ECU spec and limitations.

[Tricky-Ricky]

Its late and I'm heading for bed but I thought it might be an idea to start this thread, especially since the way the thread by zippypooz dyno run went, and I have just searched and could find nothing relating to the actual capabilities and limitations of the std ECU, especially when it comes to adding breathing mods etc, and explain just how and why its thought to negate breathing mods...or not.

[Tricky-Ricky]

WARNING! this may get a little long winded and boring to some, however it may ultimately prove useful to some.

 

I thought this might have a few replies, given the amount of arguments about dyno figures and breathing mods on the other thread.

 

Anyway this is not intended to be an argument/discussion about dyno figures, more if an how the std ECU works , and in relation to adding breathing mods etc.

 

Now I am no expert, but I have mapped a few piggybacks and stand alones, but a while ago and older tech, but I like to think I have a fair grasp on just what goes on with your average ECU and how it controls the engine parameters.

 

Now when I first bought my Skyline 350GT (Z in sheep's clothing) I fully intended to self tune using Up-rev software, so as a prelude to this I first bought an Innovate LM2 twin wide-band set up and fitted it to the cats (and yes I am fully aware that this will gave a slightly scewd AFR signal) anyway I monitored and logged as I fitted some breathing mods, long tube intake, dual exhaust and the obligatory plenum spacer, and can honestly say that I didn't see any major changes in the AFRs, and further to this the car was dynoed at Abby by Mark and made pretty much std power and toque figures.

 

Unfortunately I never did get around to buying up-rev and self tuning.

 

On to the std ECU, we all know that the ECU meters the fuel and ignition timing to make the motor run efficiently, but in order to discuss things further I am going to have to outline pretty much the whole process, so sorry! I am sure that you can find all the relevant info on-line however I think it wont relate so well if you have to keep going elsewhere for reference.

 

ECU over view.(kept relatively simple) And as I said I am no expert and if anything is blatantly wrong then those that really know like Mark or Jezz etc please feel free to correct me.

 

Basically we start at the AFM which meters/measures the amount of air that's being drawn into the engine, a simple voltage signal, the ECU uses this voltage in the form of a table made up from this voltage and RPM and load, which it uses to calculate the amount of fuel to be injected at any one time.

 

There is also a similar scale/map that it uses for ignition timing, the problem is thats where things get a lot more complicated, as there are separate maps for each part of the process and condition, there are maps for cold starting, fine adjustment for coolant temp, intake temp, engine knock, dynamic ignition timing, short and long term learned fuelling and timing maps, and last but not least lambda feedback.

 

Lambda sensors as we know report the amount of un burned oxygen in the combustion process, which is known as AFR (air fuel ratio) which in turn gives the ECU the information to know if its supplying the correct amount of fuel.

 

Now with regard to adding breathing mods etc we only really need to concern with the main and adaptive fuel and timing maps, and in particular lambda feedback, now being N/A the ECU uses lambda feedback the majority of the time, the ECU has its own pre programed comparator maps which are what it expects to see in terms of AFRs, if the AFRs go outside of these figures it will adjust fuelling to get things back to within the parameters in the map.

 

This is where I start to fall down a little in my understanding, as say for arguments sake you add a free flowing exhaust system, and intake, and as a result the engine is able to draw more air, so the ECU sees more air/voltage from the AFM and so in the lookup table it finds the correct fuelling for this amount of airflow/load and adjusts accordingly, and this will be verified by the AFRs that the lambda sensor reports, so you would then expect to see a little more power because the engine is getting a little more air and fuel.

 

But this is what I have trouble with, if this amount of airflow is outside the lookup table, limits how does the ECU behave? it cannot change the amount of airflow, but it can change fuel, so does it run things weak because it hasn't got a matching fuel table? or does it simply richen things up excessively, or simply retard ignition timing to reduce overall power? but this if too much could cause knock, I am just not sure how it can limit power from airflow increase,

So if any real expert's can actually explain the finer points of this?

 

To me if any of the breathing mods can increase the overall airflow enough to make the ECU change fueling to match, it should result in more power, but its obvious that the ECU was adapting the fuelling as my wide-band logs showed no significant change in AFRs before or after I fitted breathing mods.

