View Full Version : Explanation for oil line restrictor?


SPRAYED 01
09-17-2007, 11:15 PM
I just fired up my new single turbo forged ls1. Im loving the whole boost thing but am going to have a lot of questions as i work the bugs out.. Right now im breaking the motor in with 10w30 quaker state and am experiencing lower oil pressure than my old h/c motor.

Can some one explain what the restriction in the oiling system does. Is it in the return or feed? Just need to know the basic theory.

Thanks
Alex

gametech
09-17-2007, 11:28 PM
The bearings in the turbo will not seal at high pressure. The restriction goes in the feed side, so that oil doesn't blow past the turbo seals. The size of the restrictor will vary according to several variables, but that is the basic reasoning. The engine just makes way more oil pressure than the turbos can handle.

SPRAYED 01
09-19-2007, 10:50 PM
Could a restriction in the return cause low oil pressure?

SPRAYED 01
09-20-2007, 08:26 AM
bump for the day

smokinHawk
09-20-2007, 08:45 AM
Could a restriction in the return cause low oil pressure?
it sounds like your problem is in the engine and not the turbo part.
if you have a oil problem in the turbo circuit it will not register on your engine oil pressure gauge. you will only be able to tell if there is an oil problem in the turbo loop buy to much smoke (one cause - but not the only cause of oil smoke) in your exhaust.

that bing said the drain of the turbo will not effect your engine oil pressure.

before you go nuts though what is your oil pressure reading, how low.
with new bearings it should be going up and down with the engine rpm, as rebuilt engines will have different pressure then older engines.

SPRAYED 01
09-20-2007, 09:31 AM
At cold start idle its perfect at about 45psi. If i let it run for about 45 mins idle will go down to about 25psi and full throttle is only about 45-50psi. I think the oil is getting really hot due to the turbo.

Pro Stock John
09-20-2007, 10:17 AM
What oil pump are you running?

SPRAYED 01
09-20-2007, 11:13 AM
port ls6,same as i was in the old stock bottom end head/cam. It would never go below 40psi with 0w-40.

smokinHawk
09-20-2007, 11:27 AM
to me that oil pressure doesnt sound to bad for a fresh engine, ive seen similar.

SPRAYED 01
09-20-2007, 12:51 PM
What do you mean by fresh engine. Could it get better as the engine breaks in. It has about 260 miles on it now.

Pro Stock John
09-20-2007, 01:03 PM
Who built the new short, is it pretty loose? Any chance you tore the o-ring?

SPRAYED 01
09-20-2007, 01:21 PM
The borowski's built the short block. Their in Joliet. They said the engine was built a little on the loose side because its a boost engine. I could get any specs because it was built a year ago. I put the o-ring in with the engine on a stand and really took my time with it. It seemed to go in perfectly. It just seems to wierd that the pressure is perfect when cold, then after it heats up for about 30mins the pressure goes down slowly eventually ending up at about 23-25psi at idle.

smokinHawk
09-20-2007, 02:22 PM
What do you mean by fresh engine. Could it get better as the engine breaks in. It has about 260 miles on it now.
oil passages and bearings are normally clean(er) allows oil to travel through the engine better less resistance, less psi, least thats what somebody told me.

Zombie
09-20-2007, 02:33 PM
At cold start idle its perfect at about 45psi. If i let it run for about 45 mins idle will go down to about 25psi and full throttle is only about 45-50psi. I think the oil is getting really hot due to the turbo.

If you are using the factory gage, don't trust it to be accurate. It's dependent on battery voltage. The sensor is not regulated and is directly referenced off the battery/alternator voltage. I've noticed my voltage will drop the hotter the car gets and my factory oil pressure gage will drop along with it even though pressure is not really dropping.

Try this experiment. Drive the car for a while, wait for oil pressure to drop low. Shut car off for 10 seconds, restart and watch oil pressure read higher, then drop as voltage sags. I've seen this happen on a few cars, mine included.

Dragframe
09-21-2007, 07:16 PM
23-25 is MORE than enough oil pressure at idle... more than enough.. you are jsut paranoid.

SPRAYED 01
09-21-2007, 08:12 PM
Im not freaked out about idle, it full throttle is only about 50psi