Jump to content
SAU Community

Recommended Posts

When I broke the turbo in my R33 I found pieces of compressor wheel in my intercooler, doesn't take much imagination to guess how it might get to the engine!

yeah the compressor wheel makes sense, just always wondered how the exhust side makes it back inside the engine. but based on the threads in this forum seems to be quite common.

It's because the turbine is spinning at about a bazzillion RPM when it dies. The rotation inertia in any given piece of turbine blade is many many times more than is needed to make it travel backwards against the flow of exhaust gases. A couple of bounces in the collector and you could easily project a piece into cylinders 4, 5 or 6 ....probably more so 4 or 5.

RB26s have even shorter and straighter lines of sight between the turbine housing and their closest cylinders. That's what makes them more prone to copping a bum full when they blow.

so isn't the propeller on the exhaust side spinning the same direction as the flow of exhaust gasses and would just be flung into the dump pipe and is in a seperate housing to the intake (cold) side of the turbo?

or is it because of the design of our particular turbos that broken shrapnel bouncing inside the turbine shell is flicked back into the engine through the intake side of the turbo by the nylon compressor wheel which is sitll intact, thus causing engine damage.

i am just tring to undersatnd the weakness of the turbos in our cars, your explanation definitaly made it easier to understand though, appreciate it.

It's because the turbine is spinning at about a bazzillion RPM when it dies. The rotation inertia in any given piece of turbine blade is many many times more than is needed to make it travel backwards against the flow of exhaust gases. A couple of bounces in the collector and you could easily project a piece into cylinders 4, 5 or 6 ....probably more so 4 or 5.

RB26s have even shorter and straighter lines of sight between the turbine housing and their closest cylinders. That's what makes them more prone to copping a bum full when they blow.

In the specific case of turbos mounted on RB engines (** see note below) the turbine shaft is aligned parallel to the engine. That is to say, the turbo shaft is parallel to the axis of the case, or the crankshaft. The turbine is thus spinning around that axis. Now imagine that the only parts of the car/engine/turbo arrangement that are still present are the turbo shaft, the turbine and the exhaust manifold. We have subtracted the rest of the turbo and engine and car from the picture, so you can see a turbine spinning madly a few inches away from the outlet of the exhaust manifold.

Don't make the mistake of thinking that the exhaust gases flow through the turbine as if the turbine was a desk fan. The turbine is not an axial flow device. The exhaust gases flow into the turbine by entering at the tips of the blades and flowing inwards towards the shaft. It is only once the exhaust gas has started flowing inwards that it can then start to flow out through the exducer, which is parallel to the shaft. The exhaust gases make a kind of 90° direction change in order to follow this path. It's actually a little more complicated than that because the gases first flow around the volute of the housing and they end up flowing inwards through every blade opening at the same time.

If at any time the turbine were to disintegrate then you can imagine that the centrifugal force would send the broken fragments flying directly away from the turbo shaft in all directions. These directions are up, down, left and right, and all angles in between. They travel radially away from the shaft. The outlet of the exhaust manifold is located radially away from the turbo shaft. Now you can imagine the turbine housing back into the picture. The fragments now cannot travel very far away from the shaft because they are trapped in the volute of the turbine housing. They will bounce around. There is one direction, though, where they are fairly free to travel away from the shaft, and that is in the direction straight back out through the inlet to the turbine housing and through the outlet of the exhaust manifold. Some pieces have an opportunity to make that trip direct, or with only a slight bounce. Pieces that flow off in other directions still have the opportunity to bounce a couple of times in the housing and make their exit back through the in door, instead of out through the exducer. All in all, there is a reasonable chance of getting pieces up into the exhaust manifold, and depending on the layout of the manifold (ie the differences between RB26 and RB25) you stand varying chances of getting a bit to go all the way up an exhaust port and into the engine itself.

At no time is there any question of the turbine pieces making it into the engine via a route that includes the compressor housing and the intercooler. If a plastic compressor wheel explodes then the pieces will have to go via the intercooler to make it into the engine and this somewhat reduces the chances of them making it all the way there without getting stuck. That's a whole 'nother problem.

**This is actually true for the majority of engines, even FWD ones. The turbo is usually mounted on the exhaust manifold so that it is pretty much parallel with the engine. Aftermarket installations may or may not include some angle in order to make the dump work better or a variety of other reasons. WRXs and other similar shitheaps may have the turbo in a strange place. But most are effectively the same as the RB standard installation.

Thanks GTSBoy, makes perfect sense when you think about it actually.

