Spun a rod bearing with T-25 on 99 GS-T. HELP.

[Jaraxle]

This was the worst weekend ever. I took my 1999 GS-T with 42k on the clock to a dyno to be tuned. Mods are:

1.) 3" SS turbo-back
2.) Yonaka Bar/Plate FMIC
3.) Joe P MBC (set at 14psi)
4.) 1g bov
5.) Apexi filter
6.) AFC-II
7.) Mandrel upper piping
8.) boost/oil gauges

It was running PIG rich when they first ran it ( 9.0 @6700 ).
(is this normal for an almost stock car ?)

The tuning guys tried to lean it out a bit, doing one pull at a time.
As they removed fuel, power WENT DOWN. And they started to hear knock.
The leanest they got it was 10.6:1

They told me the engine needed the extra fuel to stay cooler, so they were going to undo their changes.

They did another pull and it knocked real bad at 5500 or so.
One last pull and the bearing gave.

This was all with 93 octane that I always get from the same station.
They never leaned it out bad.

Theories:

1.) Car overheated with FMIC blocking wussy fan.
2.) AFC-II knock wire was connected for DAY a week before. Could this of fried/damaged something ? Causing timing to be wrong ?
3.) After removing the AFC-II knock wire the knock wire to the ECU was soldered and taped up. Could this solder joint caused interference ?
4.) Rod bearing just wanted to go, and there was nothing I could do about it.

This car is babied with mobil 1 synthetic, and k&n oil filters.
I am the second owner, and all mods were done by me.

Any ideas would be appreciated.

I know I should have been logging timing.
When I connected an OBDII scanner, it wouldn't initialized/talk to the car for some reason.

Also, a day before I logged 2187hz on the AFC-II during a "fun run". Isn't this beyond what a T-25 should be capable of ?
Perhaps I have a bad airflow sensor ?

I have videos of a run right before it went pop. You can hear the engine "going bad". Hard to tell whether spark knock or rod knock from the bearing giving up.


Thanks in advance,
Jaraxle

 

[Jaraxle]

Not one person has e-mailed or responded.
Not one person has a clue ?

-Jaraxle

 

[pickens]

if you logged over 2100 hz on your AFC, then something was wrong (major boost leak perhaps, thus causing it to run really rich). On my 16g at about 20psi I see about 2000 hz on the AFC.

 

[Jaraxle]

Pickens- Thanks for the response. I knew if I provided enough information someone would have a clue. Yes I logged 2187hz two days before it was on the dyno. Once on the dyno it was horribly rich. If I had known that was out of range, I would have a running car right now. The dyno people where convinced they'd HEAR a boost leak and know it.

So what must have happened:

1.) Boost leak makes car run rich.
2.) Boost leak makes turbo over-spin throwing HOT HOT air into the engine
3.) Turbine produces excessive back-pressure
4. ) Hot inlet and high backpressure cause ECU to pull timing
5.) Engine starts to KNOCK, REAL BAD on dyno causing rod bearing to fail


Lesson LEARNED

-Jaraxle

 

[heavyD]

The main culprit of rod bearing failure is contaminated oil or lack of lubrication from low oil or extreme g-force cornering, etc. You will have to take a look at the condition of your pitsons to see what was happening in the combustion chamber. I spun a rod bearing and my pistons & head were in perfect condition and the car was running great. I know you are not to wire the AFC to the O2 sensor wire but haven't heard that wiring the SAFC II to the knock sensor causes problems (I know you are not to use the AFC knock display values).

Between the tuning guys leaning out your car and the inconsistent airflow readings, you may never know the exact culprit. But I can sympathize with you as it sucks to break your car.

 

[kpt4321]

I highly doubt that knock killed your motor.

 

[my95tsi]

while thats an interesting theory i highly doubt it was the culprit.....

Pickens- Thanks for the response. I knew if I provided enough information someone would have a clue. Yes I logged 2187hz two days before it was on the dyno. Once on the dyno it was horribly rich. If I had known that was out of range, I would have a running car right now. The dyno people where convinced they'd HEAR a boost leak and know it.

