I had dyno'd my 92 Z28 last night, came up with 282 RWHP @ 6200 and 282 RWTQ @ 4200. My Fuel Mixtures were as follows:

13.5:1 at idle
12.5:1 between shifts
10.2 - 10.9:1 at WOT.

The Dyno guy had suggested that at WOT it is much too rich, and recomended me changing that to 12.5:1 but NOT MORE THAN 13.0:1. How much HP do you suppose that can gain? Anyone had any input on that, its greatly appreciated. I have a fellow thirdgen member here who had been working with my chip & tuning it for me with his equipment.....any feedback is appreciated, thanks!
-Mike

 

My car, with the mods in my sig, picked up 15rwhp when the WOT a/f ratio was corrected to ~13.0:1 from ~10.5:1.
Bill

 

Good, i was hopin for higher #'s, maybe that'll bring me up into the 300 area! Any others? Thanks Burnout!

 

Are you running open loop idle?? Only ask because of the 13.5:1 reading.

With the variation from cylinder to cylinder on these engines, I'd recommend keeping it in the mid 12's for AFR.

You do seem to be a bit low on power though (and torque). Might be from the driveline though.

If you had some EGT probes, you could aim leaner, if you're careful. Your combo might like it.

Definitely make sure you're not knocking. Some cylinders may be too quiet for the one lonely knock sensor to hear, so check your plugs for specks after a few 1/4 mile passes. Also, after one or two passes, avoid idling for more than a few seconds before you turn it off. Pull ALL the plugs and see if any are grey ish. That'll be your lean cylinder and will dictate whether you need to make it richer overall, just to keep that one (or more) cylinder in the safe zone.

 

How do I delete a double post??

 

I have no idea what open loop is, sorry. As for my driveline, yah...it is kinda like a piece work for me now. I started off w/a built transmission, but my mods (at the time) only called for a stock replacement converter. So thats what it got. I got the dyno now to determine what stall converter to get, i'm currently looking into that and I should be complete with it by May. After that's installed, I may consider removing the catalytic converter from my exhaust and see if I can free up some more airflow. Then give it a final tune on the dyno again, around the 12.5 mark. I'm hopeful to dip into the 12's for 1/4mi & 1.7's for 60' with over 320 at the wheels. Thanks for all that info on the A/F, good to know!

 

 

What are the drive ability issues that goes along with running rich at WOT? I could understand black smoke, but other than that are there any signs.

Will running rich actually cause the car feel like you are starving it for fuel?

 

American fuel seems to burn pretty cleanly when rich. The power drop off is slower than on the lean side. The engine may sound a bit more mellow even (not sure why, but maybe to do with the cylinder pressures at EVO). You'd have to be pretty stinking rich to WOT bog for a long time, where as lean may can stay at wot bogged forever if it doesn't stall. Lean will usually spit back into the intake too. Rich may pop or gurgle in the exhaust if it's extreme.

 

Heres my dyno graph, its kinda hard to see, but maybe you can see.

 

Maybe you're hitting a bunch of knock at 4300+???

Or you're dropping a cylinder?

Or could be verrrrry rich, but it wouldn't do THAT in my best guess opinion.

You drop 10% in a very quick fashion. And the power still goes up after the big drop. I'd guess A or B above.

 

A data log would really help.

 

This?

 

No... Something like a laptop, Datamaster, and aldl cable.