Reading spark plugs

[snoboy]

OK guys I had a real good chance to read plugs this weekend. Did WOT plug cuts and though I had no camera I'll use this clicky to show you what I had.
I look just like the picture on the right that they call rich.

This is an 08 Polaris 700 CFI that is piped, ported and running a fuel controller. I've been tuning it for 2 saturdays and it's running damn good but I think I'm JUST getting into the right fuel range. So even though I'm colored halfway from the bend to the tip how close is it to get to the corner? IE. is it 1 jet size or 2 sizes. I realize I'm not actually jetting but dialing the controller is the same concept. I can tell you that my EGTs are in concurrence as they have not broken the 1200 degree mark. I know that as I step down the fuel maybe a half to a full step it's gonna get real strong. Just looking for general conversation on the plug and jetting stuff. Thanks

http://www.snowtechmagazine.com/articles/2001/baseline/baseline.php

 

[snoboy]

ttt

 

[NoSecondChances]

...it's running damn good but I think I'm JUST getting into the right fuel range. So even though I'm colored halfway from the bend to the tip how close is it to get to the corner? IE. is it 1 jet size or 2 sizes. I realize I'm not actually jetting but dialing the controller is the same concept. I can tell you that my EGTs are in concurrence as they have not broken the 1200 degree mark. I know that as I step down the fuel maybe a half to a full step it's gonna get real strong. Just looking for general conversation on the plug and jetting stuff.

Hard to tell if the color from the bend to the tip is one or 2 jets, or 5-10 degrees, or one more plug heat range, or fuel age (old vs new), etc etc. Sooooo many variables that could change that, air density as a huge factor, don't want to get into that yet. Not only that, it changes with one sled to the next and with every different modification. There is no set formula i.e. "1 jet size changes the colour 4 shades of brown and moves the line 0.8 mm closer to the firing electrode" etc. It will be different for each engine and each day. Set your baseline and go from there. If you are tuning to run on the edge, you'll have to go over it to find out where it is for your motor, which means you will have a liquid piston. If the plug is tan all along the ground electrode, no gray or dark brown on the tip or the firing electrode, you're probably good IMO. Its better to be a tad rich than a tad lean. The difference from 15 mpg to 15.1 mpg, is better than the difference from 15 mpg to "a hole in the piston".

Put electrical tape over your EGT windows until you get it jetted right using plug readings and wash, be aware that it takes wash quite a long time to develop, like hours, plug readings are better. Do a bunch of runs with different throttle positions, shutting down and keeping the throttle there. When it is bang on, then take the tape off and see what the EGT's are reading. That will be your reference point. It may be 1180 degrees, it may be 1260 depending on probe placement, pipe diameter, design etc. Mine is good at 1150 (WOT), nice brown, still slightly rich but not on the edge and gives me a bit of buffer, 1220 the alarms start to flash, this is where I'm jetted perfectly, and 1260 is where the tip just starts to show gray. Other motors might start showing gray at 1230 or 1330, dependant on lots of different factors. My mid range temps are 980-1110, from 5000 to 7000 rpm.

All that being said, for comparison, one main on my sled will raise temps about 90-120 degrees (as a very rough ballpark) but quite often I'll drop the needles a clip position or two as well when changing mains to crispen up the mid as well, so some of the temp change could be attributed to that as well. Hope this helps.

 

[F-Bomb]

reading your plugs

http://tsrsoftware.com/images/read_plugs-tsr_software.jpg if that link doesn't work type this in on your address line and it works...

http://tsrsoftware.com/images/read_plugs-tsr_software.jpg

A good light and magnifier is very helpful..the plug reads is the most accurate and instantanious result of state of tune vs timing that you can get without having a data logging air fuel system. It's archaic but it's what you have for a tool unless you have $5000 to spend! Remember that its instantanious so if you don't kill your fire from throttle position and duration of burn to position you will get a variable and inaccurate read. TIME RPM RUN, KILL, COAST, READ, and NOTE!

NOW do not cover your egt windows at anytime! I realize he is making a point about the temps that you see and what it actually means to your state of tune. Go to my website and review the DIGATRON TECH page. Tie that in with what you are doing vs your plug reads. Every single instruments reports are independant so an adjustment for him is different then an adjustment for you in your egt reports.

 

[snoboy]

Outstanding information! Thanks a bunch F-Bomb.

 

[NoSecondChances]

...NOW do not cover your egt windows at anytime! I realize he is making a point about the temps that you see and what it actually means to your state of tune....

LOL!! thanks F-Bomb, yeah, my point was not to try and tune with EGT's until a baseline is established, hope that message was understood. I talk to guys all the time that say, "I can't get over ___ degrees, blah blah", you look at their plugs and they aren't that far off. Was talking to a guy the other day, said he couldn't get his EGTs higher than 1120 so he disconnected it, thought it was inaccurate, but a look at his plugs showed he was pretty tan already, his probes were in the wrong spot, too close to the motor. If he would have leaned it, probably would have been right at the limit or over. He was tuning by the EGT's and not checking plugs, trying to keep others from the same mistake.

 

[snoboy]

LOL!! thanks F-Bomb, yeah, my point was not to try and tune with EGT's until a baseline is established, hope that message was understood. I talk to guys all the time that say, "I can't get over ___ degrees, blah blah", you look at their plugs and they aren't that far off. Was talking to a guy the other day, said he couldn't get his EGTs higher than 1120 so he disconnected it, thought it was inaccurate, but a look at his plugs showed he was pretty tan already, his probes were in the wrong spot, too close to the motor. If he would have leaned it, probably would have been right at the limit or over. He was tuning by the EGT's and not checking plugs, trying to keep others from the same mistake.

