4722 replies to this topic

[Nev]

I wish I had an oil pressure gauge on the car now, and even better would be to have one on the oil feed line to the turbo (positioned after the restrictor). Really the Garret ball bearing turbos are not meant to see more than about 60 PSI, though Garret are a bit vague on thier website. I have heard that the OEM oil pump can push out over 100 PSI, and thats just on normal engines reving to 6000 RPM, mine goes to 8000 quite regularily with the implication that the oil pressure would be even higher...

Edited by Nev, 24 March 2013 - 10:28 AM.

[Nev]

iirc the z20let and z20leh both have a common oil pump , I have not read an informed opinion that at high rpm this causing a problem, but if putting in a oil restrictor to the turbo feed has no downsides then I will remove factory fit part. But can localized oil temperatures be a factor here.

It's hard to know, but "street" wisdom/convention indicates that many people install restrictors before their Garret ball-bearing turbos on tuned 4 pot cars.

As for the K04 turbo, I never had a problem with mine smoking (using OEM oil lines), so can't advise on that really.

As for oil temps being too high, this seems unlikely to me, as the smoke is developed once the car reaches 72 degrees on idle, so the oil will be well cooled and not even up to full operating temps. I had thought a more likey candidate was poitive crank case pressure, but I (again) put my hand over the cam cover breather today and there was barely any perceptable air movement out of it at all.

Edited by Nev, 24 March 2013 - 10:53 AM.

[cnrandall]

Oil pressure at the turbo can't be higher than from the main gallery and its all controlled by the pressure release valve which will be cracking open from reletively low rpm. Even if you did have high oil pressure it would be dwarfed by the pressure inside the exhaust turbine and you would be seeing a weeping main oil seal first. The restrictor is there to control flow, not pressure as you only want a fine mist of oil over the bb core. If you do flood the core with oil you'll get loads of drag and end up coking up the bearing with burnt oil.

[Thealastair34]

i was told that you needed a restrictorat over 40psi oil pressure which i would think you have?

have you just fit the restrictor? if so go drive it see if it clears the smoke as its said that not having one can cause incorrect damaged turbo diagnosis

[Nev]

I fitted it approx 50 miles ago. Maybe I need to drive it hard for a few hundred and see if it clears, its quite possible that oil/sludge has built up in the exhaust itself, which might take some time to burn off.

[steveboyslim]

Are they hydraulic profiles Steve?

Mechanical (solid lifter).
I also have some hydraulic profiles which idealy need to be used with uprated single springs.

Steve

[Thealastair34]

I fitted it approx 50 miles ago. Maybe I need to drive it hard for a few hundred and see if it clears, its quite possible that oil/sludge has built up in the exhaust itself, which might take some time to burn off.

i would, says on the garrett site that they must be fitted and can cause incorrect diagnosis of turbo failure and having just purchased a Garrett bb core i can tell you its a mistake you dont want to be making with the price they are!

[Nev]

Well, I took the car out for a quick test the other evening, and 2 things became apparent:

1. The new water pump is leaking (or perhaps some hose above it is lose).
2. The engine was smoking like a bastard.

So, the next thing to check in the list was the turbo. I took it off and I think the photo says more than words (shows turbo inlet and the blue inlet pipe that feeds it):



It's pretty clear that the turbo "seals" have gone. Oil has been leaking out of both sides of the CHRA. This is most likely due to running the turbo with too much oil pressure. I have now retro fitted 2 restrictors, but clearly once the problem has started it won't go away.

I have rung my supplier up at CR Turbos and he is sending a despatch chap to collect it so that they can inspect it. I am hoping they can just change the bearing/seals, however I fear I might well have to stump up for a new CHRA which will be in the region of £800.

This is the price of a little mistake when pushing the limits on an engine, caused by (deliberately) omitting the £5 restrictor. Anyone fitting a Garret Ball Bearing Turbo on their Z20LET would be well advised not to make the same mistake as me

Anyway, at least the solution is easy, and I can re-fit it in just 3 hours and get driving before the summer comes and gos. Also I have a sense of relief that the engine internals (piston rings or valve stem seals) weren't to blame.

