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Discussion Starter #1
As the title says, I'm currently working on building a Megashift TCU to control the 4eat in my 2011 FXT :grin2: This thread is very much a work in progress, so formatting will change dramatically.


Background: I decided that it would be a great idea to up line pressure to enhance longevity for my VF52 swap. After doing exhaustive research, it became clear that traditional valve body mods weren't possible on the "direct control" 4eat. Starting in 2009(?), the Forester was moved to a closed loop line pressure control scheme, killing off the possibility of the resistor mod.

The resistor worked by reducing the duty cycle of the pressure control solenoid, which allowed for more line pressure. Sadly, the TCU learns around the resistor over time. In the end, a standalone controller is the only option.

"Just do an MT swap, bro": My last Forester was a manual, and while I miss shifting dearly, I now commute a lot. Furthermore, the AT is nice when starting and stopping off road.

My plan: Create a breakout harness from an Impreza TCU, and leave my factory wiring intact. The shift control, torque converter, and line pressure solenoids will go to the Megashift. AWD control and other signals will be handled by the stock TCU as usual. Several inputs such as shift lever position and wheel speed will be sent to both megashift and the stock TCU. I intend to spoof the missing control solenoid signals to the stock TCU, to avoid dash lights. Leaving the stock TCU in place should retain my gear indicator in the cluster. And if there's ever an issue, I can simply remove my breakout harness and plug the factory wiring directly into the stock TCU- instantly reverting to stock.

If this returns dash lights or doesn't work as expected, I can disconnect the stock TCU entirely and ground the MT identifier pin on the ECU, and swap in an MT ABS pump. Downside is that I will loose my cluster readout for shifter position.

My alternative backup plan is to only control line pressure with the Megashift, which will pretty much get me what I needed. Downside is I have to put up with the stock shift and converter lockup programming :icon_rolleyes:.

What I have so far:

Courtesy of RomRaider logger.....


Courtesy of an 06 Impreza....


Relevant pin out, almost completely identical (the factory connectors can be re-pinned easily!)

 

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Discussion Starter #5
Just a quick update on my progress.

Got a multimeter which supports frequency and duty cycle readouts, and the new soldering gear. Sadly my solder was mis-delivered, so a slight setback.

Hopefully next weekend I'll be able to fabricate my breakout harness, so I can determine the PWM frequency of the shift solenoids.

Also have to verify the operation of the shifter position indicator. Megashift can accept all the inputs, but I need to design a circuit to split that signal between both TCU's correctly. From a programming perspective, Megashift only has to know when it's not in drive, so it doesn't need all of the position inputs.
 

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Discussion Starter #7
Sorry I've been slow on this, I recently made a 180* career change which has taken up my time during the week. This is going to be long winded, but critical for anyone else attempting this project.

I think I've finished all the theoretical development work needed to make this project work. A major problem was how to feed Megashift the wheel speed and tachometer signals properly. The stock sensors are variable reluctors, putting out an AC signal. These signals cannot be easily "split" to feed both Megashift and the stock TCU, which I'm still intent on keeping for AWD control and ABS. Megashift can control the AWD system, but the code doesn't have provisions to adjust torque split based on wheel slip- certainly not optimal.

After digging around for a solution that didn't involve adding another VR sensor to my car, I learned about the "OP Connector" on many Subaru models. Evidently it's an unused connector left over from JDM models, and folks here use it when adding non-USDM gauges to their cars. It includes a grey and red wire which puts out a 12v square wave tach signal. Sure enough, I found it right behind the driver's fuse box wrapped in pink tape.




That makes my life a lot easier. And as a bonus, it turns out the standard VR input circuits on the Megashift can accept a 12v square wave, so I don't have to make any changes to the board. Here's a Megashfit VR input schematic for reference:






The next thing Megashift needs is a load input. For that, I am going to T a MAP sensor into one of my manifold lines. Again, the 0-5v analog signal from my stock MAP cannot be readily split between the ECU and Megashift. Theoretically it may work if the impedance of the Megashift and ECU are identical, but I don't want to chance messing up the reading at the ECU or damaging the sensor.

For duplicating the shifter position lever, I am using optocouplers to ground the Megashift position switch input on a separate circuit from the stock TCU. The Megashift uses a 5v pull up circuit, and the stock TCU appears to use a 12v pull up- definitely not compatible.
 

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Discussion Starter #10
Building one of these and installing would certainly be more than a tune! It also wouldn't be perfect, will likely loose the gear readout on the dash and potentially other side effects.

But I did finish building it. However, I am holding off on the installation due to the AWD control aspect. While it can operate it, there would be no feedback control based on road/vehicle conditions. At best it'd result in subpar AWD, at worst the clutch plates could get burned out.

My plan is to install it along with a VTD center diff swap, with manual lock control, which mirrors how that system is designed to work (minus the manual part).

What's your goal? I've done a lot of experimenting with altering the calculated torque tables to modify transmission operation.
 

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2009 Lifted Sh. 4eat, vtd, r180, 4.44
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What a timely update! I have an ez30 in my forester, but i really want to swap in an eg33 i have lying around with a turbo but still keep the 4eat. Id have to go standalone which isnt 4eat friendly. trans has a vtd diff swap already. How difficult is it to get running? i have zero experience with megashift..
 

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2011 Forester X auto
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I will like to have control over the shiftpoints and tcc lockup loads, rpms and speed.
I adjusted my sh ecu code for more grunt over 4k rpms and cooling fan activation temp among other stuff. This was using a tactrix cable and a rom tunner.

