E90 Global A Sciap

[MeanMike]

For anyone adding a PD blower to a 19-21 Global A truck, this is how you add a Supercharger Inlet Pressure sensor to alleviate the issues with the throttle blade. This may work on Global B also, I don't have one unlocked that I can test it on.

I had wanted to add this since I put my supercharger on 6 months ago, but never could figure out where to pin it in the ecu. The parameters were all there in the tune and the scanner so it had to be possible. Lingenfelter has recently come out with a new version of their baro/iat breakout box that adds a sciap over the lin bus. I asked Dave (DSX) if he could add it to his maf medic. He pointed me to look at the E99 (19 ZR1) ecu and said it was similar architecture. I got a 3 day access to ACDelco TDS and pulled the E99 connector diagrams. On the E99, connector X4 is mostly identical to the E90 connector X3 except it has a SCIAP input on pin 38.

I already had the mount and a 1 bar map from the LPE kit. I was able to make a harness from some leftover connector bodies and a few new terminals.

Connector X3 is the grey connector at the top of the ecu. Pin 38
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Onto the changes in the tune. I'm not sure if these are available in every OS, but mine is 12704801.
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And it works! Mine drove very well without this, but with it the throttle is smoothed out even more.
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[GHuggins]

There's a whole lot more in the tune needed than just that. That's why I said you might want to talk to Will_974 and see if the tables are in there. Otherwise it can just wind up making the throttle lazy or have no affect at all. You should be able to hold 60ish percent pedal with a sciap functioning correctly. Good work on the rest

[MeanMike]

I have messaged him. I’m going to drive it a bit and see what quirks it has before changing anything.

[GHuggins]

I don't know on the E90 if they are there, but there should be a second sciap activation switch that needs to be flipped, a smoothing factor or data averaging rate setting and some predefined pressure vs baro and throttle position vs rpm tables that need to be populated for the sciap to actually function correctly. I know Will is able to get into the zr1 cal as he's given me those settings that it uses, so hopefully they're in the E90's and just need to be populated too.

[wesam]

I hope Hptuners will add those tables soon

[Alvin]

Maybe one day I'll run into this issue but every SCIAP I've done so far has just instantly worked. Even on the boxed tunes that come with superchargers. Just enable it with what we have in HPtuners and good to go.

[MeanMike]

I drove it a little this weekend and to work this morning and no drivability issues. I am getting a code on startup for low baro and sciap. I assume it's due to where I got 5v and ground for the sciap. I'm going to change the source to the map sensor. Hooking it up through the LPE box was probably a bad idea as I'm not sure it's got a true ecm ground or may be pulling too much current for the 5v derived in the box.

[DSteck]

As soon as you set it to SC SCIAP TIAP, it enables the SCIAP sensor logic. There's nothing else tied to it. The weighting factor only comes in on electronically controlled recirc valve applications.

[Camaro6]

I changed the bypass valve on the Lingenfelter 2650 to a light spring one and upped the NN values. The 2020 Sierra AT4 truck I'm doing drives great now. First pull today with minimal timing and kinda fat on fuel was 859rwtq / 701rwhp on 93octane and no whiplash type hit when going into boost like before. I can pedal it all through the high kpa numbers now without it slamming into boost and commanding wot on the blade. I understand the sciap logic, but if someone isn;t looking to do all of that, then I would buy a light spring bypass valve.

[GHuggins]

As soon as you set it to SC SCIAP TIAP, it enables the SCIAP sensor logic. There's nothing else tied to it. The weighting factor only comes in on electronically controlled recirc valve applications.

Other tables sure seem to make a big difference... Because I've had some go from being a waste to have the sciap, to having full throttle control? They're also barometric pressure expected values from everything I've seen in correspondence logs while testing them and only found in the PD blower cars. Shoot me an email if you don't mind Dave.

[Alvin]

The biggest area of improvement with them is the light to medium load passing at freeway speeds. I think the ECM is using a pressure differential across the throttle body to control flow.. Like voltage across a shunt to measure current. Without the SCIAP you get that sudden spike in MAP when the bypass valve shuts and the throttle retards.. then advances again.. Causes a surge.

I've never had any difference at WOT or anything like that..

[MeanMike]

I've been driving my truck all week and other than a P0106 code that I had before this, it's all great. Where I had P0101, P0106 and P0121 randomly before, now I get P0106 every second startup. I've looked at diagnostic documents, changed settings and can't get rid of it. Even upping the temp for the test doesn't affect it. Maybe HP tuners has some of it defined wrong. I’ve just turned those codes off for now.

It has made the throttle and pedal more connected. No more jerking on decel and the throttle is more predictable and smooth. No other tune changes have been needed vs what I posted originally.

Once I felt confident in the wiring, I made a permanent harness and mounted the SCIAP sensor block on the motor. I have the connectors to build up more sensor harnesses if anyone needs one.

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