Out of curiosity, what makes the stock temp plugs not ideal for FI? Do they melt? Does the spark blow out? The reason I ask is that I installed TR6's gapped at 0.035 in preparation for boost (still NA at the moment), and was getting P0300 random misfire, mostly at idle. The code would come and go, wasn't consistent. But I just switched back to TR55's gapped at 0.055 for smog, and haven't had a misfire problem yet. And I might be crazy but it seems to run a bit smoother with the TR55's.

So with colder plugs, are misfires something you have to live with? I also have round heatsink coils and Taylor wires to put on, not sure if they will help at all.

Sorry for the dumb questions

 

Ive ran TR55s for years, then switched to TR6 with no problem.. When i went to BR7EF's is when my idle went to crap and gas mileage aint what it use to be.

Id be willing to bet you had a bad connection on a plug or two?

No miss fires here.


Only reason you need a colder plug is so it wont preignite from heating the plug up..

 

No such thing as a "cold" or "hot" plug. The temp range refers to how quickly the tip dissipates heat. This is regulated inside of the plug with the amount by changing the amount of ceramic insulator coming in contact with the metal shell. The more surface area of ceramic touching the metal shell, the "colder" the plug is.

Higher cylinder pressures (with boost) create higher cylinder heat. If a factory heat range plug is used, the tip of the plug may not dissipate heat as well due to the higher cylinder temperatures and thus it will become a hot spot inside of the combustion chamber. The hot spot may then cause preignition of fuel.

 

And he explained it perfectly.....

 

Thanks for the explanation! So are colder plugs more prone to misfires? I had a solid connection on the plugs and coils. All cylinders were misfiring roughly an equal amount when I was logging with EFILive.

 

If the plugs are too cold they will not stay hot enough to keep the tips clean and will start to foul up, usually while idling.

 

We run -9's in dirt_track_racer-81's truck. Idles fine and gets 19mpg. Don't be lazy. Work on your tune. You're reducing the heat in the combustion chamber. It's going to change some thangs

 

Dozerdan I haven't had underscores in my name for 4-5 years now.. Btw add some timing on colder plugs..

 

I couldnt tell a difference in idle going up to 7s, but when I switched to 8s and gapped at 0.020-0.022 it didnt want to idle easily, but it never stalled.

 

Like everyone said. you will have to work on the tune while changing heat range. some setups wont make a difference others are very sensitive to plug types