Hey guys, i’ve recently just changed the spark plugs and i was wondering if it’s normal to for it to be covered in black soot? They have 57,000km which is less than the recommended interval. Any ideas?

 

I recently changed the plugs on both my GS200t and NX200t. The plugs look like the below. They definitely are not as black at the ground strap or electrode tip. The GS is even tuned.

Do all plugs have a similar appearance? The vehicle may be running a bit rich or idled a lot. Are you seeing poor fuel economy or any other issue that made you change them before the interval?

 

Yes, all of them look the same. Fuel economy seemed to be normal, but i do notice that the car runs really rich during cold start. It is getting cold here and my commute is quite short so every time I start up the car it goes through that cold start cycle. Also, what tune do you have? I’ve done some searching and JB4 seems to be one of the few. I do have a BMS intake installed as well

 

Check if any vacuum hoses are loose or damaged. Unmetered air in the system can cause the vehicle to run rich.

I currently have the D3 Performance tune and I like it a lot. I am not sure if they have it for the NX yet although its available for the IS, GS and RC with the 2.0t engine.

I had the BMS JB4 before the D3. I liked it alot but the D3 offers a lot more flexibility and better boost and throttle control.

 

The vacuum regulator valve did go bad earlier this year, i’ve replaced it already. I do drive relatively short trips but sometimes even after a 15 minute drive the car still does that cold start cycle. No other car i’ve driven does that.

 

Does the JB4 improve low end torque? the engine is supposed to have peak torque around 1700 rpm but it sure doesn’t feel like it

 

It does but the gain and real torque peak is about 3-3,500rpm. Those SAE numbers must be with the engine alone on a dyno because a chassis dyno will show peak torque at around 3-3,500rpm which is also reflected in real world road manners.