Silver Ninety Three

Dyno tuned for 20 psi at KD Rotary on Friday. The NGK 10.5 race plugs were cleaned prior to the run. Stock ignition was holding up on the dyno, but I experienced alot of breakup on the ride home. Even at 12 psi. I pulled my plugs today and the leadings were somewhat fouled. Whats weird is the trailing plugs were very fouled, and brownish white. I cleaned them and put them back in, and no more ignition breaup. I'm just wondering why they fouled. Here are some pics:

Silver Ninety Three

trailing plugs

RICE RACING

Normal.

The trailings tend to run a bit hotter becasue they are not so open to the cooling nature of the mixture (isolated by small transfer hole in rotor housing)

The leadings usually foul first due to this reason, especially if you are running race 10.5 as they run cool on light load and do not reach the self cleaning temperature to keep the ground/tip and insulator clean.

With CDI you can run those plugs or cooler ALL day provided the fuel mixture is not set too rich, if it is regardless of what type of ignition you will have fouling problems especially from cold start up and lots of low speed running.

I run 11's all day every day daily driving, fuel mixture is set pretty well and I have no fouling issues, NON CDI you may be facing an up hill battle even with a perfect operating mixture ?

Apart from that your plugs look pretty normal, despite running a bit cool on the leadings.

ErnieT

iTrader: (2)

Your trailing looks like your were burning a bit lean. That may be indicative of your blip on your dyno sheet when he let off early. But it could also be the burn from race gas. Hard to tell.

Silver Ninety Three

thanks for the info, i'll see what they look like next time i pull them

RICE RACING

You may be "pulling them" more often than you like ! Once the things start fouling up it realy won't get any better as you are not fixing the cause of the problem.

With a bit of extended low load driving (wich cools the plug temp right down) you will find soon as you stand on it and the mixture starts to richen up the plug does not have enough temperature in it to burn of the fuel deposits (mostly) this is why you are getting that misfire after the dyno run.

You will find with a CDI like the CRANE or similar with the multi strike capacity below 3000rpm it will solve this problem and you will not have that misfire then first time you stand on it after a period of low load cruising, On the dyno or race track it is no worries as you have the enine temp fairly "warm" and hence the plug body is warm and it can self clean it's self provided the a/f is not too rich, it is VERY cold over there at the moment and that would not be helping you either ?

That is why you have a difference in colour between the trailing (which look normal) and the leading which look almost wet (too cold). When running spot on you will find the trailings tend to look a bit "leaner" than the leadings but not by a very big amount, when it is all running right with a strong spark with unleaded fuel depending on the amount of premix you will find the ground and tip electrode a fawn or straw type of colour with a touch of grey, on high lead gas they can come out almost very light grey almost white on the electodes, this is all fine, so long as the electrodes are not melting or pitted and you are not cracking the porcelin on the center electode ( which if all the a/f's are right for they type of gas you are using) generally means you have too hot a plug. If the car is a bit untuned on low load settings and idle it will be hard to read the plugs, but you can still get a good idea after a few good hard runs letting the car cool down then pulling the plugs straight away (they will not pick up to much colour on the cool down).

To get a good idea of what I mean go do a bit of highway driving at constant load and after 50 miles pull up cool the car down then pull the plugs, you will find they have picked up a fair bit of colour showing you what is going on in there and at what temp the plugs are running at in your engine. If they are black all over this means the plug is too cold for that type os use, if they are like your pic of the trailings this means the body of the plug is at a good temperature. They only way to keep race plugs going at low loads, is with a HIGH Energy spark and a well tuned cruising/idle map. I will shut up now, sorry for the ramble, I got carried away

Silver Ninety Three

No need to shut up, very good info. Makes alot of sence. When I left KDR I was following my friend's dad's fd. We were going slow for a while and then he got on it, and I went after naturally. Thats when they fouled. Its pretty cold, was probably in the mid 30's at the time. I had the car out last night, and no ignition poblems with the cleaned plugs. The electordes and porcelin looked fine. I guess I'll just have to ease into boost when crusing untill I get around to upgraging the ignition. I plan to go with an msd digital 6 and 2 blaster coils.