First (and on-topic), I'll add that a vehicle's "true" age shows up in Winter -- whether it's oil seals leaking more, crank bearing noises getting worse, or (gulp) rust accelerated by salt
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Originally Posted by RobertISaar
digging up the dead here, but maybe it will help somebody in the future... the TCC will likely lock up slightly harder/faster than normal(but not at the levels required to damage anything). and yes, TCC lockup is specifically delayed to allow the coolant and trans temp to raise to a higher value before lockup. if i take off with my coolant temp at ~80*F, i'm usually up to 55MPH before coolant hits 100*F, then while traveling at 55 with the TCC unlocked, coolant and trans temps rise pretty quickly, when coolant hits the 140*F mark that i have set for minimum TCC lockup, the rate of coolant and trans temp rise drops significantly. where it takes ~1 mile to get the coolant from 140*F to ~170*F with the TCC unlocked, with lockup enabled, i'll only be at ~155*F or so in the same distance. so instead of ~2 miles to get from 140* to 195*, it takes 4 or 5...
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Great discussion. For those of us with automatics, TC manipulation can be a great place to source meaninful gains in FE. Hopefully the following experience helps (aside from perhaps being lengthy and beyond the scope of the original question -- but why break tradition...)
The balance between a vehicle's (or its parts') longevity and FE, isn't easy to quantify. With a manual TC installation, I also fear temperature effects, mostly on the transmission itself: likely excessive heat from blocking the fluid cooler / radiator in Winter (no trans temp sensor), and high (but typical) Summer underhood temps. So I converted to fully synthetic fluid 6-months into the initial mod assessment (despite the cost), mostly due to its documented resistance in heat-related degredation; and hopefully, overall extended service life of the unit (also used in 2 other, non-modified, self-serviced vehicles with good success -- longest of which is with an '05 Civic at 200K miles, with the latter 80-100K miles on synth). All are Honda-recommended procedures with approved S-ATF: non-flush drain/fills with some old ATF overlap (until the 3rd change which is generally considered "fully transitioned").
So, I've taken a gamble to keep the experiment from about 3 years ago / (guessing ~50K miles), so far with no signs of premature wear to the trans (CV joints click under initial torque, but were present at baseline).
I chose direct control, after interpreting the shop manual's ECU and TCU circuitry and "Hill Logic Control" calcluations based on speed changes and throttle input. Setup: 12V power to both solenoids for hydraulic lockup "readiness" is isolated from the ECU (via the transmittion control unit/TCU) and wired to a switch. Lock (partial, half, or full) is engaged by hydraulic pressure actuation, respectively, when the throttle linkage offers added pressure at hydro-mechanical input increments. It will stay at the fullest locked position until the switch is moved to the off/open position. 3 OBD codes remain present, with the CEL illuminated with a green blinking dash light that is normally solid green to indicate transmission selector position. Minor annoyances for the gains (I just have to check codes regularly for anything new).
When disengaged, it operates as usual, but without TC lockup (this can create excess heat and lower FE, but is a great fallback when a non-EcoDriver borrows the car -- which is rare: people know it's not "normal"
)
Engaged: It acts much like a manual, but retains automatic traits: factory programmed shift parameters on accel (with harder shifts if fully-locked, input-based/early upshifts with throttle lift, which smoothly disconnects and shifts as early as desired and bypasses the annoying logic calculation for gear hold on inclines), mechanical throttle kickdown (the hardest shift condition if locked), and retains the automatic override to hold lockup until a warmup parameter is met (I'm not sure how... It's possible the TCU is bypassed by another circuit, or it's purely hydraulic). It is still possible to stall from a stop (rare condition: 2nd gear start with lots of throttle), increased compression-based decel (good or bad, depending on the condition), lower-rpm downshifts on decel (light engine lugging and DFCO interference -- it's a good reminder to switch it off), partially engages when stopped (low-rpm and rough idle) and lots of manual interpretation to avoid lugging and maximize FE.
It has been a good lesson to learn how the slushbox works, how/why processors play a role, and to accelerate more efficiently (or be penalized by lugging). For me, it has been the highest-yielding FE modification, year-round and it's great to finally have control of shifts.
Improvements: More time would need to be invested to figure out how to get rid of the CEL; 12V is direct/constant, so it drains the battery if forgotten and left on (it's easier to restart the engine and remain locked for seamless EOC highway operation, in it's current state); maybe move the switch to the gear selector stalk (currently at the "left knee change-holder bin", which is convenient for "knee operation" when it gets busy with other controls), and perhaps finer tuning of the throttle linkage to lock at a specific throttle position (current TPS value = 17 -- idle is 09, WOT is 90-something) -- there's often the decision to attempt top gear (4th) lockup and avoid lugging or leave it in 3rd/unlocked around 35-40 mph mark to hit optimal load values, maintain a minimum speed, avoid lugging, etc.
As mentioned the car is aging and I'm often concerned about warmup (especially from sitting for multiple days in a cold soak. ...if it's better for longevity to allow the car to high-idle in open loop with usual "D" gear selected and foot-brake holding. Rationale: to heat-up the trans fluid and adjoining radiator (which goes against driving slowly to warmup). This situation is common for this car's role, to wait in a short line to pay for parking and be immediately placed in a merge situation and highway speeds in rapid succession. Shut down, or let friction-into-heat help for later? For engine protection, I'm phasing-in partial- or full-synthetic oil unless it's low and whatever oil is around to add. The radiator/cooler is fully blocked by cardboard in Winter, with rising temps managed through the heater core (rarely needed if 30F or below ambient -- if it's unseasonably warm, the cabin gets toasty.
Best FE,
-RH77
RIP Maxima 1997-2012
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