Turbo health checks
Discussion
This is something new to me so you will have to bear with me.
Ive dismantled a fair bit of my cars engine bay to swap the exhaust manifold, and while it is all off I thought I would check over my turbo. Can anyone tell me what to check and how? Also, some of the intercooler pipes had oil around the silicone joins (on the inside), is this something to worry about, is it a good idea to flush out the intercooler?
Cheers
(for reference it is a Nissan turbo rebuilt with steel internals).
Ive dismantled a fair bit of my cars engine bay to swap the exhaust manifold, and while it is all off I thought I would check over my turbo. Can anyone tell me what to check and how? Also, some of the intercooler pipes had oil around the silicone joins (on the inside), is this something to worry about, is it a good idea to flush out the intercooler?
Cheers
(for reference it is a Nissan turbo rebuilt with steel internals).
It maybe a bit late if you've already reassembled everything, but just check the turbo shaft for any play. If there's any movement it could mean the bearings are starting to fail, which would explain why there's oil inside the intercooler pipes. There's not really much else to check.
aidan8888 said:
This is something new to me so you will have to bear with me.
Ive dismantled a fair bit of my cars engine bay to swap the exhaust manifold, and while it is all off I thought I would check over my turbo. Can anyone tell me what to check and how? Also, some of the intercooler pipes had oil around the silicone joins (on the inside), is this something to worry about, is it a good idea to flush out the intercooler?
Cheers
(for reference it is a Nissan turbo rebuilt with steel internals).
Yes you could flush out the intercooler , oil in the pipe work is often just condesed oil mist from the crankcase breather (quite normal), check the shaft turns freely and there isnt end float or play that allows the blades to touch the housing, you could check the waste gate is free and the actuater works , hope that helps Ive dismantled a fair bit of my cars engine bay to swap the exhaust manifold, and while it is all off I thought I would check over my turbo. Can anyone tell me what to check and how? Also, some of the intercooler pipes had oil around the silicone joins (on the inside), is this something to worry about, is it a good idea to flush out the intercooler?
Cheers
(for reference it is a Nissan turbo rebuilt with steel internals).
Yuxi said:
if there is 1 to 2mm sideways play it is knackered, there should not be any
no, there will always be some play, even with a ball bearing CHRA !!What the turbo type? is it a plain journal bearing type or a BB type?
For plain type, without oil pressure, you can see up to 3mm (diameterically) displacement, whereas a BB turbo much over 1mm is an issue. If there is no sign of compressor wheel to housing clash, i'd probably just leave it alone.
PainTrain said:
Nothing fancy like ball bearings, its a standard Nissan (garett?) turbo with steel internals. However, when I flushed the inter cooler I did get a fair bit of oil in it, so a bit more concerned about the turbo now.
Might be nothing to do with the Turbo. Could be a failing PCV system for example.Yuxi said:
0.3 maybe, not 3.0
Yes up to 3mm.Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
Richyvrlimited said:
Yes up to 3mm.
Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
I dont believe you but am prepared to be proven wrong. How does the oil seal work once the engine is switched off and there is no oil pressure to hold the shaft central at 100,000rpm? To have 1.5mm radial clearance to take up your 3mm I dont think the turbo would work very well either.Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
My crankshaft runs on a film of oil in a bearing with a few thousands of an inch of static clearance, why would a turbo fed from the same oil pump and with the same type of plain bearing need an eigth of an inch static clearance? Remember the bearing in the crank has to maintain an oil film when the rod is putting firing loads through the bearing, a turbo does not see this type of side loading.
Yuxi said:
Richyvrlimited said:
Yes up to 3mm.
Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
I dont believe you but am prepared to be proven wrong. How does the oil seal work once the engine is switched off and there is no oil pressure to hold the shaft central at 100,000rpm? To have 1.5mm radial clearance to take up your 3mm I dont think the turbo would work very well either.Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
My crankshaft runs on a film of oil in a bearing with a few thousands of an inch of static clearance, why would a turbo fed from the same oil pump and with the same type of plain bearing need an eigth of an inch static clearance? Remember the bearing in the crank has to maintain an oil film when the rod is putting firing loads through the bearing, a turbo does not see this type of side loading.
I would find a scrap one and take it apart to help you understand how the bearing allows shaft float and how the seals work
Edited by powerstroke on Saturday 18th June 07:47
Turbo seals are entirely "dynamic". That is, they rely on the shaft to be rotating to provide a "centrifugal" sealing arrangement. (i.e they use piston ring type seals) Luckily, if you have no oil pressure the engine is usually stopped, so very little oil is lost into the intake/exhaust.
