Power enrichment mode explained...Please:)

[01blkss]

hey guys i am curious about what power enrichment mode is.

I would like to know...

how i trigger it?

What i use it for?

Why are its values more important than just regulay commanded AFR values?

how do i know if i have entered it?

A couple notes are... i have never messed with it up to now and my WOT AFR was always able to be tuned exactly to where i wanted it to be at via commanded AFR tables.

Thanks
Louie

[eboggs_jkvl]

PE is WOT. USe the PE table to set the A/F when you are WOT (PE). Is that what you are asking? When you are in PE, you are off the O2 sensors and running from the PE table.

Elmer

[joecar]

B3616 "PE enable" specifies the TPS vs RPM to enter PE mode;

When you hit the B3616 curve or above it, the PCM uses B3618 "PE Modifier vs RPM" to command the AFR.

If you're running OL, PCM uses the richer of B3605 "OL fuel:air" and B3618.

If you're running CL, PCM switches from O2 sensor trimming to the richer of the last trim (or zero if the trim was negative) and B3618.

I think I got that right, I just had a brain reset...

[dfe1]

Just so there's no confusion, "PE" stands for Power Enrichment and as the name implies, AFR needs to be richer when and engine is running under a relatively heavy load, such as when accelerating at wide open throttle (WOT), or pulling a trailer up a steep grade. Higher loads translate to higher internal pressures and temperatures and a richer mixture is required for engine protection as much as power. That's why PE AFRs are so important. (If you want to see knock retard in action, just try running wide open throttle at 14.6:1 AFR.) Typically, a well tuned naturally aspirated engine will run safely at 12.9 to 13.2 AFR in PE. Turbo- and supercharged engines typically run 11.5-11.9:1 AFR when in boost. Since MAP is an excellent indicator of engine load, the switch to PE is usually triggered by a MAP value higher than 80 or 90 (depending on the engine and a tuner's preference). Also, since narrow band O2 sensors don't supply reliable data when AFRs move very far from stoichiometric (14.68:1), the transition to PE is accompanied by a switch from closed to open loop operation. Some systems will remain in closed loop, but will turn off learn control-- either way, it means that O2 sensor input is being ignored and that fuel delivery is being controlled by table values.

[TLKSCHP]

Ok just to clarify, if your PE modifier based on RPM has a value of .9 and I want it to be richer what would I change the value to?

[joecar]

Ok just to clarify, if your PE modifier based on RPM has a value of .9 and I want it to be richer what would I change the value to?

EQ = 14.63/AFR = 1/Lambda or AFR = 14.63/EQ = 14.63*Lambda

If you have EQ 0.9, richer would be > 0.9.

[zone]

so a .9 would be richer than a .8?

[Tordne]

so a .9 would be richer than a .8?

Correct.

Assuming 1.0 EQ is 14.63:1 AFR

0.9 EQ = 16.25:1 AFR
0.8 EQ = 18.29:1 AFR
1.2 EQ = 12.19:1 AFR

Etc...

[Doc]

Those were really great explanations of PE. This is how you can switch btw units. I find it easier for my brain to comprhend changes in VE and MAF tuning with the wideband to be with lambda or "1.0" scale and in the PE vs. Rpm table just plain ole standard units.

[joecar]

Yes, you have to keep aware of whether you using EQ or Lambda because the two go in different directions (greater EQ means richer, lesser lambda means richer).

I assumed that 0.9 was in EQ.