So what must have happened:

1.) Boost leak makes car run rich.
2.) Boost leak makes turbo over-spin throwing HOT HOT air into the engine
3.) Turbine produces excessive back-pressure
4. ) Hot inlet and high backpressure cause ECU to pull timing
5.) Engine starts to KNOCK, REAL BAD on dyno causing rod bearing to fail


Lesson LEARNED

-Jaraxle

 

[Jaraxle]

I've taken apart the intake, exhaust manifolds, turbo, downpipe, head.
The pistons are good, with lots of carbon deposit from running rich. The turbo is good too.
Next weekend the shortblock will come out. Depending on crankwalk (hate to mention it) and bearing design (turns out car was made Nov 98) I am going to have it rebuilt by slowboy stage II race motor (no warranty )

And finish my "project" once and for all. (fuel pump, injectors, turbo, clutch).


So I haven't actually looked at the damage yet.

The car had Mobil 1 synthetic 10w-30 from 33kmi - 42kmi. The previous owner ran synthetic redline oil. Oil filters are either Mobil 1 or K&N or mitsubishi.
How spoiled is that ?

Knock wire CAN be attached to AFC-II with no problems ?
( I know it doesn't interpret it right ).

-Jaraxle

 

[92awddsm]

I would say with it that rich, it was probable getting fuel past the rings which contaminated the oil which in turn caused the rod bearing to spin. Have you checked the oil level yet? If the oil has fuel in it, the level will be high and oil will smell like fuel.

 

[myblack98gst]

yup exactly what he said... too much fuel caused it to get past the rings into the block... good by bearings.... *knock* detonation won't damage a bearing it will burn a hole on top of the pistons though.. overheating will not damage a bearing either UNLESS it blows a headgasket or coolant passage and leaks coolant into the block and the will flush out the bearings too..

The reason for the gas taking out bearings is basically because of its cleaning ability. it washes out the oil that is supposed to lubricate and causes the bearing to run dry. Easy way to check for gas in oil is hold a lighter to the dipstick if it flames quick it has gas in it, slow burn is normal.. or stick your nose to the oil fill and smell for gas..

Cause Theory: Bad Maf sensor, Boost leak ( if it was building boost okay then rule this out), F-d up ECU, f-d up afc


Easiest way to tell about the bearing is to drop the oil pan it will be full of GOLD woohoo oh I mean Bearing deposits!!!

Sucks about the car.. The thing I dont understand is why it was not hitting fuel cut with seeing HZ levels that high.. it should have cut out LONG before that with stock injectors in place * I think*

 

[Bastard1g]

I agree with these guys when it comes to the fuel contaminating the bottom end. Check the cross hatches and piston rings for damage. If the a/f ratio was so rich that fuel was seeping past the rings, then you should be able to look at the piston rings to confirm your theory. The cross hatches help lubricate the rings in operation and it should be obvious whether or not fuel got through the rings and washed out your bearings. Since you are building a 7 bolt, ask your machinist if he can "chamfer" your thrust bearing. It doesnt take alot of time and its fairly easy.

 

[Jaraxle]

The AFC-II was an E-BAY purchase new, and it appeared new.
I wonder how delicate those MAF sensors are ?
It did get dropped about 5-6inches from one bench to a lower bench at one point
I take it an oscilliscope will have to be used to check it ?

Also, I dont think my mechanic disconnected my neg terminal when he welded up my exhaust :thumbdown

As for the cross-hatching on the cylinder walls. It appears worn (obviously parallel with rod motion), you can see a "faded" section on each cylinder. I will attach photos later for you guys to look at. My worst fear now is dropping another 3g's into the car and blowing the next motor due to some electronic failure !

Perhaps boost leak is out of the question. Most of the system was pressure tested to 25psi anyhow.

More thoughts on the 2187hz logged before the dyno session ?
That # is what the AFC is reading, so it must be the MAF.