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Does your turbo spin at idle?

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Old 08-06-2010, 04:41 PM   #1
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Default Does your turbo spin at idle?

I just installed a used mpt76 on my 5.3L and i noticed that when i start it with the filter off the wheels spins for a couple of seconds and then stops. I can see it twitching a little bit but when i spin it by hand it spins freely.

I just gave it a little gas and it started to spin again and now it seems to be spinning at idle all the time. I'm just wondering if its normal for the wheel to stop spinning at idle? I sent vcracing a message and they said that it shouldnt spin while idling and that it should only spin when there is a load applied.

I checked to make sure it was getting oil and the drain is draining properly.

Another question i have is i seem to have a bit of white smoke coming off the log since the instal. I have not ran it for long but i am wondering if this is normal after a turbo instal and how long it should smoke for? My log and all of my hot parts are wrapped so i'm hoping its just the oil and rtv and stuff burning off.
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Old 08-06-2010, 05:59 PM   #2
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It should spin at idle. Mine will spin for several minutes after the engine is cut off.
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Old 08-06-2010, 07:46 PM   #3
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Hmm i think the turbonetics is a bit differnt than the master power. I've seen some turbos where you spin them by hand and they spin for ages and others that spin for a few seconds.
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Old 08-06-2010, 08:26 PM   #4
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I haven't ran a single but my garretts are both spinning pretty fast with the engine idling. They will spool down for about 75-120 seconds after I shut off the engine from idle. Even though a single has greater mass than two twins, I would think that it should be spinning at idle otherwise the idle turbine blades would be a pretty big restriction in the exhaust. I'm sure one of the Turbo "big players" will chime in shortly.

Rick
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Old 08-06-2010, 08:42 PM   #5
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Technically your engine still has a load on it when it is idling. That load comes from friction, windage, pumping losses, etc. I have an OBD2 scanner that shows my engine at 23% load at idle. Load is just another word for airflow in this case, and since your engine is still flowing air at idle, the turbo should still spin. But it will not spin enough to create positive pressure in the intake. Rick_Vor is right, if the compressor wheel isn't spinning at idle, there's restriction in the flow due to friction in the bearings. I've never seen a turbo that doesn't spin at idle... You should turn the shaft by hand, while the engine is off of course. See if you can feel any friction that shouldn't be there. Shouldn't be any that you can feel..
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Old 08-06-2010, 08:53 PM   #6
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Does it make a difference in spin time if the turbo has ball bearings, or if it has plain bearings?
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Old 08-06-2010, 08:55 PM   #7
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You mean JOURNAL BEARINGS?! lol jfwy

I believe they claim that ball bearing turbos have 15% less frictional drag than those "other" bearings
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Old 08-06-2010, 09:36 PM   #8
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Quote:
Originally Posted by smokeshow View Post
You mean JOURNAL BEARINGS?! lol jfwy
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Old 08-07-2010, 12:10 AM   #9
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Hmm well when i spin it there doesnt seem to be any restriction. I can spin it and it will spin for a few seconds then slow down and stop. Not an abrupt stop or anything and it feels smooth. I just thought it was the difference in the bearings. Just kinda confused why it would stop. The two sides are connected correct? I can hear the exhaust side of it spinning even when the front stops.

What do you guys think? Should i run it or should i pull it apart and check it? Does anyone make a rebuild kit for it?
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Old 08-07-2010, 12:16 AM   #10
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Yes, they are connected by a shaft. You might be hearing something else when the front stops, like exhaust noise running past the turbine blades... You do have the oil lines connected, right?
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