09 sti piggback setup

Ok so I'm about to try piggyback a haltech 2500 onto the oem ecu, Never done anything like this before so I'm after some advice on what to watch out for. The CANBUS system is not supported so hence the piggyback .

Will it be easier to leave the narrowband O2 sensor in or just remove them and try to disable

How do i go about the DBW? can i disable/disconnect it and let the haltech run DBW alone

The coolant temp , is it ok to share the output to both ecu's or will there be a conflict

The MAF senor need to stay or can i pull it out

The knock senor is another question also, can it be shared or disabled

The map senor , to disable or share or double up on, one for each ecu. Plan on running 25psi at least so oem will go out of range pretty quick.

The injectors and ignition controls

The tacho needs to be shared to bot ecu's

Is there anything else I'm missing that will play up

I plan on install standalone oil/fuel pressure oil temp sensor to the elite and running a VE tune with full boost control, ignition timing and fuel control.

The cruise control is something i would like to retain but I would think the elite would have to run that seem the DBW controls will be handle by elite and piggyback the speed senors

The speed senors will stay on the oem ecu to run the dash speedo as well as the intank fuel pump and level senor while the elite will run the surge tank pumps.

I have a Boom Slang harness that is made to piggyback the ecu's together which was designed to work on the unsupported models but so many questions still. If you can help out with any of my questions it would be great so I can start ticking of these problems and get a work around going. thanks guys

From experience in the past, you're likely to have some issues trying to do what you're doing. I did this to piggy back an HKS FCON V Pro onto an 08 Sti and we ended up removing it and reflashing the stock ECU instead. In particular you will have trouble with the DBW as this really should be controlled by the Haltech but of course the factory ECU will have a fit if it isn't receiving the expected signals. We left the stock ECU controlling the DBW with the FCON and then the cruise will still work, however we had issues with the stock ECU going into a limp home mode and abandoned the project.

Even the fuel control can be problematic as the stock ECU will be trying to correct and perceived errors in closed loop and of course it will have no effect so you'll end up with a DTC for system too rich/lean. If you have the ability to also reflash the stock ECU then you could possibly get around most of these issues by disabling the appropriate DTCs but it may still be tricky.

As a general rule you can share analogue voltage inputs from sensors such as a MAP sensor or TPS, however temp sensors are a bit trickier since the factory ECU will have a pullup resistor internally. To share these signals you can splice them into the Haltech as an analogue voltage input so there's no pull up resistor active or use an analogue temp input with a software selectable pull up.

I'd just use the built in map sensor on the Elite since the stock sensor will be out of range.

thanks andre, think i will just use the haltech and scrap the oem ecu and use a racepak dash . Been a daily driver I was trying to keep that stealth look in case of police given me trouble but so be it. There's no way im going to put this motor in and be controlled by a stock ecu, there's to much money invested to not have the level of protection these pro ecu's have to offer.

i have a haltech elite 750 and im having similar issues. Is it possible to have the stock ecu control the DBW and the transmission?