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Join Date: Sep 2001
Posts: 380
Before going too far, I figured I should pull the plugs and see what they look like…I would say this is the biggest drawback of having the turbos on the side and the intercoolers pipes running up next to the valve covers. Fortunately, it’s as simple as removing three nuts and disconnecting 4 hoses.

Lower plugs 1, 2 and 3 have black, sooty dry-looking deposits; this is consistent with this bank showing a rich condition. Plug 4 is sooty with 5 and 6 showing black on only the porcelain with the strap and base ring mostly clean. Since they are not consistent across all 6, I am thinking this is a fueling issue, probably injectors. Thoughts?

How quickly do the plugs become sooty with a rich condition? Could this have happened from my initial map being overly rich before I made adjustments? Should I clean the plugs and check them again or move on to having the injectors checked and flow matched?

As an aside, what are your thoughts on the heat range of the plugs? The uppers are Denso PK20PR-P8 and the lowers are NGK PJR7A.

Old 09-13-2010, 10:55 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
David's Avatar
Join Date: Apr 2002
Location: Houston (Clearlake), TX
Posts: 9,575
Those aren't nearly as obvious as what I had. Mine were literally black and white.

When I first started my engine after EFI, I put in plain jane NGK plugs knowing I'd probably throw a few sets away. Those look pretty expensive so you could try cleaning them and then a quick drive around the block before pulling them out.

Unfortunately I don't have 2 lambda sensors so I have no numbers for comparison.

I did go from a simple in series fuel system where fuel entered one rail, crossed to the other, and out the other rail. Even though I'd gotten the OK from a reputable tuner that this was OK, I thought it was the problem and converted to a system like your's. I put the rails in parallel with dampers on each rail. There was literally no change after all that work and money. So I wouldn't worry about the fuel delivery system.

If you see some inconsistancy between different cylinders on the same side, I guess it's possible to have just one or two bad injectors causing the problem. Could you switch injectors side to side very easily?
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Old 09-14-2010, 04:39 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #22 (permalink)
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Again, what happens to O2 /AFR readings if the rings are not seated yet or some such and some oil gets into the combustion chamber?

Have you tryed moving the O2 sensors side to side.

Here is a picture guide to reading spark plugs: Spark Plugs

I am not an expert but it dose not look like there is a lean condition

Also could be an ignition issue and the plugs are not getting hot enough:

"Dry and Wet Fouling:

Although there are many different cases, if the insulation resistance between the center electrode and the shell is over 10 ohms, the engine can be started normally. If the insulation resistance drops to 0 ohms, the firing end is fouled by either wet or dry carbon."

Last edited by 911st; 09-14-2010 at 12:42 PM..
Old 09-14-2010, 12:35 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #23 (permalink)
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Join Date: Oct 2005
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"As an aside, what are your thoughts on the heat range of the plugs? The uppers are Denso PK20PR-P8 and the lowers are NGK PJR7A."

I've been running the '7' range NGKs for 4 years with no fouling. They're on the cool side for my setup.
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Old 09-14-2010, 03:46 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #24 (permalink)
Join Date: Sep 2001
Posts: 380
Today’s update…

Since my wideband controllers and sensors were suspect, I borrowed an LM2 and verified by swapping it left to right that the AFR readings are different. However, the readings were not completely consistent with my TechEdge. Looks like it is time to upgrade…I think I will order the Daytona dual channel that dickague recommended.

Since the lower plugs didn’t look great, I decided to pull the top plugs as well. Only problem is that the right rear plug is impossible to get out due to clearance issues with the power steering pump. As a result, a partial engine drop was in order to gain enough access to pull the final plug. Top plugs were consistent with lower plugs.

Next I decided to test the injectors using the Megasquirt injector test mode as suggested by Mike. As suspected, two of the injectors flowed much less than the other four. Since this was the side with the wideband output going to MS, looks like I was adjusting the fuel to compensate for the under flowing injectors and as a result was over fueling the other side. Turns out I have a total of 16 of these injectors (not sure why) so it is entirely possible that I inadvertently mixed them up. As suggested by esotoracing, I have packed the entire lot and will send them off to RC Engineering to have cleaned and flow matched.

In double checking the fuel system, it turns out that the fuel return line from the fuel pressure regulator back to the tank is the same -8an as the line going to the fuel rails and then to the FPR. Even though I laid it out to be smaller, looks like I messed up…while the injectors are being serviced, I will replace this with a -6an return line.

Since the engine is mostly out and I am in a holding pattern with the injectors, I will pull it completely and check the cam timing tomorrow. I will also double check the coil packs and the balance of the ignition system to ensure that all 12 plugs are getting good spark.

Can I disconnect the fuel system and turn the engine over without having it bolted to the car, or is this a bad idea?

Old 09-14-2010, 07:18 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #25 (permalink)

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