Edited by Nev, 05 April 2013 - 05:20 PM.

[Thealastair34]

They carnt rebuild them, I had to have a new core I'm afraid Least it's not a engine problem

[completechip]

Nev, if you look carefully at the oil inlet of the turbo, you will see that the turbo is already fitted with a 0.8mm restrictor from factory. I noticed this on my old turbo and in my new turbo as well, and it is a GT3071 Garrett. Maybe yours does not have it. I am going to take pictures so you can see clearly what I am reffering to.

Edited by completechip, 08 April 2013 - 06:42 AM.

[completechip]

This is extracted from the oil inlet of turbo, simply screw a bolt and pull it up together with this piece... http://postimg.org/image/j5h32rnuf/ http://postimg.org/image/yp30ni4sl/ More than this, I've never experienced any troubles with the turbo on the car and have never had fitted such a restrictor in place. Don't know what to say about this...

[cnrandall]

Three words... Crank case pressure

[Nev]

This is extracted from the oil inlet of turbo, simply screw a bolt and pull it up together with this piece...

http://postimg.org/image/j5h32rnuf/
http://postimg.org/image/yp30ni4sl/

More than this, I've never experienced any troubles with the turbo on the car and have never had fitted such a restrictor in place. Don't know what to say about this...

Thank you Alex, I will put a bolt in there tonight and see if the 0.8 mm part exists on my turbo.

If it is already in there, then crank case pressure can be the only other reason for the oil being blown out ...

I'm sending the turbo off to CR Turbos anyway tomorrow and they will check the tollerances on the "seals".

Edited by Nev, 08 April 2013 - 12:10 PM.

[steveboyslim]

Three words... Crank case pressure

Two words to go with your three............bleed valve

Steve

[completechip]

Nev, what is the status of your air filter? If air filter is restrictive, you get same result, oil into compressor housing towards the MAF...

[Nev]

Three words... Crank case pressure

Two words to go with your three............bleed valve

Steve

Maybe. Maybe several things, including C20LET pistons not coping with 500+ BHP. Might even be bore wash due to overfueling.

[Nev]

The turbo guys have rung me. They said 2 things really: 1. Inlet fan was moderately shot blasted due to that terrible HKS air filter that I had for approx 1000 miles. 2. Bearing seals have mild wear (8 thou instead of 2 thou), which is not a great deal but would contribute to the oil leak. I have instructed them to replace both those parts and send it back to me. This leaves me with the almost certainty that gas is passing round the rings on at least one of the cylinders... Thus engine out, inspect + replace pistons or rings likely, possible rehone or even a rebore depending on what we find in there at the time.

Edited by Nev, 11 April 2013 - 03:56 PM.

[siztenboots]

sorry to hear this , but at least a couple of problems have been eliminated

[Nev]

Thanks for the sympathy Steve, however it's not so bad in the grand scheme of things, getting the engine out and stripping it is probably only 6 hours work for me now that I'm so familiar with the car. A rehone and new Omega pistons, new sump gaskets and head gaskets will only be a matter of around £700. If it requires a rebore it's a bit more hassle as the crank has to be dropped out. At the end of the day that amount of money is pretty small for what amounts to having driven an epic car for 8000 odd miles. I've already rung Steve Milton up and he has a set of fully forged pistons in stock and all the gaskets. I could simply drive up there with the block and head and we can install them in just a few hours (assuming it doesn't need a rebore). I think the move to fully forged pistons would be a good idea as the engine is way more powerful than I ever intended it to be and the C20LET ones I currently have only been proven to around 500 BHP as far as I know. The only worry I have is that I strip it and don't find anything visibly/measurably wrong with the pistons/rings/bores. Then I would be left wondering why the turbo would be leaking. I did buy and use a compression tester, however it was so erratic in it's readings I didn't have any faith in it. If I felt like experimenting I could find an old spark plug, drill it out and fit an air line attachment to it. Then with the air feed blasting air into the cylinder it would detect which cylinders and how much they were letting past the rings.

Edited by Nev, 11 April 2013 - 04:37 PM.

[oakmere]

Nev Did you ever do a compression test?