Itinerant Air-Cooled

I have started a new thread on the topic of the terminal end.

I do feel that I have been running a bit lean and have done some AFM adjustments to correct.

I do have a exhaust leak but question. How bad does a leak need to be to create the popping?

Can someone supply a pic of a decent looking plug from a know "perfect" running engine? I understad that plug color is only part of the diagnostics. That is why I brought up the temp issue. Following the last AFM adjustment temps dropped considerably and performance was static so I feel that I am on the right track.

Thanks,

It takes just a whisper of an exhaust leak to create that popping on deceleration.

Mulcheese wrote:I have started a new thread on the topic of the terminal end.

I do feel that I have been running a bit lean and have done some AFM adjustments to correct.

I do have a exhaust leak but question. How bad does a leak need to be to create the popping?

Can someone supply a pic of a decent looking plug from a know "perfect" running engine? I understad that plug color is only part of the diagnostics. That is why I brought up the temp issue. Following the last AFM adjustment temps dropped considerably and performance was static so I feel that I am on the right track.

Thanks,

Here is Chloe's Death Valley 2013 spark plug portrait:



These would be too lean if it was just driving around town or even on the highway, but these plugs had just been through some serious ambient heat. There should be no white on the ground electrode. The ring at the bottom of the threads should be black. The insulator should have a touch of brown maybe white near the center electrode. Hot plugs have the insulator sticking out from the bottom of the threads, cold plugs have the insulator nestled within, like those in the photograph.
Colin

The following were after jetting with an LM-2 wide-band for WOT 12.8-13 or so and cruise at low-mid 13's (where a bus is happy CHT wise). You want to stay out of the 'Death zone' with these engines (14.7) when WOT and cruise. A bus can weigh easily 2.5 tons fully loaded. Combine that with it's aerodynamics and running stoich = High CHT's

NGK B5ES plugs
https://www.thesamba.com/vw/gallery/pix/1201652.jpg

Piston engine power management chart:

https://www.thesamba.com/vw/gallery/pix/1463782.jpg