NoSecondChances, I knew what you were gettin at. Appreciate all the advice. I'm working with the plugs and that's what i'll be concentrating on this weekend and then I'll see what my temps are when I get real close with the plugs.

 

[F-Bomb]

Guys please note that there is useful information on the plug reads and its way more then looking at the overall color of the end of your plugs. There are absolute results but you have to be able to see down into the porcelain plus you need to look at the various burn patterns and what they indicate. A magnifier and small light are super handy. Reading a plug for tune is much more indepth then simply examing the overall color of the hot end! (I didn't know this and neither do tons of great tuners)

Also note that different plugs run at different heat ranges as well as fuel and oil combos can alter what you would see. That is why tuning is a combination of puzzle pieces that need to be assembled for the complete picture. Putting your timed RPM vs heat responses from an EGT together with sound, response, smell, and then plug and piston wash reads is what gets you the info you need. After you have the knowledge and experience from the given application then you can use your EGT at a gauge instead of a tuning tool or "instrument".

 

[NoSecondChances]

Guys please note that there is useful information on the plug reads and its way more then looking at the overall color of the end of your plugs. There are absolute results but you have to be able to see down into the porcelain plus you need to look at the various burn patterns and what they indicate. A magnifier and small light are super handy. Reading a plug for tune is much more indepth then simply examing the overall color of the hot end! (I didn't know this and neither do tons of great tuners)

Also note that different plugs run at different heat ranges as well as fuel and oil combos can alter what you would see. That is why tuning is a combination of puzzle pieces that need to be assembled for the complete picture. Putting your timed RPM vs heat responses from an EGT together with sound, response, smell, and then plug and piston wash reads is what gets you the info you need. After you have the knowledge and experience from the given application then you can use your EGT at a gauge instead of a tuning tool or "instrument".

Great points and info F-Bomb! For sure, there are soooo many more things that go into this, however trying to go into the intricate details of it is sometimes an effort in examining the law of diminishing returns unless we are tuning a race engine. Patterns, porcelain colour, cylinder head/combustion chamber temps and patterns, center vs ground electrode colour, timing, motor design, fuel (av gas burns white on the plugs), plug heat range, etc. are all factors that will play a part in it. We have even seen different readings from just indexing the spark plugs towards the intake/transfer ports as the incoming fuel charge direction, flame kernel and combustion pattern are significantly altered with just this little change. As generalizations go, I was focusing more on the simple items (overall plug colour and general wash pattern) to try and help out. If I was tuning a race motor or this was my sled, I'd be looking at several other factors as well, not just general plug colour.

 

[Hatcher]

http://www.allautosmog.com/nitrousoxide.htmYou can read every book in the world and every video they make, but the only way your going to know is by experience. experiment. Make the thing fat rich, make a couple of runs, pull the head off, most sleds its not that hard. read the plugs, and look at the piston. next make it lean, and do the same thing. then you will know what lean and rich looks like.

Thats what I did. and I run a full wet Nitrous system with the biggest jets, its got more power then I can apply to the snow.

 

[NoSecondChances]

....Make the thing fat rich, make a couple of runs, pull the head off, most sleds its not that hard. read the plugs, and look at the piston. next make it lean, and do the same thing. then you will know what lean and rich looks like.....

good points, but I wouldn't recommend pulling the head off after only a couple runs, get a small flashlight (I got one that looks like this - http://www.nextag.com/Deluxe-Flexible-Tank-Inspection-555210988/prices-html - get one that has a long reach so you can go up the header pipe from the Y if it has a single pipe - twins aren't an issue since the couplers are so close to the motor) pull the pipe(s) off (you don't even have to remove it from the sled, just slide it back enough to get the neck of the light in there, turn the crank to drop the piston you want to look at down to BDC, put the light up the header pipe through the exhaust port and look down through the spark plug hole. You can see the complete top of the piston and wash pattern perfectly and there is no need to pull the head. Takes about 5 mins in the field to pull the pipe and plugs and inspect. Often I don't even pull the pipe, I have a smaller light with a really small neck (1/16th" wide) so I just stick it down the plug hole and can see the majority of the piston and wash pattern. its not as clear as going through the exhaust port becuz the light is sometimes in the way, but if I pull the plugs to inspect them, sometimes I will quickly have a peek to see, its good enough for me to do a quick spot check and I use it to check other things like scrapes and gouges on the cylinder walls, no broken port chamfer spots, holes in pistons, etc. Thought I broke a rod once, loud banging from under the hood, used it to confirm that everything internally was fine, then used it to inspect the outside of the motor, found a broken torque stop that busted and worked its way between the clutch and the block, was banging off the rear clutch vanes and causing a loud rattle.

 

[ZRrrr]

All very good info. Should be posted in the General section for all to see!

I used to be one of these guys that tuned looking only at plug colours. Then I learned about looking at piston wash in conjuction with plug colour. Almost learned the heard way too as I had piston start to go on me. Noticed the change in the sled and shut down fast enough to save it. Piston crown was starting to melt!!

My point is that since those days I have learned alot. Like NoSecondChances says, there are soooo many factors involved. I'm just now getting indexing.

At a recent drag race all indications were that I could jet down one more. Did a few test runs and all still looked good. Thing was I noticed the sled didn't seem to have the same power, was a little doggy, especially on top end. Again, plugs, pistons it all looked perfect. Put the old jet back in and right away the power was back. You just can't use plug colour and piston wash as an indicator, there are too many other variables involved.

I like to find days where the sled is runing amazingly well and record the details. If there is a consistant pattern to these days I know the sled is at peak performance.

My 2 cents.