60 HP gain with 10 AFR can this be right?

[Gpargament]

I have been steadily tuning my 07 c6 z06, with a speed density custom OS. My car has basic bolt-ons and should put around 500hp to the wheels. I am uploading 2 tunes one has my WOT AFR around 12.2 - 11.7 and i only pull around 530 horsepower, my injector pulse-width is around 13ms with overall injector duty cycle about 70%. The other tune put down a monstrous 580, with an AFR around 10.5. I don't like an AFR that low and was going to lean it out until i saw the torque 460 and HP at 580. with the 580 HP run the injectors are around 14.5 ms pulse-width and almost 80% duty cycle. Hence I know the 580 run is pushing a lot more gas almost 10% which could explain the 50 horsepower difference, but I was always told the best horsepower is around a 12.8 AFR, but the leaner mine goes the more power I lose. is this a mistake in the HPtuners horsepower and torque calculations? or is my car really putting down 580 with an incredibly rich AFR? I can tune it to run at 10.5 consistently, i was just always told that's a bad idea, thoughts from the experts?

I even got to 590 with 9.9 AFR but this just seems wrong

530 with 12 AFR.hpl
580 with 10 AFR.hpl
590 with 9.9 AFR.hpl

[FASSTRUK]

Is that afr from the wide band, or is that commaded from the tune?

[5FDP]

I'd almost want a second widebands opinion on this to make sure that your wideband or who evers wideband is reading good. If both widebands were really close then I guess your car just likes more fuel.

Your fueling error is really large too, that needs to be fixed if you ask me. On the 2 richer runs you are asking for 12.3 and 11.7afr but the wideband is showing 10.9 and 10.0.

[kingtal0n]

I wouldn't depend on a random software's power/torque calculations. Sometimes they can be setup to become extremely accurate but this is typically only for setups where calibration is done extensively for this purpose (it may even hinder performance to have the software setup like this as it specifically emphasizes accuracy over performance)

Many types of calculator 'math' looks solely at a/f ratio or airflow in terms of mass/time to determine power,
when the reality is far more complex than that.

In other words, the software may interpret air or fuel as more = more. Like a compressor map calculator for example
http://www.turbos.bwauto.com/aftermarket/matchbot/

If you fool around with the compressor/engine flow rate calculation you may stumble on the fact that the more fuel you seem to throw on the fire the more power it says it will make-
when this is clearly not the case in reality.

If you are truly looking for a/f ratio tuning 'gains' in terms of torque at some specific rpm range given a rate of change (power per integral of a pressure function over the area of the piston surface)
you would need an accurate method to measure work over time, such as a dynometer, which reports a realistic figure for work you can compare with previous 'runs' at that 'weight' (drivetrain weight 'load' is a factor considered in acceleration and rate of chemical reaction as I will cover slightly next).


As to the chemical reaction of combustion,
during combustion reaction molecules find partners, collisions occur with sufficient energy to break and re-form bonds.
The pressure climbs as the piston is in motion, so the reaction needs to proceed fast enough to maintain pressure given the expanding volume,
but not too fast that the pressure escalates to the point of parts failure.
This is given by the rate of chemical reaction, which is partially dependent on temperature, and also hindrance (incidence of collisions) as more branched hydrocarbons which have more trouble colliding with sufficient force and direction, are considered to be higher octane fuels (0 octane gasoline is unbranched: n-heptane vs 100 octane gasoline is highly branched: 2,2,4-trimethylpentane)
Also considered is the rate of rotational speed (w or angular velocity), and rate of change of rotational speed (dw/dt), the inertia of the rotating mass (J), Rotational friction coefficient (B)
as you see there are many factors, as basic of an approach this is still complicated to explain without math. The bottom line is the piston needs to move out of the way of the expanding gasses, force applied to the connecting rod is based on the pressure (psi, often 600-1200psi or more) and piston area surface (pie*r^2) can be 11,000lbs or 20,000lbs even in mundane applications, in order to create torque around the crankshaft axis.
During this time period, approx after 720* of rotation or TDC of compression stroke, to about 65*~ or so (guessing) of crankshaft revolutions, torque is applied based on the forcexdistance of the crankshaft 'lever' (around 720* for example when the piston is TDC, a cylinder pressure of 600psi with a bore of 3" exerts a force of approx 17,000lbs and provides 0 torque because the piston is TDC and the perpendicular distance of the crankshaft lever arm is 0.00 inches (vertical)). That means as the crankshaft rotates past 720* the pressure over the piston area begins to provide torque because now the crankshaft lever arm is providing perpendicular distance.

So finally I can explain why a/f ratio being richer might give more torque (how it happens vs a perfect 14.7:1 giving less torque). As the crankshaft rotates there are optimal positions for crankshaft lever arm to provide torque. This is probably around 735* or 740* (guessing again), just around after TDC when cylinder pressure is highest usually (for typical passenger non performance cars). Remember the initiation of combustion was done before TDC so we are essentially trying to time the peak of combustion pressure to occur right when the crankshaft is in optimal position after TDC (given some rod length which also varies) to receive the maximum force the pressure can provide to the crank as torque, and then keep it going for as long as possible while the crank still rotates. Basically, the richer air fuel ratios provide more fuel molecules than necessary (there will be some leftover at the end also) so during this time of peak pressure when the crankshaft lever arm is in 'ideal positioning', more fuel molecules will find oxygen partners given the same initial conditions (temp/octane/cyl design/etc) and the reaction peak pressure will be higher, and longer because of this. There is also the issue of fuel cooling, where excess fuel tends to cool the mixture and this can lower peak pressure and slow the reaction (lower temperature) so there is a balance between excess fuel, maximum temp, octane, and cyl-head/combustion technology (design of chamber plays a role) and even the piston, deck, tiny spaces, the design of the ring and so forth will also have a role.

In conclusion I should give a simple example. Imagine a box of hungry kittens that you intend to feed. You want to feed them all at once, but you know that if you put exactly 1 food unit into the box for each individual kittens, that some kittens might not ever find their 1 food unit, some could get lost for a while before the kitten is able to find it. So instead, you put in extra food units, so that in a very short time, every kitten is able to find a food unit, even though some food is leftover you are satisfied because each cat still gets fed (while the crankshaft lever arm was in proper position).
meow happy holidays

[Ben C]

Giving hay to horses would be a far more appropriate analogy. 0/5 stars.

[kingtal0n]

aww cmon, ur approval means so much to me though. Horses are so big, if you drop food all over the ground for them, they just scatter it around.

kittens are also cuter

[Gpargament]

Thank you all for the reply's, I will go ahead and correct my VE tables so the commanded and actual are aligned. I am speed density mode if that makes a difference I probably should have mentioned that in the beginning. I used the same wide-band on my wife's stock ls3 2008 corvette, its the aem 40-0334(i think) with obd pass thru. I also use the innovate exhaust clamp so I can go from car to car. The wideband reads exactly as it should on her stock car, which made me question whether the numbers were actually accurate, it would be weird for it to be incorrect on my z06 but correct on her ls3 c6. here is her run for 360hp and you can see the commanded and wideband are pretty much aligned. I dont think I will be able to answer this without the track. Its frustrating cause id like to put down almost 600rwhp but I also dont want to shove fuel past the rings or be running really rich thinking im going faster and in reality im going slower.

stok 08 ls3 corvette 360 hp 11.8 afr.hpl