Other things that I will like to do is to swapp my cluster for a sti one without tinkering with the bcm or so.
 

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Discussion Starter #13
What a timely update! I have an ez30 in my forester, but i really want to swap in an eg33 i have lying around with a turbo but still keep the 4eat. Id have to go standalone which isnt 4eat friendly. trans has a vtd diff swap already. How difficult is it to get running? i have zero experience with megashift..
With all the capability we have through opensource tuning, I would lean towards getting a stock ECU from an appropriate donor car and splicing wiring to make it work. Boost control would need a standalone, but that's relatively easy if you find a "Requested Torque" DBW ECU- which would allow for finer boost control through throttle angle manipulation.

Theoretically a Megashift should be as easy as building and installing. All the necessary speed/tach/load signals can be sourced from a stock car with an aftermarket boost gauge (for a load signal). The hard part for me so far has been fabricating a harness so that I don't have to cut stock wiring. The next big thing is to ground the ECU MT identification pin, and potentially swap the ABS pump to an MT unit to remove the warning light (ABS still functions with it on). My plan to get around that last step was to leave the stock TCU connected to CANBUS and nothing else, so the ABS computer wouldn't freak out, which is suggested in some MT swap threads. Not sure if that would work, but used ABS pumps are cheap.

Of course I haven't actually plugged it in yet so I could be entirely wrong....

I will like to have control over the shiftpoints and tcc lockup loads, rpms and speed.
I adjusted my sh ecu code for more grunt over 4k rpms and cooling fan activation temp among other stuff. This was using a tactrix cable and a rom tunner.

Other things that I will like to do is to swapp my cluster for a sti one without tinkering with the bcm or so.
That's certainly why I started this project. I've been able to partially manipulate these factors using ECU tuning, since the TCU reads real time outputs from the ECU to make some decisions. While my changes aren't huge, I've learned a lot. One thing I need to warn you about is that the gear ratio problems that become evident when the TCC is locked. The ratio spread is huuuuge, and upshifts oftentimes drop you so low you have to give it enough pedal to unlock again.

If you don't have a swapped center diff, or a need to support tons of extra power, I'd suggest against this mod. While waiting on the install I've been able to tweak my tune enough to make the transmission tolerable.

Things I have adjusted to improve my 4eat experience are the calculated torque tables (center diff lockup, line pressure), pedal mapping (TCC lockup and shift timing/RPM), and the timing retard on shift (transmission longevity and shift speed). More than happy to share my changes and observations on their effects.

I've spent a lot of time reverse engineering this setup...
 

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Discussion Starter #15
In for updates! Very interested in this project. Need this for the ‘03-‘05 MYs.
So long as you have a VTD trans, there's nothing stopping anyone from implementing this now. Enough research has been done to make it work on the Megashift side of things. Only thing missing car side is the solenoid frequency (easy to find with a multi and taps).

My car is halfway apart in my garage right now for a VF52 swap. Megashift is probably way down the road because I need a VTD center diff...
 

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Discussion Starter #20
Hey Everyone, I'm sorry I've been dark on this. Regrettably the project has not panned out due to how the 4EAT (and every other modern auto) operates. In doing TCU logging for this project I discovered an unexpected phenomenon that needed to be understood before moving forward. After researching it, I learned that modern automatics (4EAT, ZF8, etc.) actually "phase" between the solenoids to control shift speed- which unfortunately the megashift code cannot emulate. Traditional automatics have various mechanical bits that help regulate shift speed, even if gear selection is electronically facilitated, but the 4EAT does not have those in the traditional sense.

For example, when the 4EAT upshifts from 1st to 2nd, it will release the brake clutch (see chart in original post). The speed at which it releases is presumably dictated by RPM, engine load, calculated torque output from the ECU, and evidently pedal position. In practice, I logged the brake clutch solenoid being phased from 100% to 0% slowly over 1.4 seconds during light load shifts, and over 0.5 seconds at WOT with VF52 and raised boost. This phasing controls the rate at which fluid pressure in the valve body transitions between passageways to each clutch pack in order to change the gear. Half a second of solenoid phasing still results in some pretty hard shifts when you can trick it into doing that at medium load, so having a binary on/off with the mega shift seemed like a bad idea.

I did explore using reduced line pressure during shifts to reduce shift shock, but decided that trying to properly tune that at every load and RPM range would likely result in excessive clutch wear from all the trial and error. This is actually the strategy the car uses for reverse since that's engaged mechanically, and it's also not very comfortable either. To somewhat replicate how that would feel in forward gears you can park the car on a flat road in neutral, then pop it into reverse without holding the brake pedal. The nice little jolt is the result of a sudden clutch engagement that's only mitigated by reducing the line pressure when the TCU sees the shifter position change. It's analogous to letting off the gas when you drop the clutch in a manual too quickly to reduce the shock and bucking.

In the end this project isn't advised with megashift unless this is a race-only vehicle. Even with proper tuning I wouldn't want to drive something so harsh on the street. There are commercially produced standalone TCUs that can properly control this transmission, but I decided to shelf this due to the growing cost and electrical work needed. Truly the best option would be to crack the stock TCU since presumably adjustments could be made to shift points/speed without having to reengineer the control logic from scratch. This is likely why no true "performance" valve bodies exist for the direct control 4EAT, since its full potential is limited in software. The best we can do is raise line pressure and change pedal mapping to speeds shifts a bit and increase AWD lockup. Doesn't seem to be a way to change shift points or reliably influence converter lockup.

I've learned a lot from this, and am an open book if there's any other knowledge I can pass along to anyone that wants it.
 
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