LsxRT and 102 mm tb tips

[Matt_lq4]

I use to have a tbss intake manifold on my 6.0 Lq4. I have since switched to a Fast LsxRT intake manifold and Warr 102 mm cable throttle body. Unfortunately no matter how I play with the follower, cracker or underspeed/overspeed tables, I can't get a normal return to idle after a throttle blip...it just undershoots and stalls or catches, then overshoots in rpms, then dips down even further to a stall.

0% tps at idle is 0.53 volts, iac counts are 40, idle is 900 rpm and dynamic airflow and desired idle airflow are almost the same.
Base running airflow scan was performed and it wanted 84.2 lb/h in the 176-198*F cells.

If there are any special tips that the secret society of Fast lsxrt tuners is aware of, please let me know as this has been a huge headache. Idle timing is at 27 degrees and high/low octane tables are at 31 degrees in the idle areas to give adaptive idle some swing.

Tune is attached. Thank you

[240sxpooter]

I use to have a tbss intake manifold on my 6.0 Lq4. I have since switched to a Fast LsxRT intake manifold and Warr 102 mm cable throttle body. Unfortunately no matter how I play with the follower, cracker or underspeed/overspeed tables, I can't get a normal return to idle after a throttle blip...it just undershoots and stalls or catches, then overshoots in rpms, then dips down even further to a stall.

0% tps at idle is 0.53 volts, iac counts are 40, idle is 900 rpm and dynamic airflow and desired idle airflow are almost the same.
Base running airflow scan was performed and it wanted 84.2 lb/h in the 176-198*F cells.

If there are any special tips that the secret society of Fast lsxrt tuners is aware of, please let me know as this has been a huge headache. Idle timing is at 27 degrees and high/low octane tables are at 31 degrees in the idle areas to give adaptive idle some swing.

Tune is attached. Thank you

Probably need to attached some IDLE PID logs to see whats going on

[Matt_lq4]

I just added one now, thanks for reminding me.

[Ben Charles]

Crack blade more, iac counts will drop and change fuel... problem fixed

[Matt_lq4]

It's not that simple as I've already had the blade cracked open more and it caused all types of instability. I had to back it off (currently at .53 V tps, had it at .55-.57 with unstable idle).

This is because the other end of the iac port is very close to the blade and cracking open the blade any more exposes the engine side of the iac port. This causes its own issue, the blade is already very close to the edge of the iac hole so that will have to be left alone

[Matt_lq4]

I'll play with the proportional tables when I have a chance outside

[cobaltssoverbooster]

so to make them run you need to open the blade until the iac counts drop to around 50 or so. reset the tps and double check the counts.
once that is set you need to tune the fuel in and some of the idle airflow settings.

now you can tune the iac vs effective area. aftermarket throttle bodies have different iac port volumes and need adjustment to coincide with the new blade diameter as well.
coast down tables use iac so yeah having bad settings causes all sorts of airflow drive-ability issues.

[Matt_lq4]

I had the blade adjusted to where the iac counts around 50 but then it had a hard time starting up. I had to crack the throttle a little more to the point of 40-44 counts, at this point the engine started without throttle assistance. I had BRAF set to 91 lb/h so It's not like it was a low running airflow value either.

[Matt_lq4]

"If dynamic airflow is greater than idle desired air flow, increase the steps. If dynamic airflow is less than idle desired air flow, decrease the steps. "
That is what I was following in order to increase the steps or decrease them at whatever position the iac was at.
Do you suggest a different approach? I was only showed this method so if you have a better way I'd like to learn. Thanks

[cobaltssoverbooster]

That's the iac method I use.

[roy130.2007]

Hey did you get this sorted?? I have similar setup and issues with my truck,would love to know how you figured a stable return to idle?