Edited January 18, 2016 by Tricky-Ricky

[davey_83]

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[Tricky-Ricky]

Thought there would be more interest given the amount of comment on this over the years, yet there is still nothing concrete as far as explanation's go, just a lot of conjecture.

[delz0r]

Nissan and the guys who reverse engineer the ECUs like uprev are the only ones that really know.

[Stutopia]

The only thing I've ever read on this topic has been the section in the workshop manual, engine control, pages 25-27 - it's pretty dry reading mind

 

 

SYSTEM DESCRIPTION

The amount of fuel injected from the fuel injector is determined by the ECM. The ECM controls the length of time the valve remains open (injection pulse duration). The amount of fuel injected is a program value in the ECM memory. The program value is pre-set by engine operating conditions. These conditions are determined by input signals (for engine speed and intake air) from both the crankshaft position sensor and the mass air flow sensor.

 

VARIOUS FUEL INJECTION INCREASE/DECREASE COMPENSATION

In addition, the amount of fuel injected is compensated to improve engine performance under various operating conditions as listed below.

 

<Fuel increase>

● During warm-up

● When starting the engine

● During acceleration

● Hot-engine operation

● When selector lever is changed from N to D (A/T models)

● High-load, high-speed operation

 

<Fuel decrease>

● During deceleration

● During high engine speed operation 


 

 

Revision: 2004 November EC-25

2004 350Z

 

 

 

ENGINE CONTROL SYSTEM MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)

 

The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control. The three way catalyst 1 can then better reduce CO, HC and NOx emissions. This system uses heated oxy- gen sensor 1 in the exhaust manifold to monitor whether the engine operation is rich or lean. The ECM adjusts the injection pulse width according to the sensor voltage signal. For more information about heated oxygen sensor 1, refer to EC-198 . This maintains the mixture ratio within the range of stoichiometric (ideal air-fuel mixture).

This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 is located downstream of the three-way catalyst 1. Even if the switching characteristics of heated oxygen sensor 1 shift, the air-fuel ratio is controlled to stoichiometric by the signal from heated oxygen sensor 2.

 

 

Open Loop Control

The open loop system condition refers to when the ECM detects any of the following conditions. Feedback control stops in order to maintain stabilized fuel combustion.

● Deceleration and acceleration

● High-load, high-speed operation

● Malfunction of heated oxygen sensor 1 or its circuit

● Insufficient activation of heated oxygen sensor 1 at low engine coolant temperature

● High engine coolant temperature

● During warm-up

● After shifting from N to D (A/T models)

● When starting the engine




 

MIXTURE RATIO SELF-LEARNING CONTROL

The mixture ratio feedback control system monitors the mixture ratio signal transmitted from heated oxygen sensor 1. This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio as close to the theoretical mixture ratio as possible. However, the basic mixture ratio is not necessarily controlled as originally designed. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic changes during operation (i.e., injector clogging) directly affect mixture ratio. 
Accordingly, the difference between the basic and theoretical mixture ratios is monitored in this system. This is then computed in terms of “injection pulse duration” to automatically compensate for the difference between the two ratios.
“Fuel trim” refers to the feedback compensation value compared against the basic injection duration. Fuel trim includes short term fuel trim and long term fuel trim. 
“Short term fuel trim” is the short-term fuel compensation used to maintain the mixture ratio at its theoretical value. The signal from heated oxygen sensor 1 indicates whether the mixture ratio is RICH or LEAN compared to the theoretical value. The signal then triggers a reduction in fuel volume if the mixture ratio is rich, and an increase in fuel volume if it is lean. 
“Long term fuel trim” is overall fuel compensation carried out long-term to compensate for continual deviation of the short term fuel trim from the central value. Such deviation will occur due to individual engine differences, wear over time and changes in the usage environment. 


 

 

Revision: 2004 November EC-26 2004 350Z

 

 

 

FUEL INJECTION TIMING

Two types of systems are used.

 

Sequential Multiport Fuel Injection System

Fuel is injected into each cylinder during each engine cycle according to the firing order. This system is used when the engine is running.

 

Simultaneous Multiport Fuel Injection System

Fuel is injected simultaneously into all six cylinders twice each engine cycle. In other words, pulse signals of the same width are simultaneously transmitted from the ECM.
The six injectors will then receive the signals two times for each engine cycle.
This system is used when the engine is being started and/or if the fail-safe system (CPU) is operating.

