How do piggy back ECUs know which map is being used?

[phosty]

I have been reading through as many of the posts here as I can about ECU piggy back controllers (Unichip, MapEcu2, Haltech Interceptor, etc etc) and also been reading up on the various manufacturers websites about their products.

I think I have a basic understanding of how they work - they modify the original ECU signals for timing and injectors to move the engine operating points to where you want it to be.

However one area I am still struggling with - how do the piggy back ecu's know which factory ecu map is in use? Looking at the dumps from the VR4 ecu that AderC posted ( http://www.clubvr4.com/forum/showpost.php?p=275373&postcount=44 ) there seem to be at least 3 distinct maps for fueling and 3 for timing. Presumably these are for cold start, normal warm, and maybe safe mode (when the knock sensor detects knocking??)

If the piggyback has the facility to provide more than one map (I think the Haltech and MapEcu2 both have dual maps) how does it know which to apply at any one time? As far as I can figure out they are only selectable manually.

So it is up to the user to select the appropriate map for the current condition of the engine. Unless there is a signal/value that can be picked up from the factory ecu which provides this data.

If the piggy back ecu only has one map (Unichip??) then it's adjustments will be made to all factory ecu maps regardless.

Does this not mean that cold start could be affected or worse that limp mode could be affected?

Finally, under light load the factory ecu reverts to closed loop mode. If the piggyback ecu doesn't get a signal to turn off it's adjustments during closed loop mode won't the two ecu's just end up fighting each other?

[Nutter_John]

ok simple answer , they don';t care

for instance with the mapecu2 what you are actually doing is not adjusting the injector cycles but the airflow seen by the ecu , so the ecu thinks it has less or more airflow at a given point . so on our cars we run rich on full boost so what you do is reduce the amount of air that the ecu is seeing and this in turn reduces the amount of fuel it adds .

As for timing it is done in the same way , you can advance or retard the timing over the stock settings

The systems use a map to define this , so at 3500 rpm and 0.8bar of boost tell the ecu it is seeing X air and adjust the timing by x degrees

Hope that helps

[valmes]

I have been reading through as many of the posts here as I can about ECU piggy back controllers (Unichip, MapEcu2, Haltech Interceptor, etc etc) and also been reading up on the various manufacturers websites about their products.

I think I have a basic understanding of how they work - they modify the original ECU signals for timing and injectors to move the engine operating points to where you want it to be.

However one area I am still struggling with - how do the piggy back ecu's know which factory ecu map is in use? Looking at the dumps from the VR4 ecu that AderC posted ( http://www.clubvr4.com/forum/showpost.php?p=275373&postcount=44 ) there seem to be at least 3 distinct maps for fueling and 3 for timing. Presumably these are for cold start, normal warm, and maybe safe mode (when the knock sensor detects knocking??)

If the piggyback has the facility to provide more than one map (I think the Haltech and MapEcu2 both have dual maps) how does it know which to apply at any one time? As far as I can figure out they are only selectable manually.

So it is up to the user to select the appropriate map for the current condition of the engine. Unless there is a signal/value that can be picked up from the factory ecu which provides this data.

If the piggy back ecu only has one map (Unichip??) then it's adjustments will be made to all factory ecu maps regardless.

Does this not mean that cold start could be affected or worse that limp mode could be affected?

Finally, under light load the factory ecu reverts to closed loop mode. If the piggyback ecu doesn't get a signal to turn off it's adjustments during closed loop mode won't the two ecu's just end up fighting each other?

Your aim with a piggy back is to adjust for constant changes (like bigger injectors), leave alone those parts of the map (all relevant ones) that are closed loop ("no load" or "partial load") and only take control over "open loop" (acceleration part).

So, basically, piggyback is not for control - it's there for adjustments...



I think I have a basic understanding of how they work - they modify the original ECU signals for timing and injectors to move the engine operating points to where you want it to be.


As far as I know only EMU controls injectors directly... all other piggybacks including MAP2 can only alter/replace airflow signal.

[phosty]

Ah - I see I didn't understand it as well as I thought. I downloaded the MapEcu2 manual from their website and had a read bearing in mind what you told me.

So the fuel adjust maps in the piggy back ecu's actually modify the air flow signal to acheive the target AFR (rather than fuel or injectors). I also read that the MapEcu2 allows voltage adjustment of the O2 sensor signal before it gets into the factory ecu thus allowing adjustments in closed loop mode too.

How does this sound:

Assume you are cruising on a motorway, partial throttle. The factory ecu is in closed loop mode because it can sense the throttle position (via TPS). Since it is in closed loop mode it is trimming the fueling (injectors) purely using the O2 sensor - the fueling look up tables are not being used and it is ignoring the AFM signals (which the piggy back ecu may have modifed - but that doesn't matter since it's in closed loop mode).

