After taking a short breather I'm back hard at figuring out why the hell my tuner could not tune the car. After speaking to Jeff at PowerDynamix I am satisfied that it's not the transmission or the higher stall converter messing it up. Common sense is telling me it's another issue with boomslang's p&p harness at this point. I need to do a full write up for pinning an Infinity 506 ECU because this harness has let me down several times now. I bought it for the ease of install after speaking with him directly about how well it would work. Long story short, it didn't come pinned for a boost controller, didn't come pinned for VVT, and at this point I know what that means. This harness is for a MK4 Supra with a 4 speed auto trans and therefore the harness is not even going to be pinned or pinned right for VSS to work. Since the harness physically connects to the GS300 and IS300 ECU, it is marketed for them, but not actually right for them. Now if my theory is correct, can anyone that understands what the Infinity ECU "needs to see" tell me if my approach to fixing the issue is correct?
On an Infinity 506 ECU C1-29 is default for VSS. According to diagrams I'm looking at, the OEM ECU has connector E4-5 for whats called "speed in". Would this be the correct place to wire in VSS? I don't know why my tuner is having this issue in the first place. The guy before him was able to tune the car without VSS, but he's gone now and this new guy can't seem to make it work without it. I'm pretty sure this is why the car has a cut-out issue. So I'm just going to try and get VSS working to make him happy.
If this is the case I have to suggest not buying the boomslang P&P harness because you are paying for simplicity, but not getting it. In fact it's even more complicated what you think it's all good and you have to diagnose why it's messed up. Anyways, I'm not comfortable just hooking up wires wherever to give it a try. Need to know the best place to grab VSS signal from.

 

I'm not sure why the VSS should have an effect on your tuning. I have a Haltech Elite, but I'd be surprised if the AEM takes this signal to a different source. The VSS (Drivetrain sensor) is routed to one of my Synch Pulsed Inputs (SPI) on my ECU.

Happy to post or share with you my boomslang pinout table if you'd like. FWIW, I'm utilizing the Aristo ECU. GS ECU should be extremely similar.

 

Oops repeated so deleted

 

I think the diagram of the pin layout of the harness would be worth sticky ing not just for fixing an issue bit for helping understand the communicatons to the curious like me.

 

Vss is the only thing not reading and the only clue we have so far as to why it's not working. Jeff said it could give issues because if the computer thinks the car is standing still it won't go into power (although I do think there are ways around this that my tuner isn't seeing). Remember, the Infinity ECU is kind of an odd setup because it is still a piggy back off of the factory ECU, but a stand alone as well. The factory ECU is still a factor and has to allow signals to pass through and to the Infinity ECU. As I research this it seems to be covered enough times to be important to have VSS. Many topics on this on Supraforums. They have whats called the "odometer wire trick" to get signal. I'm trying to figure out how that works on this car. But I'm thinking I will pin C1-29 directly to the speed sensors's input on the factory ECU and see what I get. I could always lab scope it on the wire to see if it gives a wave form at the end I'll be pinning to the Infinity.

 

I'd be curious what the issue is the tuner is having for which the VSS signal is needed. I understand the situation of the piggy-backed nature of the ECUs - pretty standard for all of us that want to keep a street car. While it does add a a layer of complication, I don't think it's responsible for the challenges you and your tuner are facing.

Attaching image of my boomslang harness pinout in case it's of any help.

 

Well apparently VSS is very important. Now that I am picking up signal, the car is back to hauling ***. Needs tuned still, but going into boost and pulling all the way through the RPMs. Here's my theory as to what's going on: The VSS and WSS sensors must be working together to give actual vehicle speed to the ECU. While on the dyno it thinks the car is staying still at 0 MPH. Even though the tuner disabled these parameters, the car must have went into a stored limp mode, because all I did was disconnect the battery and when I went to mess with it, it worked fine and shows VSS on my scanner.

So here's what I think will happen. I'll go back in for tuning and on the dyno, the car will go into limp mode again because it isn't moving the front wheels. So how to I bypass this? I know it's possible because the tuner before this one figured it out. Car made over 400whp before blowing. But this tuner doesn't see to know how. I explained that to him but he said he needed VSS. So I took it to figure it out. Now I've explained to him that VSS is there, but he just needs to be able to put it in a dyno mode. I don't really get why it's even happening. When I have to smog the car, it is ran on a rear wheel dyno too and taken up in rpms, but it never trips out. Was it just a fluke? Maybe it wont happen again?