RETed

What the **** crawled up your ***?
I've tried to be nice about the whole thing, but you seem to have a problem with all my answers.


That's right.
Major force would be radial...but what opposite force would work against the compressor wheel normally turning?
NOTHING.
Unless there was a major failure, there is very little force that prevents the compressor wheel from turning...at rest.
Under boost, the wheel is already turning...so basically you'd need to torque the compressor wheel off the shaft to have it stop and turn the other direction.
This can happen under extreme conditions.

The godamn compressor wheel is in a shape of a cone...roughly.
The airflow flows axially unto the top of the cone and then radially out the base.
The general position of the airflow is necked from the top to the bottom.
THINK ABOUT IT.
If you blow from the compressor OUTLET to the compressor INLET, it's going to push down on the cone.
So what does this force contact?
The fricken thrust bearing...




You do know how an "oil journal bearing" works, right?
There is no contact between the turbo shaft and the oil journal bearing.
The shaft FLOATS on a thin film of oil.
It's NOT the oil journal bearing that suspends the turbo shaft.
It's oil (pressure) that suspends the turbo shaft.
In fact, this oil (pressure) helps damp the vibrations of the turbo shaft.
These oil journal bearings are not designed to support axial forces on the shaft.
This is where the thrust bearing comes in.
This thrust bearing is design to fight axial forces on the shaft.
Take the godamn turbo apart, and it'll be obvious.

No, that pic I posted is not confirmed from compressor surge.
I think I said that it was possible from compressor surge.
Extreme compressor surge CAN crack a thrust bearing like that.


-Ted

HAILERS

I'm fairly sure why Jacobcarmill does not have the sounds that I have. He does not have that hugemongous Greedy front mount intercooler that takes place of the bumper and he does not have all the volume on his outfit that the Greedy has in the intercooler/pipes that I have. I think it's the extra volume of the Greedy that makes mine tinkle/clank when the throttle is closed.

I have another series four turboii. Stock intercooler. With the stock bov in place, I see no fluctuation of the afm voltage on the SAFC when the throttle is shut after boosting. If I unplug the stock bov's vacuum hose, I will see that fluctuation on the safc/afm voltage reading, but not to the extent of the other car that has the Greedy. I hear no afm flap slamming shut/open/shut/open etc.

I decided to not drive the car. I got the Apexi bov and now I've gotta figure a place to put it on the intercooler piping............and install a pipe for the bac. I like my bac.

Oh! About Higgi's air filter. I've a Fluke digital thermometer *K probes* in that very same area where his filter is. I see regular readings of 150 degrees in that area when driving. I know he's gotta be working overtime making a cold air box of some sort. I mean 150 degrees in the compartment......not in the intercooler piping right after the turbo, which is going to be a lot hotter.

White_FC

...What the **** crawled up _your_ **** buddy, I was simply pointing out I never said that and since you were replying to my post with that comment I felt I should point that out..

You have a problem with my answers aswell, whats the big deal, it's called a discussion.

Having fairly recently stripped appart my turbo I can tell you that the torque required to remove that front nut was alot more than even 50psi could apply on the compressor wheel...
I would venture to say that if the front nut comes loose for some reasons it might not have been installed properly. However, I have never seen this happen, although if you say its a possibility, my compressor wheel nut must have been done up ALOT tighter than those peoples...

Dude don't yell at me to THINK ABOUT IT if you don't understand it yourself.
So what if its a cone? Pressure is not on the cone, its on the fins.
Have a look at how the air flow enters through the compressor cover, it cirtainly doesn't smack the cone straight on, it hits the fins.. This is actually why you get compressor surge in the first place, but.. you don't agree with that?
The wheel will get pushed 'down' some by the force hitting the fins, but that would be directly down, as opposed to what your talking about (it getting pushed back because of its conical shape)
And this sideways, or 'downward' depending on how you look at it, force should get aborbed by the main bearings.

Gee.. So sorry, of course the shaft isn't directly in contact with the actual bearing...
That has _nothing_ to do with what I was getting at though.

The main oil journal bearings DO get worn out generally from high rpm abuse, overboosting (I hope we're in agreeance with this so far...).
When they DO get worn out, the shaft tends to wobble. This is, as you can imagine, rather detrimental to the thrust bearing.

All I was asking was how you can make that assumption that it CAN crack it if it is well known that the common cause of thrust bearing failure is from the main bearing failure....
Thank you for saying your not sure if that one was or not.

RETed

Wow, and you came to this assumption out of your ***?

You do know that thread locker is used on that nut, right...


This is why I use the terms "axially" or "radially".
You have a problem using those two terms?


Hey, you're the one that brought up the thrust bearing and supporting the shaft...

Sure, but if the turbo is used under normal operation parameters, this is minimized.
Are we assuming all turbos are abused?



I've seen thrust bearings cracked like that from compressor surge.
It was not that particular picture, but the results were similar.


-Ted

jon88se

Compressor surge is something you want to avoid. End of story. A couple years back at our shop, a friend of mine decided to remove his stock BOV on his 2G Eclipse (it was an automatic Spyder) and put it on one of his old school turbo Z-cars. His explanation was that the Eclipse was an automatic and there was a constant load between shifts since you never let off the gas, minimizing the effect of a BOV. After a quick drive, we DID notice compressor surge but only if he would suddenly lift off in gear after loading the car. He said he would avoid doing that...

2 months later, his ported/clipped big 16G died due to bearing damage. Apparently, 3K miles of occasional surge with 18 psi of boost was too much. He thought it was a bad turbo, so he got another one. A few months later the SAME thing happened. He smartened up and got an HKS SS BOV and to my knowledge, that turbo is still on the car and operating normally. 4 years later

White_FC

50psi -> Kg/M^2 = ~35,000
The surge is only ever going to be acting on one or two compressor fins at the most at any one time.
Gives an area of around 20mm^2
Acting at a radius of about 35mm.

35,000*0.02*0.035=14Nm.
I can assure you it took ALOT more than 14Nm to loosen the bolt.

And that changes this how exactly?
Does the torque from the compressor surge circumvent this thread locker or something?

Not at all

No, I did not.
No idea where you got the idea that I thought the thrust bearing supported the shaft?
This is what I said.

"When the main bearings get loose, the shaft wobbles(regardless of how well it's balanced...) and the wheel can hit the thrust bearing?"


So turbo main bearings never die even when used under normal operational parameters? Turbo repair places must be struggling to make a living..

How do you tell the difference between cracked from compressor surge or it's death of natural causes from the main bearings failing?

HAILERS

Just FYI: I installed a Apexi Twin Chamber BOV into the Greddy FMIC intercoolers feed pipe about two feet from the turbo, and now there is no more clanking afm vane/flap sound and the voltage reading on the SAFC's amf voltage does not bounce around when I let off the throttle after boosting. All's well once more and I'm sure we'll have world peace any minute now, every day will now be spring like weather, North Korea will kill that little shrimp dictator and join S.Korea as one state.........and Michael Schumacher will win the Japanese Grand Prix Sunday. Back to NORMAL.