jes

Engine is a stock '91 TII w/Mazda ECU, FCD, custom FMIC, Bosch 61975 fuel pump,

80mm DP, 3" exhaust. The air tube for the CAT is temporarily blocked (no CATs).

It currently has a new [stock] Hitachi turbo on it, and pulls ~10 # max boost.

In general, it runs like a scalded cat , starts at first twist of the key, hot or

cold. No evidence of anything out of the ordinary, except it smokes after long

periods of idle.



The following have been eliminated through debug:

• turbo, turbo seals and more turbos... $$$
  
  
  
• tweaked turbo oil flow down to .040" using clear drain tube
  
  (did someone install a high volume oil pump?)
  
  
  
• disconnected hoses for oil purge valve and vent after AFM
  
  
  
• block OMP oil lines & OMP air lines (oil is pre-mixed)
  
  
  
• passes "5000 rpm decel. test"
  
  
  
• EGT is in range...
  
  
  
• AFR @ ~15 MPH: 14.95
  
  
  
• using Autometer electric fuel pressure gauge,
  • line pressure, fail: 42 PSI, spec: 34.1-39.8
    
    (when key is turned off pressure drops to 39)
    
    
    
  • hold pressure, pass: 34 PSI, spec: > 18
    

Is 2 PSI over on fuel pressure at idle going to cause these kind of problems?

The car doesn't seem rich at idle, it doesn't make your eyes water. I

assume if it's going rich enough to wash down oil (one of my theories...), it

would have to be seriously rich! I can get an AFR reading at idle to eliminate

that mystery... I would replace the fuel pressure regulator with an aftermarket

one, but the S5 fuel rail has the FPR attached.



When I was debugging turbos and seals, the turbos were dry on the engine side

and soaked on the turbine side. That's why I thought this was all a turbo oil

supply problem.



In it's current state, there is no path I know of from oil galley to intake.



I'm hoping that another set of eyes can see something I missed...



Thanks

Judge Ito

how many miles on the engine?

Hyper4mance2k

My guess is that the side plates are either out of spec or your oil control rings or springs are going or gone.

Jeff20B

My Cosmo did that. I switched to 20w50 and it went away. The oil seals are worn.

jwteknix

how much oil does the engine eat?

j9fd3s

we had an fd do that exact same thing, it turned out do be the apexi turbo kit has you put the metering pump vacuum feed in front of the turbo.



we tried a number of different tests:



what do the plugs look like? if the engine is using oil, they will have a light brown deposit, its kind of fluffy looking.



is there oil pre turbo?



post compressor?



on this car, we actually physically disconnected the turbos oil supply, and stopped the turbo from spinning (be careful!)



it can smoke if its too rich, but its gotta be REALLY rich (or lean and misfiring), and it'll be brown or blackish smoke, oil is whiter or blue, and the oil smoke, will go almost straight up.