ISCDuty ... FN1862 & DEBYCP

[Coz_KB95]

Ok, Figured I would start a new thread as the subject of the question is unique from my previous one with the Bank to Bank Fueling variances.

After a ton or reading, re-reading and a significant amount of math, i'm making some progress on the getting idle setup. My question is about the relationship between ISC dutycyle, the multipliers in FN1862 and the min clip from DEBYCP.

With the throttle stop set in the way I have it now, FN875 configured for .800 lb/min at 800rpm, and nubase set to 800rpm ... the logs are telling me that my ISC Duty Cycle should be flowing about .105 lb/min of air ... however the min clip in DEBYCP is set to .120 lb/min. I believe the slightly lower ISC dutycycle is the result of the top most mulitplier in FN1862 applying the 0.172 trim to ISC airflow at running/warm engine temp and max ATMR and ECT. Would that be correct?

If it is, does that mean that the ISC min clip (DEBYCP) is actually being ignored or bypassed based on the mulitplier from FN1862? Or is the ISC actually flowing the minimum .120 lb/min. I'm trying to dial in on ITHBMA and while the difference is small I'd just like to understand the behavior. Do the FN1862 dutycyle mulitpliers sidestep DEBYCP?

[decipha]

no

isc multiplier should be 1.0 at the top right cell == operating temp and full time running

ithbma should be adjusted to get air correction to 0 at base idle

in your case ithbma should be around .7

that would give you .8 × 1.0 - 0.7 == 0.1 idle air required from the isc transfer

the debycp min clip should also prevent ipsibr from running away and trying to go full negative once it cant remove anymore air

[Coz_KB95]

Thank you!

Would you be able to confirm that the default values for FN1862N in your T4M2 base file are geared toward Mechanical Idle? Here's a snap of the default values in T4M2:

If this is for mechanical, should I just lift some starting values from J4J1 or T4MO. I will be tuning startup air regardless, but figure that starting with the right-sized values will save me alot of pain, trial and error while tuning this one cell at a time, at specific temp and runtime.

Appreciate all of the knowledge you are sharing!!

[decipha]

that was back in the gap, if youve dialed it in then no reason to not use it but since you hadnt might as well just simplify it.

apparently i never posted an updated t4m2 file. Ill toss one up first chance I get.

[Coz_KB95]

Very much appreciated as always ... Thank you!