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Lost another seal on my K27HFS

I've been through two sets of seals on my K27 HFS in the past 2000 miles. At $5-600 per pop, it's starting to dent my wallet, so I'm trying to head off a third replacement.

On this latest set of seals, the gentleman who replaced them said the exhaust side bearing has been getting very hot- enough to discolor that bearing and the exhaust side blades are white (when cool) from heat. His diagnosis was a lack of oil to the bearing resulting in a hot bearing which resulted in a failed seal.

I have good oil pressure into the turbo and the scavenge pump is working properly.

Another theory is that my rich tune (which I requested for safety) may be allowing fuel to get through the exhaust side which then ignites after the turbo resulting in an "afterburner" effect which heats the exhaust side beyond design limits.

If anyone has any suggestions, I'm all ears.
Old 08-21-2008, 10:25 AM
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Just curious, is Ultimate Motorwerks doing the rebuilds each time? I have an HFS, also and haven't encountered these probelms. If memory serves me, your car is EFI, correct?
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Old 08-21-2008, 10:34 AM
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Quote:
Originally Posted by sand_man View Post
Just curious, is Ultimate Motorwerks doing the rebuilds each time? I have an HFS, also and haven't encountered these probelms. If memory serves me, your car is EFI, correct?
Yeah it's EFI- Autronic SM4. Ultimate did the first rebuild and a local guy did the second.
Old 08-21-2008, 10:50 AM
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When I think of the 930s at the track that I've seen, really tossing the fire (Brian Keith Smith and Craig 930RS come to mind), I'm not sure what to think about the "overly rich" theory. I guess it's possible, but I'd imagine these turbos to really withstand the fuel flames.

As for oiling, I once talked to a guy that roasted his turbo because the gasket that went between the turbo oil supply line and the turbo housing was partially blocking the orifice, and starved his turbo. He didn't indicate if he made the gasket himself, or what...just one of those weird stories you hear from people who once owned a 930.

With another failure under your belt, I bet Kevin at Ultimate Motorwerks would like to see this turbo. I know that when a JE piston fails or a Pauter rod lets go, the manufacturer often wants see it for themselves to record, document, and offer their theory.
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Last edited by sand_man; 08-21-2008 at 11:12 AM..
Old 08-21-2008, 11:07 AM
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Old 08-21-2008, 01:53 PM
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I think Jim means the afterburner effect is secondary combustion of unburned fuel burning in the turbocharger during wide open throttle acceleration.
It can be caused by a too rich air fuel ratio during boosted acceleration.

That can burn up the bearing, turbine shaft, and oil seals from excessive heat.

Not saying thats definately the cause, but it is a possibility.
Old 08-21-2008, 02:47 PM
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You cannot have combustion @ the turbo or in the exhaust system when you are running rich unless you have a gaping hole somewhere allowing OXYGEN to be drawn in to allow the process to happen... Unburned fuel turns in to flames once it comes out of the tailpipe and has oxygen. You can however run very lean and have elevated exhaust temps. (If you are a drag racer you would program this via your ecu [anti-lag] to purposely alternate your cylinders rich / lean to get fuel and oxygen into your exhaust to force combustion and spool the turbo sitting still... fine for racing as you are going to chuck the turbo in short order anyways) I would check your oil flow rate before turbo and after pump. Make sure you do not have a sealed oil drip tank and that it is vented to allow the suction pump to do its job. (many people don't seem to realize why Porsche put a vent line on the factory turbo oil tank)
Old 08-21-2008, 03:26 PM
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Quote:
Originally Posted by JFairman View Post
I think Jim means the afterburner effect is secondary combustion of unburned fuel burning in the turbocharger during wide open throttle acceleration.
It can be caused by a too rich air fuel ratio during boosted acceleration.

That can burn up the bearing, turbine shaft, and oil seals from excessive heat.

Not saying thats definately the cause, but it is a possibility.
Gotcha. I guess I was thinking of the "classic" over run situation...hot turbo, hard acceleration, clutch in for the shift, then flames.
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Old 08-21-2008, 05:26 PM
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I'm hearing what E-Man's saying, lean or oil starvation, makes sense.

I burnt out two successive GT Garretts in a very short space of time, after changing to a K27HFS i melted a piston. Was most likely a lean issue for all scenarios, just had a ****e shop looking after the car at that point and i didn't know enough to work it out for myself.