 

FUEL SHUT-OFF

Fuel to each cylinder is cut off during deceleration or operation of the engine at excessively high speeds.

 

 

Electronic Ignition (EI) System

 

SYSTEM DESCRIPTION

The ignition timing is controlled by the ECM to maintain the best air- fuel ratio for every running condition of the engine. The ignition tim- ing data is stored in the ECM. This data forms the map shown.
The ECM receives information such as the injection pulse width and camshaft position sensor signal. Computing this information, ignition signals are transmitted to the power transistor.

 

e.g., N: 1,800 rpm, Tp: 1.50 msec


A °BTDC


 

During the following conditions, the ignition timing is revised by the ECM according to the other data stored in the ECM.

● At starting 


● During warm-up 


● At idle

● At low battery voltage

● During acceleration

 

The knock sensor retard system is designed only for emergencies. The basic ignition timing is programmed within the anti-knocking zone, if recommended fuel is used under dry conditions. The retard system does not operate under normal driving conditions. If engine knocking occurs, the knock sensor monitors the condition. The signal is transmitted to the ECM. The ECM retards the ignition timing to eliminate the knocking condition. 


 

 

Revision: 2004 November EC-27

2004 350Z

EC

[davey_83]

I'm sorry but I'm laughing inside...... delete this useless post or not but there's been such strong views towards this topic however when it comes down to it silence fills the room.

 

Please someone put this to bed............

[Floydbax]

But this is what I have trouble with, if this amount of airflow is outside the lookup table, limits how does the ECU behave? it cannot change the amount of airflow, but it can change fuel, so does it run things weak because it hasn't got a matching fuel table? or does it simply richen things up excessively, or simply retard ignition timing to reduce overall power? but this if too much could cause knock, I am just not sure how it can limit power from airflow increase,

 

Isn't the throttle electronic and controlled by the ECU? This can regulate the airflow to within maps despite any breathing mods, if the flow exceeds any parameters! - I'm off to the pub

[Stutopia]

I'm sorry but I'm laughing inside...... delete this useless post or not but there's been such strong views towards this topic however when it comes down to it silence fills the room.

 

Please someone put this to bed............

 

What is it you're looking for?

 

There were tons of posts on the other thread, offering a bulk of opinions one way and a number of others another way. If you are expecting a "definitive" answer on this thread, any different to the views expressed on the other one, get set for disappointment.

[glrnet]

It's been debated for years it seems http://my350z.com/forum/engine-and-drivetrain/110331-self-adjusting-ecu-myth-or-true.html

[davey_83]

In the nicest possible way, so why was the thread started....

 

All I've heard so far is heresays without any backup. Saying something over and over doesn't make it any more true. I'm new the whole 350z/370z and when I hear something that doesn't make sense, il ask the question.

 

The ecu doesn't dial out any gains seen once it's had chance to learn the extra air going in and out of the cylinders. Ecu see's more air, resulting in a lean burn so adds extra fuel to maintain ideal normal driving afr. Using super unleaded fuel which arguably is better than when the car was launched for the UK market back in 2003, all helps with high rpm ignition timing and boom gains in power.

 

If with bolt ons the ecu manages to control the afr in a way it see's fit, most gains from the remap for n/a vehicles generally come from advancing the ignition timing.

 

That's my 2p anyways.

 

What's the standard base ignition timing for the early DE's?

David

Edited January 18, 2016 by davey_83

[Floydbax]

What's the standard base ignition timing for the early DE's?

Early DE's were limited by the restrictive mapping of the 'gentlemen's agreement' between Japanese and German/other Euro manufacturers of keeping power output below 276BHP

[Tricky-Ricky]

First off SuperStu I have read that in the manual, and its just a general explanation of how the system works, and really doesn't offer any incite on how it responds to breathing mods.

 

Floydbax although I see your point I really don't think the ECU is able to modulate the throttle on a full time basis to modulate the airflow, especially since it also has to respond to normal driving input as well.

And regarding ignition timing, I think you will find that if the std map is limited in some way, and its unlikely to be just timing based anyway,

it would be far easier to get more that the usual 300BHP from the DE motor, if that was the case.

