Turbo problem diagnosis

Benzsc1 · #1 01-04-2010, 06:02 AM

Guys as some of you may know I am looking to build a D24T with IC and now have three turbos to ch0osse from two are the AIRresearch Turb's that I asume come as standard on a D24T the other is a Garrett AR48 which I understand is the Turb's of choice used on the later VW LT High Torque engines although that is not 100% as i need to confirm it.

I am wondering how I can check to see if they are any good one of the AIRresearch blowers has play and feels a bit like its catching on what I call aluminium mould!!! The other AIRresearch spins freely and has no play in the shaft the Garrett spins freely but has some play in the shaft TBH I have always worked on N/A cars and even TD's have not been my forte but I need to start somewhere I would even be up for re-building a turbo If i knew what I needed bothparts and toold wise.

Any help would be appreciated

Si

Slimlavud · #2 01-04-2010, 06:38 AM

Quote:

Originally Posted by Benzsc1

Guys as some of you may know I am looking to build a D24T with IC and now have three turbos to ch0osse from two are the AIRresearch Turb's that I asume come as standard on a D24T the other is a Garrett AR48 which I understand is the Turb's of choice used on the later VW LT High Torque engines although that is not 100% as i need to confirm it.

I am wondering how I can check to see if they are any good one of the AIRresearch blowers has play and feels a bit like its catching on what I call aluminium mould!!! The other AIRresearch spins freely and has no play in the shaft the Garrett spins freely but has some play in the shaft TBH I have always worked on N/A cars and even TD's have not been my forte but I need to start somewhere I would even be up for re-building a turbo If i knew what I needed bothparts and toold wise.

Any help would be appreciated

Si

Hi Si
I have stripped and rebuilt a few turbos and there is a lot of dramatic nonsense talked about them by so-called experts, i think.
I have always found a little play even in new turbo shafts - the reason is that they are plain journal bearings - you can't spin a rolling element bearing like a roller or ball bearing very fast. Journal bearings need a little play to allow for oil under pressure - the correct scenario is for the metal shaft to not ever touch the bearing/bushing metal - always be separated by oil under pressure as in a main or big end bearing.
I have found a little extra play in the shaft will not lead to any disasters or oil consumption if the seals are OK, the oil is kept clean and the oil drain is clear. Seals are ceramic or usually Viton - they should be changed as a matter of course - get them from any good bearing supplier. Balancing - I have not ever re-balanced a shaft and have had no problems, but, if even a small particle of metal is missing from a vane or hub or the shaft itself, the balance will be out and it will go bang eventually - if not sooner! Go to a scrapyard and get a worn-out turbo for nothing and strip it to find out more and get some practise. I found many fittings seized solid on old turbos so it can be useful to have oxy-acetylene or other heating gear on hand.
And if you have a good standard d24 turbo spare, I would really like to get hold of it. Mine has lots of play but still runs fine and does not burn oil but it cannot be that long for this world... Cheers, Slim.

Benzsc1 · #3 01-04-2010, 07:18 AM

Hi Slim,

Cheers for the info I will have a spare turbo soon I just need to establish which one I am going to use based on your info I know at least two are OK as I siad this is all fairly new to me as my forte is petrol Mercs which generally are not turbo charged especially the 70's/80's kind I work on!!

I will let you know soon as

Cheers Si

Jason · #4 01-04-2010, 07:38 AM

The only play you really need to watch for is end play, in and out of the shaft. Axial play is normal, as Slim said when oil is pressurized to the turbo, it supports the shaft as it "floats". The Garret may be a nice upgrade, do you know the specs on the compressor side? The stock D24T turbo will push 20lbs of boost easily and with an intercooler you will be in good shape. Some have said the stocker will go 25 but I feel at that point you should be upgrading the turbo if your trying to make that much boost and power.

Jason

Benzsc1 · #5 01-04-2010, 07:53 AM

Hi Jason,

I will have to properly check the specs and type of the Garrett turbo I will also take some pics I had littel time at the weekend so only noted quickly it was a AR48 it seems to have a much smaller hot side than the original and has a circular exhaust outlet but still mates up to the standrad TD exhuast downpipe I did check that. The inlet manifold also has a smaller intake bore than the standard D24 manifold (Bannana)as i call it. buts its notably shorter and sits alot closer to the inlet ports as does the oblong TD manifold your Volvo chaps are used too its actually a very similar shapr but the guy reassured me the parts came out of an LT truck not a Volvo.

Just out of interest why would the Garret be a good upgrade over the AIRresearch? I take it they put the same charger on the Volvo D24T?

Jason · #6 01-04-2010, 08:30 AM

If the turbo has a larger compressor housing it should be able to flow more air, and make more boost at a lower discharge temp. Be aware though that if the exhaust side is too big it will be slow to spool up. The stock D24T .36 A/R hot side spools very quickly and gives great driveability. With the heavy truck your trying to move, the stock turbo may be the way to go. With the intercooler, correct pump mods and fueling, you should be able to get close to double the hp out of the engine with around 20lbs of boost.

Jason