The red lines (the lower set) is on motor, on the blue lines (the higher set) is on an NX 100 shot.

The HP curve looks awfully flat to me, like I am maxing something out. It makes me wonder if the heads aren't up to the task of making any more power. Anyone with a really good handle on interpreting dyno graph's care to hazard a guess?

The car is a 92 vette with a 383, 11:1 compression, ported LT1 heads, hotcam, and an edelbrock shorty headers. I have since moved to a custom grind cam from comp cams (.565/.576, 232/242, 114). The car doesn't seem to be any faster, but I haven't got it tuned yet, or been to the dyno to confirm.

 

Almost impossible to differentiate the colors..... but it appears that on the N/A run your A/F ratio crept up from 13.0:1 at 3,400rpm to around 14.0:1 at 4,800rpm. That would generally be too lean to make max HP. The N/A A/F ratio would typically be in the 12.8-13.2:1 range. It does vary from engine to engine, but your A/F chart seems to just go too lean, from the start. Like I said, hard to read the chart, at least on my screen, so I might be off base. Running lean, the engine is not going to make the power at the top end.

You also have an extremely flat N/A torque curve, with a little more peak at the low end. I would think running it richer would fatten up the curve at the top end.

Your nitrous run seems to have ended with the A/F ratio closer to 11.3:1. Nitrous will typically "flatten" the HP curve, since it will give you a huge torque surge at lower RPM, and then the torque gain willl taper off at the top end. Since HP = torque X rpm the net effect of the fat bottom end torque is to "level" the HP curve.

 

Ya, the colors are kinda hard to tell apart. You interpreted everything right though. About 2 weeks prior to installing and dynoing with the N20 kit, I made a couple pulls on motor. At the time, the car had the stock air intake on it. See that graph here:



The AF ratio on that NA pass was about 12.8:1 at 2700, and crept up to about 13.2:1 at 5500. The car made 370 RWHP vs the 349 it made on the 2nd dyno day.. I attributed the loss to the removal of the air intake system. I removed the factory air intake and threw together a hodge podge of parts to build an intake suitable to the N20 kit. I don't really see how that would cause the AF ratio to climb into the 14:1 range though. Would it have anything to do with immediately makeing an all motor pull after an N20 pull?

So, in your opinon, everything looks pretty normal then? Other than the lean NA pull? No comments on what might be holding me back?

 

Yep the graphs are hard to see, and Fred is right...the car is lean on the motor.

Kinda looks like you might be slipping the converter when you hit the squeeze. See the way it hits? Has a hump, gets real smooth, then has the bobble in it about 4500...where I guess the converter clutch grabs again as the TQ is falling off a little.

Just a guess though.

 

Thanks for the reply, but my car is a 6 speed. No convertor. the clutch hold 6k drops, and pulls 1.6XX sixty foot times, so i don't think it is slipping, but maybe?

The pull I made about 2 weeks prior to the N20 pull was almost dead on for A/F ratio. I still don't know why it ran lena on the NA pass.

Thanks.

 

That's a manual? Jeez, start the run NA down at 1500rpm then. Get a nice smooth graph/curve like the other one posted.

 

???

It was in the sig both times, lol.