Signs of running lean vs. running rich

[judasentinel]

Well, as the subject line says, I am wondering what the signs of leaning out would be. As far as I understand, if the car is sputtering and backfiring, its a sign of running rich. If the reverse were the case, what would be the signs and symptoms? I dont have a gauge to know, otherwise I wouldnt be asking this question. But my car seems to rev just fine between 1000-4000 rm and after that, it starts to act as if something is holding it back and then its gone again. But then at around 8 psi of boost and full throttle, around 6500+ rpm, I can hear a sound that is produced when you slowly bang a few metal rings together. I wonder if its because the car is leaning out, running too rich at high rpms or the turbo acting up or knocking.

There is also a bit of a loss of power in the higher rpm range (5000+), where the car seems to have hit a plateau in power, especially in the 5th gear. Is it possible that its a knocking sound due to leaning out or the turbo being dry for some reason (by dry I mean not lubricated enough)?

Any ideas?

[kelaog]

If you're hearing a metal on metal sound you are pinging. What kind of octane are you running? Have you checked your timing? Also pull the codes from the ECU. If you're pinging it'll throw a code for sure.

If anything else your turbo might have developed some shaft play (that sounds dirty) Take off the piping connecting to your intercooler on the turbo side see if there are any metal flakes around. If so, time to throw out your turbo.

[judasentinel]

Its surely metal on metal sound and is happening at around 6500 rpm onwards, but only when I am driving, not when I just rev it up. Would detonation only occur when I am driving or also when I just rev the motor up at 6500+ rpm?

What could be the cause of it? My timing is set at around 5 deg BTDC at idle and when I last measured it on dyno, it advanced to a max of 27 deg. If I set the idle timing to 15 deg, it would detonate even more.

As for the turbo, I like the "shaft play" pun, lol. But in all seriousness, it works perfect in first gear, spools really well and I get that kick, but then in the second gear, the I can hear the air going in, then it hits a flat spot at 5000 rpm. If I continue to press, it goes thru that flat spot and then sputters thru to higher rpms where it starts to give out that metal on metal sound. Third and fourth are just fine but again in 6500+ rpm that metal on metal sound is back.........and then I back off.

My concern remains as to WHY this could be happening. I know my ignition timing is not set too advanced. Any thoughts, ideas? What to check?

BTW, Paradis, kelaog, my idle problem is solved. It was too much fuel and TPS (thanks, Mike).

[cortexx]

the load on the engine being driven at 6500 and revving freely at 6500 is totally different , sounds like detonation followed by the ECU pulling timing to protect the engine maybe ? really hard to tell without being there

If your running a power fc and a data logit record the data and post it up here (if you can screen shot it)

[Skym]

Lean engine can make engine stumble before accelerating (transient throttle enrichment is leaner than it should be).

Stock ECU would pull ignition timing early. At least it did on my car when it went very lean at 3500rpm. Torque drops off very quickly on dyno graph after 3500rpm.

I describe it as nails in a jar type sound. Had that when CAS was advanced too much. Lesson learned the hard way. Base ignition timing should be at 15 degrees BTDC, as ECU adds ignition timing on ignition map to base ignition timing (can see this in tuning software) to reach ATDC where ECU fires sparkplug.

[evilgtr]

Now that's a old thread revival. 4 years..