I was just confused as i thought the only way it goes into the engine is via the intake, but pieces flicking back inside through the exhaust manifold is quite possible based on your explanation.

Its a pretty bad design i guess (maybe a longer manifold runner could minimise it), as the chances of a turbo failing is quite likely when they get old, even if you dont run extra boost.

But then something as simple as a leaking radiator hose or a snapped auxillary/timing belt are also likely to blow an engine, so this is just an added risk you need to be aware of when buying a turbo car i guess.

In the specific case of turbos mounted on RB engines (** see note below) the turbine shaft is aligned parallel to the engine. That is to say, the turbo shaft is parallel to the axis of the case, or the crankshaft. The turbine is thus spinning around that axis. Now imagine that the only parts of the car/engine/turbo arrangement that are still present are the turbo shaft, the turbine and the exhaust manifold. We have subtracted the rest of the turbo and engine and car from the picture, so you can see a turbine spinning madly a few inches away from the outlet of the exhaust manifold.

Don't make the mistake of thinking that the exhaust gases flow through the turbine as if the turbine was a desk fan. The turbine is not an axial flow device. The exhaust gases flow into the turbine by entering at the tips of the blades and flowing inwards towards the shaft. It is only once the exhaust gas has started flowing inwards that it can then start to flow out through the exducer, which is parallel to the shaft. The exhaust gases make a kind of 90° direction change in order to follow this path. It's actually a little more complicated than that because the gases first flow around the volute of the housing and they end up flowing inwards through every blade opening at the same time.

If at any time the turbine were to disintegrate then you can imagine that the centrifugal force would send the broken fragments flying directly away from the turbo shaft in all directions. These directions are up, down, left and right, and all angles in between. They travel radially away from the shaft. The outlet of the exhaust manifold is located radially away from the turbo shaft. Now you can imagine the turbine housing back into the picture. The fragments now cannot travel very far away from the shaft because they are trapped in the volute of the turbine housing. They will bounce around. There is one direction, though, where they are fairly free to travel away from the shaft, and that is in the direction straight back out through the inlet to the turbine housing and through the outlet of the exhaust manifold. Some pieces have an opportunity to make that trip direct, or with only a slight bounce. Pieces that flow off in other directions still have the opportunity to bounce a couple of times in the housing and make their exit back through the in door, instead of out through the exducer. All in all, there is a reasonable chance of getting pieces up into the exhaust manifold, and depending on the layout of the manifold (ie the differences between RB26 and RB25) you stand varying chances of getting a bit to go all the way up an exhaust port and into the engine itself.

At no time is there any question of the turbine pieces making it into the engine via a route that includes the compressor housing and the intercooler. If a plastic compressor wheel explodes then the pieces will have to go via the intercooler to make it into the engine and this somewhat reduces the chances of them making it all the way there without getting stuck. That's a whole 'nother problem.

**This is actually true for the majority of engines, even FWD ones. The turbo is usually mounted on the exhaust manifold so that it is pretty much parallel with the engine. Aftermarket installations may or may not include some angle in order to make the dump work better or a variety of other reasons. WRXs and other similar shitheaps may have the turbo in a strange place. But most are effectively the same as the RB standard installation.

Edited by Bugzs15

Not a "bad" design, not when you consider the assumptions that Nissan were working under. In Japan most cars only get a short life expectancy on the road. After that they are no longer worth considering because it becomes expensive to keep them on the road. So Japan is far worse (in some ways) than even most other countries and car manufacturers from the point of view of design life of components. Most cars are disposable enough these days (and I really mean from the mid 80s onwards). Jap cars are 10x more disposable, at least from the engineers' point of view. So a turbine that will hold together for much more than long enough at stock boost is not going to cost them (m)any warranties. A few people will wind the boost up and maybe a few will explode that way and get warrantied. That's manageable. As soon as these cars are on a boat to Australia or NZ, they are no longer the problem of the Nissan engineers, so it doesn't matter what sort of foolishness gets done to them.

The fact that the majority of RB20 and RB26 ceramic turbos can live quite a long life at quite a lot more boost than standard says that Nissan didn't do a bad job of over engineering them even with the disposable car mentality.

