Cammed Car Tuning - I am seeing alot of DISABLED LTFT's...explain?

[Cantalope Kid]

See title and educate us all please? I learned this from a cat up in Austin, TX (Tahnk You, Brian!) and it really smoothed out a large cammed Vette I was working on.

Just wanted to pass along the info. to those in the not so KNOWing world (NOOBS!).

[Cantalope Kid]

Back to the top for some help for this noob helper...

[WS6FirebirdTA00]

I rarely ever leave them on in any car unless it has stock manifolds. Poorly learned numbers will hurt performance, especially in OL.

[Cantalope Kid]

Point taken. Thanks for the info. Using this as my basis on all future tunes!

[Gh0st]

Ditto to LTIT, no bueno.

[b00sted]

I've seen alot of guy's doing STFT only too now.

Seems like if the tune is correct, you just rely on the STFT's to make the minor adjustments that are sometimes necessary. I'm gonna go that route with my cam-only car.

I'm not exactly sure, but it seems like the overlap of the cam is causing the sensors to read lean at idle, causes the STFTs to jump which in turn causes the LTFTs to jump.

Does the LTFT value vary with RPM? Meaning if it's +15 at 900 rpm, is it going to be +15 at 3000 rpm(assuming something else isn't causing it to change)? Or are there different values stored for different RPMs? (Think like the VE table but with only one row)

[Cantalope Kid]

Basically your STFT's update your LTFT's which is stored data for future correction. Basically your car is learning how to hold a 14.7 AFR by referring to the stored LTFT's values. If its still off the STFT's try to make corrections, and when they are happy they make suttle updated to the LTFT's until things are within spec.

[Ryan L]

Cliff Notes: LTFT and LTIT off (assuming everything else is tuned correctly) ?

[WS6FirebirdTA00]

LTIT off can be hairy at times.

[Cantalope Kid]

LTIT off can be hairy at times.

Thank you for the previous explanations in this thread. Please educate us WS6FirebirdTA00 with the why behind this above statement. We're all learning from your input. Subscribing...

[WS6FirebirdTA00]

Well, if you leave the LTITs off, there are times that it could cause a hanging idle when the STFT reset to zero. May not be noticed right away, but may come back as weather conditions change in an area.

[Cantalope Kid]

I knew I could count on you! Thanks for the info. Hopefully it will be searchable useful info. in the future for someone. Unsubscribing.

[Frost]

I leave LTITs and limit their correction.

I axe LTFTs on any cars with internal mods (because I will be doing full VE/MAF tuning anyway)...