Jump to content

Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse

- - - - -

This is NOT EJ22 related sorry.

  • Please log in to reply
14 replies to this topic

#1 Skip


    Flatuous Blather

  • Moderator
  • 8,991 posts
  • Latrobe, Pennsylvania

Posted 29 January 2005 - 11:06 AM

Two retrofits I'm working on and would like some feedback on.

1) I drive a 2.5+ hour commute most of it in the dark these days.
Many white tails, not uncommon to see half dozen each way.
I run some serious lights and do not like blinding oncoming drivers.
Thus I have to drive with my finger "on the trigger" which I find uncomfortable.

So I am wiring up a foot controlled trigger for the dead pedal.
Something like American cars used to have but adapted to the Subaru lighting system.
Which we know is a bit more complex than the old cars.

I will be using a Bosch high/low beam control flip flop relay.
This will be controlled by a momentary spst switch
with a large mushroom shaped control button.

Should I write this up and submit it to the USRM ?

The second is a bit more complicated but concerns the use of the FT 4EAT automatic transmission.
I have a Mac Automotive oscilloscope and am wiring it to the control wires for duty solenoid C.
This is the solenoid that controls the rear drive in this transmission.
I plan on building a control module to allow the driver to select
1) locked in four wheel drive - used only on snow and other traction limited surfaces
2) Front drive only - similar to inserting a fuse in the FWD box, some feel this helps fuel economy.
3) Dial in rear drive percentage for "special" circumstances.

For these items I need to know what the duty cycle signal looks like that is sent to DS C.
I will build a pulsing circuit using a IC 555 to mimic the TECU output.
Thus the O-scope.

I plan on interfacing with the TECU so that it will not get it's
panties in a bunch when the system is activated.

Read not trip an error code while preserving the solenoid windings from a direct battery voltage application.

Is this a marketable devise or just another "gizmo" that has little merit?

Thanks for reading.
All comments welcome and appreciated.

#2 Snowman


    Midnight Passenger

  • Members
  • 3,538 posts
  • Haines

Posted 29 January 2005 - 11:29 AM

Idea #1: Definitely a good idea. Though I'm not sure I would use something like that, it would surely be a good read and could provide the inspiration and technical info for further projects.

Idea #2: This sounds like something that would involve some costly electronic bits, no? If that's the case, I kind of doubt that it would really take off as far as popularity, but it is a great idea, and it certainly wouldn't hurt anything to look into.

#3 bushbasher


    exhaust fume addict

  • Members
  • 1,707 posts
  • Sooke B.C. Canada

Posted 29 January 2005 - 12:14 PM

555 timers are certainly dead cheap. doesnt sound like there would be more than 10 bucks worth of parts on the circuit board.

#4 baccaruda



  • Moderator
  • 6,950 posts
  • SpoVegas, WA

Posted 29 January 2005 - 01:47 PM

#1 sounds cool. you could also get an auto dimmer from a 59 cadillac and mount it on the dash :cool:

#2 also sounds cool as long as there are some good instructions for us non-wizards.

#5 ballitch


    Certified Subaru Nut

  • Members
  • 1,000 posts
  • Salem, OR

Posted 29 January 2005 - 02:45 PM

i say do both of them, necessity is the mother of invention. you have obviously spent a good deal of time thinking this through. Is it bad to drive the AWD with the FWD fuse in? I think it is there for emergencys only, not for daily driving, can anyone tell me otherwise, i want to know if im FOS. That would be a great off-road asset though, sometimes all you need is FWD and sometimes you want 50/50 split at 50 mph, and not having to select gearing to 1st or 2nd gears, that way oyu can modulate the throttle for better control of vehicle, instead of having to give too much gas for a downshift and waiting for Duty Selenoid C to do its damn job.


#6 MilesFox


    Catch this Fox!

  • Members
  • 10,686 posts
  • Madison/Milwaukee, WI

Posted 29 January 2005 - 03:06 PM

1. yeah make a write up tat wouldbe good. i myself have thought of using an old ford style hi beam switch

2. if you can make it work that would be very useful for automatic full times as it would make the 4wd more versatile to the needs of the driver

#7 subeman90



  • Moderator
  • 2,805 posts
  • Akron PA

Posted 29 January 2005 - 10:26 PM

RE idea #2: I see a need for a 4th position. "normal" for those times when you are on a wet/rain covered surface. I totally like the idea though....and I might even be inclined to buy an automatic one day if I had a gizmo like this available.....

As always Skip....you mind is always think huh? :D


#8 ShawnW


    Subaru Master Technician

  • Administrator
  • 12,955 posts
  • Denver, Colorado

Posted 30 January 2005 - 01:09 AM

I always liked the floor headlight switches so yes to #1.

#2 would make me nervous unless somebody as skilled as you made it and tested it like I know you would enjoy. (thats a yes to #2)

#9 TomRhere


    Certified BRAT nut!!!

