sr20 t25 oil burning/smoking and restrictor question-Calling Samnavy- - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-20-2008, 12:38 AM   #1
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Default sr20 t25 oil burning/smoking and restrictor question-Calling Samnavy-

My sr20 t25 smokes out of the tail pipe upon startup and smokes a bit from the turbo itself too. I had thought this could be oil's from install on the mani and dp itself but now after about 100 miles or so its clearly coming from the turbo. If you look closely it appears to be a bit wet on the CHRA itself on the exhaust side.
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Ive read over samnavy's thread
https://www.miataturbo.net/forum/sho...ng+restrictors
And it looks like Sam's had the same issue as i may. My question is, are the -4AN lines that begi provided flowing too much oil to the turbo causing smoking and possibly lower oil pressure?

Today when i left work i even noticed a bit of oil on the tail pipe as well as spitting onto the ground a bit.

The details of my setup is in the sig, what do you guys think? I need a restrictor? What size? Should i just swap to a -3AN line and sell this 100 mile use braided line here?
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Old 05-20-2008, 01:35 AM   #2
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A restrictor might do it... pop-rivet or the ATP piece.
But since you're getting oil on startup, the only real place that could come from would be the engine... either in the form of blowby, or residual oil in the intake due to a leaky compressor seal.
If a restrictor doesn't fix your problem, then you're pressurizing the crankcase.
It's getting ever popular nowadays to run a catch-can... I'm almost on board. Currently I've got the 323GTX PCV valve and properly routed valve-cover breather. But I also have no burning oil issues that I know of.

I'd start with a new PCV valve if you run one, check your IC piping to see if you're pushing oil into there... then restrictor.
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Old 05-20-2008, 02:48 AM   #3
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Quote:
Originally Posted by samnavy View Post
A restrictor might do it... pop-rivet or the ATP piece.
But since you're getting oil on startup, the only real place that could come from would be the engine... either in the form of blowby, or residual oil in the intake due to a leaky compressor seal.
If a restrictor doesn't fix your problem, then you're pressurizing the crankcase.
It's getting ever popular nowadays to run a catch-can... I'm almost on board. Currently I've got the 323GTX PCV valve and properly routed valve-cover breather. But I also have no burning oil issues that I know of.

I'd start with a new PCV valve if you run one, check your IC piping to see if you're pushing oil into there... then restrictor.
Ive got the pcv valve, i also have setup a diy oil catch can with an air compressor filter in line. Did you end up going with the pop rivet or the atp piece?
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Old 05-20-2008, 03:05 AM   #4
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PCV is a brand-new OEM 323GTX unit. I tested it myself before Nick installed it.
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Old 05-20-2008, 09:24 AM   #5
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If your drain is set up correctly, then it looks like it's time for a restrictor. I've been using the same aluminum pop-rivet for about 10k miles now.
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Old 05-20-2008, 06:52 PM   #6
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Sam, you think a restrictor in this case would help with a low oil pressure issue as well? I have never had to deal with restrictors since I opted to use a -3AN line to avoid the issue entirely.
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Old 05-20-2008, 07:34 PM   #7
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The pop rivet restrictor only lowered the oil pressure ~7 psi at the turbo during my testing.
Rebuilding your turbo is another option if the restrictor doesn't help. I used -4AN line on a heavily used SR20 T25 with no restrictor for a year and it never smoked. Try the rivet and see what happens though, it's a cheap experiment.
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Old 05-20-2008, 07:46 PM   #8
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He's got two different things going on here.

1: I can't see "smoking on startup" being an issue with the turbo. The turbo has no heat in it yet... the smoke on startup almost certainly is coming from oil inside the cylider somehow.

2: Seepage on the turbine housing. This is definitely due to oil getting backed up in the CHRA. Causes of this are well known.

Bad rings COULD cause both... but I highly suggest a compression check to rule out the possibility of a blown head gasket.

Sav, I've never heard of anybody having low oil pressures due to running a -4an line. I noticed zero difference in my pressures. Perhaps somebody else can chime in here, but I very highly doubt -4an is larger than the oil passages inside the block... and that's the only real way it would have the potential to cause a pressure drop.
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Old 05-20-2008, 07:48 PM   #9
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I saw around 65 psi of oil pressure at the turbo with a -4 line.
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Old 05-20-2008, 10:16 PM   #10
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Head gasket was replaced 17k miles ago, turbo was rebuilt by me using sam's writeup, so the turbo has approx 100 miles on it freshly rebuilt. Corkey himself did a port job and overlooked the turbo before install.

I picked up some 1/8th aluminum pop rivets ill try and get those in tomorrow when i put my oil temp sensor in.

As for the low oil pressure i have a thread going in the 'general miata' section but i have seen about a 5-10 psi drop all around since the turbo install. Today it did not smoke from the tailpipe on cold start in the morning at all, however the turbo still smokes a bit, not driving it till the pop rivet goes in tomorrow and ill see if that cures some of my issues.
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Old 05-21-2008, 12:23 AM   #11
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The lower oil pressure could be due to oil temperature. The turbo add's alot of heat to your oil and will cause a large drop in oil pressure after alot of boost. You should be running synthetic oil and you might need an oil change if you're currently running a dyno oil.
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Old 05-21-2008, 01:25 PM   #12
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Got the pop rivet in last night and took it for a test drive, first impression was it spooled much louder and felt to hit full boost sooner too. water temp gauge rose quite fast which led me to check my coolant level. Looks like the main leak i see on the ground everything is cool leaking from somewhere around the intake mani. Hope to get those hoses sorted out tonight and get my oil temp sensor in as well to see where im at.

Would too much oil cause the turbo not to spool as fast? The car seams to pull a bit harder at 8 psi.
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Old 05-21-2008, 03:16 PM   #13
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Hmmmm.... very interesting. There's nothing about pressurizing a CHRA that would cause the shaft any resistance. It's probably in your head. It will take an hour or so of driving to get all the oil residue off the outside of the turbine housing. I'd also pop an IC hose off and check to see if there's any oil puddled in the bottom of there.
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Old 05-21-2008, 04:56 PM   #14
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Sam, you don't think over-oiling the CHRA would increase resistance and decrease spool time?

Nick, keep a DAMN close eye on those boosted AFRs in the 2-3.5k range if you are spooling faster. Probably nothing to worry about since Jerry's boosted cells were so fat on your car, but just keep an eye on it.
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Old 05-21-2008, 05:32 PM   #15
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I'm visioning the inside of the CHRA. The oil cavity in the center section only has about 1.5" of the shaft exposed to the oil. I'm no physics expert, but a heavy'ish steel shaft "floating" in a fluid of any kind shouldn't find that much resistance from the fluid when the pressure of the fluid rises. We're not talking thousands of PSI here... 50-60psi at wot once the engine is warm.
Somebody smart can chime in... does the fluid exert an appreciable amount of resistance to a spinning shaft submerged in it? I can't see it being that significant.
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Old 05-21-2008, 07:27 PM   #16
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I poped one of my hoses off today and a pool of oil came pouring out =( . So I went and bought the GTX PCV and a catch tank. When I hook up the catch tank I am going from Valve Cover to tank, then should I vent that to air or back to the intake?
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Old 05-21-2008, 07:38 PM   #17
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how is your breather line routed?
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Old 05-21-2008, 08:19 PM   #18
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currently back into the intake before the turbo

edit: does the turbo create any kind of vacuum?
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