I took my S2000 to a dyno today and did a test run. The AFR measurement was done with the sensor placed behind the exhaust.

Mods:

• Snorkel "AutoTecknic Carbon Fiber Cooling Plate/Intake Snorkel"
• K&N FIPK + AEM DryFlow Filter
• HJS 200er Kat (since ~1.000km)
• Supersprint Catback

Now I am curious if I am running too lean?
The guy from the dyno said it is still fine but in another forum I got a few people telling me that I am running dangerously lean and could potentially damage my engine.

I could only find a few stock dyno charts with AFR measurements and when comparing them it seems not to differ too much?
RPM - Stock - My run
5000rpm - x.xx (xx.x) - 0.90 (13.30)
5200rpm - x.xx (xx.x) - 0.96 (14.09)
5400rpm - x.xx (xx.x) - 0.95 (13.95)
5600rpm - x.xx (xx.x) - 0.94 (13.80)
5800rpm - x.xx (xx.x) - 0.93 (13.65)
6000rpm - x.xx (xx.x) - 0.92 (13.51)
6200rpm - 0.95 (14.0) - 0.97 (14.4)
6400rpm - x.xx (xx.x) - 0.96 (14.09)
6600rpm - x.xx (xx.x) - 0.96 (14.09)
6800rpm - x.xx (xx.x) - 0.96 (14.09)
7000rpm - 0.9 (13.2) - 0.95 (13.95)
7200rpm - x.xx (xx.x) - 0.95 (13.95)
7400rpm - x.xx (xx.x) - 0.94 (13.80)
7600rpm - x.xx (xx.x) - 0.93 (13.65)
7800rpm - x.xx (xx.x) - 0.93 (13.65)
8000rpm - x.xx (xx.x) - 0.93 (13.65)
8200rpm - x.xx (xx.x) - 0.91 (13.36)
8400rpm - x.xx (xx.x) - 0.86 (12.62)
8600rpm - x.xx (xx.x) - 0.83 (12.18)
8800rpm - x.xx (xx.x) - 0.82 (12.04)
9000rpm - x.xx (xx.x) - 0.82 (12.04)

My high quality dyno chart: https://files.bestmail.ws/s2k/Dyno_110420.pdf

Thanks in advance!

 

14 is
ok

 

So is my 14.4 still okay or already enough to be worried? ;-)

Made a screenshot but the high quality .pdf is linked in the first post.

 

If we tell you to worry are going to tune it or just not drive it anymore?
I had a EP3 with bolt ons many years ago, drove a few track days and just some general hard driving.
Then went to have it tuned and found out it was running ~16 AFR up top, it made some nice gains with more fuel there

 

I will most likely start by going back to stock catalyst and see if that brings me back to a richer curve.
@flanders you already told me my AFR was fine. So that is another vote for leaving my 200 cat in the car

I converted all the values from lambda to AFR and put them into an excel diagram. I hope I read the original diagram correctly and didn't fail at converting. Too late here already lol.

 

You are already running way to rich, you need better flow :P
It's pretty normal to have a lean peak just after vtec, I'm not sure it's worth to tune it out completely.
I had to ad absurd amounts of fuel to get it down on mine but sometimes it still peaked a little bit.

 

Thanks @flanders but then you get opinions from e.g. @s2000Junky has a good explanation why I might run too lean:
https://www.s2ki.com/forums/s2000-un.../#post24713750

 

Reading at the tailpipe location might be enough to make the small difference you are concerned about 12-13's are good for power, the small area of 14's isn't good for power but is still safe and perhaps with the reading error at the tailpipe you might be closer to 13s in that small area of the rpm band. Definitely not anything to worry about safety wise.

 

.92 LAMBDA is usually great with NA setup. You then gradually taper down to .85 LAMBDA and keeping you combustion temps nice and cool that way. I think all of this looks good other than 6200-7400 RPM area.