Quick spark plug question.

Before tuning my car, my tuner threw in a set of new plugs, because he said my old ones were not looking so hot. He threw in a set of NGK BPR8ES and told me that i needed to change them out sooner than the platinum, because the coppers crap out quicker. So, I am changing my plugs out now... not realizing that he put the BPR8ES I bought the BPR7EIX, and when I was throwing in the plugs I realized he put in the 8's... is there any harm, given my set up in running the stock heat range verse one step colder? The car seems to drive fine with 7s now, I just don't want my car to blow up, because I was running stock heat range when I really should've been running one step colder given my setup/boost level (see link for parts list/setup).

https://www.evolutionm.net/forums/se...ne-review.html

Is there a rule of thumb for running stock heat range vs one step colder?

Please let me know your thoughts.

 

How much boost you running? And I believe the ones you bought are iridium.

 

Yeah, I went back to Iridium for this change because the Copper ones the tuner had put in, in a pinch, seem to crap out rather fast (for me at least). I don't want to be changing spark plugs as frequently as the Copper seem to require. Plus, the Iridium ones I got were pretty cheap all things considered.

Either way, boost hits 25-26, settling back to 21 by redline. I am tuned on 93. The cars been running like a dream, no knock, no issues (crossing fingers now).

 

What's your mods? If your on stock turbo at that boost level you should still be on a stock range plug as you aren't really making enough power to where you need a colder plug

 

An easy rule of thumb is for every 75-100 horsepower you add, use one range colder plug.

 

^ not true. Its not needed until your making a good bit of power

 

For everyone who asked... Mods and boost level (with dyno graph) are in the link in the original post...

^^Yeah, Joe, I sorta figured I was fine.... just being paranoid. I did a search on this thing, but didn't have any luck finding any info on heat ranges.

Thanks!

 

I'm not saying you can't go colder, but I don't think its necessary at this point. I make a good bit of power over stock and I'm still on stock heat range plugs

 

I read the plugs to determine before changing heat ranges. If the plugs don't have a red hue to them you are not too hot. Static compression, fuel type, boost level and ignition power all play a role in what heat range will be needed. That makes it very difficult to make a blanket statement on when to change heat ranges other than reading the plugs.

Another problem with running a plug to cold is fowling if you run big injectors. I had 8s in my car with 1600cc injectors and the plugs fowled very easy making the car run sluggish until getting into boost to clear it out. It was a major PIA at the track if I shut the car off and fired it back up in the staging lanes because I would have trouble getting the car to build boost leaving the line. Most injectors will not put up with less than 1.0ms of IOT without failure and when they get to be 3-4x what stock is, it becomes a lot of fuel at idle. Thats why most of us running large injectors bump the idle up to 1K-1100 RPM.

Personally I like the Iridiums because they do not burn up as fast and seem to deliver better spark energy with weak ignition systems.

 

I gotta say... maybe just the placebo effect, but I feel like my car is more responsive now... maybe I was running plugs that were too cold, or got use to running it a little rough as the plugs started to go (more likely the reason).... either way, the car (never felt slow, but) feels like it woke up all of a sudden...

 

Most likely 8s were too cold. Based on your mod list and HP range with stock compression, you wouldn't be creating enough cylinder pressure to effectively use a cooler plug.