ORIGINAL: myring
Hi Xairflyer,
There are a lot of things I can learn from your post even though I stripped my jj1200 many times. Rocking method would be useful to me because the turbine will be changed soon.
Installation of NGV is very difficult to me. On the one hand the position of NGV determines the position of the case which shall align with all screw holes and glow plug collar on the CC, on the other hand, fitting the NGV onto the end of the tunnel affects concentricity of NGV which is very important. So it seems only one position for the NGV. Up to now, I can not get even gap of turbine blades by stripdown many times.
Sometimes it cooled down the turbine wheel was sticky, but I can't find any problem. I think it may be caused by improper gap of turbine blades.
How good of a fit is your NGV on your tunnel ? how good a fit are your bearings in your tunnel ?
My NGV is very tight on the tunnel.
If you look at it from this point of view,
If your shaft is streight, new bearings, your tunnel machined true and the bearings a nice fit, your Diffuser and NGV all machined true, as is the machining of the compressor and turbine wheel, then it has to run true without any contact.
If the shaft is bent, the tunnel worn, the hole in the diffuser, NGV, compressor or turbine wheel not in the centre, all these things will make it run out of true and make contact with the NGV or Intake.
The outer case does play a big part, as it screws to the NGV and can pull it out of line. causing the turbine wheel to touch.
I would like to see the hole in the NGV with a better locating collar about 10mm long this would keep it true on the tunnel. Other designs are the same as this one so maybe there is a reason why it is not made like that.
If you are happy with your bearing fit in the tunnel and the fit of the tunnel to the diffuser and NGV, I would put it together without the case and get it so it is running freely, if it wont then you have a problem with one of the parts listed.
If it does then the problem is the case (more likely).
Slide on the case and look at how the holes line up with the threads, and the gap between the ngv and the case, is it even ?
If you find that that maybe a hole or two is close to the edge, then this will pull the case one way or the other, enlarge the hole ! drill it out slightly bigger, it is not a problem. The threads were bad on one of my case to front cover holes, so I re threaded the 2.5mm out to 3mm.
If you do find that there is a slight gap between the NGV and case on one side, then if you screw it up to the case it will pull the NGV out of line so your turbine wheel will now rub again.
To fix this you either have to try and reform the flange on the case (not easy) buy another case, or allow it to go further forward on the side of the gap, by slotting/enlarging the holes at the front of the case.
You could also drill/tap new ones, either way you are trying to slightly pull the case inline with the NGV not the other way which causes the binding.
Hope you get what I mean