Are your AFR's supposed to change??
 

I recently changed my plugs to the NGK iridium plugs (BPR7iex......I think that's the p/n) set with a gap of .027 and I now notice that I seem to be running richer across the board. Is this normal?

I installed my AEM Uego a couple of days before changing the plugs and had an idea of what my AFRs were and while I was running rich and "occasionally" run of the scale it's doing it much more frequently and consistently with the new plugs.

I'm about to start tuning for the richness but I like to know if each time I change plugs if I'll have to adjust AFRs.

BTW, the old plugs were also NGK iridiums but another p/n.

Thanks for any help.

You are probably not burning all the fuel because the gap on the plugs are too wide. I run .021 on my plugs because the stock Evo ignition is not very strong.

Interesting.........the only thing though was that I had the same gap on the older plugs.

Question for the Tuners
 

Any other input\thoughts?


Tuners, would love to get some feedback.

Thanks.

the new plugs are 1 heat range COLDER than stock. if you are making a minimum 75-100hp over stock then they will work fine. NGK says u will have to retard timing a pinch & add fuel to compensate. if you are running at least 30psi of boost or more, you may need even colder plugs...

yeah your defiantely going to run richer with a colder plug