zoomzoom_8

Hey everyone,

Could someone help me interpret this chart. I was playing with the Hymee Scanalyser and made a quick 1st gear run and finally got it in a chart format.

It looks like I went lean at the end, but I had let off the gas then (notice rpm).

I am trying to get a baseline in all the gears so that when the turbo is on, i can compare to make sure i am okay and to also help in tuning.

Any comments are very helpful! Thanks everyone. By the way, the Hymee product seems very nice!

Chris

dannobre

iTrader: (3)

looks like the lean spot is off throttle.....that's normal fuel cut when you are off the gas.

The rest looks normal..you dropped into open loop at about 5600 and the thing went pig rich from there :D

zoomzoom_8

so how did you tell that it went into open loop? And what is considered pig rich? haha, i am too new, promise i will help someone as lost as me when I find myself!

dannobre

iTrader: (3)

If you follow the graph of the A/F you will notice it takes a huge dive at 5600. That's where it drops out of closed loop ie...feedback loop mode and into open loop. It looks like you are about 11:1 ish. If you change the scale for the A/F from 10-16, it would be easier to read :D

army_rx8

^indeed :D but it looks liek it is operating as a hungry rotary liek sloves to eat pigs. lol soory stupid joke.

just curious as i am looking for a scan tool...hwo do you liek the Hymee one? what are you using to read it..laptop..carputer? (sorry off topic)

takahashi

You can log the open loop and close loop in your run zoom zoom.

Replace the open loop with a value say 100.

Close loop with a low value say 50.

Then you can plot close and open loop on the graph too!

Hope this helps...

Rather than guessing when the open loop is like a lot of people. I will use Lambda rather than AFR zoomzoom, since you are assuming the AFR is 14.4 at Lambda 1:1. And depends on the fuel - it varies. Since the sensor only detects O2 and it comes out as Lambda.... sco can explain it much better than me. That is what I get told from day 1 of beta testing sCANalyser.

BUT! If you keep using the same fuel and similar condition than it is ok. BUT don't hold too much on the absolute value - that is what I am saying - Hence, I use Lambda rather than AFR for all my runs.

If you know what I mean

zoomzoom_8

I am a total novice but really like the program. I was up and logging data within minutes of the UPS truck leaving so the user interface is EASY. I am using a laptop, but I do have a laptop with a cracked screen that I am planning at some point to make a carputer and have this running for my gauges.

army_rx8

cool....that would look nice. i'm think of the same thing..i have a few desktops sitting in teh basement doing nothing and i want to put them into use :D......was thinking of mounting it in the trunk.....but havn't really done anythignyet (i've been busy)..hehe so good luck to all of u in our projects :D

zoomzoom_8

Thanks for all the great tips guys, I am going to try them and I am sure I will be back for more advice! One thing though, now I see the open loop but what excatly is open loop and closed loop mean?

army_rx8

ahh glad you asked i just learned tha tin school..lets see if i mess it up or not. closed loop (not sure if it aplies to us)..is when the ecu uses a set map to run teh car....closed loop is where teh ecu uses input from the sensors to adjust things in teh runnign of the car (i.e. ignitions advance afr etc.)

open loop is not as good as closed loop..but usually most cars use it before everythign is within operating temps. (closed loop woudl casue teh ecu to mess things up if everythig is cold...liek before teh cat lights off)

that was teh fast version hope it made sense..as i am tired and about to go to bed.

army_rx8

so open loop...car iisn't using input form sensors just going off of a per-programed operating peramitors...closed loop uses the sensors and adjusts everythign according to what will be most effiecient

some one correct me if i'm all f'd up

zoomzoom_8

okay I think I understand that now, so why does the 8 kick into open loop at 5600 rpm, the car was already warmed up?

takahashi

zoom zoom, the ECU sends a signal to the OBD saying they are in close loop or open loop and you can display that in sCANalyser. So I am telling you to log them. Select one of the dial and change it to Fuel Status... or something similar.

So you don't need to guess when the close or open. It is THERE in front of you :D

Army explanation is spot on btw

Cheers
Taka

sco

Taka is right... FuelSystemStatus will show you whether you're on open or closed loop.

