Question about 4.44 tranny and Valve Body - Page 2

svxfiles · #16 03-08-2006, 02:22 PM

Quote:

Originally Posted by Hocrest

As often as you go there, I figure you should have a key to the place by now.

I think I'll bring up this idea to the liquer store guys!

Budfreak · #17 03-08-2006, 09:13 PM

Quote:

Originally Posted by svxfiles

I think I'll bring up this idea to the liquer store guys!

You should have your own EZ Pass card for the liquor store and own stock in every company that makes asti by now.

Your not doing something right.

Myxalplyx · #18 03-10-2006, 09:17 AM

What a pain in the butt the removal of the SVX TCU is. I climbed underneath the steering wheel and stared upwards using my special yoga technique and tried to remove it. Time was short both days I tried due to rushing from work and heading to class. I noticed three nuts that needed to be removed but getting the wrench on the last one was somewhat difficult. I started to remove the plastic covering that is over the ECU itself but wasn't sure if it was necessary. I will play with it tomorrow since I am off work.

I may have to check before and after G-Tech runs rather than the dyno. Looks like Xotic Motorsports is having some problems.
Xotic Motorsports Thread at NASIOC

Earthworm · #19 03-10-2006, 10:49 AM

Having long fingers/wrenches definitely helps

Myxalplyx · #20 03-19-2006, 01:25 PM

Just finished testing out a 1998 2.5RS TCU with the 4.44 tranny that is installed on my SVX.

Good news: The TCU is a direct plug in to the SVX TCU harness. Driving around town, everything seemed normal. Car shifted smooth and firmly just as it had before. No drivability issues that I could point out.

Bad news: WOT is a big NO NO. Going from 1st to 2nd gear, the car would bog big time. A huge power loss, as if someone stepped on the brakes for a second. I thought the 2.5RS TCU would make the car shift quicker than the stock SVX TCU because it is for a 4.44 tranny but there is some relationship between the TCU and ECU that was not in synch while using the 2.5RS TCU. Even going from 2nd to 3rd gear created the same stall/power loss in between gears. I had to actually let off the gas from going full throttle and the gas pedal again in order to make it transition correctly. I kept my foot on the gas once and it just chugged along until I let off and started again.

I am not sure if I have to let the TCU and ECU get used to each other by driving around for a while. Perhaps someone else can try this. Every time I park my SVX for over a day, the negative battery terminal has to come off so I do not drain the battery. I am having issues with that right now. So the ECU and TCU would always start off fresh instead of starting from where they learned each other previously.

That is all for now.

intelisevil · #21 03-19-2006, 09:29 PM

I have read that our SVXi are the only Subarus where the ECU and TCU actually communicate with each other. If this is true, the ECU might be expecting some response that it's not getting.

Doesn't the fuel get turned off to half the engine between WOT shifts to soften the shifting? (Urban myth? Proven or Disproven?) If this is true, the ECU might be waiting for the TCU to politely tell it that "I am now in the next gear, please feed me more power again" (or the Japlish equivalent).

This would fit the 'Bad news' scenario.

Dan

Myxalplyx · #22 03-21-2006, 04:50 PM

Quote:

Originally Posted by intelisevil

Doesn't the fuel get turned off to half the engine between WOT shifts to soften the shifting? (Urban myth? Proven or Disproven?) If this is true, the ECU might be waiting for the TCU to politely tell it that "I am now in the next gear, please feed me more power again" (or the Japlish equivalent).

This would fit the 'Bad news' scenario.

Dan

Dan,
I have dyno evidence that may support your theory. Look at my dyno plot from 1st gear all the way up to the top of 3rd gear. The car goes WAY lean in between shifts.

Would this lend support to the 'urban' myth? I mean, if 18.1:1 air/fuel ratio isn't cutting fuel, I don't know what is. You know something else? I pulled up various dyno plots of modification in different stages of my FWD XT6, AWD XT6, Outback Sport (Even my Toyota Matrix just to throw in) and NONE of them shows this extreme drop in fuel delivery between gears. This sucks! What can be done to eliminate this?

oab_au · #23 03-21-2006, 05:34 PM

It can be eliminated but the trans won't like it.

Harvey.

Myxalplyx · #24 03-23-2006, 07:54 AM

Quote:

Originally Posted by oab_au

It can be eliminated but the trans won't like it.

Harvey.

How? You may PM me with the answer if you like. Thanks!

Earthworm · #25 03-23-2006, 11:03 AM

I wonder if instead of eliminating it could it be controlled in a way similar to the smallcar shift kit?

Myxalplyx · #26 07-19-2007, 02:48 PM

Just bumping this up since crazy ideas keep popping into my head.

I still do not like the lose of fuel between shifts. Harvey stated that the fuel can continue to flow instead of being cut off between shifts. I have already contacted Level 10 and have been considering a valve body (Hydrosystem) job. I told them I would like to have the shiftingon the firmer/harder/quicker side. The car feels like it shifts great but I sat down last night to look at a few things.

On the 1st to 2nd gear, the SVX is not making any power for 4.1 seconds on the dyno (29.7 to 33.8 second mark). On the 2nd to 3rd gear shift, it is not making any power for 2.6 seconds (59.5 to 62.1 second mark). That is a total of 6.7 seconds of power loss. I do not have data for the 3rd gear to 4th gear gear change time since I never took it that far on the dyno. Even still, 6.7 seconds of power loss out of a car that has been ran in the low 15 second range seems significant.