If the piggyback provides O2 voltage adjustment (i.e. MapEcu2) then this means adjustment of closed loop mode is possible.

If you floor the accelerator, the factory ecu detects it from the TPS and now moves into open loop (and ignores the O2 sensor signal - which may have been modified). Since it is now using its internal fuel tables and therefore using the signal from the AFM the piggyback ecu fueling adjustments now have an effect.

So long as the factory ecu uses the two separate modes (open loop and closed loop) and only uses either the AFM or O2 sensor respectively (i.e. not both at the same time) the piggyback ecu doesn't need to know what mode the factory ecu is in - in can safely adjust either signals simultaneously without them interfering with each other.

Am I getting there?

[Nutter_John]

When you first map the MAP2 you disconnect the stock O2 sensor , this way you are just running on the normal fuel table ( this means that the ecu is not trying to trim the fueling that you are altering ) . The MAP2 also monitors the TPS and you can set a value to enrichen the fueling upon a quick change so as you say your cruising and hit the loud pedal hard well the ecu sees it and moves the fueling to match , so does the MAP2 .

Benh or Gowf are the most experienced on here with the Map2'S , Paul C also has one installed and he is mapping this himself

[Gowf]

As john has said above.... The easiest way to start with the Map2 is to disconnect the stock O2 sensor as it will not be trying to trim the fuel. Once you have mapped it for cruise you then may reconnect it as it then it will trim the fuel to achieve stoicometric afr. As you have correctly said once the right foot is down it doesnt care about trimming so you can then map for the open loop stuff.

The Map2 does have the ability to map within closed loop mode, but in all honesty it is far easier to do it without the stock sensor as there is no fluctuation at all.

[phosty]

Hmmn, I have just been reading back over my first post in this thread and I am still confused how different factory ECU maps are handled by piggyback ECU's (if at all).

As you have pointed out most, when in open loop, piggybacks modify the air flow signal (Load?) into the factory ECU to fool it into changing the fuelling/timing - but this will still be according to the factory standard maps (albeit at a different air flow / load than the car is currently experiencing).

So if the factory ECU has more than one map the actual piggyback will apply the same air flow modifications regardless of the current factory map (assuming open loop mode).

Do you not need to be careful to make sure that the piggyback modifications are safe for whatever factory map may be currently in use? i.e. cold start / warm cruise (as I said above the ECU dumps for the VR4 seem to show different 3 maps).

[Turbo_Steve]

Kind of.....the idea is (as Valmes mentioned) that you're aiming to make "global" adjustments. So in theory, you're taking ALL the maps and saying "I've fitted 20% bigger injectors, so I need 20% less fuel throughout the map".

Of course, the reason you fitted those bigger injectors is because you need more fuel, so there comes a point where you let the factory ECU know that more air is going in, so it gradually uses more of them.

As valmes has said , very few piggybacks directly control the injectors. I'm generally averse to telling lies to the factory ECU: If you tell it that there is less air, i.e. less load, it will generally assume that it can change load point on the ignition maps as well as the fuel. So whilst you're busily adding fuel, the ECU is probably using more timing than you'd like at high RPMs.

This is especially problematic on the Scoobs, which tend to have a detonation harmonic at 6000rpms over a specific boost (varies per engine). You use a piggyback that tells the ECU that there is less load than there really is, and the ECU tends to run more timing, which needs even more fuel to try and compensate. So you end up with a "boggy" part of the map.

Until recently I believed all piggybacks worked this way, but (as valmes corrected me) they don't have to: Some (like the EMU) offer direct control, and TBH are nearer to being a standalone than a piggyback. Rather than lying to the ECU, they effectively 'compensate' at the output, rather than the input. So the ECU works as normally as possible up to it's limits, and then the EMU 'takes over'. It's very clever....much like this simplification isn't.

[phosty]

Ahh.

Just to check - EMU = E-manage Ultimate??

I tried googling for EMU (duh!) but I didn't think Australia's tallest native bird would help much in tuning engines....

[Turbo_Steve]

That's the fella. IF you can find it at the sort of prices Valmes can (do a search on here) then you're laughing.

If you're not in a hurry, though, it might be worth waiting to see if anyone cracks the factory ECU reflash mechanism (assuming there is one).

[Nick Mann]

The talk of re-flashing gets stronger all the time. I think I read that the guys in Russia have managed it? It will get sorted at some point. Can you wait, or even can you afford to be the guinea pig?

[phosty]

Hmmn, EMU's are ~£300 delivered (not inc import duty if they get caught) on eBay at the moment......

Isn't the MAPECU2 about £600ish????