Not a "bad" design, not when you consider the assumptions that Nissan were working under. In Japan most cars only get a short life expectancy on the road. After that they are no longer worth considering because it becomes expensive to keep them on the road. So Japan is far worse (in some ways) than even most other countries and car manufacturers from the point of view of design life of components. Most cars are disposable enough these days (and I really mean from the mid 80s onwards). Jap cars are 10x more disposable, at least from the engineers' point of view. So a turbine that will hold together for much more than long enough at stock boost is not going to cost them (m)any warranties. A few people will wind the boost up and maybe a few will explode that way and get warrantied. That's manageable. As soon as these cars are on a boat to Australia or NZ, they are no longer the problem of the Nissan engineers, so it doesn't matter what sort of foolishness gets done to them.

That's probably one of the reasons why USA-spec cars (e.g. USDM JZA80 Supra) got steel wheel turbos.

I st my gtt back in nz to 16-17 psi and after 15,000kms it did a turbo bearing and through the exhaust compressor blades into the exhaust pipe drifting on a cold motor :S

replaced it with a r33 turbo and dropped it to 14-15 psi and from what ive heard still going strong

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Hi, is the HKS  Tower Bar still available ? negotiable ? 🤔
    • From there, it is really just test and assemble. Plug the adapter cables from the unit into the back of the screen, then the other side to the car harness. Don't forget all the other plugs too! Run the cables behind the unit and screw it back into place (4 screws) and you should now have 3 cables to run from the top screen to the android unit. I ran them along the DS of the other AV units in the gap between their backets and the console, and used some corrugated tubing on the sharp edges of the bracket so the wires were safe. Plug the centre console and lower screen in temporarily and turn the car to ACC, the AV should fire up as normal. Hold the back button for 3 sec and Android should appear on the top screen. You need to set the input to Aux for audio (more on that later). I put the unit under the AC duct in the centre console, with the wifi antenna on top of the AC duct near the shifter, the bluetooth antenna on the AC duct under the centre console The GPS unit on top of the DS to AC duct; they all seem to work OK there are are out of the way. Neat cable routing is a pain. For the drive recorder I mounted it near the rear view mirror and run the cable in the headlining, across the a pillar and then down the inside of the a pillar seal to the DS lower dash. From there it goes across and to one USB input for the unit. The second USB input is attached to the ECUtec OBD dongle and the 3rd goes to the USB bulkhead connected I added in the centre console. This is how the centre console looks "tidied" up Note I didn't install the provided speaker, didn't use the 2.5mm IPod in line or the piggyback loom for the Ipod or change any DIP switches; they seem to only be required if you need to use the Ipod input rather than the AUX input. That's it, install done, I'll follow up with a separate post on how the unit works, but in summary it retains all factory functions and inputs (so I still use my phone to the car for calls), reverse still works like factory etc.
    • Place the new daughterboard in the case and mount it using the 3 small black rivets provided, and reconnect the 3 factory ribbon cables to the new board Then, use the 3 piggyback cables from the daughterboard into the factory board on top (there are stand offs in the case to keep them apart. and remember to reconnect the antenna and rear cover fan wires. 1 screw to hold the motherboard in place. Before closing the case, make a hole in the sticker covering a hole in the case and run the cable for the android unit into the plug there. The video forgot this step, so did I, so will you probably. Then redo the 4 screws on back, 2 each top and bottom, 3 each side and put the 2 brackets back on.....all ready to go and not that tricky really.      
    • Onto the android unit. You need to remove the top screen because there is a daughterboard to put inside the case. Each side vent pops out from clips; start at the bottom and carefully remove upwards (use a trim remover tool to avoid breaking anything). Then the lower screen and controls come out, 4 screws, a couple of clips (including 3 flimsy ones at the top) and 3 plugs on the rear. Then the upper screen, 4 screws and a bunch of plugs and she is out. From there, remove the mounting brackets (2 screws each), 4 screws on the rear, 2 screws top and bottom and 3 screws holding in the small plates on each side. When you remove the back cover (tight fit), watch out for the power cable for the fan, I removed it so I could put the back aside. The mainboard is held in by 1 screw in the middle, 1 aerial at the top and 3 ribbon cables. If you've ever done any laptop stuff the ribbon cables are OK to work with, just pop up the retainer and they slide out. If you are not familiar just grab a 12 year old from an iphone factory, they will know how it works The case should now look like this:
    • Switching the console was tricky. First there were 6 screws to remove, and also the little adapter loom and its screws had to come out. Also don't forget to remove the 2 screws holding the central locking receiver. Then there are 4 clips on either side....these were very tight in this case and needed careful persuading with a long flat screw driver....some force required but not enough to break them...this was probably the fiddliest part of the whole job. In my case I needed both the wiring loom and the central locking receiver module to swap across to the new one. That was it for the console, so "assembly is the reverse of disassembly"
×
×
  • Create New...