Dirty smoky exhaust over 4500 RPM
02-12-2016, 01:27 PM
#1
Pro
Thread Starter
Dirty smoky exhaust over 4500 RPM
I've mentioned before how I get a burned oil smell over 4000 or so RPM. The other week I drove behind my car, and could see that under WOT it would kick dirty carbon-y smoke. Not blue, not white.
I had been assuming that it was overfilled oil aspirating back through the AOS breather. AOS seals are new and dry. No visible oil drips externally.
Would this point to bad rings, or bad valve stem seals?
I don't really feel like doing a rebuild.
I had been assuming that it was overfilled oil aspirating back through the AOS breather. AOS seals are new and dry. No visible oil drips externally.
Would this point to bad rings, or bad valve stem seals?
I don't really feel like doing a rebuild.
02-12-2016, 01:44 PM
#2
Three Wheelin'
I know valve seals show their signs at start-up when oil that has leaked into the cylinder is combusted and blown out as a cloud of exhaust. Hopefully that helps.
02-12-2016, 02:03 PM
#3
Rainman
Rennlist Member
Rennlist Member
In my dyno testing I've always noticed the car BLASTS black smoke out the pipe in the higher rpm range.
Even with the stock AFM/DME...I think the tune goes rich a bit at the high end.
Even with the stock AFM/DME...I think the tune goes rich a bit at the high end.
02-12-2016, 02:10 PM
#4
Pro
Thread Starter
I had a BMW R100GS/PD motorcycle which would let oil drip into the lower cylinder when it was on the side stand. So, I am familiar with a puff of blue on startup. That's not what's happening here. And, I got good numbers on my emissions test, below 4000 RPM.
OK, maybe I won't worry so much, then! :-) Thanks for the feedback!
02-12-2016, 02:15 PM
#5
Rainman
Rennlist Member
Rennlist Member
Oh, that's interesting. Then that would be consistent with mine. I am running a different chip, stock AFM at high elevations. So, I would expect it to be a bit rich.
I had a BMW R100GS/PD motorcycle which would let oil drip into the lower cylinder when it was on the side stand. So, I am familiar with a puff of blue on startup. That's not what's happening here. And, I got good numbers on my emissions test, below 4000 RPM.
OK, maybe I won't worry so much, then! :-) Thanks for the feedback!
I had a BMW R100GS/PD motorcycle which would let oil drip into the lower cylinder when it was on the side stand. So, I am familiar with a puff of blue on startup. That's not what's happening here. And, I got good numbers on my emissions test, below 4000 RPM.
OK, maybe I won't worry so much, then! :-) Thanks for the feedback!
Funny you mentioned 4500rpm. That is approximately the RPM where the AFM flap door swings wide open (where WOT airflow finally overcomes the spring tension).
Since the AFM can't measure incoming air with the door stuck wide open, and the DME has pre-set WOT fuel tables, and is ignoring the O2 sensor at WOT...the DME is pretty much guessing how much fuel to actually put in (since it doesn't have an actual air measurement or AFR input). So it would make sense to default to rich, for motor safety.
