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Self swapped Woods beast
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637 Posts
Very nice write up. You could tie into the ebrake wire to auto cancel the lock when you pull it no? It goes to ground when pulled.
 

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'99 OBS
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117 Posts
Discussion Starter #22
Very nice write up. You could tie into the ebrake wire to auto cancel the lock when you pull it no? It goes to ground when pulled.
Thanks!
Yes, you can do that. But at that point, all you would do is revert to the stock configuration - which is still a 90/10 torque split at 0% throttle on the MPT cars, and subject to lockup when the throttle is opened. On my car with it's ailing transfer clutch, it's no big deal, but in a newer car with tighter tolerances, and/or the VTD system, you risk unnecessary abuse to the AWD transfer components.

What needs to be done is to introduce a full voltage signal to the solenoid when the handbrake is pulled. This is a little more complicated since the native signal is pulse width modulated (PWM), so I'm investigating construction of a PWM controller.
The development of a PWM contoller opens up the option to have variable torque split in the MPT cars, and some degree of variable diff lockup in the VTD cars (unconfirmed until I get hold of some VTD documentation.

There are other PWM sources to pull from in the car, so the controller may be unessesary, but I'm always looking for odd challenges. Not to mention I was sad to see the Torquemada project die, and would love to see something similar come to fruition.

In the short term, I've come up with a working version of the handbrake mod using discreet/analog components, and will write up the how-to as soon as work calms down. Development of a microcontroller version will continue as well....
stay tuned.....
 

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Big Bad BH "Slow White"
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169 Posts
The only need for a µC would be to pull off the fully-variable trick, right? I mean, 100% PWM is just DC (battery voltage to the solenoid). I'm guessing that's what your current handbrake mod accomplishes. I think that would be good enough for a lot of people, though the manual control knob would be hella cool, no argument there.

I also think it would be fun to make an analog gauge for the PWM output to the solenoid. That way we can watch it bounce around as we drive, and better understand what the car does normally, as well as be able to easily tell if the manual torque control system is working.
 

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'99 OBS
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117 Posts
Discussion Starter #25
The only need for a µC would be to pull off the fully-variable trick, right? I mean, 100% PWM is just DC (battery voltage to the solenoid). I'm guessing that's what your current handbrake mod accomplishes. I think that would be good enough for a lot of people, though the manual control knob would be hella cool, no argument there.

I also think it would be fun to make an analog gauge for the PWM output to the solenoid. That way we can watch it bounce around as we drive, and better understand what the car does normally, as well as be able to easily tell if the manual torque control system is working.
I love the idea of an in-car gauge to monitor rear wheel torque split! Great idea.:clap:

Yes, the microcontroller would only be necessary to get more control than on/off for the transfer clutch. As you stated, the low tech on/off switch with a handbrake interrupt would satisfy 80 - 90% of the drivers out there, so the variable controller option would only be a personal project for now, unless I saw a definite need for it.;)

I am looking into the possibility of making kits for this, but I want to have a few more miles on it before it gets put in other people's cars.

If you think you might be interested in something like this - feel free to speak up and reply here. The more people I know are out there, the more serious I'll get about it.
 

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Self swapped Woods beast
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637 Posts
I did this mod about a year ago to my 90 legacy ss. It was pretty sweet. I didn't think of the e-brake interrupt tho at that time. Now I don't have a 4eat car thank the lord!! Good to see someone helping people get a little enjoyment out of having a slush box. Fine work!!
 

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2000 RS SRP
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199 Posts
So because the MT has a 50/50 split you can't lock the rears with the ebrake? Is that true for all Subaru MT's?
 

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'99 OBS
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117 Posts
Discussion Starter #28
So because the MT has a 50/50 split you can't lock the rears with the ebrake? Is that true for all Subaru MT's?
That is correct.
With the exception of the STI , all the manual transmissions will attempt to lock the front wheels shortly after the rears since the center diff's main job is to keep all the wheels rotating at the same speed.
It doesn't know the difference between acceleration and deceleration, so it just does it's job.
Knowing that, you can see that a handbrake turn won't work very well, and is definitely not good for the parts involved.

I've never driven an STI, so, STI guys feel free to correct me if I'm wrong, but I believe the DCCD center differential in the STI is electromagnetically controlled and applying the handbrake will trigger it to "open" momentarily.

The standard 5mt has no such feature, so the front and rear wheels are mechanically bound by the viscous center diff. The lowly 4EAT isn't intended to have the feature either, but the wonderful thing about electronics is that they can be fooled.

Viva la Slushbox!! (at least until it breaks)
 

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MY98 2.5RS Coupe Brilliant Red
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880 Posts
Thank you both, defcon5 and dbaldock9 for the write-ups, pictures and information. Seeing it and having a decent write-up in one place instead of sifting through threads all across the internet will make this project much easier to complete.
 

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'99 OBS
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117 Posts
Discussion Starter #31
Can we get a circuit diagram laid out for this?
Speedfreek0o: I'd love to do that , but trust me, you don't want my hand scribbled crap. Since I'm not an electronics guy by trade, I have no access to any kind of schematic layout program and I have yet to find an inexpensive (free) one.

If anyone has any leads on a good application for that, I'll gladly post the schematic. Until then, you'll have to wait until I hack one together in Photshop (graphics guy by trade)
 

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'99 OBS
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117 Posts
Discussion Starter #33
This is what I use:

http://www.cadsoftusa.com/freeware.htm

I'm a computer engineering student and have created many schematics & board layouts using Eagle. If you don't have time for the learning curve, just send me your notes and I'll transcribe them for you.
Nice find - that looks perfect, and it has a Mac version. I'll check it out, and see how the learning curve goes. If it's too much for me, I'll take you up on your offer.

