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Smoke on boost, Anybody experience this?

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Old 06-09-2018, 01:10 PM
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GPA951s
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Default Smoke on boost, Anybody experience this?

So on the Dyno my car was smoking on boost, ALL the intake/intercooler tubes are super clean no sign of oil. The plugs look perfect and the car made good HP.. However, when I got up on boost it smoked blue smoke like crazy... I took off the Turbonectics turbo and put on a freshly rebuilt factory kkk turbo. Took it for a shakedown on the street and no smoke.
Took it to the track, During my third stint I came into a Righthander uphill (toe of the boot WGI) and got a oil Wiff.... looked in the mirror and saw a cloud of mosquito killing blue smoke... pulled the car in.. The motor is tight, Fresh everything, pistons, rings, head, The only thing I can think of is that I Vented the AOS to a catch can and on boost I have oil in the return tube (motor mount to pan) backing up into the Ex turbine. Does anyone have any Experience with this scenario? I think the way that return line is plumbed into the pan the crankcase needs the venturi effect of being vented in front of the turbo. Thanks Guys..
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Old 06-09-2018, 01:49 PM
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Tom M'Guinn
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You might pull off the drain hose and make sure it's clean and not gunked up, along with the mount. If you're not already, I'd vent the crank to atmosphere to see if that helps (pull the oil cap and cover with pantyhose or the like). A slight vacuum in the crankcase helps drain the turbo, but as long as there isn't a lot of pressure in the crank it shouldn't prevent two different turbos from draining. I get some pressure in my crankcase under heavy boost and have no smoke. Not to be a wet blanket, but I'd probably want to check the rings with a leak down test too....
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Old 06-09-2018, 02:07 PM
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Sounds to me like the oil seal on the turbine shaft is leaking into the exhaust.
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Old 06-09-2018, 02:15 PM
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Tom M'Guinn
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Originally Posted by cruise98 View Post
Sounds to me like the oil seal on the turbine shaft is leaking into the exhaust.
On two different turbo?
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Old 06-10-2018, 12:21 PM
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Yea that was my thinking.. Two different turbos? That are both pretty much new? Sounds like a systematic problem... When I switched the Turbos I did blow out the motor mount and the line to the pan... BTW Even after all of this, the Oil itself is so clear that it is hard to read on the dipstick. Tom, I DO have the AOS vented to atmosphere... THAT I think is my issue. The AOS Needs that little bit of vacuum to create negative pressure in the crankcase under boost Hence the factory has that AOS vent tube in front of the intake to the turbo. Im Boosting to about 14psi BTW.
Im going to have the Turbos checked out and re-do my AOS venting back to a more Factory type setup. I will do a leakdown just out of curiosity.
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Old 06-10-2018, 02:34 PM
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I'm sorry I can't help but it sounds like you are on the right track to finding the root cause of your problem. My research came up with 8 lbs of vacuum is ideal for a daily driver. The electric vacuum pumps can be adjusted to whatever you desire with the right electric switches. You just "t" into the brake booster hose is my understanding.

Off topic: May I ask you if your engine is 2.5litre & do you have any ideal how much torque and hp the 2.5 engine has at 14psi? I heard the factory head gasket is "approved" for 17 psi, is this true?
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Old 06-10-2018, 04:07 PM
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A while back I put a map sensor on the crankcase and saw at least a couple psi under boost and seem to recall others reporting the same or more. None of us have blue smoke under boost, so I’d keep an open mind about the root cause...
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Old 06-10-2018, 07:52 PM
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Originally Posted by Noahs944 View Post
I'm sorry I can't help but it sounds like you are on the right track to finding the root cause of your problem. My research came up with 8 lbs of vacuum is ideal for a daily driver. The electric vacuum pumps can be adjusted to whatever you desire with the right electric switches. You just "t" into the brake booster hose is my understanding.

Off topic: May I ask you if your engine is 2.5litre & do you have any ideal how much torque and hp the 2.5 engine has at 14psi? I heard the factory head gasket is "approved" for 17 psi, is this true?
Its originally a 2.5 block but its at 4.100 now.. 14 psi boost made 305 ftlbs and 271 hp at the rear wheels. I have a Cometic gasket on it.. on the street for a couple of hits every once in a while Im sure a bit more boost would be fine but this is a track car and lives above 4500 all day long Any more boost for a track car will cost allot more money There is no longevity for these engines above that on the track, it can be done but with allot more money....And BTW I Torqued the head to 85 ft lbs with Raceware studs...
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Old 06-10-2018, 09:16 PM
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4.1 litre??
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Old 06-11-2018, 11:01 AM
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Valvesteam seals?
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Old 06-11-2018, 11:50 AM
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Originally Posted by GPA951s View Post
Its originally a 2.5 block but its at 4.100 now.. 14 psi boost made 305 ftlbs and 271 hp at the rear wheels. I have a Cometic gasket on it.. on the street for a couple of hits every once in a while Im sure a bit more boost would be fine but this is a track car and lives above 4500 all day long Any more boost for a track car will cost allot more money There is no longevity for these engines above that on the track, it can be done but with allot more money....And BTW I Torqued the head to 85 ft lbs with Raceware studs...
It does help using metrics with a metric car, it does confuse people.
Could be valve stem seals. or stems

Originally Posted by Dan Martinic View Post
4.1 litre??
He means 104mm bore. or 4.1 inch bore.
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Old 06-11-2018, 02:36 PM
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When you vented the AOS to the catch can, was the catch can open to atmosphere or connected back to the J-boot or MAF?
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Old 06-12-2018, 12:41 PM
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Originally Posted by Paulyy View Post
He means 104mm bore. or 4.1 inch bore.
Thanks. I was getting very interested in the 4 litre motor though
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Old 06-12-2018, 01:59 PM
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Originally Posted by Dan Martinic View Post
Thanks. I was getting very interested in the 4 litre motor though
https://rennlist.com/forums/944-turb...a-thing-3.html

Scroll though that. It's been done, hopefully we get to see it run this October. It may or may not be running at the moment as it's all secretive at this point in time. I have very high hopes.
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Old 06-12-2018, 02:36 PM
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Twin turbo 4 litre.. before I can even begin to understand what is happening at the engine, I need to wrap my head around the entire construction of this.... racecar? Insane!!!

Some beautiful pics ..esp that exhaust piping ‘art’
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