  • Members
  • 4,600 posts
  • Hillsdale, Mi. USA

Posted 30 January 2005 - 05:06 AM

Count one more vote for #1.
Never understood the reasoning behind moving the dimmer switch off the floor. Some of those switches on "newer" cars are a real PITA to get to for replacement.
Don't have a 4EAT vehicle, as of yet, but I'll cast a vote for #2 anyways.

#10 Skip


    Flatuous Blather

  • Moderator
  • 8,991 posts
  • Latrobe, Pennsylvania

Posted 30 January 2005 - 08:19 AM

I thank you all for taking the time to reply.
I appreciate and highly respect your input.

Item one will be completed this week.
The control switch is the worrisome item..
It must be semi sealed as to protect it from
salt slush and other loose impediments.

I am also sensitive to using parts "off the shelf"
for any person wishing to build this system.

Item two is still in the development stage.
I have to get the TECU in a position where it sends
a maximum duty cycle signal to DS C in order to record
the parameters of said signal.

I will extensively test
this devise on both an 89 and a 94 FT 4EAT before
releasing any details.

Once again thanks for the time taken to
give your feedback on these projects.

I will update this post as the project progresses.

#11 ron917


    Subaru Fanatic!

  • Members
  • 431 posts

Posted 01 February 2005 - 12:38 PM

Item two is still in the development stage.
I have to get the TECU in a position where it sends
a maximum duty cycle signal to DS C in order to record
the parameters of said signal.


If I understand correctly, for my '99 4EAT, the following conditions exist:

1. DS C at 100% duty cycle for FWD, installing the fuse causes this.

2. DS C at 0% duty cycle for 50/50 split - no power to DS C locks the clutches. Driving with the selecter in 1 or 2 should cause this.

3. DS C at some other, variable, duty cycle, controlled by the TCU for "normal" operation.

My plain is to simply wire a switch into the DS C control line for either normal (switch closed) or 4WD (switch open). This would be useful on snowy roads, so the rear wheels remain locked in.

I see no point in FWD, except as a "limp home" mode.

Not sure what conditions would require a driver-controled, fixed duty cycle as you propose, but it sounds like an interesting project.

Do keep us informed!

#12 Skip


    Flatuous Blather

  • Moderator
  • 8,991 posts
  • Latrobe, Pennsylvania

Posted 01 February 2005 - 01:08 PM

We both have the same understanding of DS C

It controls a drain (if you will) for the clutch pack
hyd. pressure.

ergo if DS C gets a 100 % duty cycle signal - the drain
is opened fully and no pressure is exerted on the clutch pack.

This means 0% transmitted to the rear drive.

Here we differ a bit though. I do believe this signal to be a
modulated wave form and not a constant 12 Vdc signal.

There is speculation that a constant battery voltage signal on these windings could cause them to fail prematurely.

Result - drain is closed -> all pressure on the clutch pack
50/50 split =>
binding in turns ect. Infamous problem with our cars.

The fuse in the FWD receptacle tells the TECU to send the 100% signal (and to light the dash FWD light).

**Please remember this is also used if you fit the "donut" spare.**

It is also my belief that
there are some drivers that prefer to have the rear drive at a more aggressive percentage for handling purposes on some surfaces.

Thank you very much for your response.

#13 oddcomp


    Subaru Master

  • Members
  • 1,763 posts
  • longview ,wa

Posted 01 February 2005 - 01:51 PM

i think i remember reading that most electronic controlled trannies with solenoid packs
use pusle width modulation for 2 reasons
more precise control i mean hell 30-40 pulses a second versus eitehr a full open or full closed state.. is alot more controled
and also during those fast open closed cycles the windings never see anything near full voltage or amps
alot like fuel injection systems
i think some in fact suby's use resistor packs as well <did not read the whole thread just skimmed it> for some of the solenoids

#14 ron917


    Subaru Fanatic!

  • Members
  • 431 posts

Posted 02 February 2005 - 08:03 AM


What you said makes sense. The scope will tell all. Is the one you will use a DSO that can dump the captured signals to a computer? I'd love to see them.

#15 mudrat79



  • Banned
  • 697 posts
  • Eugene,

Posted 02 February 2005 - 11:41 AM

Morning Skip.....

RE: #2 .....I remember reading somewhere in one of the Aussie Sites that there was a Shop down there making something similar.....It was a Plug and Play Toggle switch Kit that allowed
2WD front Mode, 2WD Rear Mode only , and 50/50 Front to rear

I Remember this cause I wanted to buy into it to use it to run my Tranny for the Rubicon run......I called the Outfit and Inquired, But the Guy was very Duh-Huh about it.....?????

He did however tell me he thought it was all done by turning Solinoids on or off....????

I can tell you that In 50/50 mode, you still don't get a true 50% to the rear.....When I set My trans up to run this way, and Was running just the rear drive line and No front Axles, the thing wouldn't climb over a 6" curb on its own...:(
I had to go inside and Play with the Valve Body for the rear clutch pack to get it to do 50/100 % to the rear........:)

Then it Climbed..... :slobber: :D

Have fun.....Let us know how things progress, Hope this gave you some food for thought......:)


0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users