Idle Issue

[Brewster]

1990 GT 306
Pro-m 75mm MAf
24lb FRPP Purple Injectors
Shorty Headers
GT-40 upper and lower intake
75mm BBK Throttle Body
GUFX - A9L2

Issue I'm having is its starting and running good but I can't get IPSIBR under 0.70 lbs/min and if I lower the TB set screw approx 1/4-1/2 a turn it will then come down and idle where were commanding but then on a restart its back up to 0.70 ish and then if I open the TB set screw a bit ( engine not running) and re start I can get the numbers down to 0.000 but then its idling to high. Can't seem to find a happy medium within 1/4 turn or so of this set screw.

Smoked the exhaust and intake manifold with no leaks found and all systems seem to be working decent. Any ideas?

x3 logs attached, Warm idle should show commanded being met but IPSIBR is to high

Warm-Idle-2 shows idle screw opened up a bit and the IPSIBR is 0.000 but idle is to high of course

Warm-Idle-3 is with the TB screw turned back down 1/4-1/2 turn and its idling, then I shut it off and restart it and the IPSIBR is back up.

[decipha]

Its doing exactly what you told it to do. You have obliterated the idle air model.

FN875 never requires any adjustment. You raped the isc multiplier and basically have the idle air valve shut off and then commanding more air as the engine gets more stable which is completely backwards.

All the logs are useless as the engine wasn't running long enough to check the throttle stop.

The throttle stop is to set idle air for a stable engine. That means 200+ degree ECT and its been running for at least 255 seconds or 5 minutes.
Everything prior to that is done in the isc multiplier table to get IPSIBR to stay near 0.

[Brewster]

K so I've always had issues with incorporating the mechanical idle changes on the idle air write up. Especially FN1861, dividing the entire table all cells by 6 does not end up with the top row resulting in a value of 0.172. So I manually set up the top row to that and still divided the rest of the table by 6 and obviously was not sure of the exact end result so far.

I thought I was following instructions to incorporate mechanical idle control which seems to have worked well on others I've messed with but can't say I've fully understood the function and how to apply it.



To incoroporate Mechanical Idle Control in your tune, simply set:
PSIBRN 0.0000
UPDATM 255
FN875N Y-axis to all 0.600
ITHBMA 0.000
FN800 Allow 0% ISCDC at 0 lbs/hr, remove clip of 10%, Clip max ISCDC to 98%, reduce 100% values
FN1862 / FN1861 Divide entire table (all cells) by 6, this will result in a value of 0.172 at the top warm ECT cells that the engine normally operates

[decipha]

That's only if your starting from a stock gufb tune. The a9l2 already has simplified idle control to just dialing in the isc multiplier.

[Brewster]

Can you take a peak at the current warm up to idle with a few free revs near the end.

Also during the fuel tuning process is it best to make your wideband match your lambse and reset kam here and there to see where the current KAMRF ends up and how close it gets to 1.000 or should it update fairly quickly as you go.

[Brewster]

And here is a warm start with a few free revs and back down to idle at the end.

[Brewster]

Also let me know if you want me to make a separate thread for this but I can't seem to get FN035A and WOT fueling to settle in and be steady. I see the MAF is somewhat not so linear on the way up how its reporting.

Attached is the current .bin and log

[Brewster]

Does the screen material actually help straighten the airflow compared to a honey comb style filter ?

[decipha]

they both do

[Brewster]

If ACT is acting up can it effect WOT fueling in OL?

I don't see any tables or multipliers that would affect fuel? I'll be changing the location of ACT sensor this weekend and or confirming what's happening but thought I Would inquire if it can affect fuel. I see the ACT acting up on a WOT pull but don't see the Lambse changing and is steady so not sure if this is legit or not with a bad ACT sensor and or install of.