The journal bearings use dual bushings to limit the maximum surface velocity and the oil shear (i.e. the rotating shaft is a clearance in another collar, that is a clearance in a bearing tube) The rotating collar spins at approx half shaft revs. Due to this arrangement the dynamics mean that the assy actually "orbits" rather than spins perfectly around it's mass centroid, and it is a bad idea to try to constrain it competely, as the bearing loads will go up massively (rather than just letting it find it's own "centre")
Without oil pressure, this system creates a large amount of play, that is also amplified by the "overhang" of the compressor and turbine wheels (ie. the bit you can touch is further out from the centre of the bearing system, so it will move more)
The thrust system uses a flanged collar and "ramps" to pull a dynamic wedge of oil into the gap between the collar and the thrust faces. (old skool turbo mods used to include 360deg thrusts, which are not used as std on proddy turbo's because they make assy difficult / slower etc).
The thrust system does a lot of work, as the balance of differential pressures within the system act over large areas, and hence try to push the spinning system one way or another.
Modern "high precision" ball bearing units control shaft float to much higher levels, but rely on modern "thin" oils to provide dynamic lubrication at high velocities etc
The journal bearings use dual bushings to limit the maximum surface velocity and the oil shear (i.e. the rotating shaft is a clearance in another collar, that is a clearance in a bearing tube) The rotating collar spins at approx half shaft revs. Due to this arrangement the dynamics mean that the assy actually "orbits" rather than spins perfectly around it's mass centroid, and it is a bad idea to try to constrain it competely, as the bearing loads will go up massively (rather than just letting it find it's own "centre")
Without oil pressure, this system creates a large amount of play, that is also amplified by the "overhang" of the compressor and turbine wheels (ie. the bit you can touch is further out from the centre of the bearing system, so it will move more)
The thrust system uses a flanged collar and "ramps" to pull a dynamic wedge of oil into the gap between the collar and the thrust faces. (old skool turbo mods used to include 360deg thrusts, which are not used as std on proddy turbo's because they make assy difficult / slower etc).
The thrust system does a lot of work, as the balance of differential pressures within the system act over large areas, and hence try to push the spinning system one way or another.
Modern "high precision" ball bearing units control shaft float to much higher levels, but rely on modern "thin" oils to provide dynamic lubrication at high velocities etc
powerstroke said:
Yuxi said:
Richyvrlimited said:
Yes up to 3mm.
Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
I dont believe you but am prepared to be proven wrong. How does the oil seal work once the engine is switched off and there is no oil pressure to hold the shaft central at 100,000rpm? To have 1.5mm radial clearance to take up your 3mm I dont think the turbo would work very well either.Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
My crankshaft runs on a film of oil in a bearing with a few thousands of an inch of static clearance, why would a turbo fed from the same oil pump and with the same type of plain bearing need an eigth of an inch static clearance? Remember the bearing in the crank has to maintain an oil film when the rod is putting firing loads through the bearing, a turbo does not see this type of side loading.
I would find a scrap one and take it apart to help you understand how the bearing allows shaft float and how the seals work
Edited by powerstroke on Saturday 18th June 07:47
3mm!
Richyvrlimited said:
Yes up to 3mm.
Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
That must be some really thick oil you're using there! Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
3mm
AndyS2 said:
Richyvrlimited said:
Yes up to 3mm.
Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
That must be some really thick oil you're using there! Journal bearings use oil to fold the impeller in place as opposed to a BB turbo which uses a Ball Bearing.
With no oil in the journal there's lots of play. As long as there's no impeller to housing interference and no fore/aft play it's normal.
3mm
Ironically, I now need to get a turbo rebuilt. I don't think I can be bothered to DIY it, so can anyone recommend a surrey/northeast hants co. that can rebuild it - or alternatively is it better to go further afield mail order etc?
It's off a Renault 25 V6 turbo (same as alpine GTA also I think). Not aware of anything wrong with it, but the turbo on my current motor is showing signs of wear and I've got a later spec (water cooled bearing housing) spare one in the garage that has sat there for a long while that I'd like to use.
Thanks
M
It's off a Renault 25 V6 turbo (same as alpine GTA also I think). Not aware of anything wrong with it, but the turbo on my current motor is showing signs of wear and I've got a later spec (water cooled bearing housing) spare one in the garage that has sat there for a long while that I'd like to use.
Thanks
M
I don't normally like giving recommendations. If the job goes well you get nothing out of it and if it goes badly you get blamed. However I'd suggest Owen Developments if you want a turbo rebuilt. At least you'll know it's been done properly on state of the art equipment rather than being cleaned up and slapped back together.
http://www.owendevelopments.co.uk/index.asp
http://www.owendevelopments.co.uk/index.asp
Yuxi said:
OK so I looked at some of the engines in our benchmark area today, both competitor engines and engines we have designed for other OEMs or ourselves. Many had turbos, none of them had any more than about 0.3mm total radial play i.e. TIR of 0.3mm None of them had more than about 0.3mm clearance between the compressor fan and the housing. The engines range from ones 20 years old to one that is not yet in production which uses a Borg Warner China turbo.
3mm!
They are almost certainly ball bearing turbos. Plain bearing turbos do have a noticeable amount of radial play even when new, IME 3mm seems entirely possible on a well used turbo, a new one I'd expect to be rather less than this. Axial play should be almost non-existent though.3mm!
Edited by Mr2Mike on Thursday 30th June 13:28
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