silverstream

Well, in the stock High Octane Fuel Map, 500rpm is "13.6" all across.

I don't have a AF meter to measure if it hovers around 14.7, but by "looking" at the various parts of the maps, it's really odd to have 13.6 at 500rpm.

TurboTJ

The values in the fuel map typically don't correspond to an exact air fuel ratio. The units of the map should be noted somewhere in the window.

At idle, (assuming the engine is warm) your car is in closed loop mode. During this, the stock ECU tries to obtain an air fuel ratio of 14.7:1. It uses the values in the fuel map, and then manually adjust it up or down slightly to reach the target.

tephra

iTrader: (6)

no in closed loop it doesn't use the map at all...

silverstream

So, lean out idle, set to open loop, run at 16:1 ?

TurboTJ

Huh? Then how does it get an original starting value???? Have you ever setup a closed loop control system? You start with the value in the fuel map, then apply modifiers (which account for coolant temp, intake temp, etc.) resulting in your best guess at how much fuel to inject. At this point, the ECU looks at the estimated value and actual value and adjust accordingly. You must have an initial guess!!!

You probably don't want to do that. Without a wideband. Closed loop mode is there for a good reason. Since I can't talk you out of leaning out idle, I recommend buying a wideband gauge and plugging that into the ECU. If setup properly, this will let you run in closed loop at 16:1.

Here's some good info:
https://www.evolutionm.net/forums/ec...o2-system.html

tephra

iTrader: (6)

two words:

injector scaling

The values in the fuel map are "modifiers" in themselves. We just visualise them as an AFR.

But regardless for closed loop I dont believe the values in the map are referenced at all...

silverstream

Take a look at these.

Totally original High Octane Fuel Map, and a MapTracer showing "Count".

This is taken on a typical traffic congested scenario, lots of stop and go, no chance to rev up.

You'll notice that 500rpm, load cell 30 & 40 are clocking up 5x that of cruising cell at 2000rpm load cell 70-80.
What make it worst is, the fuel map have 13.3 right at 500rpm across the entire < 80 load. There must be a reason why Mitsubishi did this...

But right off my head, all other cells in low load area are 14+, why is it that only the 500rpm cell assigned 13.3 ? There's a huge potential to lean thing out here

TurboTJ

The values in the fuel map ARE used in closed loop. You need an input before you can have a result. For example, lets say the map has a value of 12 (not necessarily the actual AFR). Then, because your engine is a little cold, a modifier map tells it to add an additional 10%. The amount of fuel injected will then be 10.8 on the first cycle. In closed loop, the ECU then measures the output and adjust accordingly, adding or subtracting fuel for the next cycle, up to a maximum value (roughly 10%).

This is important in case your o2 goes bad. For example, if your O2 got stuck reporting the engine to be lean, you don't want the engine to add 10 times more fuel. in this case, it could only add 10% more fuel (engine should still run).

At idle, you are at 14.7:1 in closed loop. Read the article I posted and research "fuel trims"

RazorLab

iTrader: (8)

Closed loop works on voltage from the 02. The voltage is mapped to Stoich, (example 0.5v = Stoich) which is the input you are suggesting, which the 02 sensor tries to always hit by adding/subtracting fuel trims. The narrowband has no idea what AFR the car is at, it only knows voltage. The narrowband is only accurate in a very small window, usually 0.400v to 0.800v

The article you referenced from mrfred, shows his *patch* referencing the fuel map in closed loop.

One the car goes into Open Loop, a simplified version is that it ignores the 02 sensor and runs off the fuel map as a modifier of a base setting (the unsimplified version has many other modifiers set after the base setting).

I'd give a suggestion that people that have actually disassembled the ECU code could know a little bit more about it then others.

Raptord

iTrader: (10)

Fuel map values are NOT used in closed loop. They are only used in open loop. The closed loop input come from the front o2 sensor, as Razor already said.

+1. I'm fairly certain Tephra knows the difference between closed and open loop...

C6C6CH3vo

iTrader: (9)

Correctto,

Closed loop is just a on/off switch to remove or add a small IDC percentage in order to maintain a favorable oxidative environment through catalyst, eg 14.7.

What I would like to know is if one of the tables in the v7 has an effect on the degree of closed loop IDC % at switch point. Any know specifically? I was thinking I can maintain a tighter closed loop AFR window with my simulated feedback, like a 0.4 AFR window, less zigzag

Fast_Freddie

iTrader: (50)

I wish there was a way besides inducing open loop, wiring the wideband into the front O2 or using zietronix to change the target stoich value/voltage the ECU is trying to hit...

RoadSpike

iTrader: (5)

I think I know where the .51 volts is in the ECU if you want it.

Far as quickness for the switching point I think your limited to the mhz the cpu has.

TurboTJ

I don't understand how anything you said disagrees with anything I said. All I am saying is that the ECU references the base fuel map in CLOSED LOOP. As you mentioned the narrow band oxygen sensor can basically only measure if the car is rich or lean.


Referencing the base fuel map (in CLOSED LOOP) solves two problems.
1. If the O2 sensor goes bad, the car should still be capable of running. This is why the feedback system is only allowed to adjust the AFR by a certain amount (~10%).
2. Any closed loop system needs a starting value in order to come up with a correction. That is, when it transfers into closed loop mode, it needs a "guess" of the correct amount of fuel, before it can measure the outcome. Here is a pretty good article on Control Theory: http://en.wikipedia.org/wiki/Control_theory

I suggest that people who have dissassembled ECU code, Tuned aftermarket standalones, and have a graduate degree in engineering know a little bit more than the previously mentioned "others"....

Fast_Freddie

iTrader: (50)

Well lets see if we can adjust the stoich voltage and see if it will alter closed loop AFR... I am about to switch back to E85 pretty soon, and if this works it would be great...

Also can you do me a favor and look at the routine and see how stoich is calculated after a voltage input is received from the front O2... we know the front O2 is basically a switch and works in conjunction with the STFT to maintain stoich, but I would like to know exactly how the IPW/IDC is calc'd afterwards.


Thanks