Parallel Install experiences (More specifically DBW)?

[jrandombob]

Hi Guys,

I've just started my MS3 journey, I'm doing a turbo upgrade on my 2004 N16 S2 Pulsar (QG18DE engine) and need a new ECU to support it (no tuning options for the factory ECU), I'm building on MS3.

There's a couple of catches though, pretty much everything in the car is integrated into the ECU (thanks Nissan...) so I need to retain that for "non essential" functions, the second catch is that it has a Drive-By-Wire throttle.

I'd like to avoid having to find an S1 (cable drive) throttle body, IAC valve and pedal triplet (plus ancillaries, looming and such). Has anybody done a parallel install where they left the DBW throttle in place, under control of their Factory ECU?

I hope it'd be OK, because I'd hope they'd be keeping the DBW algorithm as simple as possible (less possibility for error). But I'm a little concerned it might freak out and throw codes (I just opened the throttle 20%, what the hell is my RPM doing, cut throttle, drop to limp-home). Just wanted to see if anybody out there has experience with this sort of setup.

Thanks,

-J

[q4_fre]

I have a Alfa 166 V6 with DBW that I would like to install MS on in the future. This is a Bosch Motronic system.
Would be nice with some feedback on this subject if any of you have any experience, I am wondering about the exact same thing..

[Redtruck-VA]

I'm currently installing a MS3pro parallel with my OEM PCM (DBW) on a 2003 Dodge Ram hemi. The truck is now driving on the MS3 with the OEM PCM in the background. However it is hardly parallel as I've installed a LSX drive by cable TB to run it. Some of the issues that have to be over come is the OEM PCM has a "target idle" embedded in it's programing and will control the FBW the best it can to maintain "that" idle. If it is unable to set the idle then it will throw DTC's. The FBW is controlled initially by an Accelerator Pedal Position Sensor that sends a signal to the PCM to position the TB throttle blade. Then there is the TPS that verifies the position. The APPS signal on my Ram actually uses two redundant signals to verify the throttle command which also go to the Transmission Control Module. If any of these are out of sync with one another or the internal table you get a limp mode. I'm in the process of trying to remove the APPS and substitute the signals using TPS signals. I'll post the results in a few days if there is interest. My recommendation is before starting , have the service manual and all the PCM/TCM/APPS pin-out printed and know what signals are needed to keep everything happy. A stand alone install is very easy compared to this type of install. Good luck..

[jrandombob]

Some of the issues that have to be over come is the OEM PCM has a "target idle" embedded in it's programing and will control the FBW the best it can to maintain "that" idle.

Yeah, I expected that was a potential issue, being that there's no external IAC Idle will have to be handled by the factory ECU, I'm not targeting anything the Factory ECU is likely to think is particularly odd as far as idle goes so hopefully that won't catch me.

The FBW is controlled initially by an Accelerator Pedal Position Sensor that sends a signal to the PCM to position the TB throttle blade. Then there is the TPS that verifies the position. The APPS signal on my Ram actually uses two redundant signals to verify the throttle command which also go to the Transmission Control Module. If any of these are out of sync with one another or the internal table you get a limp mode.

That's fairly typical of DBW systems I've seen, two Accelerator Position signals, usually on differing curves, e.g. on the Nissan there is one that goes 0-5V as it opens and the second goes 0-2.5V, (GM (I think), have an implementation that includes a THIRD sensor which goes 5-0V), then there's dual redundant TPS, one going 0-5V the other going 5-0V.

If yours is similar you could probably arrange something pretty easily, you could directly feed the TPS back to an input that does 0-5V, and if you've got a 0-2.5V input you can scale the 0-5V from the TPS with a simple resistor divider, it's a bit more fiddly if you have an input expecting 5-0V, but a pretty simple inverting Op-Amp circuit (gain of -1) would cover that for you (make sure you use a rail-to-rail Op-Amp).

It'd be awesome if you'd let us know how you go.

While I think of it, out of curiosity, why do you need to retain the Factory ECU in your setup? It sounds like you've already divorced most of the critical engine management areas from it, or is there some linkage with the TCM you can't break?