Also the so called "gentleman's agreement" was for earlier cars, and was abandoned before the Z arrived.

 

davey_83 I agree to a point, especially the debated for years but nothing concrete has ever been published that I have seen, which I s why I broached the subject.

 

I am hoping for a reply from someone who is either willing to disclose the full facts, or who works in ECU/map side the industry.

Everything else is conjecture, but well thought out theory is always interesting.

[davey_83]

The general thinking from that link to the same debate over on my350z forum way back in 2005 is that and I quote:

 

there is no way the ecu can equalize or negate the power gains added by parts. if you add an intake and exhaust to the car, the ecu will not re-adjust itself back to stock HP etc....

 

That's was a trader from a tuning company in the days. Also Nissan, supposed when they use to get involved with such matters on a technical level concluded the same.

[Tricky-Ricky]

I am inclined to agree with that, I added breathing mods, the AFRs remained the same, which to me says that the ECU has adjusted fuelling to accommodate the extra airflow.....BUT the dyno showed a std BHP figure, however the engine could well have been making less power from wear and tear before the dyno.

 

But it was a low mileage engine that had very good even compression figures, and I also leak down tested when I got it, if only I had dynoed it before hand, but the fact that I was intending to self tune it made me not bother.

 

My naturally suspicious side does make me think that it could be a well maintained myth, after all if you where able to increase power by simple bolt ons, it wouldn't make tuners so much money,

Although I am not saying that it helps to optimise ECU settings, but the number of people that run breathing mods for a long time with no ECU tweaking without any detrimental effects says that the ECU is able to adapt fuelling to suite.

[Richf]

Its true that the ecu can adjust to air flow and minor changes but as far as I am aware it only runs closed loop for parts of the map so when the engine goes to full load etc and at high rpm the ecu will just refer back to a "target" setting on the map for afr that it is set at from stock, it doesn't "know" what the afr is as the lambda sensor cannot react fast enough or accurately enough.

 

For those that have an interest in mapping I can fully recommend the courses that Jez Horsham runs

 

http://www.emacademy.co.uk/

[Tricky-Ricky]

I am pretty sure that on the DE ECU closed loop is pretty much full term, N/A is not like turbo there is no need to adjust fuelling in line with boost pressure,

Airflow voltage is used to scale the maps so there is always a target figure, so as far as I know lambda feedback is used pretty much full time, in any case once a fixed map is used its usually deliberately rich as a safety measure, and this would be also make sense if there is no knock control on the DE ECU at high load/RPM.

 

Since only the J spec is supposed to have narrow band, and the UK wide-band this would be able to cope no problem, its how most modern ECU are configured especially the lean burn type.

[Richf]

I am pretty sure that on the DE ECU closed loop is pretty much full term, N/A is not like turbo there is no need to adjust fuelling in line with boost pressure,

Airflow voltage is used to scale the maps so there is always a target figure, so as far as I know lambda feedback is used pretty much full time, in any case once a fixed map is used its usually deliberately rich as a safety measure, and this would be also make sense if there is no knock control on the DE ECU at high load/RPM.

 

Since only the J spec is supposed to have narrow band, and the UK wide-band this would be able to cope no problem, its how most modern ECU are configured especially the lean burn type.

 

I've logged the output of the lambda on my 370 when on the dyno and although its a wideband its VERY slow to respond to afr changes

[Floydbax]

I think you hit on one of the problems in your title, 'limitations' I seem to remember Mark posted a very informative piece a while ago showing some of the ECU map constraints. I think the parameters within which the ECU can govern mapping aspects are too limited to compensate fully to breathing modifications, I.E. the figures exceed the range of mapped possible target points.

 

I also think it's already proven that if you have a standard, unfettled old engine (which they all are now!!), then it WILL have lost power over it's lifetime, no matter of how well it's been cared for, so that adding basic breathing modifications allows the ECU to alter its settings to a map which will maximise its power by virtue of making it run properly and will therefore actually make a sustained gain in power.

 

I'll link to the article when I have more time later.

