(1989 240sx SE, KA24E) Got dyno results, is it supposed to get this rich?

[Nanaimo]

Hi!I had a baseline dyno run done at ZenSport in Central Saanich (Vancouver Island, BC, Canada) today. I've crunched the numbers, and it seems to be getting very rich, very fast as the RPMs climb.At 2200 RPM it's 12.7, but by 4300 it's hitting 10.8 (average of 3 runs).

Is this amount of richness on purpose? Is it a good thing? Is there a cheap/easy fix like cleaning the MAFS or something?

Is there anything else I can learn from this graph (besides that my car is way under spec power)?

(I've inverted the AFR axis so that up is richer)(These are average of 3 runs. The runs were farely consistant)

(It was shooting black crap out the exhaust during the dyno that Chris said was unburned fuel)

[Nanaimo]

I forgot to mention... This was on ~93 Octane Chevron (1/2 tank 92, 1/2 tank 94), so it's unlikely it was knocking.

[Nanaimo]

Anyone?

[JNM240]

Well, first thing you have to realise is that the 140HP the KA24E makes is measured at the CRANK, not at the WHEELS. So your ~115 HP to the rear wheels isnt really all that bad, for a stock motor. Second, have you gotten a tune up? Line new plugs, wires, cap, rotor, ect? Inspect everything and replace as needed. My 2 cents worth.

[Nanaimo]

Well, first thing you have to realise is that the 140HP the KA24E makes is measured at the CRANK, not at the WHEELS. So your ~115 HP to the rear wheels isnt really all that bad, for a stock motor. Second, have you gotten a tune up? Line new plugs, wires, cap, rotor, ect? Inspect everything and replace as needed. My 2 cents worth.

It's ~105, not 115, I have had a tune-up, and a tune up won't fix an out-of-spec air-fuel ratio. From other threads it sounds like it's probably either (the MAF or intake thermometer (or grounds or connectors on these)) or (fuel pressure too high) or possible (oxygen sensor), possibly combined with a plugged CAT (result of running way too rich for a long time).

I'm going to check for codes tomorrow morning.