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

[Nanaimo]

(sorry for the cross-post, I got no response on the 240sx Tech after 12 hours)

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 a non-cheap way of fixing it?

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)

I forgot to mention... When I use fuel with a higher sulfur content than Chevron (ie Petro-Canada) the sulfur smell is MUCH more pronounced than other cars.

[e1_griego]

Here's my single cam dyno (just had 2.5" not-so-good custom exhaust). The blue line is the stock run (and the red line is after some ecu tweaking). AFR from the stock run is also in blue.



Alex

[Nanaimo]

Alex

~Stochiometric AFR? What octane are you using? Does it ever knock? Did you chip the stock ECU or use an aftermarket ECU?

[e1_griego]

Look again...it's not at 14.7:1. The line is at 13:1. Every now and then it pings on really hot days (90-95+). I only run premium as a result.

The ecu tuning was done using ROM editor. We actually ended up getting about 127 or 128whp outta her (compared to 115whp w/ stock ecu) after playing with the tune.

Alex

[Nanaimo]

Every now and then it pings on really hot days (90-95+).

Sounds like it won't be a problem for the climate where I live.