L83 with LT4 blower

[Jenson]

After a week of ordering parts that didnt come with the "kit" my buddy bought, I finally fired this his truck up yesterday with what I thought was a good base tune. Within about 20 seconds it seemed something was way off as the IAT climbed past 105. The MAF/IAT sensor area of the intake tube was cool to the touch and only show 98 with a temp gun. Then I noticed the boost valve was closed at idle and opening with throttle. I am hoping the boost valve is the culprit for both of those issues, the idle never doing anything other than -30 degrees of timing (even after pulling 100ft/lb out of it), and trims over 35% no matter what. IAT ended up at 156 while ECT never went over 160.

Needless to say my buddy wants his truck back. Is the IAT relocated to the LT4 MAP sensor with these setups? Should MAP sensor be NA-MAP instead of NA-TIAP? I copied the map estimations and characteristics from an LT4 car so I assume those to be correct.

[Jenson]

So the boost valve seems to be operating properly now with the driver side port atmospheric. Timing still at -30 and headers glowing, so I threw LT4 torque tables at it, stayed the same. Then I put them back to 100% stock and it goes into reduced engine power mode pretty quickly. Codes 0068 and 0121 are present after a flash and key on even with them disabled

[cadillactech]

What parts did you use to do the swap? Sensors/injectors/fuel system? Is the L83 stock?

Remember, if you have stock L83, your engine has a full point more compression, the cam is different and the calibration data in a Z06 ECU will not be plug and play.

[Jenson]

Stock L83. It looks like he ordered a kit from C-8 parts. Injectors and fuel system are stock. LT4 Map sensor with the break out harness to reach the back of the blower. It ran better with the LT4 torque tables, didnt go into limp mode at least. However, everything I have thrown at the torque tables leaves me with -30 of timing at idle.

[cadillactech]

It looks like it is retarding timing because your idle speed is so high. Do you have a vacuum leak?

If no vacuum leak, try adjusting the idle torque reserve values.

[Jenson]

No vaccum leak that I have found. That was one of the first things I checked. I tried lowering and raising the reserve values this morning as well.

I really dont understand how it can throw codes 68 and 121 when they are set not to run

[Jenson]

Moved vacuum hose that goes from bottom of blower to PCV to behind throttle body. Also removed valve cover pcv to be atmospheric just to see. Idle went way down but still pulling 30 degrees

[kevin87turbot]

There are a few things that are causing issues. It sure looks like a vacuum leak as well, but let's try a couple of changes first.

Change to idle tables to increase the idle speed from the stock 500 rpm up to 750. See how it reacts. If it's just a small vacuum leak, the timing should go positive.
You'll also need to change the P0068 threshold to a high rpm...8000 will work nicely. I would also disable the virtual flex fuel mode as well.

[Jenson]

I did change the idle speed to 750, 850, 900, just to try and get it to quit pulling timing. Stayed the same though. I tried all kinds of different routing of the vacuum hoses, created vacuum leaks on purpose, plugged all sources. I moved that 0068 from 0 to 8000 as well with no difference. I have not disabled the virtual flex fuel yet, it has a real sensor on it now but I dont want to get into that yet since it wont even idle. It now is set to 750, it idles at 750, still pulls 30 degrees and goes into reduced power mode withing 15 seconds

[MORLOK]

Your tune still has the stock L83 throttle info in it under Airflow > Electronic Throttle.
I think the max area for a LT4 throttle should be 5,074 (based on a tune I have from a 2015 Z06).

The computer is opening the throttle way to far, getting too much air, expecting too much torque, so it retards timing to try and back it down.

Update the throttle area in the tune, flash the tune, turn key to run, start scanner, and then click "throttle cleaned" under Vehicle Controls & Special Functions. This function allows the comptuer the close the throttle more to find a good idle. I have heard it can be finicky though, so it may take a couple try's.

Good Luck!

[Ben Charles]

Your KPA at idle is 90…. You have a vac leak

[Jenson]

Running the stock L83 throttle body...thought I wouldnt have to do any relearn stuff. Pulled the belt today to see if idle would change, it runs the same without the belt. Definitely leaning towards a vacuum leak. The only place it can be at this point is the map sensor, the lid, the adapters, or hopefully one of the sensor block offs at the front.

[MORLOK]

In your log the MAF is showing 3.5 lb/min airflow at idle and your throttle blade is at 23%. My l83 runs at 8% throttle and .7 lb/min airflow. The ?vacuum leak? is coming from the throttle blade. For some reason the computer is opening it too far.

[Jenson]

So this one was absolutely a vacuum leak. The riser plate on the passenger side had a .035" lip towards the front that allowed a tiny little leak. That is all fixed now, he went to LT4 injectors and HP pump since we had to pull the blower back off.

The only issue I have now is at WOT...I keep going up in driver demand at 100 but it simply stays at 60% throttle. I believe the demand is up to 889 now at 100. Any help is much appreciated. Tune attached, I forgot to save any of the logs

[cadillactech]

Logs are automatically saved now, you should have them in one of the HP Tuners Folder.

Log engine torque, MAX torque, Peak torque and every other torque parameter you can find. Most likely something is limiting throttle because you are over a torque limit.

Post it up. Glad you found the vacuum leak.

[Jenson]

Logs are automatically saved now, you should have them in one of the HP Tuners Folder.

Log engine torque, MAX torque, Peak torque and every other torque parameter you can find. Most likely something is limiting throttle because you are over a torque limit.

Post it up. Glad you found the vacuum leak.

Shit yeah!!! Thats a lot of logs in there! He actually sent it to Vengeance racing yesterday and they looked at the tune, ran it on the dyno, and said it alls looks good other than the 60% throttle. So he is chasing TB, TAC, Pedal, and the wiring harness extension now. Log is attached, let me know what you think, more eyes on it the better IMO

[grandam75]

There are more torque values to log but after looking at the tune I would suggest to raise the trans and axle torque limits. Also zero out acceleration based rpm limit (12067). Then make a new log with max tq, peak tq etc
Side note, the VVE on these are not set up for boost in higher rpm, at least raise that portion so it does not slope to 0 as pressure ratio goes up. Transmission need to get a realistic tq reading or it is not going to shift well.

[Jenson]

Thank you grandam! I did raise the trans torque limit to 1000 in 1-4 at one point during logging. I Changed the VVE to a 3 bar and have been filling it in as I go, been meaning to fill in the upper range and obviously forgot. I will look into all of those suggestions, thank you so much!

[c5racr1]

I have a 2018 Silverado 1500 5.3 non flex fuel with a 6 speed automatic. I installed a LT4 charger with lt4 injectors, Lt4 High pressure pump and LT4 Throttle body. I'm wondering if you would care to share a start up file so I could at least get this thing started nest week. I used The ADM kit.