Jim, can you log your fuel? If you know beyond doubt that you're rich enough then you need to look at your oil. I'm led to believe that too much oil will cause the same failure as too little. One will blow the seals and the other burn them out. It should be a reasonably simple thing to diagnose with the right equipment
Old 08-21-2008, 06:00 PM
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Quote:
Originally Posted by sand_man View Post
I once talked to a guy that roasted his turbo because the gasket that went between the turbo oil supply line and the turbo housing was partially blocking the orifice, and starved his turbo.
+1

I also met a guy who toasted his new turbo trough gasket strangling the oil supply line.
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Old 08-22-2008, 03:52 AM
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More info:

Kevin, the builder of the turbo believes that it's a case of afterburner effect.

As posted on another board:
"The heat generated by unburnt fuel igniting in the turbine housing is so extreme in rich fueling situations. The lube/oil supplied thru the bearings just isn't enough to cool and remove the extreme heat. When your turbine shaft is blue and purple all the way thru the bearing housing to the compressor wheel. You either do not cool your turbocharger down or your fueling is off.

Until resolved you will go thru turbochargers..

You can do a google search with regards to fueling issues and turbocharger failures.. Here is a patent and link..
"
Old 08-22-2008, 10:09 AM
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Originally Posted by JBL930 View Post

Jim, can you log your fuel? If you know beyond doubt that you're rich enough then you need to look at your oil. I'm led to believe that too much oil will cause the same failure as too little. One will blow the seals and the other burn them out. It should be a reasonably simple thing to diagnose with the right equipment
JBL,

I should be receiving my NGK A/F ratio wideband sensor on Monday. Then I will be logging my fuel along with AFR's.
Old 08-22-2008, 10:11 AM
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What about ignition timing? If you don't run enough advance, the late ignition can lead to the exhaust gases that are still burning on the way too the turbo. As well as a lack of power.

If it's tuned overly rich for conservative reasons, it's likely it may have too little ignition advance as well.

Have you dyno'd the car? Is it making the h.p. it should based on popular concensus?

Overly rich mixture will also wash down the cylinder walls, acclerating ring/cylinder wear...

Good luck...
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Old 08-22-2008, 11:18 AM
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I pinged Kevin if he wants to chime in.
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Old 08-22-2008, 11:48 AM
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How rich would it have to be to get gas past the rings and dilute the oil?

I would think that once it has washed the oil off the walls and damaged the rings, you would have other issues as well.
Old 08-22-2008, 11:59 AM
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Quote:
Originally Posted by JimCulp View Post
More info:

Kevin, the builder of the turbo believes that it's a case of afterburner effect.

As posted on another board:
"The heat generated by unburnt fuel igniting in the turbine housing is so extreme in rich fueling situations. The lube/oil supplied thru the bearings just isn't enough to cool and remove the extreme heat. When your turbine shaft is blue and purple all the way thru the bearing housing to the compressor wheel. You either do not cool your turbocharger down or your fueling is off.

Until resolved you will go thru turbochargers..

You can do a google search with regards to fueling issues and turbocharger failures.. Here is a patent and link..
"
The unburnt fuel cannot be burned unless there is excess oxygen in exhaust gases. With other words, it cannot ignite before it reaches the air. I don't believe that your turbo is burned by "afterburner effect". I do believe that you have a problem with lubrication. Exhaust gases have temperatures upwards 900 degree C and can glow red while working. Chances of burning the turbocharger bearing by occasional overrich condition which ignites in air is mirth. Unless you are running very delayed ignition, it's something else causing it.
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Old 08-22-2008, 03:24 PM
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I have some rough AFR's now with my NGK AFX installed.

Idle- 12.7
Overrun- 14.5
On boost- 10.5

These are just with my first time back in the car with the AFR meter- not scientific by any means.

Last edited by JimCulp; 08-30-2008 at 04:59 AM..
Old 08-29-2008, 03:14 PM
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Quote:
Originally Posted by JimCulp View Post
I have some rough AFR's now with my NGK AFX installed.

Idle- 12.7
Overrun- 14.5
Under boost- 10.5

These are just with my first time back in the car with the AFR meter- not scientific by any means.
For EFI and "under boost", 10.5 is rich - FWIW.
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Old 08-29-2008, 04:07 PM
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For EFI and "under boost", 10.5 is rich - FWIW.
What would optimal numbers for the three situations be?
Old 08-29-2008, 05:19 PM
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Originally Posted by JimCulp View Post
What would optimal numbers for the three situations be?
I tuned mine for 14.8:1 @ idle, fuel cut on overrun (so it could be 19:1) & 12.0:1 under full boost. I also typically cruise around 14.9:1
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Old 08-29-2008, 05:36 PM
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