exhaust gases out of the oil system.

We could use an example. Okay, assume you have a typical turbocharger with an oil feed line with no restrictor. This allows 80-120 psi oil pressure inside the bearing assembly and places 80-120 psi pressure on the oil seals. On the other end of the oil seals you have let's say 20 psi of boost pressure, and for fun let's say we have 20 psi or exhaust pressure. This pressure on the other side of the seal makes the net pressure on the seal 20 psi less. So the seals really see 60-100 psi of oil pressure. This is what they were designed to handle and actually make use of the high oil pressure to keep intake and exhaust gases out.

There's a problem with this situation on smaller turbos. Small turbos typically have smaller oil drain outlets. Improper oil drainage is the true cause of compromised turbo oil seals. There usually is no way to drain oil fast enough from a smaller turbo with it's small outlet to keep up with the flow of oil through the turbo. Once the oil in the drain backs up to the bearing the pressure placed on the turbo oil seals usually increases until the oil seals are compromised.

The problem gets even worse with ball bearing turbos (as compared to journal bearing) where the bearing operation introduces much more air into the oil (frothing) than typical journal bearings. This creates a much quicker overload of the oil drain, causing the backup to happen faster.

Have you ever wondered why a larger turbo oil seal could handle higher oil pressure than a smaller one? It doesn't make any sense at all. It's not that the oil seals are weaker in small turbos. It's that the oil drains are smaller.

Have you ever wondered why ball bearing turbos needed restrictors when a journal bearing in the same application wouldn't? It seems to make sense that a ball bearing has tighter tolerances than a journal bearing, so it would need less oil, but why would it need less pressure? And why would more oil (flow) in the feed line be a problem? The reality is that the ball bearing can pass just as much oil as a journal bearing, it just makes it more frothy due to the tighter tolerances and design. It's this highly frothy oil and eventual oil drain back-up that causes the observed problems with aggressively feeding a ball bearing turbo.

Big turbos usually have big oil drains and can run largely unrestricted lines. Small turbos have small oil drains and usually require a restrictor. It is true that this restrictor lowers the oil pressure seen by the turbo oil seals, but the lower pressure is not the solution to the problem, it is the lower associated flow of oil that solves the problem. Too aggressive of a restrictor can actually cause a different problem. You can lower the oil pressure with a restrictor so far that the oil seals can no longer keep the intake or exhaust gases out of the bearing section and bearing failure can occur. This is the real problem the turbo manufacturer has with their seals and more likely the cause of failure in overly restricted feeds (usually blamed on not enough oil/lubrication).

I know this is going to be controversial so if you need anything clarified, don't hesitate to ask.
Title: Re: Oil restrictor needed for T28?
Post by: James5 on 11:27, Sat 10 December 2011
Quote from: "DeanGT5"
Mark - It did read high with the old engine spec but that was on the original gauge. Yes thats with two inline as I have the T2 bolted on at the mo and the pipes a little short. I remember James said he had packed the pump.

It did drop to 40psi when the fan kicked in but I thought that was just Renault electrics  :lol:

Yeah I packed it once with vaseline to assist with getting oil into it after I replaced the pump but i can't remember if the pump I replaced it with had a shim in it as I know the original pump did I am not sure if I swapped the shim over.

With ref a restrictor for the turbo that's really down to what bearing you have in the turbo and our oil pressure.
Title: Re: Oil restrictor needed for T28?
Post by: DeanGT5 on 13:29, Sun 11 December 2011
The turbo has been fitted with a 360 journal bearing, im going to replace the filter (it was a new one but cant remember what make) try the turbo now ive cleared all the breather and see what happens