Shift at peak HP or peak TQ? 2000 camaro 3.8, A4

[salvador]

So should put the RPMs at peak HP or peak TQ?

[salvador]

Re: Shift at peak HP or peak TQ? 2000 camaro 3.8, A4

Internal combustion engines operate at their peak efficiency (producing the most power or using the least fuel) when the correct ratio of oxygen and fuel are introduced into the combustion chamber.

Changes in the oxygen content of air result from changes in the weather (barometric pressure, temperature, and humidity).

Measuring oxygen concentration in air is difficult; other measures are commonly used to estimate oxygen content. For example, determining changes in the density of the air (i.e., how much a given volume of air weighs) can produce a reasonable estimate of changes in oxygen concentration.

-Density means mass (kg) per volume (m3), so if air is more dense it means there are more grams per volume.

-Air density is inversely proportional to temperature (greatest impact). So that means if its colder outside your car is going to suck more grams of air per volume.

-Air density is inversely proportional to altitude (less impact). So that means if you live at a higher altitude your car is sucking a little less grams of air per volume.

-Air density is inversely proportional to humidity (least impact). So that means if its raining or is very humid your car is sucking very little less grams of air per volume.

One such rule of thumb is that a five percent (5%) change in air density may require re-adjustment of the carburetor jetting. High air density readings indicate more oxygen in the air, thus more fuel is needed (richer tune), while low readings indicate less oxygen, requiring less fuel (leaner tune).

Air-fuel ratio (AFR):
(Air mass) 14.7:1 (Fuel mass) this means per every 14.7 grams of air there is 1 gram of fuel

For this text purpose anything above 14.7:1 is lean and below is rich.


-Tips: buy good O2 sensors and spark plugs plus a good wideband tune.


-Open loop is used when the 02 sensors are not warmed up, failed or when an enrichment mode is active

-Close loop in this mode the fuel controller is operational

-Power enrichment only works at full throttle (unless is tune not to work only in WOT)

-O2 sensors do not work during WOT

[bowtienut]

Re: Shift at peak HP or peak TQ? 2000 camaro 3.8, A4

For best acceleration, you want to shift beyond your HP peak, so you're still in the meat of the POWERband when the rpm's fall into the next gear.
For a HP peak of 5200, I'd target a shift point of 5400 to 5600.
BUT....all electronic valvebody transmissions including the 4L60E exhibit a lag from PCM commanded shift to actual shift, simply because of the time it takes for the mechanical bits to move in the valvebody and pressurize the fluid in the next gear's apply circuit. So the WOT shift point in the program needs to be set lower than desired actual shift point. For a trans in good shape, to target a shift point of 5500 rpm, I'd set it at 5100 as a starting point. Then datalog to determine the actual shift point, and adjust the program accordingly. Remember to move your rev limiter up from the stock value by at least the same amount that you move your shift points up.

[salvador]

Re: Shift at peak HP or peak TQ? 2000 camaro 3.8, A4

Thank you :)! very well explained :tup: