How They Do That!

[ecupro]

Wonder, Wira 1.6 Auto. This engine did not have o2 sensor for close loop. When tunning, they only allow to adjust the VR,variable resistor ( Lean or Rich ). My question is, how the stock ecu know that the a/f in range ( 14.7 ) ?
Those who drive on Toyota, SEG ( Malaysia ), also do not have o2 sensor. Only VR to adjust. How they do that ?
Any Si fu.......
Thank you.

 

[nova]

No closed loop, no need loh.:regular_smile:

 

[dolly]

take a few of the same engine (perhaps hundreds or thousands). Run them on the same map and figure out the distribution. Alter fuel map to accomodate MOST of the motors, apply compensation for barometric pressure and temperature.
Keep ignition timing at a very conservative value so nothing blows up (and allowance for lower octane rating fuel)...

my 2sen, and how i would have done it xD

 

[cuscostrutbrace]

i think they have the CO instrument fitted to the exhaust when tuning the VR

 

[Useless]

ecupro,

u the sifu la....

my poor 2 cents assumption....
factory obtains economy and power maps (assumed 2 maps) under testing conditions. hence there is a need to determine the point of switching between these two maps. i think the and the would be the determining inputs. to ensure that the output is achieved, a gas analyzer would first need to be used to preset the CO output from the VR screw. i believe that only after presetting all base points, only can desired results be obtained. Just as we need to preset the ignition timing for the ecu by the strobe lamp for older generation cars before we can obtain optimum torque.

sorry if i am muttering nonsense :P

cheers.

 

[e819]

co2 sensor??

 

[ecupro]

Well, to make this more wonder, like joeker say, stoich( 14.7 ) at idle, lean at cruising and rich at WOT.
My wonder will be, how the ecu know that you are cruising ( engine run on lean )!
How They Do That ?

 

[dolly]

if map based, then based on the load (pressure) seen. if afm based, well then based on the volume of air entering. Either that or tps based

 

[ecupro]

Bro, most ecu have loading feed back sensor (Map,Hot-Wire...Tps....)
In this case, only don't have o2 sensor.
When come to cruising, how the ecu know that you are cruising ? ( lean on engine ) How They Do That!

 

[Useless]

sigh...

my assumption...(at per instance)

condition 1:
if tps=30%, airmass=30kg/h, ecu to output "lean map"

condition 2:
if tps=30%, airmass=20kg/h, ecu to output "rich map"

makes sense?

rgds

 

[ecupro]

Si Fu Brian, I think the air mass flow wrong lah.
If air mass flow more air, the volume should be more, right! ( 30kg/hr , and not 20kg/hr ), in this case, more fuel will be added.( Rich )

Correct me if i am wrong, Si fu Brian, where are you attach to ? Look time did not see you!

 

[Useless]

correct me if i am wrong sifu leow...
if we are at crusing speed (lets assume TPS=30%), the airmass would always be at a fixed value (lets assume 30kg/hr, with maybe +/- 5% tolerance due to other external factors i.e air temp, baro press, coolant temp, etc).

if we jab the throttle instantaneously (lets assume TPS=30%), the airmass would not be 30kg/hr, not will it fall in the tolerance of +/- 5%. i might be wrong here to say airmass is less (at the instance), i am thinking that the sudden opening of the throttle valve decreases vacuum in the manifold. therefore airmass is less? Or maybe as long as the airmass measured has a great positive or negative difference from 30, then output is extra fuel?

but i am thinking again maybe the Wira 1.6 Auto is more straight forward. The VR just increases or decreases the multiplication factor for fuel. Therefore setting it correct at idle will have a high chance to produce close to 14,7 at light driving conditions.

i am working in KL now. sent u a short PM. yes long time no see. will contact u if i am heading up north to ipoh.

regards

 

[cuscostrutbrace]

Sifu..

The ecu knows the car is cruising from the sensors,vehicle speed,rpm and manifold pressure.If this 3 parameters is deviating not more than 5% or stays constant for a certain period of time,the ecu assumes the car is cruising and enter closed loop leans the mixture a bit.

If sudden throttle opening,accel enrichment comes in thats why it becomes rich for a certain period or time (or rpm) and decay after that.Then if the 3 parameters stabilize again,the cruising mode comes in..

The time in and time out determines how fast the ecu go into closed loop and start leaning the mixture during cruising.Thats why short trip increases fuel consumption .

correct me if i'm wrong

 

[Maxx]

hm.. my engine doesnt have o2 sensor too.. turbo summore.. hahha :_:

 

[ecupro]

cuscostrutbrace,
No bad at all, you are upgrade to Si Fu level.....ha..ha..ha
Time is very important factor.

 

[Useless]

no lambda sensor how to close loop? :P

 

[cuscostrutbrace]

No lambda sensor ka?In that case the ecu just starts refering to preset fuel table for cruising lor..

 

[jswong]

An open-loop ECU doesn't care about stoichometry, right? Probably it's like this..

If the ECU was designed for closed-loop operations but the manufacturer isn't implementing it for the car, probably they can fix the lambda sensor input to 0.5 volts (stoichometry), and just let the ECU do the fuel injection by referring to the air-fuel maps. Whatever the airflow sensor input, the ECU will just signal the injectors according to the map and won't perform any compensation because it will see that the result is 'correct' at all times.

Maybe we can try fixing the Siemens ECU's lambda sensor input at 0.5 volts so that it doesn't compensate for anything, and see if an SAFC can work with it then...

 

[RSI]

Cruising means the TPS is low. Period. That is how the ECU knows you are cruising. So the AFR gets richer as the TPS gets higher.

 

[RSI]

Lambda sensor has no purpose other than running the catalytic converter at maximum efficiency to achieve lowest emission. AFR of about 14.7:1 or lambda=1 yields the lowest emission. You can get better fuel consumption by NOT running closeloop. i.e. running leaner than 14.7:1 during cruise.