But then again I guess you also need a stand-alone bloost controller for the EMU if you want to up the boost too?

[Nutter_John]

about 800 fitted and mapped , the emu will be around 400 , then you need to fit it and get it mapped so probably not that much in it

[Gowf]

about 800 fitted and mapped , the emu will be around 400 , then you need to fit it and get it mapped so probably not that much in it


True, but its a long way from aberdeen to guildford.

Give benh a PM or phone the garage. There was a group buy on map2's last year, so i'm sure he'l give you a decent price. But yes they are around £600 RRP

[phosty]

The MAPECU2 also includes a harness ready for splicing in to the loom as far as I can see from their website....but I see lots of car specific harnesses (for a fair amount of cash too) for the EMU.

Does the EMU not come with a non-specific one you can splice in yourself?

[stuartturbo]

Rhd japan do do a pucker loom extension
https://www.rhdjapan.com/jdm/FIELD-One-Touch-Coupler-Engine-Harness-Extension-15036

[Eurospec]

Piggy back ecu dont really have a direct interaction with the multiple individual maps stored in the factory ecu's. They work pretty much as the guys have indicated.

The easiest way to think of it is that they intercept the singnals the normal ecu recieves, and modifies them. The result is a certain afr, or boost or timing result from the outputs of the stock ecu.

Map2 will, through its O2 table, let you map closed loop, although i have to say i think mitsu got closed loop pretty much spot on, so all you do is map 'flat' there, or maybe force it out of closed loop earlier (more aggression in the map profiles) to pick up a bit of response.

No doubt your question comes from the fact that the stock ecu will choose from multiple maps, which it selects based on various parameters. The fine differences between the maps (cold start idle adjust etc) are not removed by fitting a piggyback. Perhaps the best way to say it is that fitting a piggyback is like altering the main fuel, boost and timing tables (this is pretty much what most tuners will do in a remap on a stock ecu), which are read by all subsequent maps in the ecu. By doing that (like when you remap something like an evo etc) you change the parameters you want, but you preserve as much of the niceties provided by the stock ecu as possible.

Bear in mind that any piggyback is always a compromise. You arent accessing the individual tables. The only way to have a racecar when you boot it, and a pussy cat when you want it to be, good cold start characteristics, air con control, active knock control and all the other features you would expect from a normal car is to go standalone. With say an autronic or aem you can get the car to behave perfectly, but the time taken to achieve it is significantly more.


Hope that helps,

Cheers,

Ben.

[phosty]

Thanks Benh - that just about sums it all up nicely really. Something to think about.

Stuartturbo, I bought one of the Field One-Touch Harnesses from RHD in November. A word of warning - make sure you get the right one! The Field One-Touch website has the wrong harness listed for the Auto VR4

http://translate.google.com/translate?hl=en&u=http://www.field-net.co.jp/lineup/onetouch/tekigou/mitsubishi.html

We need a CN-4 (same as manual) not the CN-70 as listed. RHD were fine about the return but is was annoying all the same. Just make sure you specify the CN-4 when you make the RHD order - if you tell them what car you have they will just look it up on the Field On-Touch website (and get the wrong one).

[stuartturbo]

they should have know that as mine was sorted long before then
I went through the palarva of returning the lead to them picture etc and getting the correct one.I told them the manual and auto where the same ECU's then /lol

[Turbo_Steve]

God we really REALLY need to get the reflash for our factory ECUs sorted...it will change everything.

[VR4 MAD]

God we really REALLY need to get the reflash for our factory ECUs sorted...it will change everything.

I couldn't agree more..............this just seems to be taking forever to sort.

It has been mentioned (rumoured?) that the Russian VR4/Mitsi club guys or an associate has achieved this but it's never been confirmed or explained how this was done. From what I can gather (and I'm no expert), the memory chip in our ECU can't be reflashed so a new flash-able memory chip needs to be substituted.

We really need someone to find out more for us and talk to whoever does the ECU reflashing to:-

a) confirm that it can be done

b) find out the general methodology (ie chip replacement needed?)

c) what software is used (ie custom software developed by the guys doing this or software readily available commercially - ECUFlash?)

d) either get us detailed instructions how to do the reflashing or possibly arrange for some of our ECUs to be reflashed.

I remember in a previous discussion about the Russian reflashing that they tried the Mines chip maps but the Russian fuel wasn't good enough to use with that fuel map so went with a custom map for their quality fuel.

But we could use the Mines fuel maps. :pimp2:

I would think Valmes must be the best person to enquire into this for us as he speaks the language, knows our cars intimately and could well already be a member of the club in question, and may actually know the guys doing this reflashing.

Valmes, you reading this..................:iloveyou: Hello, hello, can you help.........................Please please /rally

Just my thoughts.

/toycar