EMS vs Piggyback (update, post #11)
 

Here is the food for thought. We know that standalone (AEM EMS) will produce bigger gains, than piggybank (e-mange blue).

Both can add fuel while in boost, both can retard timing while in boost, both will be in open loop at WOT and both can maintain constant AFR while in open loop at WOT.

Then, what features or systemsof stand alone EMS tend to produce bigger gains, taken in to concideration that everything else is being equeal? :shrug:

Re: EMS vs Piggybank
 

Frist thing, you aren't directly controlling anything with a piggyback. You're taking a signal, modifying it and sending it out to the injectors/coils. The computers weren't designed to work together and piggybacks are universal.

And no, you will not be in open loop at WOT. With a sotck ecu and piggyback you will ALWAYS be in closed loop.

Also, you don't have direct control over the ignition and the ecu can relearn over what the piggyback is doing to correct it.

FYI AEM isn't the only standalone. Kpro is a standalone unit as well. Preference as to which depends on the user. But...most everyone I've talked to about it before switching over to the kpro suggested I do just that for many reasons and I am glad I did.

Re: EMS vs Piggybank
 

question..im sure its probably been covered before but since were on the subject..

whats the difference between open loop and closed loop.. or even better lol what does that mean?? anybody care to explain.

Re: EMS vs Piggybank
 

This is very in depth question but to be short and brief in Closed loop operation your air/fuel is based off feedback from your 02 sensorrs. In open loop the air/fuel is based directly off a map. The problem with tuning in closed loop is that when you try to make adjustments with your piggyback the ecu will always try to override correct the changes to stay at stoich 14.7 or around there which is too lean for a boosted application. I hope that helps... that is only the tip of the iceberg though. I'll add some links with more explanation.

Re: EMS vs Piggybank
 

Open loop means you have a preprogrammed map for fuel and ignition and it doesn't change unless its based on a parameter that you've specified, eg: coolant temp, air temp, etc.

Closed loop means the oxygen sensor is continuously changing the air/fuel and ignition values to keep them at a constant.

Re: EMS vs Piggybank
 

So, D17 ECU never switches to "open loop" then?
It only runs closed loop?

Re: EMS vs Piggybank
 

Yes, it adjusts fuel and ignition based on the o2 voltage at all times...unless you have a check engine light and depending on what it is, I'm not positive but I believe there is a preset map for safe running of the vehicle when certain sensors malfunction, ie: o2 sensor, map, etc.

Re: EMS vs Piggybank
 

piggybank?? i thought it was a piggy"back" if thats the case, EMS puts a hole in the Piggybank. lol ok im out, srry to thread jack

Re: EMS vs Piggybank
 

The D17 can be open loop all the time, as I have witnessed it first hand tuning a few of them. Typically this was caused from a faulty primary O2, but almost all of them with respect to normal dealings where in Open Loop when WOT and at idle. The cruising is when closed loop O2 feedback comes into play.

Typically ignition signal modification is not relearned, but fuel trims are. The ignition timing on some of the piggybacks like the E-mangle and such are also indirectly altering timing as well.

With a piggyback, if you are tuning and not paying attention to LT and ST fuel trims, you can throw the ECU into a frenzy and cause it to begin working against you. You can get favorable results from a piggyback to an extent, but depends heavily upon how well you massage the ECU into getting what you need and what it wants. It takes a good ODB2 scanner, time, patience, know how and some good tuning.

The e-mangle modifies incoming injector and map pulses and spits out the modified signal based upon what you plug into the support tool. The e-mangle does NOTHING at all with manipulation of O2 sensors. PCS XFC and now the AEM F/IC do as far as piggies. Both have a form of O2 spoofing, which is pretty trick and helps keep the delivery to where you need it, but once again if you tune that unit incorrectly, it can still not work right for you.

The F/IC has a pattented way of modifing ignition timing, which no other piggyback does. They do it in a scaled down version of their EMS and alter the cam and crank timing signals. This is great because you will get more accurate and better results this way. So far, as far as tools for the trade and sophistication of equipment, for piggies, AEM F/IC FTW

Re: EMS vs Piggybank
 

Yeah, I knew about the o2, I mentioned that. So the map on the stock ecu runs open loop at wot at all times, assuming everything is functioning properly? That's news to me.
I was referring moreso to the fuel maps, but what conditions will cause a relearn to the ignition map?
Yeah but its such a hassle and so difficult to get everything perfect, most GOOD tuners won't touch anything but standalones.
That's the only real pro I can see to running the aem fic is that it taps into the additional sensors for readings and has a more accurate detail of where the engine is at vs. just using an rpm signal.

But this is good stuff to learn. These details are what people need to read and absorb, myself included. I'm not a tuner yet but one day...

Re: EMS vs Piggybank
 

Do you know at what TPS % ECU starts to operate at open loop?

F/IC has o2 sensor voltage map, that means one can fool ECU as wether it can stay open loop even while cruising?

I think if it is open loop 100% of the time it wil make tuning much more easier.

Re: EMS vs Piggyback (update, post #11)
 

I just installed srt4 577cc injectors and adjusted fuel trim to -58%.
When I first start the engine A/F shows at around 1:16.
I played with fuel trims and enriched idle fuel trim in the idle zone (0-1000 rpm) to -54% correction.
When I start the engine the A/F shows about 1:15, but half a minute later it drops back to 1:16.
It looks like short fuel trip does its trick.
Now I'm confused. I know I'll crack this later when my OBD II scanner arrives, but now I'm not happy, since I dont know what to do yet.

Re: EMS vs Piggyback (update, post #11)
 

I think you have your ratios backwards, at first I didn't know what you were talking about. It would be 15:1, 16:1, parts air to fuel, not the other way around, otherwise, the car would not run and your cylinders would literally flood.

That said, I don't understand your issue...does the car idle smoothly? At idle, there is no load on the engine so you can run leaner and its fine. My idle is 15-16:1 and its fine. It just depends on what afr the engine runs smoothly at when idling....

Re: EMS vs Piggyback (update, post #11)
 

I know that I can have it run leaner when there is no load or slight load.
It idles ok, but several times a minute it will kind of go off beat for a sec or so.... but no issue when driving or accelerating.

Re: EMS vs Piggyback (update, post #11)
 

This is normal. Stock PCMs do this all the time.