Which carburetor circuit is most responsible for sparkplug coloration?

idle
progression
acceleration
main


Put bigger chokes in dellorto (from 39 to 41), went up on main fuel from 230 to 250. Kept main air the same Plugs are mostly an off-white with the faintest hint of tan. This after hauling butt on the hangover run x on new year's day. PLEANTY of full throttle.

 

That's burning lean, I think.

Ray

 

that does sound lean, but also what heat range plug are you using?

 

br8eq14 ngk

 

Those are for streetdriven stock 12A engines
Get colder plugs unless its your carbsetting ofcourse.

 

you mentioned keeping the main air jets the same, what are they?

 

Need to go colder as stated atleast 1 step to begin with.

 

Mains, either step up on the fuel or down on the air. While that answer may sound simple, it's not as you need to take into consideration driveability. Emulsion tubes may make a difference too.

Post your full setup and hopefully someone with better tuning experince than I have will chime in.

 

i got some new stock 3rd gen platinum 9's i can put in there. now i think about it, my other streetports ran 9 heatranges too. thanks guys.

 

It is hard to tune a rotary carb based on purely spark plug color.

When tuning a carb, it is hard to get a true spark plug color test unless you start with new plugs in a warm motor, and then operate the engine in only one narrow range of rpm & throttle opening, then push the clutch in, kill the engine, and pull over and inspect the plugs. Operating in many rpm & throttle opening settings will draw fuel from many different carb circuits, and will confuse you as to which circuit is the one producing the color you see on the spark plug insulator.

 

+1

You took the words out of my mouth. Without following the above procedure, the idle circuit will have the most affect on the plug color because thats the last circuit being used before the car is shutdown.

 

okay, update

put the 3rd gen 9 heatrange platinums in there. switched back to 39mm chokes to get some lowend back. retuned carb.

wideband says WOT is in low 13's: perfect.
idle is steady and wideband says idle is in low 13's: perfect
progression is wonky, it's either smooth and in the 13's or sometimes rich into the 11's. Not good but much better and okay for now.

The 9's are black, a little wet, and smell of gas.

Put the br8eq14 ngk back in, car starts better, idles better, has much better throttle response, crispy, and the posterier dyno says more HP.

Tailpipe is not as dark with the 8's, exhaust smell at idle is not eyewatering anymore.

The 8's are an ashen grey color, dry, and don't smell like gas. I'm keeping the 8's in.

Stock plugs for REPU are BR7ET so with the 8's I'm already one heat range colder than stock. And considering most of the driving the REPU does is short trips around town it just makes sense to go hotter than a 9. It's not like I live my life a 1/4 mile at a time afterall. After my next autocross I'll check the plugs health.

Anyone try those Iridium plugs? Supposed to be the bee's knees.
NGK B8EIX
The Spark Plug
Serious Enthusiasts Rely On

Designed specifically for the performance enthusiast. Iridium IX offers extreme ignitability, improved throttle response and superior anti fouling

Fine Iridium tip ensures high durability and a consistently stable spark
Iridium alloy has extremely high melting point, perfect for today’s high-tech, high-performance engines

“Trivalent Metal Plating” has superior anti-corrosion and anti-seizing properties

Outstanding acceleration, high fuel efficiency and durability

Ultimate design, technology and performance

 

I havent bought new EV plugs but IIRC, iridium replaced the EV series plugs. Im referring to the motorcycle plugs such as B8EV's to B10EV's

 

I tried the iridium once in my Se. Idle went to crap and performance went down. Took them out and went back to stock ones with no problems.

 

interesting, Doc. i had just opposite experience with them (actually it was the B_EVs and then they got replaced by the B_EIXs).

at any rate, i swear by those plugs. i believe in them so much that i want to try them in my Renesis (just need to confirm they will physically fit safely). anyway, my old 13B Dell'Orto setup used to foul the stock plugs out like nobody's business. i switched to the EV-type and it never fouled again. then after i replaced that engine with my streetport 12A/Nikki setup, i used the EIXs - 7 leading, 8 trailing - and they performed great.

Drivefast7, i think you should give them a try. i don't think you'll be sorry.

 

I just put Autolite 2626 in the SE and it runs great. I put those 2626's into the 85GSL last year and they're still working good, too.

 

You sir, are a braver man than I. I think that the reports of people chipping apex seals on Autolite plugs are true. I bought a blue 83 GSL for parts one time, with a blown 12A. Just for kicks, I took the plugs out and sure enough they were Autolites. I'm convinced that they were responsible for the death blow. Who knows, maybe it was just coincidence. I'm not going to try to save $10 on plugs, just to find out though....

 

here's a good read on plugs http://www.dragstuff.com/techarticle...ark-plugs.html and the links on the bottom of the page are very good too. Lotsa pics that explain what the situation is.

 

Not all autolite's are bad. I use the race autolite plugs with no issues.