QUOTE=milindh;35687]Hey Clark
Would you please explain the difference beween the true programmable units and the piggyback units. My understanding is that one type, the piggyback ones ( I think), alters either the info coming into the EFI brain or the signal going out to the throttle body. Since the OEM EFI brain is always trying to maintain the EPA and factory madated A/F ratio the job of the modifier is to fool the brain into thinking it's actually doing what it's supposed to be doing. Kinda like some women I know.
Anyway, as you can see my knowledge of how these things work is almost nothing. Or maybe you can recommend some online or print source for this info. Actually this is probably more like what I'm needing. I'll bet it's a huge subject. I've seen some Donny Petersen articles in AIM on some of the different units but I'm missing the basic knowledge. I know carbs pretty well and I'm not anticipating getting an FI bike any time soon but I would like to expand my knowledge.
Thanks
Mike (milindh)[/QUOTE]
What I mean by small piggyback systems is these cheap modules that plug inline with the fuel injectors.
I would go with a system that can manipulate the total fuel map. Also keep in mind that the 2007 bikes do have a closed loop O2 system as you stated keeping the fuel adjusted for EPA regulations.
A lot of people don't this but the factory closed loop ECM mapping is set for "basically" cruising load. There is a MAP sensor and a TPS that sends a signal to the bike's ECM to let it know what the throttle position and load is on the engine. "Open loop" means that the O2 sensor system is turned off..."Closed loop" means that the O2 sensor system is on. The system is in closed loop during cruising load and goes into open loop somewhere around 60% throttle (I can’t remember exactly). So if you are cruising and throttle hard the system goes into open loop and the "base map" takes over.
The Power Commander disconnects the O2 sensors and uses an O2 sensor bypass device that fools the ECM into thinking that the O2 sensors are still working while it is running off of the base map.
The SERT (SE Race Tuner) has the ability to turn the O2 sensors off at any throttle position or leave them on. You can manipulate the base map to fit your engine’s fuel mixture needs. If the system goes into closed loop, it will only self adjust itself to 14.6/1 A/F ratio.
The Thundermax and Daytona Twin Tec have the ability to self adjust to whatever A/F ratio that you tell it to. They both have a built in recorder that lets the tuner know what cells in the map that needs to be changed. The O2 sensors basically creates it's own voltage determined by the amount of unburned fuel in the exhaust. The voltage signal is sent to the ECM to do the adjusting. The problem is that the O2 sensors cannot cover the entire A/R ratio band on any of these so-called “self tuning” systems. They have parameters that keep them from doing this.
The data recorder that the T-max & Twin Tec has will record the data and show the areas that are out of the parameters. Then the tuner can manually adjust to compensate for the parameters. The biggest problem with both of these systems is finding a tuner that understands the system and knows how to make adjustments.
All of these systems have good points and bad points. That is why I suggest asking different tuners around your area what they prefer. Most will say the SERT or the PC because that is the system they know best. I personally like the systems in this order:
T-Max, Twin Tec, SERT, PC. But that's my opinion.
There is so much to talk about when it comes to these systems. I'm going to work on an article for the forum to try to explain the differences between the more common systems. It will take a while to do. I do have an article on my website that covers the SERT that may help you.
http://hemrickperformance.com/tuning.aspx
I hope that I haven't totally confused you. Maybe it helped. 
Dyno Tuning 
what is the best fuel injection module for screamin eagle road king 2007 
Linear Mode
