Stryk3r

Hi again guys....i just rebuild my engine and in my previous i told u about the missing thing well...i removed my plugs....my leading plugs when removed were black in color but my trailing blugs were completly rust brown???what is this isgn of and what is causing this and what all to check please advise ...and is this ormal or something majorly wrong.......





regards

Jeff20B

Could be a bad component in leading ignition system.

Lynn E. Hanover

Plugs tell you what was the last thing that happened before you shut down. The lower the chamber temps at shut down, the less accurate they are.



So if you shut it off at idle, and it had idled for a few seconds before shutdown, then the plug color on the porcelain, not the shell, will tell you that you are using unleaded fuel, (black powder look) and the engine was no being used at a high power setting when you shut it off. The recessed plug will seldom tell you anything except the brand of fuel. It is protected from the hurricane of the flame front going by. The rotary does not lend itself to plug reading exactly like a piston engine, but you can get some ideas from reading them. The four ground electrode style plugs shield the porcelain from most of the color changes you need to determine tuning state. But if you would like to try a few passes at plug reading, here is what you do.



Pick a full throttle RPM that you want to know about. Pick a remote location. With the engine at full temperature, in a gear that you can control wheelspin with the brakes, go to full throttle, and with your left foot, hold enough brake pressure to maintain the RPM you have selected. So you are at 6,500 RPM in third gear, just keep rolling in more throttle at the same time you add more brake to keep the engine at 6,500 RPM. In some cars there is so much power available, that you just cannot do this, without loosing control of the car. Just forget it and put it on a dyno, and read the tail pipe and the computer at full throttle.



But if you can do this for 5 seconds, release the throttle, brake to a stop as fast as you can safely with the clutch pedal on the floor. As it comes to a stop, switch off the engine. That is called a clean cut. So the period of time from full throttle to a full stop at idle and switched off is as short a period as possible. So hop out and pull a leading plug and look at the porcelain. Snow white all over, too lean. Off white all over with a bit of tan on one side, just about perfect. Tan all over, tending too rich. Dark brown all over, to rich.



If you never get anything but white or off white, put in a set of ice cold plugs and try again. Hot street plugs tend to stay clean all of the time, and run at higher temperatures to keep the porcelain clean, so they burn off any coloration from combustion products.



The lack of lead in motor fuels has made plug reading a lost art. The phosphor based compounds tend to show only shades of black, no matter the condition of the engine. You can also get a good read by looking about an inch inside the tail pipe after a hard run. All black is rich. A reddish brown (the color of the trailing plugs) is closer to lean enough. The very end of the pipe may be black all of the time. Pay no mind to that.



Lynn E. Hanover

Maxt

Could be a pile of things...

Check the compression difference between the front and rear rotors, when I had compression problems with my ra seals, the plugs would show up like that, check your fuel distribution, and make sure all your injectors are working, and feeding equally..Max