Pro Stock John

iTrader: (34)

So last year I made two passes (10.x@140; 9.4@144), and then melted a vacuum line. No boost. Well it turns out 10 minutes later the turbo has issues. That's why I didn't take it to Memphis last year. Fixed the turbo.

This year I was busy and only recently had a chance to run the car. Drove it around the street, and then made two 10 second passes at GLD when I was making license passes... 10.05@138, and 10.6@115. As you can guess the 2nd pass had issues. Melted another plastic line, and then saw oil in a different vacuum line on the inlet side of the turbo. We decided to pack it up.

Block is tired, not a big deal it happens.

But the damn turbo is fugged up. AGAIN. Appears to have had oil issues again, and this time it snapped the shaft.

I'm running a -4 feed, NO restrictor, and a -10 drain. So the turbo starved for oil but it pushed oil through both seals???????

I'll send it back to Precision for inspection, but at this point I don't get what's going on. I was talking to a well regarded tuner and he said he's mostly seen stuff like when there is an oil drain issue, like 90% of the time.

I'm sorry to air out my dirty laundry but enough is enough. Do these turbos have bearing problems? I'm all ears. I was just about to buy a 88/98 to fit a local class but I'm not doing dick until I get to the bottom of this.

Saleen91

Damn John!!!

Sorry to hear that man. I'm running the same oil feed/return that you are. The only oiling issues I've had is with my seals. After a season, two at the most, I wind up needing new seals as my turbo is smoking oil out of the exhaust. Even then, it's not enough to damage anything.

BTW, you can see in my sig what type of seal/oil burning issue I have after a full season.

stevewix

Everything is the same on my turbo oiling setup with the exception of my (admittedly overkill) -6 feed line. Same turbo, everything. My turbo drooled a little oil when it was new, but hasn't leaked since it got a few miles on it. I'm actually surprised I've never had any trouble with it, must've gotten a good one as it doesn't even smoke after it sits for a few months.

It's for sale BTW in the classifieds ... If you buy it you'll have one to play with while you shoot at the one that won't work
https://ls1tech.com/forums/showthrea...4#post10199374

You probably are simply on a run of bad luck. Might try flushing out the oil feed line. It is worth noting, the pressure in my feed line runs about 20-25 at idle, and no more than 40psi.

Pro Stock John

iTrader: (34)

It was pissing oil through both seals, it's getting oil.

Anyone have a durable 91-98mm turbo for sale?

Shawn @ VA Speed

iTrader: (3)

first off-turbos dont have oil seals,they do have a metal ring on the turbine side looks like a sealing ring in an auto trans.oil drain problems do cause most of this type of problem-either the turbo is too low to drain properly to the oil pan or if you have too much crankcase pressure it will hinder the oil drainig back to the pan,the oil has to drain into the pan higher than the oil level.I have had the gt4788's on my car for 4 years now,they have 350-400 passes on them-have never been rebuilt and are as tight as brand new.It's not a turbo issue.

Pro Stock John

iTrader: (34)

Cold leakdown was 35 Shawn. Right I meant the metal ring.

Here is a pic:

Saleen91

John,

Yup 8.30's -8.50's with the same boost/tune all year long with an a/a intercooler.

I know my setup has a little bit of blow-by and I'm not running a vacuum pump or an oil scavange pump. Addressing that MIGHT buy me more time between freshen-ups on the turbo...but considering I'm typically down every winter for some sort of upgrade, it's not that big of a deal to me.

Shawn @ VA Speed

iTrader: (3)

you have 35% leakdown?Your turbo is certainly high enough,but where does the drain go in the engine.Also i know it has oil leaking out now,but that doesnt mean its getting oil and the right time.I would put a gauge in at the turbo-just beacuse its getting good oil at idle doesnt mean its getting enough at high rpms -15 psi idle 40-45 wot

NA$TY-TA

iTrader: (21)

Good Point Shawn.

John,

You can buy my 91mm Turbo.......... Ill even bring it to ya in Memphis...........

Kyle

427

iTrader: (3)

Maybe you should buy a supercharger??

(head under table waiting for flying ****)

Kurt

onfire

iTrader: (17)

Crankcase pressure is probably causing the oil pass the seal. Been there, fought that demon...doesn't hurt the turbo though.

Melted vac line stopping boost doesn't make sense...should overboost if it's a gate line. Unless it's a vac gage line burnt...still makes boost but doesn't show it on the gage.

Broken shaft is probably unrelated...are you running a bov?

Pro Stock John

iTrader: (34)

Tial 50mm BOV
HKS II WG

OUTLAWZ RACING

iTrader: (9)

Im a little meager in these high hp builds, PSJ do u think there is too much oil in the pan? I mean when your in it do you think the pressure is pushing oil above your drain causing it to slow down or even stop?

Keith

I think a YSi would be good for you.

On a brighter note, the Merc sure looks like it's coming along.

LASTLS1

iTrader: (7)

I run a restrictor and 2 -10 drain lines.

Turbo LS1 SS

iTrader: (7)

maybe you have TOO much oil flowing through there. just a thought. i have my feed restricted to .074" (WAYY smaller than wide open -4an), with a -10an drain on my S88. no issues. -4an is quite large at 60psi

smokinHawk

iTrader: (48)

the drain sounds fine to me, i have the exact same thing, 4an, no restrictor, with a 10an drain.

Fireball

iTrader: (21)

what about excessive backpressure on the turbine? I've always thought that 8xx to the wheels sounded way too low for 25 psi...how much boost have you ran since the last rebuild?

FWIW, I'm running an unrestricted -4 feed and -12 return on my setup...where are you picking up your oil feed from?

Pro Stock John

iTrader: (34)

A friend has a 408ci + GT47-88 and made 920rwhp on a load dyno, I'm guessing my numbers are pretty similar if I went to the same dyno.

Precision says run no restrictor, but one of the turbo gurus on here said to keep the idle oil pressure North of 10psi. I can ask my buddy to check the oil pressure right now so that we have that data.

veee8

iTrader: (40)

Where is the drain located? Do you have a T4 or T6 88? I always thought the rwhp was a bit low, but too many variables could cause that, such as a non load dyno etc... This is a 346ci, right?