Dealing with Phantom knock?

[s1ngletracker]

I'd like to tap into some of the more experienced members here...

Has anyone successfully eliminated phantom knock? I'm getting a good amount of it on my 1g. Its weird, one pull will be just fine, and literally the next pull will be riddled with knock and timing will get pulled.

A few things I've been told to check:
CAS
Replace turbo/exhaust manifold gaskets
install improved lifters
PCV Valve

I dont think I'm actually leaning out or anything, but at some point soon i'd like to get a wideband to make sure.

[s1ngletracker]

Oh yes, and I should say my 1g is bone stock, other than an MBC... but it 'knocks' even at stock boost levels. So while I'd like to know my AFR, I wouldnt actually be able to tune it.

[jrohner]

And your base timing is correct?

[s1ngletracker]

yep, 5* BTDC with the plug grounded.

[sleepydsm]

Have you modded the car in any other way, doing anything that might produce more vibrations or rattles?

[s1ngletracker]

Nope! I believe this to be a problem with the car since I got it.

Any ideas?

[s1ngletracker]

I'm starting to think this is a fueling issue (read: actual knock, not phantom)... the problem seems to be getting worse. The car just refuses to pull hard under boost. Occasionally it pulls fine, but it seems to be getting more and more rare, and only when its completely warm and has been running a while.

I'm starting to suspect my fuel pump, filter, injectors, etc. I might grab a dummy gauge and see if i'm really lean under boost.

[jhaan_dude]

give me a call ill help you trouble shoot i got a couple of ideas

[s1ngletracker]

I would, but I don't believe I have your phone number... Why not just share the ideas here?

[Shane@DBPerformance]

Just look at your O2 voltage in your datalogger. That's free and better than a narrowband O2 gauge.

[s1ngletracker]

ah yeah, good call. I just don't know how to convert voltage to A/F... any idea?

[Halon]

Run the tank down real low, and go put a couple gallons of C16 in it, and see if the knock goes away.

[s1ngletracker]

Where can I get C16?

[Shane@DBPerformance]

Originally Posted by s1ngletracker

ah yeah, good call. I just don't know how to convert voltage to A/F... any idea?

You can't convert volts to A/F without a wideband gauge. .5v on a narrowband is 14.7:1, it is only accurate right around .5v. The stock ECU and stock narrowband O2 only care if it's richer or leaner than .5v/14.7, not by how much.

The dummy gauges don't read in A/F either. They just have huge ranges covering rich, stoich, and lean.

But any ways, your O2 volts should be like .92-.98 under boost, unless you have a 1990. And even with a perfectly flat wideband A/F of like 11.0:1, your O2 volts will change, instead of holding a consistant .96v or whatever. You could have a perfect A/F and your volts might go from .90 to 1.00 across the RPMs. So they are almost useless for tuning outside of idle/cruise.

[s1ngletracker]

How does the O2 look on this log?

LINK

[s1ngletracker]

I realize the stock narrowband O2 is inaccurate, I just want to know if i'm rich or lean... not exactly how much.

Let me phrase it this way. Do you know what voltage represents stoich on the stock O2?

[Halon]

Stoich is 14.7. So if he said .5V = 14.7, then he is saying .5V = stoich.

[Shane@DBPerformance]

Don't log so many useless things and edit your logs to just pulls. I only saw 1 row in that whole thing that was 100% throttle.

Does it knock at cruise or full throttle or part throttle with some boost?

.5v is stoich on a stock O2.

[s1ngletracker]

the problem is most prominent at part throttle with boost.

Yeah, sorry about the messy log. I just realized that there wasn't much full throttle. If 0.5v is stoich, i'm at least not running TERRIBLY lean. I'm hitting about 0.90v

[Kevin 1G Drummer]

I believe Shane said 11.0 AFR is roughly .9 volts at WOT, so you shouldn't be lean at all. From the way I understand it, >.5v = rich and <.5v = lean.