I plan on adding a piggyback to the ECU in my car, but don't want to use the added horsepower all of the time. I have heard of a button that you can buy that will actually toggle between the normal ECU and the piggyback ECU. DOes anyone know anything about this or where you can purchase it? Any information would really help! Thanks!

 

WHY??

 

I actually did something like that with my S-AFC on my Evo before I removed it.. The wire that gets cut for the MAF sensor.. I added a switch so I could switch between the S-AFC and bypassing it.. I used a DPDT switch with the "Middle" contacts being the stock ECU and MAF wire, one side was a jumper (essentially directly connecting the stock wires back together) and the other side had the connections to the piggyback.

Obviously this is only useful if your piggyback only intercepts the MAF sensor, and everything else is just tapped in to get signals to the piggyback.

There is a legitimate reason to bypass a piggyback, most importantly to troubleshoot a problem, since you would be tricking the ECU with the piggyback, it makes sense to "put it back to normal" if you plan on putting an OBD-II datalogger on it for any particular reason.

 

piggy back is actually tuned with an obd-2 tool so that it is kept withing the parameters of the ecu. Where the piggy back becomes effective is at full throttle where the ecu goes into open loop and uses predefined maps for fuel and timing. You can still connect the obd-2 mitsu scan tool and log all day long. The car will be identicle to stock everywhere but open loop operations. The scan tool in open loop will show the timing and fuel within specs and even a tech would not be able to tell the piggy back was there. The car is unchanged as a daily driver its only full throttle/open loop operations that have been changed.

Switching it is ok it won't hurt but i really can't understand why you'd do it. An AFC is harder to dial in as far as obd specs go during idle and drivability conditions thus when you'd take it to be checked a switch would be awesome. It's also usefull for smog. But for the piggy back its just not going to do anything except make you slower when you put your foot all the way down.

Maklibu is right on how to do it. Just use the DTDP switch, from radioshack,etc. You'll be set then.

 

I his defense, a piggyback on/off switch would be nice. If you don't plan on doing any spirited driving and would like to revert to cheaper, normal pump gas, you'd be able to, right?

 

boe, u said that when it goes into open loop during WOT it changes the fuel curves and timing, etc, so why wouldn't that show in a obdII logger when your at wot?

 

obd2 scan tool shows that you are in open loop and then shows parameters pertaining to that part of the program. That part of it has a window of adjustablility/mins-max values. The car still is within these settings so there is nothing out of the ordinary that the tech would notice. If he sat there and disected the car comparing to a stock car he'd see less fuel and a few degrees advanced timing in certain area's. This is won't happen as it would take about 8-10 hours of work to accomplish. Not going to happen if things are withing parameters. Mitsu. is just going to hand the car back and say its fine!! We did this on purpose so that no one would have a problem with taking the car to mitsu.

Basically you need to look/find the piggy back to know its there. It's just that simple.

 

But it would be nice to be able to switch back and fourth to run 87 pump gas around town, saving money. Then switch it back on for racing. Although, in its defense, I do believe you get about 2 mog more when running on the piggyback (unless you're a leadfoot), so that makes up for the gasoline costs a little.