How can you tell if a spark plug is too hot for your application? i am running tr55's on my engine in my sig. but i am having a serious engine miss around 2200 rpm..popping in the exhaust. These plugs have like 10 minutes of run time on them. Plug wires arent crossed. Double Checked that twice. Opti is new as well as the coil.

 

This write up helped me out:

http://forums.bimmerforums.com/forum....php?t=1282968

I'm running TR-55's on my engine with no problems. You might try one heat range colder.

 

The tip of the plug will be white and, if pretty far off you'll see the electrodes eroding away. The plugs you chose are the stock heat range..the rule of thumb is 1 range cooler for every 100 hp increase. Try a set of TR6s gapped to .035"

 

TR6's here. The 55's appeard a little too hot from the markings on the strap.

 

Too cold and you will just carbon foul foul the plug, too hot and you may detonate. When you overheat a plug it can appear as some blistering on the insulator and you could also have little purple spots on the insulator if you are detonating. You need a magnifier to see this. Best to start too cold and use as cold a plug as you can run without fouling out.

 

Well put.

 

Fuel injected cars with a good ignition system and tune have very little tendency to foul plugs. So, when in doubt go colder. However, your problem does not seem like it would have anything to do with the heat range of the plugs. What leads you to consider that it does?

Rich

 

Thanks for all the input on Spark Plug choice. I will definately look into that 1 range colder per 100 hp. As far as the misfire goes, i dont think it is an engine miss as the engine doesnt really shake much. It sounds more like it is down in the headers. Its a pop and it isnt really steady either. Would a knock sensor cause it to have pre-ignition? The knock sensor is retarding timing like 5-7 deg. @3500-4000 rpm.

 

Anyone have a good recommendation for a tr6 plug? If so, got a part #?

 

The knock sensor does not CAUSE detonation (which is not "pre-ignition"). It's simply a tiny piezo microphone that picks up various engine noises that are often the result of detonation (knock). If you have 5-7deg of knock retard, the PCM is pulling timing, because the knock sensor is picking up the sound of knock.

You need to determine if it's "true" knock, or false knock. What grade fuel are you using? Have you tried using higher octane to see if the knock retard disappears? That would confirm true knock, requiring a check of things like the ignition advance, A/F ratio, coolant temp, etc. to see what is causing the knock. A hot plug will cause problems. Or the 12:1 SCR plus the specifics of the cam may just be too much for the fuel available in your area.

If you feel your engine is "shaking" "down in the headers", do you possibly have a metallic rattle that the PCM is interpreting as the sound of knock?

 

What gap size are you running?

 

NGK's TR6 plug has a stock number of 4177, this is for the standard copper version.

I use a gap of 0.035" and have a smoother running engine from idle to redline that I did at a gap of 0.050". There is also less chance of a high compression engine "blowing out" the spark....