Truth About Is200 Ecu?

SpOcK · March 8, 2004

I've read here some talk about the IS200 ecu's ability to re-/self-learn a new program in the course of time after any changes in the engine's operating environment.

Wouldn't that kind of a negate the stuff that a piggy-back ecu does?

e.g.

- air-flow meter senses "a", and sends it to std ecu

- piggy-back ecu catches the message in the way, alters it, and then tells to the original ecu that the air-flow meter said "b".

- then the std ecu, unlike it anticipated, gets the message "b" and acts accordingly

- if the piggy-back ecu from there on then keeps telling that "a is b", wouldn't the std ecu then change it's program "for good"

I recall one member here telling that he's used HKS' F-con (or Greddy eManage?) and that he'd "maxed out" every setting the gadget had, just to make ANY difference and to fight against the std ecu learning the new stuff.

I'm not 100% sure I know what I'm talking about here, but I guess you got the picture what I'm after.

Any one? Mark? :duh:

RX-Men-8 · March 8, 2004

I would say no to that one. The piggyback ECU is imho able to shift the equilibrium in any parameter the ECU tries to regulate. To show this you can reverse the reasoning here. The ECU wants to see value "a" and adjusts fuel/air/ignition timing settings accordingly. It adapts (and maybe learns) until it gets value "a" on its input. If a piggyback ECU is intercepting and changing the readings, the actual value "c" you want gets changed into value "a" and the ECU is happy.

For the specialists, one caveat: in any control system the control loop needs to converge. This means every change in settings should get the readings closer to the equilibrium. It is certainly possible to create a diverging control clycle. This is very bad, as this always ends up in a setting in min. or max position (hitting the bottom or the ceiling). The ECU will not be able to get out of this situation and may need a reset afterwards.

Cheers,

RX-Men-8

ColinBarber · March 8, 2004

I think whilst you are accelerating the ECU uses it's pre-programmed map as parameters are changing all the time and therefore cannot get accurate feedback from the sensors. If this is the case a mod should make a different although the fuel trims will limit it's effect.

Once the engine is cruising then it will rely more on the O2 sensors to make adjustments and therefore wipe out any effect the mod is having.

I guess you could alter the O2 sensor signal rather than the air flow signal to gain more control.

However for big mods then you need to remove engine control from the standard ECU to something else like the HKS F-CON pro.

SpOcK · March 10, 2004

Once the engine is cruising then it will rely more on the O2 sensors to make adjustments and therefore wipe out any effect the mod is having.

But that in turn would negate the piggy-back ecu manufacturers' claims of better fuel economy, wouldn't it? You can't make any difference in economy while accelerating, but rather on cruise. And if the std ecu over-rides the piggy-back's effect on cruise, then there's no use trying to lean the mixture to gain better economy -> makes manufacturers' claims bull...

However for big mods then you need to remove engine control from the standard ECU to something else like the HKS F-CON pro.

I guess that wouldn't be an option, 'cause since 01/2001 the OBD-II system has been mandatory in EU. None of those aftermarket ecu's have the OBD-II (at least none that I know of), and they're all "only for of-road use"...

ColinBarber · March 10, 2004

Most engines are running correct fuel when cruising. I think the biggest gains are in acceleration which normally over fuel.

As for having a non OBD-II engine management, who is going to know? Would never be checked in the UK.

tdiplc · March 10, 2004

I have my arm around Colin on this one :D

The o2 sensors are closed loop and are used to control the fuel under cruising and idle conditions. It is possible to remap the fuel parameters but the self learning will always default back to the original settings.

Depending on the car, the full load fuel parameters are set by throttle angle, map sensor, air flow, mass flow etc which can be successfully mapped.

Most standard Japanese cars come from the factory WAY over rich (probably to increase the life of the cats). Correcting the air/fuel ration results in more power, better economy, longer engine life and more leaves on the trees.

Hope this helps :)

SpOcK · March 10, 2004

As for having a non OBD-II engine management, who is going to know? Would never be checked in the UK.

I don'tknow about other countries (I think it should concern other countries including UK as well, since it's an EU regulation), but at least here in Finland they've started to take read-outs from the OBD-II -system from the beginning of 2004 as a part of the MOT. So a newer vehicle (2001->) won't pass the MOT without the OBD-II in tact.

There's even been some debate in the media of the "dead standard" vehicles WITH the OBD-II not passing the MOT, because they've not been driven "correctly". For the OBD-II to work correctly and for it to be able to complete all its self-diagnostics, the vehicle has to be driven along a certain cycle (includes cold-starts, full-throttle accelerations, high-way driving, idling, etc).

That's why some of those "grand-ma's shop-carriages" won't pass MOT, 'cause those grannies have defenitely NEVER even gone full-throttle...