So I was helping a fellow mini guy out fix and tie up some loose ends on his car and I checked his plugs because he had a 17% pulley , catless headers , exhaust and intake ( unsure if tuned ) and when I pulled the plugs I knowticed they were still the stock plugs and stock heat range.
so eventually I found his issues ( cracked hard line and fpr vacuum line was off ) ..
so after fixing the stuff he let me take it for a test drive and I was 100% expecting to hear or feel detonation BUT NONE. The car was running great so I brought it back and advised him to get some plugs asap , range colder which he did next day.
then he calls me back saying after he installed the new plugs he felt a powerloss.. I figured a line had to have popped off again so I jetted over to his place and inspected it and everything was good.. so then I used my inpa to reset fuel trims and throttle settings ect thinking maybe that had something to do with it but no.. I drove it my self and it really did feel slower. So we threw back in his old plugs and it really did make the car much more peppy.
so here what I wondering, is the consensus on range colder plugs false just like it is with stock intercooler being 2nd best one available ???? It was in my tuning experience I ONLY ever used range colder plugs if adding nitrous or going from n/a to boost.. but adding abit extra boost on an already boosted engine I can't imagine it causing knock issues..
I've allllllllllllllways felt I was chasing power in my built mini and that's kinda seemed to be since upgrading my pulley and going range colder plugs along with it long ago.. I think if I'm feeling better tomorrow ( rheumatoid arthritis been killing me with weather change ) I will swap my oem heat range plugs from my other mini into my built one and fire up inpa and check knock and timing ect ..well, I will check all that befor I swap plugs so I can compare data...
but what's your guys thoughts on this....... ?

 

A one or even two steps colder spark plugs will NOT hurt performance...IF...the rest of the engine is in good condition..! This makes NO sense, a spark is a spark. All a colder plug does is it transfers the heat that the plug obtains from the combustion process to the cylinder head in a slightly faster rate than its hotter brother.
Please explain to us how this could hurt performance.
IF...the computer mapping is correct for the modifications and working correctly and the knock sensor is working properly, the computer SHOULD reduce the ignition timing WAY before you can hear it..! It "might' show up on the spark plugs if they are fresh, but hear it, I seriously doubt it, Maybe if "Superman" was around, he might hear it !

Maybe over time, an engine that's not good with the ring seal, and oil gets on the spark plug, and the plug is not hot enough to burn it off...yes, THAT will hurt performance, but NOT a fresh spark plug (too cold or not) in a good running engine..

That's how spark plugs work.

As to your friends problem, with the changes that you mention that he's done, and the possibility of the fuel mapping not being changed to properly adapt to the said changes...yeah, the possibility's are endless.

Mike

 

Could the plug be too cold and it not getting correct heat settings and ecu detecting it and somehow not have as aggressive timing or knock or something? There's SOMETHING causing this. Like could plug heat range determine cylinder Temps and then effect the burn rate at combustion and just not be as effective ? I'm stumped too, it's a knowtiveable power change from one set of plugs to the others and both sets look like they were firing well , no lean or rich conditions though the cold plugs were pretty new so kinda hard to read but imo they all looked normal...
am I correct thinking that inpa might be able to display what parameters are running differently while I change plugs ? Like should i look at timing and knock and fueling percentages ? Lol there's alot of numbers I will not be understanding fully but atleaat I can compare ..

 

Theory: The hotter plugs are causing knock but the ECU kicks into action before you can hear it (as OCR mentioned). But instead of just retarding timing it dumps more fuel into the cylinders to cool down the burn. With colder plugs it doesn't do this and runs a little leaner. Probably not enough to notice by looking at the color of the plugs but enough to effect the butt dyno.

 

What is the make and model of the plug used previously and presently?



I run NGK's in the 7 heat range as per factory spec for JCW and never had any problems.

 

Theory #2, OP has proven time and time again to be borderline incompetent.