LS2, BTR3 Idle surges and hangs

[LsIS300]

Like many others on here I am new to the HP Tuning, however I am very mechanically inclined(Engineer) and familiar with terminology. I just recently installed a 06 LS2 from a GTO into my 05 Lexus IS300. Problem I'm having is at idle the car is surging kinda bad and the throttle seems to be hanging quite a bit. I made quite a bit of changes but none seem to have fixed my issue. I do not have a wideband yet but it's on order. Also, I have not driven the car either because I'm trying to get this problem fixed. I would appreciate any advice from anyone that wouldn't mind helping out. I have attached a copy of my current tune and a log from it just idling. The only modifications are BTR3 cam (Specs: 231/244 .630"/.615" 112.5+2.5) and Long tubes with no cats and Spintech 9000s, also just a regular cold air intake and I'm running a return style fuel system with the Corvette Filter/Regulator. Once again, any input would be much appreciated.


Jacobs LS2 IS300 Current.hpt
First Startup.hpl

[Ben Charles]

Got your email!! Let me know, I’ll fix this up for ya

[lowmpg]

You can adjust your BRAF to see if more airflow helps. Use the scanner controls while it is live and you can adjust timing (only allowed to decrease) to test. On a side note, your low octane has been made to duplicate your high octane table. Not a fan of that myself. Also, cylinder volume is wrong for a 6.0 LS2, should be .75. Let us know what helps.

[2xLS1]

Did you mean to say returnless fuel system with corvette filter? And what is your intended use of the car to pick a S3 cam? I'm betting it has a stock torque converter.

[LsIS300]

No, it has a fuel return with the 58 psi. Corvette fuel filter/regulator with the return on it. I intend to road race/drag race and street drive the car. No converter, it has a T56 trans.

[blindsquirrel]

A return system specifically means that there is a regulator with a little vacuum hose that references manifold pressure and adjusts fuel pressure in a 1:1 ratio. If manifold pressure goes from 40kPa at idle to 100kPa at WOT (60kPa rise) then fuel pressure also rises by 60kPa.

Your Corvette regulator is just a fixed bleed that dumps back into the tank. It has no method of referencing fuel pressure to manifold pressure. Other than its location in the plumbing it is no different than a returnless system with the dump located inside the tank.

[LsIS300]

Sorry about mis-referencing that, I just was trying to explain how my fuel system was set up. Thanks for the clarification.

[blindsquirrel]

The difference is important, because the injector data has to change when going from a returnless to return style system. Mis-identifying the type of fuel system could lead to setting up the tune wrong.

[eXo3901]

You might want to reach out to one of the pro tuner people on here to get that tune setup correctly for the cam. Lots of tables with changes that don't make sense. I am not one of the pro tuner people.

If this is a straight transplant with only that cam change, start by looking at a stock 05-06 GTO file. There is alot of stuff changed in your idle->rpm, idle->airflow, and airflow->dynamic tabs. In my opinion, most of what is changed probably should not be when starting out. Find a stable idle, tune everything else then fine tune those tables later if needed.

Your adaptive idle spark settings cannot work because your idle/coast tables are the same as your HO/LO tables. You need a "window" of sorts for idle adapts to work within, from my experience.

The over/underspeed spark tables could probably be set to stock and cut 50% to let the cam lope, but you still need some control.

In gear/reverse, set your base airflow to 12g/s 200-800rpm, 13g/s at 1000rpm, and 15g/s at 1200rpm through the rest of the table. Copy that profile to the park/neutral rows and subtract 2g/s. Set the ECT multi at 198Fdegress back to 1.0250. See if that gets you anywhere. I predict the car will still surge a good amount unless you also address the notes I made above.

If none of that works then see my first comment again.

Also, log Dynamic Airflow, MAF Hertz, Manifold Air Temp, Cylinder airmass, Intake valve temp, Injector Tip Temp, and O2 voltages.

[LsIS300]

Thanks for the recommendations. I will get those changes made today and get a log to share.