I am new to race fuels and really high compression, I am now running 14:1 and 110 leaded sunoco race fuel,
I am noticing on the end of my plug base where you would commonly see black soot with pump gas that I have a tan coating that smears when I rub it. Actually it looks like little speckels around the base, but I can smear it and it rubs off farely easy. its almost rusty looking actually. when I shine a light in the plug holes I can see a golden tan coating on the piston, but no speckles like I see on the plug base. the porcelain of the plug is toasty tan.

what do you guys reckon it is - something to do with the lead in the fuel?
can I assume this is building up in other areas - like maybe the exhaust ports, and maybe on the valves?

 

I've never ran Sunoco fuel but every race fuel I have ever ran in my life the plug should be off white to dove gray all the way to the end of the pipe.
You won't see the common black to tan color that you do with pump gas.
It's hard to say without seeing a really good picture of the plug but I don't like the description of speckles usually. Little speckles or little shiney ***** are usually a sign of detonation. But with a true 14 to 1 and 110 fuel you should be fine.
It's funny you are seeing any tan or golden color at all with race gas. All "Trick and ERC" plugs look off white to dove gray with no tan at all; ever; no matter how you jet it. Maybe Sunoco puts some type of additive in the fuel? I just don't know?
I don't want to make you nervous, but it almost sounds like a small amount of oil contamination coloring the plug and piston?

 

I run sunoco and VP. The VP makes for a medium gray color on everything but the sunoco is a brownish gray.........on the plugs and all the way to the pipe. I think it is very normal since it is sunoco. My $0.02

If it isn't, I have the same problem you do hightower...........but only when I run sunoco.[img]i/expressions/face-icon-small-smile.gif[/img]

 

My thoughts are you need to run a colder plug.
Tip maybe too hot and when raw fuel comes in contact, the fuel burns and leaves this residue.
Lead fouling will form a yellow brown coating on the porcelain and start to burn off the tip of electrode. Does not sound like you have this problem.
You also stated that you had to jet down, maybe your top is fine but your bottom/mid is maybe alittle lean. Does your motor slightly backfire when doing a high speed down shift.
You may have to turn out your pilot screw more.
If no backfire, then raise your needle one notch.

 

Thankyou, all 3 of you have good points and info -

it is possible I may be lean at low or mid, I have not dyno tuned this setup yet, all I have so far is saddle time on the jetting, I have no backfiring at all no matter where I am at in the rev upon decel or shifting, and also response feels great everywhere in the needle's range, everything feels awesome but I need to dyno to get it spot on I'm sure.

I am running the stock plug dr8ea, and I have read that I may need a cooler heat range with this compression, I will take OMR's advise and go cooler, see where that gets the appearance, and also dyno tune as soon as I can.
my pipe tip is dull gray as I have always heard to expect, but inside the chamber from what I can see thru the plug holes the top of the piston is tan but sounds like it is a trait of this particular fuel.

Should I go dr9 or dr10? I see HPR recommends dr10, but they also say 116 octane for their piston where my CP I'm told can run 106, even though I run straight 110.

 

Just a quick perspective on octane........remember that two different 14:1 pistons will have quite a margin of compression ratio variance when you actually test them in the motor. HPR tends to play it safe on Octane recommendations and in some brands of fuel 116 is the next step up from 110. They have actually found that with their piston, 110 is ok for on off riding and trails and duning and such, but 110 will be shy on wide open flat track where you spend a longer duration of time at high rpm under heavy load.

Regardless, I would listen to your piston manufacturer for octane recommendations. MHO

Good luck Man![img]i/expressions/face-icon-small-wink.gif[/img]

 

Thanks for the really good info DS. That is really good info to keep in the back of my cob webbed mind!!! [img]i/expressions/face-icon-small-wink.gif[/img] Learned something tonight!!!!
HT, I would run a 9 and see where the heat range is on the strap and go from there.

 

Cool guys, thanks again.
Funny you mention the strap Doc, seldom do people mention it. right now, I can't really confidently make out the burn line, due to the crap on it I have described. on one plug I think I can i.d. it, right on the corner of the elbow but not very certain, but on the other its totally consealed.

 

Hightower, please keep me informed if you find out anything more about this. If you switch fuels and the tan/brown goes away let me know. If you can get some really high quality close-up shots of the plugs that would be really interesting to me. The more I learn the lucky-er I get.
Thanks again Hightower; great post!!!!

 

I will post again after I get the new cooler plugs, and let you know how things progress.
I have already cleaned the old plugs of the deposits, so I cannot get a pic of that - wish I would've thought of it sooner.
There is a sunoco gas station between home and work that carries the 110 that I am running, and any other race fuel besides it would require me to make special trips on into the city (Indy) to aquire, which would get old and become a burden. Hopefully I do not have to change fuels, but if this deposit doesn't go away after changing plugs and/or jetting, I may have to cause I really don't like what I am seeing.

One more notion - would fuel age play a roll? This station does not sell much 110 in the winter, maybe its been there for a while. I know they sell a buttload of it in the summer, close to Indy and several tracks.
Like I said, it performs well as I am absolutely loving the power I've added this winter.