3rd gear t/c lockup

[whackem04]

IS there any way to get the tranny to hold the t/c in 3rd gear and still shift into 4th normally? I want it to go through a cycle of 1-2-3-3lockdown-4-4lockdown. My intention in this is to try to get better gas mileage around town while the tranny is on its last leg. Please feel free to give suggestions.

[Taz]

Hello whackem04,

I’m assuming it’s a 4L60 (A4) that you are working on. If so, the convertor may be locked in 2nd, 3rd, and 4th gears. The convertor may or may not remain locked on upshifts - despite selecting this option.

For mileage, I will setup the “Normal” shift pattern to shift into to 4th gear as early as possible, and lock the convertor shortly thereafter. The “Performance” (Tow / Haul) pattern is set more aggressively, permitting a choice of mileage and performance (or towing) shift patterns at the flick of a switch.


Regards,
Taz

[whackem04]

You assumed correctly, 4l60e. I already have the truck shifting very nice and everything is to my liking for the most part but what i was trying to do was get a little more on the mileage by locking up the t/c. I attached my current config . Any tweaking would be appreciated.

[Taz]

If you would like some fuel mileage related changes to the tune, as an example of changes you may be interested in trying - please post your current tune.

Some potential changes may be made to the transmission shift pattern, TTC lockup parameters, and DFCO parameters.

Another option is to reduce the magnitude of the PE enrichment - a GM programming technique is to use additional fuel for cooling (engine / cats) - which consumes additional fuel and may decrease power output / efficiency slightly as the optimal AFR is not being commanded.

Lastly, depending on the OS you’re running and the emission testing procedures in your particular area, enabling Lean Cruise may also be an option.


Regards,
Taz

[whackem04]

Thanks for the review and taking your time to look at it Taz. The rest of the info for my truck would be: S&B intake, ported throttle body, all emissions removed, edelbrock shorty headers,3 in header back exhaust true dual, stock tranny, 2200 stall, small cam, and e fans. anything else let me know.

[Taz]

My apologies for the delay … between work and clearing snow (hopefully the last large accumulation of the season) I didn’t get a chance to look at your tune until tonight.

I swapped in a Camaro trans segment - to facilitate the torque convertor remaining locked during low or zero % TP during periods of deceleration / coast. As long as the convertor is locked, then DFCO should become active - if the remaining parameters are met. I also altered the DFCO parameters.

The low % TP shift speeds were altered below 31.3% and then blended into your existing shift speeds. This will get the vehicle into 4th gear sooner - potentially promoting improved economy. The TCC parameters were altered to function in consort with the shift speed changes.

Depending on your camshaft profile and vehicle weight the above settings may cause the engine to “lug” excessively in 4th gear if travelling below 35 MPH. The attached tune is intended for the purpose of example, and changes may be required to function appropriately in your particular vehicle.

In your tune, stoichiometry is set at 14.63 AFR. Your maximum enrichment (PE) is 1.4 EQ or roughly 10.45 AFR. Setting the maximum PE to 1.2 EQ (roughly 12.19 AFR) should be a safe. This may reduce fuel consumption, and should increase efficiency (and power output). Tuning on a dyno is the most accurate and least time consuming method to maximize your tune (for power & efficiency).

Lastly, your tune uses OS 12212156 which is compatible with enabling Lean Cruise.


Regards,
Taz

[whackem04]

I really appreciate you looking at my tune. Ill load this up in the morning and let you know ASAP. Thanks!

[whackem04]

As far as Lean Cruise, what would be some good starting parameters to start from.

[Taz]

On a North American built vehicle platform enabling Lean Cruise (LC) requires a *.cax file specific to the PCM OS, then a Full Flash (Calibration & OS) of the PCM.

LC came enabled from the manufacturer on some Gen III Holden produced vehicles. The LC parameters from one of these vehicles are a good starting point.

There is a lot of information regarding *.cax files in the Tuning - Petrol / Gas - CAX Files portion of this Forum. Reading through some of those threads may assist you in understanding how LC functions, and if its implementation is “right” for your vehicle application.


Regards,
Taz