07 - 08 Infiniti G35X (VQ35HR, AWD, AT) ECU and TCU compatibility with aftermarket units in parallel

Hi guys. I’m looking to see if anyone here has tried the following on this vehicle or a 5 speed automatic late model 350 / G35 or 370 / G37.

Does anyone know if the CANBus version of the automatic transmission on this car will continue to shift properly if one were to install a motorsport ECU in parallel configuration, or would it experience issues?

I’m also wondering if the AWD and VDC will continue working via the stock ECU or if the transfer case solenoid can be manually controlled by the motorsport ECU, or if either is known to work. Keeping the AWD is more important to me than keeping the VDC.

I’ve heard of tuners setting up the aftermarket / motorsports ECU to control the fuel injectors and coil packs while leaving control of the dual DBW throttle bodies and a few other systems to the stock ECU.

In the near future, I’m thinking of installing an aftermarket unit in parallel with the stock ECU, then using UpRev to control and tune the transmission (it seems to be the “mechatronic” type. This is the closest word I can currently think of to describe it), toggle certain OBD-II codes where necessary, and tune the throttle map.

I’m also unsure wether or not I would be able to control cam timing with the aftermarket / motorsports ECU, control it with UpRev on the stock ECU, or end up with the loss of variable valve timing.

If anyone has tried this before or knows with 100% certainty that the ECU and / or TCU will crap the bed, just let me know it’s not likely possible at this point in time. I understand that some applications and combinations would take an enormous amount of effort reverse engineering CAN messages (among other things) to make work, and I’m wanting to steer clear of that type of undertaking because it would not be feasible for me.

Thank you!

You basically have to deactivate all the diagnostic monitors and torque limits in the stock engine ECU. You will also have to force open loop.

Are you planning to use a piggyback as an interceptor like the one AEM sells?

Hi Raymond,

Is there any way to go about this? I have a Nissan Consult III and the UpRev reflash system on hand, if either are capable of it. I never learned how to deactivate diagnostic monitors or force open loop. I believe UpRev hides the codes but doesn’t deactivate the monitors themselves, but I could be wrong. If I’m correct, there is a table in UpRev that when changed, indirectly modifies the torque convertor lockup RPM and seems to have other effects on shifting and drivability.

I was thinking of piggybacking a Haltech Elite 2500 or AEM Infinity 708 to the stock ECU and intercepting / modifying fuel, spark, maybe cam timing (or leaving that to the stock ECU), etc. I’ve seen many parallel ECU kits that work on these cars, but they’re advertised as “manual only” and most are RWD.

Thanks for the reply!

Based on your screenshots on the tables available in the other thread:

The biggest thing you need to think about is the MAF sensor. The Map 1 Torque management (rpm vs load vs engine torque) is used for shifting and other functions by the AT. That table's load axis is the base fuel schedule. The base fuel schedule (which is proportional to calculated load) depends on the mass airflow transfer functions for each MAF sensor, and the Map 1 fuel compensation. If your MAF isn't there then you won't have the correct signal. Now, if you are getting really creative you can generate a CAN signal to the transmission to keep it from freaking out. But now you gotta ask yourself if the juice is worth the squeeze. Some of these boxes will actually let you delete the MAF sensor(s) and trick the ECU with a look up table, but man that is a lot of work to delete those sensors for limited gain (some reduction in air induction restriction).

Since Uprev can control fuel, spark, and cams, as long as your MAF is scaled decently and you get the injector settings close enough you should be ok without needing an extra box that is fighting the stock ECU. With some crazy boosted plumbing it could get tough, but N/A I don't see enough benefit of throwing another expensive box in there.

If the MAF is scaled correctly and you still need more fuel, your main knobs are the K factor and the Map 1 fuel compensation, or if you can't make those work, intentionally biasing the target air fuel ratio table richer (set it to 11:1 to get 12:1, whatever, just make it work). If you need to change spark, change spark (just move the main table up and down). If you need to change cams angles, change cam angles, although you will want to double check your AFR's. The only thing that MIGHT get tricky are the big injectors you have, but there's no evidence that you are beyond what the stock ECU can handle if tuned well.

If you DO want to run one of those boxes, at the very least you need a functional and well scaled MAF sensor and Map 1 Torque Management table. Then you need to turn off basically all the codes related to fuel and spark (or spend a lot of time figuring out which ones need to be turned off individually). UpRev doesn't give you access from what I can see to the fuel trim limit scalars to force open loop, but you could try setting the entire Map 1 fuel target table to a value below 14.7 to see if it deactivates fuel feedback. I'm not sure if Uprev will let you deactivate knock control or not. If you don't do this, the closed loop fuel control and the knock feedback could end up fighting your interceptor box.

People definitely make these things work (BMS JB4 etc for various BMW products) but they are IMO inelegant solutions that require a lot of testing to make sure all the modules play nice with each other.