What did you do to your Fiesta ST today ?

[SteveS]

Ever since changing to step colder ngk plugs I've been having misfires under full throttle. I gapped to .026(originally .030) and it's much improved but still misfiring a under wot. I'm in dizzy e30 tune. He suggested I gap to .028 which still wasn't enough. Should I go back to OEM plugs?

If step colder plugs cause misfires, yes, the answer is to go step hotter. The fascination with step colder plugs eludes me. It is not a magic formula for power. If, after your tune, the engine was running fine without preignition, and a plug check did not show signs of plug overheating, then there is absolutely no reason to change to colder plugs because the only expectation would be that you would have misfires, fouling, and eventual problems from unburned fuel.

 

[WolfDampf]

If step colder plugs cause misfires, yes, the answer is to go step hotter. The fascination with step colder plugs eludes me. It is not a magic formula for power. If, after your tune, the engine was running fine without preignition, and a plug check did not show signs of plug overheating, then there is absolutely no reason to change to colder plugs because the only expectation would be that you would have misfires, fouling, and eventual problems from unburned fuel.

I'll try my OEM plugs when I'm off Sunday and check what their gap is at. If I am correct a -1 octane adjust ratio means no knock? I've also never had negative ignition corrections with my OEM plugs. I do want dizzy to tune it up to the max when I get my revision tho. So I'll try tightening the gap to .024 as well, but if I'm tightening the gaps just to make the same power that sounds counterintuitive

 

[WolfDampf]

FYI if you're doing the focus coil conversion do not get denso coils. I thought denso was an "OEM supplier" so it would be fine. SVTdesignFab recommended Bosch and I should've done that. The connectors on the denso coils are straight which makes it a hassle to install as they make contact with the adapter plates. The Bosch coils are slanted up so you can connect them easy. I got some Bosch coils on the way and I'm guessing that it's going to fix my high rpm misfire issue as well

 

[Grsemky]

FYI if you're doing the focus coil conversion do not get denso coils. I thought denso was an "OEM supplier" so it would be fine. SVTdesignFab recommended Bosch and I should've done that. The connectors on the denso coils are straight which makes it a hassle to install as they make contact with the adapter plates. The Bosch coils are slanted up so you can connect them easy. I got some Bosch coils on the way and I'm guessing that it's going to fix my high rpm misfire issue as well

What did the coils run ya?

 

[WolfDampf]

What did the coils run ya?

That's the part that gets me mad 😂. When I ordered them the denso coils were 4$ cheaper per coil. Now the densos are 29$ and the Bosch are 24$