Power loss in 1st to 2nd gear has been as low as 84whp and from 2nd to 3rd gear as low as 92.5whp. How significant a drop in the 1/4 mile time can be achieved if you could turn these times of power losses to 100% power gains? In other words, make your shift change from 1st to 2nd and 2nd to 3rd power gain as much as it orginally lost after a valve body job.

I am thinking this is one of two pieces of the puzzle I am trying to get resolved to get the car to run in the mid 14's.

One of three pieces of the puzzle to get it to run in the high 12's.

Nevin · #27 09-04-2007, 10:21 PM

Ok, this is slightly off topic, but it also addresses the "what to do with the powerloss between shifts" question. In the probe comunity, a popular modification within the ATX crowd is what's known as the IAT mod or "intake air temperature" mod. Basically, you flip a switch that momentarily disconnects the IAT sensor and what this does is two things based on one reading. It tells the car that it needs to warm up, since basically the ECU is just seeing that it is cold outside. When this happens, the fuel cut between shifts is eliminated (to help warm up a catalytic convertor faster) and the line pressure in the transmission is increased to basically help it warm up faster as well.

By doing this mod, my 1/4 mile times came down over half a second, and shifting into 2nd from 1st often results in chirping the tires, or actually laying down a couple patches of rubber from the firmness of the shift. It definitely puts a smile on my face when I use the IAT mod. :-)

Now yes to be fair I know I am comparing two different cars, but I'm just curious if there is any sort of sensor on the SVX that can be tricked the same way to accomplish the same thing. Bear in mind that it is not activated all the time, it is simply switched "on" ( IAT circuit interupted) by the driver when they wish to have a firm shift, and then can be switched "off" (IAT circuit connected) just as easily.

So please, someone tell me that there isn't some way to do this on our cars, and I'll let it go. However, if it can be done I would also be willing to give it a go.

sd2649 · #28 09-16-2007, 10:57 PM

My SVX does the same "braking between shifts". It also does it for about the same amount of time. I have paperwork of transmission replacement from the previous owner, and it has ALWAYS done this since I bought it. If I am racing, I just pull back on he throtle right before the shift and then press it back to the floor a few seconds later. If I press it immediately AFTER the shift has preformed beautifully, it "brakes" again. You just have to wait a certain amount of time before you floor it again. I noticed that sitting in the car, with the ignition on, but the car not running, if you press the gas, you will hear a "Click" from under the dash right before you reach the floor board. What sensor or thing is doing this, because that point seems to be the exact time that the "braking" occurs when driving around. Harvey! please pm me if you know a way to disable the throttle cut-off. Is there an easy wire that I could have switched, so I could save the tranny during normal driving?

sd2649 · #29 10-06-2007, 11:02 PM

Quote:

Originally Posted by Myxalplyx

Just finished testing out a 1998 2.5RS TCU with the 4.44 tranny that is installed on my SVX.

Good news: The TCU is a direct plug in to the SVX TCU harness. Driving around town, everything seemed normal. Car shifted smooth and firmly just as it had before. No drivability issues that I could point out.

Bad news: WOT is a big NO NO. Going from 1st to 2nd gear, the car would bog big time. A huge power loss, as if someone stepped on the brakes for a second. I thought the 2.5RS TCU would make the car shift quicker than the stock SVX TCU because it is for a 4.44 tranny but there is some relationship between the TCU and ECU that was not in synch while using the 2.5RS TCU. Even going from 2nd to 3rd gear created the same stall/power loss in between gears. I had to actually let off the gas from going full throttle and the gas pedal again in order to make it transition correctly. I kept my foot on the gas once and it just chugged along until I let off and started again.

I am not sure if I have to let the TCU and ECU get used to each other by driving around for a while. Perhaps someone else can try this. Every time I park my SVX for over a day, the negative battery terminal has to come off so I do not drain the battery. I am having issues with that right now. So the ECU and TCU would always start off fresh instead of starting from where they learned each other previously.

That is all for now.

As I stated before, what you describe above is EXACTLY what my SVX does every time I try WOT. I was wondering if anyone has ever heard of such a thing without the TCU being replaced. As I mentioned, The tranny was replaced by the previous owner, and it has done this ever since I acquired the car. I really don't want to shell out the cash for a new TCU just to find out that there was some other sensor/wire put in the wrong place. Anyone have any idea on what I might do to troubleshoot this one????

Myxalplyx · #30 10-08-2007, 04:48 PM

Quote:

Originally Posted by sd2649

As I stated before, what you describe above is EXACTLY what my SVX does every time I try WOT. I was wondering if anyone has ever heard of such a thing without the TCU being replaced. As I mentioned, The tranny was replaced by the previous owner, and it has done this ever since I acquired the car. I really don't want to shell out the cash for a new TCU just to find out that there was some other sensor/wire put in the wrong place. Anyone have any idea on what I might do to troubleshoot this one????

Purchase a used TCU for an SVX to test out. Some people frown on purchasing used electrical equipment and I can not blame them. I shopped at http://car-part.com/ for all my used car part needs. An SVX TCU should be able to be acquired at a reasonable price, certainly better than a new one. This is where I purchased different year used Impreza and Legacy ECUs for my Outback Sport to test out on a dyno. Cheap prices!