Quick update: I just got back from the Sno*Drift Pro Rally in northern Michigan, and I have to say - the system works GREAT. We usually stay away from the official spectator areas, so we end up on some "seasonal" roads which basically means they never get plowed and you enter at your own risk. Maybe trucks will have beat things down and you'll be fine, maybe not. With about 3 feet of snow on the ground, this can be a risky undertaking.
Through two solid days and over 250 miles on snowy fire roads and two tracks, the car never let me down once. Even after a little driver error had us buried up to the driver's side axles - with a little pushing, she popped right out, and kept on going. This is quite possibly the most effective mod I've ever done - especially if you factor in the low cost.

Not to mention, it just makes the car flat-out fun to drive.
 

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needs more cowbell
95L, 07 2.5i, R6
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9,281 Posts
Very cool mod and nice of you to post it for us. Good job on the pics as well. One thing to add about resistor heat dissipation would be to put some heatsink paste between the resistors and sink.(unless you already did) Or use the resistors that have the sink made around them ($$$)
 

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IG: @RHD_Adventures
2005 Legacy GT Wagon 5 Speed
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1,834 Posts
defcon,
Not sure if I've met you before, but you live in Detroit and I'm assuming you're on xceedspeed correct? I drive the white 05 RX-8 at the current moment, but because of finanical woes my dad is buying my car (the first day he saw it and drove was the day he told me he would be the first to buy it with out hesitation) and I'm going back to my paid off 96 Impreza L coupe with the wonderful, glorious auto tranny and hella cheap insurance. Why I'm telling you this I have no idea, but I do know you live here, I live here and well I suck at any sort of electronics esp hooking wires up (started a small engine fire wiring fogs a different way... different story for different time, lol). So a few questions to you:

1. Can I meet up with you once I get my Subie back (it's in Colorado at the moment) and give you money for parts + a 6 pack, haha?
2. How long did it take from start to finish to wire everything together?
3. Have you ever heard of the RX (ok dumb question)? Subaru made it from 86-89 and it had basically this exact mod done except they put it in with there manual. The RX had a 5 speed, high/low full time 4wd, and a center locking diff control for 50/50 torque split. Not sure if that helps what so ever.
4. If memory serves me right there was a guy on nasioc or clubwrx... I think nasioc, that was building manual DCCD controllers for the WRX owners that did the STi trans swap. Not sure if that would help any, but I can attempt to locate my conversations with him about it. Maybe it might work for controlling the torque split that you talked about doing later down the road.
5. As of right now the only "torque split / whatever you want to call it" mod I have on my 4EAT Impreza is a toggle switch for the "on the fly" FWD. Easy thing I know. How would this work though with your mod? Would I have to basically take it out/uninstall it? Or would I be able to still use it? I guess what I'm thinking is: normal 90/10, your mod AWD 50/50, and "my mod" FWD 100/0. What do you think? It could also be used as maybe a fail safe so you don't accidently hit the switch.
6. You would be able to use this on wet roads as well correct?
7. How well do you think this would work with the other trans mods you can do? Ie. auto trans cooler, torque converter, valve body (I think that's the other mod)?
8. Live anywhere near Mount Clemens? Every other Monday there is a group of Subie owners (past present, and future) that meet up at Madisons for dinner. We're the ESSO group on IWSTI. You should come up. I would be curious to see this in person.
8. Lastly, I've been wanting something like this for ages! Glad someone actually did it. Madd props to you mang! Thanx...:banana:


Jonny Walker
 

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2001 2.5 RS Auto 4 Door
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505 Posts
Great DIY. I would love to buy a plug and play kit from you. I don't have the time to make the kit but putting it in seems to be a no brainer.

How's $40 sound?

Subscribed.
 

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'99 OBS
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117 Posts
Discussion Starter #37
Hey guys thanks for the interest.
2slo4u: I'm trying to track down some thermal paste, but my electronics retailers around here are decidedly....umm, lame. The resistors don't really get too hot, but the paste would add another layer of protection. Good call.

The Korean: you've got a PM heading your way. :) Fair warning - I have expensive tastes in 6-packs....

L8APX - I can't take full-on orders right now since I'm not an official vendor, but what I'm doing right now is building "kits" for the cost of parts and shipping. This way I can get the word out, AND get a few field testers at the same time (clever monkey, no?)
The good news is that this usually only costs about $30 - $35 depending on where I get my parts. Anyone interested in this should be aware that this is NOT a commercially produced product - it is simply homebrew/DIY at it's finest. That's why it only costs 30 bucks. What you'll receive will require cutting and splicing one wire (2 splices) and finding a suitable ground. That's it! (well, you gotta mount the switch too, but that's up to you)

Mods - if this is getting too close to the limit of my Non-Vendor status - please let me know. I intend on keeping this on the "up and up", and for now, it doesn't look like I have enough interest to go to a full Vendor account. As soon as it looks feasible, I'll sign up ASAP.
 

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Thanks for the write up. But some of us are limited to doing our own work such as changing brakes or oil changes, we're not that electronically inclined to take on such project...so definitely set up a kit for us feeble minded trolls :stafiseiz

And assuming this works across all makes with 4EAT before '02 right? I have a '98 Legacy. Thanks a bunch :)
 

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1998 Impreza L
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Speedfreek0o: I'd love to do that , but trust me, you don't want my hand scribbled crap. Since I'm not an electronics guy by trade, I have no access to any kind of schematic layout program and I have yet to find an inexpensive (free) one.

If anyone has any leads on a good application for that, I'll gladly post the schematic. Until then, you'll have to wait until I hack one together in Photshop (graphics guy by trade)
Updated Pic:
 
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