11.5:1 AFR 230*F oil temp...black oil

[hustler]

I have a turbo miata street/track toy.

I'm running it at 11.5:1 in boost, with about2000 miles on the motor now. I changed the oil for the second time (after 500-mile break-in) and noticed that the Rotella 5w40 dino was very dark...well, as black as black can be. Oil temps never went above 230*F so I've ruled out excessive temps.

A friend who builds force inducted track cars claims that fuel contamination will be an issue, and I should expect to change the oil after every track day because of the rich mixtures.

I switched to Rotella 5w40 synth yesterday. Do I need to worry about color? Could the blackness result from assembly lube still in the motor? What indicates fuel contamination?

 

[UncleRunkle]

OK, I misread the post!! AFR not CR, anyway, what's your CR and could you use higher octane to lean out the mixture with a retune?

I would assume you are running a rich mixture simply to avoid detonation, What octane fuel are you running?

Definitely need more details.

BTW I assume you meant rotella 15w40 dino as I don't believe they make a dyno 5w40.

 

[addyguy]

You didn't switch......Rotella T 5W-40 is synthetic, there is no 'dino' version.

Lots of 'stuff' causes oil to get very dark/black. In this case, break-in causing extra stress on the oil would be the culprit. If the rings haven't 'seated', you'll get excessive fuel in the oil.

If you are going to be changing the oil after every track even, I'd stick with a 15W-40 HDEO to keep cost down...it will protect just as well...

 

[Bulli]

yes it could very be dark from assembly used. some assembly lubes are dark in color.

I also don't know why ur running a 11:5.1 on a turbo engine.??

Either way either your rings are installed wrong or not to spec and let gas in the oil, if your running extra rich that isnt helping either..
did u tune the car or just trying to lucky running it of the ecu?

 

[hustler]

I had dino/conventional oil in the white jug in it for teh first 2k, now I'm on Rotella Synth in the blue jug. I planned on evaluated my UOA data to tell me if I need to switch to Redline after a few hours on the track.

The motor is at 8.5:1 static compression. I'm running 93-octane fuel. 11.5:1 AFR made max torque, and the motor is hitting MBT at 15psi (from a gt2860rs) without detonation. I kept going richer, and it kept making more torque (251lb/ft on a dynodynamics http://i44.tinypic.com/29z1kqt.jpg ) The fatter mixture also helps keep EGT and the turbine below 1700*F.

 

[hustler]

Originally Posted By: Bulli
yes it could very be dark from assembly used. some assembly lubes are dark in color.

I also don't know why ur running a 11:5.1 on a turbo engine.??

Either way either your rings are installed wrong or not to spec and let gas in the oil, if your running extra rich that isnt helping either..
did u tune the car or just trying to lucky running it of the ecu?



I'm running 11.5:1 AFR because that's where it made the most torque and its a safe # for track cars...ask anyone who puts together racecars, even OEM's tune turbo cars that fat or even further. , I'm fairly certain the builder installed everything correctly (he does tons and tons of these motors), compression was between 172-174psi on all cylinders with 2% leak, and I spent about 3-hours on the dyno tuning fuel, spark, and enrichments. Its as well tuned as any car can be, and the motor came together perfectly.

Also, I'd like to go with an oil I can run mutiple track days on. I'm going to let the UOA's tell me what to do in that department.

 

[JoeFromPA]

I think you need a few more flushes and further break-in to determine if the oil is getting contaminated fast or just absorbing assembly lubes/break-in process.

Probably worthwhile to you to do an oil analysis at some point when you think it's "shot".

Joe

 

[Steve S]

Tuning for max power requires a richer mixture will get you more blow by .WOT gets more blow by than a lean cruise .I would guess that if the oil doesn't get too hot syn oil may not buy you anything. I would agree with doing a few more oil changes and see what happens . The dino testing shoud tell you the good rebuild.