Thread: Read my plugs please

Tweet

Someone out there care to read my plugs for me. I'm not sure what the pink on the insulator tip means. These weren't from a proper plug reading run, just driving around (can't find the right plugs locally, so I'll have to order them, so the only ones I have are the ones in the engine that have about 1300 miles on them). Also, anybody know a good source for non-resistor plugs? Bosch doesn't make non-resistors any more (these here are resistor, but everything else about them is correct at least...or correct for a factory spec engine at any rate).
Thanks in advance

http://www.dragstuff.com/techarticle...ead-plugs.html

Yeah, I had seen that website, and others, but I can't figure out what the pink means.

Depending on how many miles are on them it looks like it's way 2 lean to me! Lon

About 1300 miles on the plugs. It does seem a little lean at WOT. Bosch CIS injection (K-jetronic, not KE-jetronic) is such a hassle. Sometimes I wonder if I'd be better off with carbs.

A shot from above showing more of the prcelin would help... Looks a bit lean from what I can see now... Have you checked it with an air-fuel ratio monitor????

No, unfortunately I don't have access to an A/F ratio meter. The engine only has 1300 miles on it too, fwiw (well, 1300 post initial break in miles, so more like 1800 miles after the first bed-in running - no I'm not only doing a 500 mile break-in, but the first 500 miles were done with different oil and some mixture and timing differences) . I know before the engine went in, some dunderhead had blocked off the warm up regulator (which also does high throttle enrichment)...what I don't know is if someone other than me replaced it or not (I thought someone had, then that person indicated that he hadn't...so now I have to figure out if someone else did). I could just adjust the main mixture screw at the top, but my understanding is that on Bosch CIS, that is mostly just for idle mixture, and given the one black ring I'd say idle mixture is good where it is.

I'll take a better shot tomorrow.

Any ways , what are you running? You know type of car and motor, timimg maybe.



You can buy a pretty cheap air/fuel monitor for cheap from Summit, about 125 dollars the last time I bought one.

Even cheaper but just as good ,maybe better, you can make your own. You will need to get a O2 sensor bung (5 dollars) and get it welded into you exhaust (20 bucks). Then get a O2 sensor (65 dollars) plug in some 12 volt power and the other wires go to your volt meter and thats it. One thing to keep in mind though is if you are running headers you need a heated 02 sensor . For anything running a 02 sensor and headers the sensor need to be heated. A heated 02 sensor will give you consistant results since the tubing of the headers are thin. The exhaust will cool down quicker and give false readings .

If you have a newer system and have a 02 sensor in the vehicle just plug in your volt meter.

Heres a basic guide http://www.cfm-tech.com/oxygen_sensor_tuning.htm

1300 mile, they should by now represent the "burn". On a new motor I would worry about pre-ignition and heat build up with those plugs. If anything you want it a little more rich for break in. JMO, Lon

Originally Posted by BigTruckDriver

Any ways , what are you running? You know type of car and motor, timimg maybe.

You can buy a pretty cheap air/fuel monitor for cheap from Summit, about 125 dollars the last time I bought one.

Even cheaper but just as good ,maybe better, you can make your own. You will need to get a O2 sensor bung (5 dollars) and get it welded into you exhaust (20 bucks). Then get a O2 sensor (65 dollars) plug in some 12 volt power and the other wires go to your volt meter and thats it. One thing to keep in mind though is if you are running headers you need a heated 02 sensor . For anything running a 02 sensor and headers the sensor need to be heated. A heated 02 sensor will give you consistant results since the tubing of the headers are thin. The exhaust will cool down quicker and give false readings .

If you have a newer system and have a 02 sensor in the vehicle just plug in your volt meter.

Heres a basic guide http://www.cfm-tech.com/oxygen_sensor_tuning.htm

It's a modified Mercedes 117.968 motor (1986-1991 560SEC/SEL), which is an overhead cam, 5.55liter V8 (though mine is 5.65 liter, has lumpy cams, and 10:1 pistons, and everything else to match. Timing is 10 degrees BTDC at idle). The exhaust (jet-hot coated tri-ys to downpipes, to cats, to a single pipe - set up by a nextel cup shop this way to make the most area under the curve though peak power is a little lower than a dual exhaust to the end system would have been). It does have O2 sensors...in a way. The factory set up has O2 sensors that do nothing other than give you a convenient point under the hood to check the voltage. Currently, there are O2 sensors but they do nothing other than plug the O2 sensor bung holes.

Originally Posted by Brigrat

1300 mile, they should by now represent the "burn". On a new motor I would worry about pre-ignition and heat build up with those plugs. If anything you want it a little more rich for break in. JMO, Lon

When it was first broken in, it was set to run rich, but with the tolerances of Mercedes engines (to give you an idea, piston to cylinder wall clearance spec is 0.0005") things were pretty well seated after the first 500 miles. These are aluminum blocks, but they aren't sleeved. As I found out after JE misled me and then told me, oh well, didn't work, if you find someone to make custom sleeves for it will give you a discount on another run of pistons, the way they make it work is by being very careful in piston material selection and extracting the silicon from the block after the cylinders have been machined. So the builder (uh...my new builder, who knows better than to take JE's word on using JE pistons in an MB engine) who did the initial break had then adjusted the mixture to get it pretty close, and left the final mixture tuning to me (for the best as where I live is ~20F cooler than where he is).

Well...I would have posted a better photo today but there is no need. The base of the insulator tip looks just like the tip of the insulator tip, just minus the pink color (so the base of it looks like the exposed part in the second photo in the original post).

The two pictures are two different plugs, right? The "pink" one has a good color to it... if you call it "tan" that's about the shade you want all over the porcelain... the hue will vary depending on the kind of fuel you run (what fuel do you run?). The area we can see in the photo points to part throttle mixture. The other "white" plug looks too lean in this same area. From the second picture, it appears to me that timing is about right where you want it with the "blue" line about at or just past the apex of the bend. Also from the second picture it looks like you are rich at idle based on the soot on the threads...

Carb or FI? The two plugs you show are quite different... which cylinders did they come from?

Here's another link on plug reading:
http://www.4secondsflat.com/Spark_plug_reading.html

Hope some of this helps...

-Chris

It's actually two pictures of the same plug, just different sides of the plug. I was running Chevron (I run Chevron whenever I can find it) but barring that I run Shell (which is much more readily available to me than Chevron). It came from cylinder #6 (driver's side, second closest to the front of the car). Yeah, idle smells rich too, but I'm able to smooth out the idle considerably (lumpy cams) by richening even more, so I don't know what to do.

It's fuel injected (Bosch CIS injection aka Bosch K-Jetronic...not to be confused with CIS-E/KE-Jetronic, this is much more like a mechanical injection than that).

How far down is the full throttle portion? If you go down below the point that can be seen without a pen light (even if holding it in the sun), the insulator becomes black (and there is a very clear line where this stops and the pinkish white starts).