TCC Experiment
 

I'm working at getting better mileage, while P&G works great in the city and I'm happily enjoying 32mpg city (22mpg EPA), I want better freeway mileage. Since my engine turns close to 2750 at freeway speeds I'm not keen on throwing the transmission out of gear then back. If I revv match the engine and transmission take up the slack to the rear-end quickly and beat up my u-joints.

Even in town when I'm not coasting in neutral if I just had the drive train a little looser I would get a couple extra economy points. So, lets make it loose.

My transmission's torque converter lock-up profile isn't like most cars. To help with keeping steady speeds on grades the torque converter doesn't unlock until a shift is required. For example, I'm doing 55mph and let off the gas. The torque converter will stay locked until I hit the gas hard enough to require a down shift. or it's slowed to a point the engine is slowing lower than 1500 rpm.

I'm installing a microswitch in the signal line to the transmission so when I'm at idle the connection is broken and the converter unlocks. I'm installing an indicator light inside the car so I can tell whether the converter is locked or not.

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The switch isn't part of this project, that's to the inverter I installed last year. And no, it's not centered, the previous owner had an alarm system installed and I just stuck the LED in there.

I'm needing to build a bracket to mount the switch to so I'll be doing that in the next couple days.

Hmmm, swings and roundabouts there... gain distance on the glide... but if you're locked up with fuel cut the motor isn't sucking as much as idle...

Well, I haven't installed the microswitch yet because I was wanting to monitor TCC behavior first, but i have noticed some interesting things.

The transmission doesn't lock until 37mph, after that it'll lock any chance it gets. 37mph means that at lockup the engine is turning 1600rpm. If I let off the gas it will stay locked until the car drops below 35mph (1500rpm in OD).

When I'm on the freeway and the torque converter is locked, if the transmission is put into neutral it doesn't unlock, i move it back to drive it will remain locked as the transmission shifts back into gear again. It will unlock in neutral but only after the car has slowed to 35mph but will not lock on its own if you neutral coast past the 37mph mark.

It's interesting to watch its behavior while driving, pressing the OD off button to downshift results in a Off....On reaction, while upshifting back into OD results in an Off..On reaction, much faster. The PCM will unlock the torque converter but stay in gear as sort of a middle gear while under moderate acceleration. This is unlike my old car that used to lock the torque converter even during WOT runs in 2nd gear.

One thing I wonder, if I am driving my normal 30-35mph daily speed through town the converter remains unlocked, are gains to be had if I drive 37-38mph as opposed to the normal 35, I know we say to stick with the speed limit(and slower speeds) but you have 1800rpm vs 1600rpm between those speeds(37 being lower rpm).

You probably get 5 - 10 % better FE with the torque converter locked as compared to not locked. I'd get it to lock at 37 mph and then slow down slowly to keep it locked at 35 or whatever the slowest speed it will stay locked at.

Also it is probably more efficient with it locked at a slightly higher RPM than unlocked at a lower RPM. So is it locks up at a lower speed when the OD is off it would be better to have it locked with the overdrive off at 30mph if it does that even if your engine is running at 1800 RPM locked as compared to 1400 RPM unlocked in OD

My information is old but we learned in autoshop that an unlocked torque converter results in about a 10% loss in energy being converted to heat.

I was doing a thing in my Escort that appeared to work well, which was to go 5mph over the limit to get into 4th, and then easing it back to "legal" where it stayed in. Would see approx 1mpg gain using that method.

you're missing one critical point about this: the switch is only to unlock it when the throttle plate is closed and the engine is compression braking. it'll still be locked/unlocked normaly at all other times. IE longer glides from less engine braking because as you say, 10% losses with the TC unlocked and that goes the other way as well.

Sounds like i need to build my engine monitor. CC per cylinder per minute, rpm, gear, TC status all that jazz...

https://store.earthlcd.com/ezLCD-001-...7&category=187

Since I've learned how the TCC acts on this car, I'm installing a 3 way switch for the TC that has OFF-AUTO-ON.

Off - switch to a dummy load for the PCM and will disconnect the TC solenoid so it never engages.

Auto - the circuit is pass-though, the PCM does its normal thing.

On - switch to a dummy load for the PCM and will engage the TC solenoid to keep it locked at all times(gotta remember to take this off or I'll stall the engine at a stop so that means a nice red light if the brakes are pressed and it's in this mode)

The reason I want to do this is because of a trip I took this weekend. To keep 65mph I was pressing the gas enough for the TC to stay unlocked almost the whole trip and I got 23.5mpg. On the way back, the TC was able to stay locked for the majority of the trip and I got about 26.2mpg. This car gets a turbo for sure.

Anyone here used an aftermarket transmission computer before?

Don't forget to leave it on Auto or unlocked when there's a chance of shifting.

New update, I built the control circuit for the 3 way switch.

I have the green indicator and the red indicator, the red one is much brighter and comes on if relay A is activated and the brakes are pressed as a reminder to turn it off. The red light also has a half-on mode where it glows dimly to show that you aren't in auto mode regardless of whether you have it in TC off or TC on modes.

It also incorporates a dummy load for the PCM when I'm not in Auto mode.

I still need to label the modes but it's a work in progress. I can extend this a little further by having it where the TC will automatically unlock if an input from the vehicle speed sensor is too low but I didn't feel like getting into that.

I have 5 inputs: Brake signal, TCC in from PCM, 12v, relay A activation, and relay B activation. There are 4 outputs: Gound, Green indicator, Red indicator, and TC output.

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