Help me read my nitrous plugs!

GrandSportC3 · Posted: Thu Jan 18, 2007 10:38 pm Post subject: Help me read my nitrous plugs!

Ok, finally made my first nitrous pass..
My launch was not as hard as it usually is (lost .1 at the 60' mark compared to my previous runs). I started spraying after shifting into 2nd gear. Picked up 4 mph in the 1/8 mile (compared to naturally aspirated runs in the same temperature) but had to get off the nitrous shortly after the 1/8 mile as the car started swaying again really bad. Still gained 5 mph compared to naturally aspirated runs in similar weather. The tires were expanding more than when I ran 125 mph and started rubbing against the frame again Sad

. Therefore, I didn't make any more passes as the car didn't feel save at the last 2 - 3 seconds.
I also had a pretty bad backfire when shifting 2-3 on the nitrous..

I still had a new best ET (by 1 thousands of a second) Laughing

Now I have a few questions:

1) Can the plugs with the different heat range and the 1/2 inch nitrous plate cause the .1 loss at the 60' mark?
2) what could have caused the misfire?
Here is one of my plugs (the others looked just like this one)

The pictures are not too good...so let me describe the plugs. The rim is light to medium gray (looks darker in the pics), the ceramic is white with 2 black spots left and right of the tip. The top of the tip is light to medium gray and the back of the tip is dark gray to black.

I will do some more grinding on the frame near the trailing arm to get some more clearance for the tires so that they won't hit the frame again. Next time out, I will spray off the line as I've lost a tenth compared to previous runs. When I activated the nitrous button, I could feel the car pulling harder but it was not all that impressive.. I expected a more intense effect. Well, I still gained 4 mph in the 1/8 so I know that it's doing it's job Laughing

af2 · Posted: Thu Jan 18, 2007 11:05 pm Post subject:

Are those V plugs? If so that is why the read is left to right. They look on the lean side from the pictures but it is hard to make a final decision.

GrandSportC3 · Posted: Thu Jan 18, 2007 11:09 pm Post subject:

af2 · Posted: Thu Jan 18, 2007 11:24 pm Post subject:

10sec.et · Posted: Thu Jan 18, 2007 11:49 pm Post subject:

little better resolution...was the best i could do.

GrandSportC3 · Posted: Fri Jan 19, 2007 12:24 am Post subject:

pro60chevy · Member Joined: 01 Jan 2004 Posts: 406 16.00 points

Here are three articles on how to read spark plugs. It's going to be hard to acurately read your plugs if you drove back to the pits after the run.

http://www.dragstuff.com/techarticles/reading-spark-plugs.html

http://www.maxracesoftware.com/spark_plugs.htm

http://www.strappe.com/plugs.html

William Jones · Posted: Fri Jan 19, 2007 6:53 am Post subject:

That plug looks pretty good for a nitrous run if it was pulled before the ride back to the pits. But is hard to give you a definite answer looking at pictures. Was there any specks on the porcelain? During your 2-3 shift when it back fired did you may be hit the rev limiter that could cause the back fire? Keep in mind with added power at the shift points the engine will gain more rpms during the gear changes than usual.

GrandSportC3 · Posted: Fri Jan 19, 2007 7:35 am Post subject:

GrandSportC3 · Posted: Fri Jan 19, 2007 7:36 am Post subject:

Paul P · Posted: Fri Jan 19, 2007 9:42 am Post subject:

The quick absence of a load on the engine during the shift could have caused the backfire too. What is up with the swaying of the car in the rear? Is there a way to use some sort of a track bar to help keep it more stable? A loss of control at the speed this occurs would really suck.

See Link Below same link Pro 60 Chevy referred to. Scroll down to "Other Things To Look For" where it explains the black pepper spots on the plugs.

http://www.dragstuff.com/techarticles/reading-spark-plugs.html

GrandSportC3 · Posted: Fri Jan 19, 2007 10:07 am Post subject:

86GN · Posted: Fri Jan 19, 2007 10:30 am Post subject:

If those are a NGK -8 plug, my guess on the black areas is that the plug was starting to foul from the ride back. Notice how the ground strap shadows the porcelin.

Personally I've found NGK's to be on the cool side for each range.

I've run 40 psi on a 9.5:1 motor with TR 6's in it on C-16. That was absolutely pushing things and at that point needed a colder plug, but it worked and didn't hurt anything. On the Corvette I use -6's NA, -7's on the 125 that I've used so far and did so to be safe.

If you could cut the threaded part of the plug off you'll be able to get a much better read on what was happening at the end of your wot blast. Timing wise things look safe. Fuel wise you need to get a look at the hydrocarbon ring to see. Ottoscopes are worth their weight in gold when it comes to reading plugs.

I'd guess the colder plugs dropped off the 60 ft. You probably got into the window switch when it popped going into 3rd.

I've leaned the corvette out to the point that it's lost power on the 125 hp and things have been fine. I've been very conservative with the timing so far.

GrandSportC3 · Posted: Fri Jan 19, 2007 10:47 am Post subject:

William Jones · Posted: Fri Jan 19, 2007 12:14 pm Post subject:

If you are shifting at 6500 and the switch is at 6800 there is a good chance you are hitting it. That is pretty close you get about 300 rpm increase during a shift. Maybe next time try moving the window switch up a little more.