[Tricky-Ricky]

I am pretty sure that on the DE ECU closed loop is pretty much full term, N/A is not like turbo there is no need to adjust fuelling in line with boost pressure,

Airflow voltage is used to scale the maps so there is always a target figure, so as far as I know lambda feedback is used pretty much full time, in any case once a fixed map is used its usually deliberately rich as a safety measure, and this would be also make sense if there is no knock control on the DE ECU at high load/RPM.

 

Since only the J spec is supposed to have narrow band, and the UK wide-band this would be able to cope no problem, its how most modern ECU are configured especially the lean burn type.

 

I've logged the output of the lambda on my 370 when on the dyno and although its a wideband its VERY slow to respond to afr changes

 

Interesting, and a little worrying for what should be a slightly more advanced ECU in the 370Z, I know my Innovate setup was very fast to respond.

[Tricky-Ricky]

I think you hit on one of the problems in your title, 'limitations' I seem to remember Mark posted a very informative piece a while ago showing some of the ECU map constraints. I think the parameters within which the ECU can govern mapping aspects are too limited to compensate fully to breathing modifications, I.E. the figures exceed the range of mapped possible target points.

 

I also think it's already proven that if you have a standard, unfettled old engine (which they all are now!!), then it WILL have lost power over it's lifetime, no matter of how well it's been cared for, so that adding basic breathing modifications allows the ECU to alter its settings to a map which will maximise its power by virtue of making it run properly and will therefore actually make a sustained gain in power.

 

I'll link to the article when I have more time later.

 

 

You see that's my point, what happens when the std ECUs airflow takes things beyond the target value? what does the ECU do to prevent damage from running too weak, if the airflow is outside the parameters that its capable of compensating for? I have seen people running cosworth plenum's along with exhaust filter etc without a remap yet they don't sustain any damage, and how is it able to run the correct AFRs for the increased airflow...without making more power, even a worn engine would still make more power from increased airflow and fuel.

[Floydbax]

I'd say it's a similar thing to when you get your UpRev and have a different map for power and for economy. The power one dumps a little more fuel in to give more bang and the economy runs leaner. The engine is fine doing either of these and they are within it's tolerances, similarly even if the breathing mods exceed the map parameters then it will still run OK just not at optimum.

[MJC]

Sorry for taking a relatively simple view of this topic but, this whole conversation is based on the potential possibility that the car could actually take in more air than the parameters allow for?

 

All a performance intake/filter provides is an easier or cooler passage for the intake air into the system- it does not provide any means for the intake air to be inducted at any greater pressure than normal, so it could be argued that it would be impossible to induct air at an excessive parameter unless forced induction was adopted which would require a ECU tweak to operate.

 

Surely the millions of £££'s the manufacturers spend on engine R&D couldn't be rendered useless by a £15 filter sold in Halfrauds?

[Floydbax]

Kind of exactly. Nisan produced millions of Zeds and there are for many reasons differences in their engines no matter how we'd like to think they all left the factory exactly the same they just don't. It didn't stick each one on a dyno and tweak the mapping because the generic mapping in the ECU and the engine can handle pretty much all those minor differences and also anything you can bolt onto it up to FI, at which point the ECU maps can't compensate. I do know however that when I changed my stupid tiny Apexi for the massive K+N I could feel the engine breathing better

[Richf]

I am pretty sure that on the DE ECU closed loop is pretty much full term, N/A is not like turbo there is no need to adjust fuelling in line with boost pressure,

Airflow voltage is used to scale the maps so there is always a target figure, so as far as I know lambda feedback is used pretty much full time, in any case once a fixed map is used its usually deliberately rich as a safety measure, and this would be also make sense if there is no knock control on the DE ECU at high load/RPM.

 

Since only the J spec is supposed to have narrow band, and the UK wide-band this would be able to cope no problem, its how most modern ECU are configured especially the lean burn type.

 

I've logged the output of the lambda on my 370 when on the dyno and although its a wideband its VERY slow to respond to afr changes

 

Interesting, and a little worrying for what should be a slightly more advanced ECU in the 370Z, I know my Innovate setup was very fast to respond.

 

Yep I was able to see the live data from Jez's innovate wideband (Bosch sensor) and compare it to the data coming off my oem wideband and it was consistently lagging behind, this was without cats btw . I've innovate stuff myself and always found it good , had wideband sensors and displays in both my r33 and Evo 6 and i used to map the latter myself.