With AFR - using lambda (or equivalence ratio as it is termed in the OBD specs and our software) avoids the need to know the stoichiometric ratio of the fuel you're using. Lambda is what is reported by the O2 sensor as what it does is compare the amount of oxygen in the exhaust versus the amount of oxygen in the atmosphere - it knows nothing of what fuel you're using.

If you want to use AFR reliably, the stoichiometric air to fuel ratio is configurable. If you go into Tools|Options and you change this to the stoichiometric ratio for the fuel. You'll see below the default setting of 14.64.



Basically AFR is [stoichiometric ratio] * [lambda/equivalence ratio]

Hope this helps explain things

Cheers

sco

sco

Not quite.

In simple terms... basically there are a set of conditions where the PCM will stay in closed loop... basically when it thinks you're cruising along. Staying in closed loop minimises emissions at the expense of performance. When the PCM works out you're not trying to cruise (e.g. you've put pedal to the metal) it switches to open loop and uses a table to lookup how much fuel to put in to maximise performance.

It's a lot more complicated than that in real life (e.g. the PCM dumps in extra fuel at high RPM to keep the catalytic converter cool) and it's also playing with things like ignition timing as well as the amount fuel to name a couple of things, but switching between emissions optimum operation and performance optimum operation is the fundamental principle.

Richard Paul

iTrader: (5)

SCO, could you come over tomorrow and help with getting my system to work. It's not just me Guitar Junkie was here all day and we couldn't get things to work.
Something about not finding a port. We sure could have used it when we were on the dyno.
The car is no better, in fact it is back to where it was before. I might sell this SOB if I have to spend any more time and money on it.

sco

I'd love to come over, but if I left now I wouldn't get there until late on Sunday your time and I fear I won't be much help after 17 hours of flying

r0tor

iTrader: (1)

how do you get an 11:1 a/f ratio when the stock sensor bottoms out at 12:1????

sco

r0tor, how did you come to that conclusion?

I just checked a recent log file... lowest lambda I've got is .758169 = AFR of 11.09959 if you use 14.64 for stoich.

r0tor

iTrader: (1)

theres been some discussion about it already... i think mazdamaniac checked into it a while back and found the lowest a/f its capable of was 12:1. I'd check with him.

Rasputin

Open loop / close loop conditions are not only dependant to RPM, but also to absolute load.
At lowish RPM, it demands a high load to go into open loop mode. Even there, the AFR remains close to stoich. With increased RPM, the open loop mode cuts in at lower loads. Also, at WOT, the fuel enrichment increases with speed and most of it is part of the catalyst temperature protection strategy. Basically, the extra fuel is there not to provide optimum power, but to cool down the catalyst. I've never liked that when I had to calibrate engines that way at Ford, but for car manufacturers, it still is the easiest way to do it I'm afraid.

AFR of around 20 as you see on overrun in your graph actually is a complete fuel cut-off on deceleration. It says 20 because that the max lean limit of the sensor/PCM system.

Fabrice

Hymee

iTrader: (1)

Whatever Rasputin says - it is Gospel!

He used to do this EFI tuning/calibration stuff for a living at Ford.

Another thing I would like to add about closed loop and open loop, and the relationship to AFR/Lambda. My trusted tuner Phil Laird from Graphic Skills Racing taught me this:

By definition, closed loop means the PCM is constantly adjusting the fuelling such that the AFR is stoich. I.e Lambda = 1.0. Hence, whenever the Lambda value deviates much from that, you can be pretty sure it is in open loop. Like sco said, in open loop, the "feedback loop" is broken, and the Lambda sensor's value is ignored, and the PCM simply dumps in as much fuel as it thinks necessary as determined by it's lookup tables and overall fuelling strategy.

Cheers,
Hymee.

Hymee

iTrader: (1)

Thanks mate. That is a nice feedback to get!

Cheers,
Hymee.

sco

Thanks. I missed that discussion. Dug up an old thread to discuss further here: https://www.rx8club.com/series-i-major-horsepower-upgrades-93/greddy-turbo-afr-using-canscan-62700/#post931387

neit_jnf

so why wouldn't a car manufacturer just run closed loop all the time and adjust for changing conditions in real time? can this be done with a stand alone? or is it just better to tune the car with a static map?