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Help me read my nitrous plugs!
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GrandSportC3
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Location: Lakeland, FL
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1968 Chevrolet Corvette

PostPosted: Thu Jan 18, 2007 10:38 pm    Post subject: Help me read my nitrous plugs! Reply with quote

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


Last edited by GrandSportC3 on Fri Jan 19, 2007 8:14 am; edited 2 times in total
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af2
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1933 Willys Coupe

PostPosted: Thu Jan 18, 2007 11:05 pm    Post subject: Reply with quote

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.
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GrandSportC3
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1968 Chevrolet Corvette

PostPosted: Thu Jan 18, 2007 11:09 pm    Post subject: Reply with quote

af2 wrote:
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.

I'm not sure what a V-plug is? The plug has a little groove in the center of the electrode.. Does this make it a v-plug?

The gray part is a little lighter than in the pics.. The tip and the rim of the plug are light gray (as they should be) but I'm not sure about the black spots on the ceramic part.. Maybe I should try to raise the fuel pressure???
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af2
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1933 Willys Coupe

PostPosted: Thu Jan 18, 2007 11:24 pm    Post subject: Reply with quote

GrandSportC3 wrote:
af2 wrote:
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.

I'm not sure what a V-plug is? The plug has a little groove in the center of the electrode.. Does this make it a v-plug?

The gray part is a little lighter than in the pics.. The tip and the rim of the plug are light gray (as they should be) but I'm not sure about the black spots on the ceramic part.. Maybe I should try to raise the fuel pressure???


If there is a groove they are a V plug. I use the same style. More fuel is definitely needed!
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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Thu Jan 18, 2007 11:49 pm    Post subject: Reply with quote

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





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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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GrandSportC3
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1968 Chevrolet Corvette

PostPosted: Fri Jan 19, 2007 12:24 am    Post subject: Reply with quote

10sec.et wrote:
little better resolution...was the best i could do.






Perfect - thanks! That's closer to how they actually look!!
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pro60chevy
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PostPosted: Fri Jan 19, 2007 4:58 am    Post subject: Reply with quote

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
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William Jones
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PostPosted: Fri Jan 19, 2007 6:53 am    Post subject: Reply with quote

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.
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GrandSportC3
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1968 Chevrolet Corvette

PostPosted: Fri Jan 19, 2007 7:35 am    Post subject: Reply with quote

pro60chevy wrote:
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


Thanks!! I still don't see any explanation for the black spots on the porcelain.. I do think that the rest of the plug is ok...
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GrandSportC3
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1968 Chevrolet Corvette

PostPosted: Fri Jan 19, 2007 7:36 am    Post subject: Reply with quote

William Jones wrote:
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.

I went back to the pits as it is very dark at the end of the track.. However, I took the first turn off. Don't think that this changed the reading too much..
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Paul P
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1971 Chevrolet Chevelle

PostPosted: Fri Jan 19, 2007 9:42 am    Post subject: Reply with quote

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
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GrandSportC3
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1968 Chevrolet Corvette

PostPosted: Fri Jan 19, 2007 10:07 am    Post subject: Reply with quote

Paul P wrote:
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


The swaying might have to do with the fact that I'm mixing bias ply fronts and radial rear tires..
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86GN
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PostPosted: Fri Jan 19, 2007 10:30 am    Post subject: Reply with quote

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.
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GrandSportC3
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1968 Chevrolet Corvette

PostPosted: Fri Jan 19, 2007 10:47 am    Post subject: Reply with quote

86GN wrote:
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.

Hmmm. I thought that heat range of the plug show on the rim and jetting on the tip and detonation shows on the porcelain?? I'm thinking in spraying off the launch the next time out to make up for the lost .1

I doubt that the window switch came on as I never went close to where it shuts off.. I shifted at 6500 and the window switch turns off the nitrous at 6800 RPM..
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William Jones
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1971 Ford Mustang

PostPosted: Fri Jan 19, 2007 12:14 pm    Post subject: Reply with quote

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.
_________________
Take the horse out off the barn and let her RUN BABY RUN!!!!!

92 LX 454ci Clevor 9.24@142.53 N/A
71 Mach1 454ci Clevor 10.16@134 N/A 3850lbs race weight "Lost in fire"
03 Cobra Bone stock 12.42
68 Falcon 363ci 10.55@126 N/A
95 GT 363ci 11.08@118 N/A
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