[Redtruck-VA]

My engine management is all MS3, the OEM PCM unfortunately runs everything from voltage regulation, instrument cluster to the lights including much of the trans. I initially had planned to have them parallel, but the OEM PCM wants to generate and verify most all of the signals. There is also diagnostic self checks that are done with the various signals to insure they are within a preset parameter (internal table) of the PCM. When out of range, they throw codes. Once I have the truck running clean on the MS3pro, I still have a idle issue that needs attention. I hope to get someone who does actual PCM reflashes to kill the functions I am not needing. Good luck..

[jamies]

I have done a vQ35DE with MS3, the only issue we were faced with was a check engine light due to the factory ecu not detecting the coils being connected, but I ended up using 2.2k resistors from the factory coil outputs to ground which resolved this problem. Other than that all worked well, TPS was taken from the throttle body TPS.
The only other potential problem I can see is a CEL coming on due to AFR's being out of spec but thats expected

[jrandombob]

I have done a vQ35DE with MS3, the only issue we were faced with was a check engine light due to the factory ecu not detecting the coils being connected, but I ended up using 2.2k resistors from the factory coil outputs to ground which resolved this problem. Other than that all worked well, TPS was taken from the throttle body TPS.
The only other potential problem I can see is a CEL coming on due to AFR's being out of spec but thats expected

Yeah, COPs and Injectors are easy enough to provide termination loads for should it be necessary, I suspect my ECU is smart enough to check if they're there and whinge if not. What year is your VQ35DE from? If it's around 2004 it's probably a good bet that its ECU is not dissimilar to the one in my car (Hitachi 32-bit), and from the looks of the pinout over here http://msextra.com/forums/viewtopic.php?f=131&t=43611 if it's an '04 (probably 00-now) it's the same ECU hardware...

Hmmm, didn't think of the AFR issue, unfortunately this ECU has a WBO2 pre-cat and a NBO2 post-cat, easy enough to set my Wideband controller up to lie to the Factory ECU about the NBO2 sensor output, the Wideband may be a bit more challenging... Might have to do some research into how one would go about "faking" a nernst cell. But hopefully emissions codes wouldn't be enough to force it to limp-home mode.

[jrandombob]

...the OEM PCM unfortunately runs everything from voltage regulation, instrument cluster to the lights including much of the trans.

Ugh that sucks, sounds like Dodge are worse on this count than Nissan...

[jamies]

I have done a vQ35DE with MS3, the only issue we were faced with was a check engine light due to the factory ecu not detecting the coils being connected, but I ended up using 2.2k resistors from the factory coil outputs to ground which resolved this problem. Other than that all worked well, TPS was taken from the throttle body TPS.
The only other potential problem I can see is a CEL coming on due to AFR's being out of spec but thats expected

Yeah, COPs and Injectors are easy enough to provide termination loads for should it be necessary, I suspect my ECU is smart enough to check if they're there and whinge if not. What year is your VQ35DE from? If it's around 2004 it's probably a good bet that its ECU is not dissimilar to the one in my car (Hitachi 32-bit).

Hmmm, didn't think of the AFR issue, unfortunately this ECU has a WBO2 pre-cat and a NBO2 post-cat, easy enough to set my Wideband controller up to lie to the Factory ECU about the NBO2 sensor output, the Wideband may be a bit more challenging... Might have to do some research into how one would go about "faking" a nernst cell. But hopefully emissions codes wouldn't be enough to force it to limp-home mode.

From memory it was an 04 / 05, it was an auto and customer installed a turbo and couldnt do anything with the factory ecu.
Re the AFR's i think it would only bring on the CEL, i dont think it would put it into LHM.

[jrandombob]

From memory it was an 04 / 05, it was an auto and customer installed a turbo and couldnt do anything with the factory ecu.
Re the AFR's i think it would only bring on the CEL, i dont think it would put it into LHM.

Yep, that'll be the same ECU hardware (ironically enough the same reason I'm strapping MS3 onto mine Kinda sad that Nissan don't do more with this platform to support tuning, it's a beast of an ECU), probably a fair bet that the firmware will not be too far off. Thanks for the feedback.

Looks like I'll be OK.. An Emissions CEL doesn't really bother me, just don't want it to suddenly cut the throttle when I'm putting it under load.

Plan B was an aftermarket DBW controller, but it looks like that won't be necessary. Thanks again.

[spyrstas]

Nice thread and informative!