Running too lean?

Originally Posted by Paskii

Thanks for the info Felix good to know that nothing is wrong or damaged.

Originally Posted by LakeShow

I have some black residue on my stock exhaust. Car is completely stock for now. Maybe it won't happen when I get my CBE.

Originally Posted by b1adesofcha0s

Well I have already upgraded my exhaust (CBE, intakes, and HFCs installed) so I will need a tune to fix it.

Originally Posted by Skull Crusher

Carbon deposits. You can't tell from your exhaust tips if it's to lean. Carbon is the black residue left over from the burnt fuel. With 10-15% ethanol used in most fuel today, it leaves a black carbon residue which is collected at the exhaust tip or exit. Every automobile today will have this residue.

You need to run a spark plug chop test and actually look at the base of the spark plug insulator with a magnifying glass. If it's really dark brown or black you're running rich. If it's really light tan, light gray or chalky white you're lean. What you're looking for is; a medium to dark tan. You can install a A/F Gauge but it's readings are more relative to the climatic conditions.

If your running an intake, headers, test pipes or HFC's, cat back and improved intake manifold you might be a tad lean, possibly. If not, there's no way the ECU will allow a lean condition.

Another way to tell is to pick a specific gear 2nd-4th, hold a specific RPM at around 3700-4000 and see if the Z surges slightly. You'll know exactly what I mean if you feel it. If it does, then it could be an indicator of running lean. You will also develop a lean "POP" under deceleration in every gear but will be progressively louder under higher rpm load in lower gears.

Originally Posted by Felix 808

Anytime, but another note on that is if you see white smoke or heavy steam, that is a bad thing. H2o no problem

Originally Posted by Skull Crusher

Carbon deposits. You can't tell from your exhaust tips if it's to lean. Carbon is the black residue left over from the burnt fuel. With 10-15% ethanol used in most fuel today, it leaves a black carbon residue which is collected at the exhaust tip or exit. Every automobile today will have this residue.

You need to run a spark plug chop test and actually look at the base of the spark plug insulator with a magnifying glass. If it's really dark brown or black you're running rich. If it's really light tan, light gray or chalky white you're lean. What you're looking for is; a medium to dark tan. You can install a A/F Gauge but it's readings are more relative to the climatic conditions.
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Originally Posted by Paskii

Serious, wait is it normally to see smoke on a cold start. It does go away after you warm it up and drive a bit. If I do see heavy steam or white smoke what does that mean?

Originally Posted by Motordyne

^+1

Soot can deposit on the tips and bumper even if the engine is running lean. And yes, running rich will make more soot but its not all about the A/F ratio, combustion efficiency is why its still an issue with lean running engines.

The reason there is soot is because of incomplete combustion. Even if run lean, not all of the gasoline is completely reacted with the oxygen. The partially oxidized gasoline creates carbonacious particles or soot.

This is where the stock catalytic converters do their job of cleaning up the exhaust flow stream. The stock cats "catalyses" the remainder of unreacted gasoline and force it to react with any remaining free oxygen to form water vapor and carbon dioxide. Both of which are much better in terms of cleanliness.

In the case of the 370Z engine, it won't allow the A/F to go to any extreme for very long. The objective of the ECU and stock cats is to burn all the fuel. Between the ECU and the stock cats very little soot is emitted.

But once test pipes, ART pipes or HFC's are used, some soot will make it through. The best that can be done is to tune it on the slightly lean side of optimum and go with it.

Originally Posted by Felix 808

That is fine it's just condensation & water vapor, it disapates. Perfectly normal, especially on cold mornings. Like you said it goes away, so don't panic. If you are driving off & billowing white smoke that keeps building that's a blown head gasket. Problems like these do not go away.

Originally Posted by Felix 808

That is fine it's just condensation & water vapor, it disapates. Perfectly normal, especially on cold mornings. Like you said it goes away, so don't panic. If you are driving off & billowing white smoke that keeps building that's a blown head gasket. Problems like these do not go away.