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LUDELVR
04-29-2016, 09:00 PM
So here's the situation: I just had the engine rebuilt with a sleeved block, rods and lower compression pistons, a refreshed head etc. etc.

The turbo setup was a revhard log manifold, older journal bearing t3/t4 turbo with 630 injectors and running FCON. Initially, the setup made 371whp and 250ft/lbs on a dyno dynamics dyno at 16 psi of boost. It ran for an entire summer with no smoke on start up. Last year, the car started blowing smoke on start up and I took it to the shop. They pulled the turbo and said it was a blown turbo so I had that replaced.

Fast forward to this month. The turbo was replaced with a modern borg warner unit along with the downpipes and charge pipe being changed and a new motor mount with a hasport one because the turbo was hitting the stock motor mount. They dyno'd the car again and it made about the same amount of power but at around 14 psi of boost. In any case, I was supposed to pick up the car but yesterday, my tuner said that the car was again blowing smoke on start up. They looked at the new mount and found that the insert had melted because the turbo was sitting so close to it and the engine had sunk about 2 inches. My tuner is saying that this might have caused the oil drain to start backing up and causing the turbo to smoke but I've had this setup for years and I've never had issues with it smoking.

On this log manifold, the turbo does sit fairly low but there is enough of a bend for the oil to drain into the bung that was welded on the oil pan.

Now, they are making a metal insert to put into the motor mount to see if that will stop the smoke but what else could this be? Could the turbo sink low enough because of a motor mount that it would start causing oil to back up into the turbo?

It's funny though because I didn't have this issue with the stock motor mount but that eventually took a $hit because of the heat from the turbo. Could that inch or so from the material melting on the mount, cause the oil line to back up though, causing it to smoke? Seems like such a small thing.

rx7_turbo2
04-29-2016, 09:13 PM
It's entirely possible.

The turbo on my old FC sat very low, there really wasn't much height to get a decent slope on the drain line. Every once and awhile in wouldn't drain properly and push oil past the turbo seal and start smoking. I rejigged things a few times, changed the drain line location a number of times, eventually I got it pretty much sorted. I also found the oil pressure was an issue, placing a restrictor in the oil feed line was also part of the solution.

sr20s14zenki
04-30-2016, 09:41 AM
I believe hondas run fairly high oil pressure do they not? If you have a sufficient size drain, you may need to look into a restrictor as turbo2 stated. your drain should be MINIMUM -10an

LUDELVR
05-01-2016, 08:52 AM
Originally posted by sr20s14zenki
I believe hondas run fairly high oil pressure do they not? If you have a sufficient size drain, you may need to look into a restrictor as turbo2 stated. your drain should be MINIMUM -10an

I'm certain that the oil drain size is adequate as I have had it that size for years so I'm pretty sure that's not the problem but I'll double check.

It only seems to have happened when my old journal bearing turbo went south and I started noticing oil on start up, like a lot. A steady stream. Got the Borg Warner on and while dynoing, no smoke but all of a sudden, I was told that there's smoke on start up and the mount insert had melted.

I just find it difficult to see how such a small thing can cause the turbo to back up oil and smoke that much. Really frustrating considering I've spent a lot of money and it's not working where my ghetto setup didn't smoke at all...until I pushed it past its limits and blew it! Haha

sr20s14zenki
05-01-2016, 09:51 AM
Is it possible that maybe its not turbo related at all? Maybe you have a bad valve seal. I realize its all probably new, but its not hard to fuck up seating one of them. That would be fairly easy to diagnose. Take turbo manifold off and inspect inside the ports. see if theres any fresh oil or extra carbon buildup. I had a honda once that i suspected rings on, so i got a new bottom end. When i was changing the head over, i looked into the port and ho lee fuk, there was enough burned oil build up to make the valve twice its diameter. Totally possible.

zieg
05-01-2016, 10:47 AM
Originally posted by LUDELVR
Could the turbo sink low enough because of a motor mount that it would start causing oil to back up into the turbo?

Thing about this is it's not just the turbo sinking, it's the whole engine. I personally can't see the angle changing enough to be a problem so unless the drain line was tied to the subframe or something, it would just sink with the rest of the engine.


Also, if they switched you from a journal bearing turbo to a ball bearing, yeah you definitely need a restrictor in there...