Why do plugs show carbon buildup with advanced timing

You need to check your lambdas to see how rich you're actually running. If you have a lot of advance then you need more fuel to help keep detonation in check. If the advance is too far though, you won't get proper combustion and this could show up as a rich condition as well.

FWIW, I had their 3071 tune and it ran rich also. Providing all of your hardware is sorted, contacting them might be a good idea to make sure your engine is running right/safe.

Thanks for the feedback. It's only running slightly rich according to my narrow band sensor so I figured advancing would cure this symptom (My base PW is 21). The car has just not had the oompff it used to upon acceleration and it already seems very advanced, but adding the 2-3* at the base helped with power, though not with the sputtering sound.

Before I changed my plugs to NGK B7KREs today (gapped to .028) it was shaking upon acceleration, no knocking or anything. I'm thinking I may have some back pressure and need my cat changed?

QuattroPwr said:

If it's true that black sooty plugs mean overfueling and/or too much timing retard, why is it that my engine with such high advance fouling plugs so quickly? The average @ 3000+RPM was 35* to 40* timing. This seems really high to me right?

034 set the initial tune and it worked great for the first 5000 miles, but I think it really needs to be dialed back. I can only run 91 octane here in CA and these kind of advance numbers make me think it was tuned with 100+ octane.

The engine is 3b w/GT28RS turbo @ .63 A/R, 42lb injectors. I'm thinking I should dial back both the timing and fueling. Gas mileage has been horrible? Any thoughts? Thanks!

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do not get ahead of yourself. at what map do you see 35-40 degrees? that is very normal for a light cruise condition. sooty plugs probably running too rich. separate things.

pkw said:

do not get ahead of yourself. at what map do you see 35-40 degrees? that is very normal for a light cruise condition. sooty plugs probably running too rich. separate things.

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I probably am getting ahead of myself. That was under light load, which if normal, leads me to believe that the fuel probably needs to be dialed back some.

Took the new plugs out for inspection and a little surprise, the #1 plug is clean as when I first put it in, the other four are sooty around the bases, white at the tips? What can be gleaned from this?

I also noticed that my idle timing was around 25*, lambada slightly high .95. Timing seems high. Where should into from here? My next step is still the cat I believe

QuattroPwr said:

Took the new plugs out for inspection and a little surprise, the #1 plug is clean as when I first put it in, the other four are sooty around the bases, white at the tips? What can be gleaned from this?

I also noticed that my idle timing was around 25*, lambada slightly high .95. Timing seems high. Where should into from here? My next step is still the cat I believe

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what ecu configuration are you running? It will help to figure things out. If it is a sem running solely on map, then something that plugs the engine's flow, that was not doing so during initial tuning, will cause a rich condition because it changes the engine's VE. I do not run more 20 at idle when I do a timing map, but it depends how idle is controlled also. A car can like 15-20, and if you need to for a reason, 10ish can work but it bugs me using something that low because the engine really loves 18ish so much.

I'm not sure what config I'm running, I can download it and post it though if that helps. I had 034 initially setup the tune at their shop, but since then I have had the head resurfaced/valve job/stem seals and lifters replaced due to an overheat. I do know that the fueling map is only MAP based, and the ignition MAP has not been setup yet. Would that be wise? I use the GM style idle controller.

What you're saying make sense, but there are a few acronyms i'm not familiar with here. SEM and VE.

I suspect the cat only because the car has gone through a number of these rich periods when I was trying to tune things

ignition map not set up yet? thought it was tuned at 034?
sem = stand alone engine managment
ve= volumetric efficiency =how well the cyl gets filled.
so a clogged exhaust system hurts that = less charge but enough fuel for more charge = too rich.
..and..
only thing odd about your plugs is they do not look the same. if it is running an ecu with individual fueling offset, that could do it. normal for plugs to look both rich and lean because those are normal conditions at different times.

What ecu are you running? FWIW, I'm running 12* at idle with VEMS...

QuattroPwr said:

I'm not sure what config I'm running, I can download it and post it though if that helps. I had 034 initially setup the tune at their shop, but since then I have had the head resurfaced/valve job/stem seals and lifters replaced due to an overheat.

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but none of that should change your tune

pkw said:

ignition map not set up yet? thought it was tuned at 034?
sem = stand alone engine managment
ve= volumetric efficiency =how well the cyl gets filled.
so a clogged exhaust system hurts that = less charge but enough fuel for more charge = too rich.
..and..
only thing odd about your plugs is they do not look the same. if it is running an ecu with individual fueling offset, that could do it. normal for plugs to look both rich and lean because those are normal conditions at different times.

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Thanks for the schooling.

I'm running the IIc system and no, the main ignition map under basic settings was not setup by 034 in their tune, though the ignition timing control was. Since this sounds like an important element to VE, how should I go about getting a good base? Upload something from the downloads section on their site? I sorta feel like this is a crap shoot considering all the variables in a given setup. Maybe a screenshot would be more useful?

I'll get a back pressure test this week and see if the CAT actually needs to be replaced. As of right now it's literally spraying fuel out the tailpipes getting upto operating temperatures with lambda numbers all over the place. Even at operating temp the lambda is still about .5 too high, even after advancing and lowering idle adjustment trims.

Thanks for the input, this has been occupying too much of my conscious lately.

QuattroPwr said:

Thanks for the feedback. It's only running slightly rich according to my narrow band sensor so I figured advancing would cure this symptom (My base PW is 21).

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First off...don't believe anything you see out of a narrow band sensor. All they are good for is telling you if you are above or below stoich PERIOD. Get a wideband in that car before you hurt the engine.

I run about 20* advance at idle in my car if that helps.

I figured that would be the next upgrade I should be adding in addition to an airbox. 034 has a lot of different options on their site. Any recommendations ?

QuattroPwr said:

pkw said:

As of right now it's literally spraying fuel out the tailpipes getting upto operating temperatures .

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that is not fuel, that is basically, nasty water.

QuattroPwr said:

I figured that would be the next upgrade I should be adding in addition to an airbox. 034 has a lot of different options on their site. Any recommendations ?

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I like AEM. They are more accurate than Innovative.

What do you think about the 034 wideband kit? It's a few hundred less and hooks up with the IIc system directly.

QuattroPwr said:

Took the new plugs out for inspection and a little surprise, the #1 plug is clean as when I first put it in, the other four are sooty around the bases, white at the tips? What can be gleaned from this?

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Sometimes I think we're all guilty of missing what's right in front of us. Basically my connection to the coil was not secure. Fixed the problem right up

Glad it was so easy of a fix!