2G blue wire mod

[Bender]

Bunch F4/W4 KM transmission knowledge

-John

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I knew these were a little backwards since they had a control solenoid to basically blow off pressure, compared to the typical supply pressure design.

I just assumed that it followed the same logic that the shift solenoids follow.

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Now it makes sense why it sends the signal to the ECU to pull timing when it shifts, because the pressure just isn't there.

 

[HighPSI TSi Guy]

Only the 2G's pull timing on shifts. And PCS does operate all the time. Transdude is correct in that it is a bleed-off type system to reduce pressure vs a supply pressure system. That is why disconnecting the solenoid yields full pressure, since the solenoid is not dumping any pressure, the pressure stays "full". It's really kindof irrelevant to the situation though, end result is still the same. Line pressure is varied while driving based on what gear you are in, and your throttle position. Off the top of my head I believe it is a 16 column map, the PCS is modulated based on the value for it's current state as you drive around. So yes, I can dial in the line pressure vs throttle no problem, I do this for lots of people.

Someone mentioned not being sure how a PWM signal works, it is a fixed voltage, pulsed signal, at a set frequency. This is why a resistor is not properly adjusting the signal. A resistor underpowers the solenoid and malfunctions it to cause a change in behavior. The proper way to change the behavior of the solenoid is to alter the PW modulation.

 

[the_mork]

Since this topic has already gone slightly off topic in several very useful ways I thought I might ask if there is a system to identifying potential targets for picking up an eprom tcu for a 2g, are they more common in certain years, non-existent in some, or just randomly thrown around?

 

[Bender]

I have yet to see a non eprom 2g TCU. Still wouldn't hurt to check I suppose. The nice thing about 2g TCU's, is unlike 1g's, they are interchangeable throughout the years.

If you are having trouble locating some, I believe I still have one 2g left.

Line pressure is varied while driving based on what gear you are in, and your throttle position.

So I was right, with the exception of I thought it was speed based, not gear based.

 

[knochgoon24]

I have yet to see a non eprom 2g TCU.

You have just sparked my interest. I never did install that rig I put together this spring. I'm happy enough with the shift kit installed. However, this thread is once again relevant to my interests.

I can solder a socket in myself without a problem and would just need a chip burned.

But I'm not sure I'd be happy with a chip just burnt by someone else. I would want to keep changing settings. If someone wouldn't mind pointing me to a site that talks about burning your own TCU chips, I would appreciate it. I saw one mention of it, but it was for 1gs.

With the shift kit, my 2-1 shifts are a bit harsh sometimes. Especially when rolling to a stop.

 

[Bender]

2-1 shifts are always the harshest, and with the IPT valvebody/shift kit and aluminum bushings, mine chatters your teeth. For this reason, I don't down shift into first until my car is already stopped.

 

[knochgoon24]

I'm not shifting it manually. For some reason, it just downshifts to 1st a little bit early when coming to a stop. I did turn that pressure screw a little more than the shift kit said though, so I probably deserve it.

 

[the_mork]

Same thing here, I've changed my driving habits slightly and it doesn't happen very often, easing to a stop below about 15mph reduces the clunk significantly. It is an effect of the black spring and the pressure adjustment. If you didn't want the clunk you should have gone with the red spring, but we both know the way our cars are driven that the red spring just wasn't the right way to go.

 

[knochgoon24]

Yup. One thing I have noticed is that it is more severe when my battery voltage is just a bit lower than normal from a high electrical load due to accessories. Installing a higher output alternator to keep the voltage more stable helped.

I had my alternator, a nice 140amp one, go bad a couple weeks ago and limped my car on just battery power for longer than I should have. As the voltage dropped, the shifting got worse and worse. Go figure. Now the new alternator, a 65amp Autozone replacement, doesn't hold a steady voltage at low rpm, so the shifting isn't as precise. I need to get the 140amp one repaired.

 

[the_mork]

Interesting, personally I keep a well maintained charging system for the purpose of keeping my garden hose sized injectors predictable. I'm honestly surprised at the idea of minimal fluctuations in voltage affecting shift quality that much, or at all really.

 

[chico904]

Just wanted to chime in, and say I am relieved that I am not the only one who has the "clunk" that comes from the car downshifting form 2nd to 1st with the black springs in. I was starting to think it was the fluid possibly.

 

[definitiveno]

Mine clunks too.... It's the primary reason I am looking for a shift controller. Without the clunk I'd be fine with a tuned tcu. I wonder if that's some thing that can be remedied with a tune? Ask it not to downshift until under a load? Come to a stop, car leaves trans in second, light turns green , gas pedal goes down and trans drops to first?

 

[transdude]

Come to a stop, car leaves trans in second, light turns green , gas pedal goes down and trans drops to first?

This is already how they work, if that is the question.

-John
IPT Performance Transmissions
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[definitiveno]

This is already how they work, if that is the question.

-John
IPT Performance Transmissions
Facebook- IPT Performance Transmissions

But after the shift kit alot of ours seem to be downshifting before we come to a stop and before the application of a load, perhaps some revisions to the code could fix it.....

 

[Bluefire16]

Buy a shift box from EAGLEtalonTim on here. Its a great product, and works amazing. You can turn it on or off when you want. I have had it for over a year now personally and LOVE IT. I wouldnt drive without it.

 

[transdude]

But after the shift kit alot of ours seem to be downshifting before we come to a stop and before the application of a load, perhaps some revisions to the code could fix it.....

You are feeling a 3-2, not a 2-1. This is an artifact of mechanically increased pressure in most cases- nothing electrically is going on that is abnormal.

This can be a bit annoying but it is better to live with it than to compromise transmission longevity by reducing pressure across the board.

Just my .02

-John

 

[forcefed86]

IMO, The worse the engagement feels to the driver the better it is for the tranny.

The smooth gear changing is a result of slipping. Slipping generates heat and wears the parts. Less slip the greater the longevity on or off power, or so it was explained to me.

I run a full manual valve body in the "race car" Feels like the engine is gonna fall out everytime I shift.

 

[ramsack]

I have felt my car downshift from 2-1 when coming to a stop, but only when slowing down slowly and it hits like 2 mph. I know it's first because I could count. I don't have the car anymore but I loved the shift kit and I disabled the pressure control solenoid by blocking it off rather than messing with the electronics.

 

[Absit]

Interesting thread and I've got a question for it. My car's main purpose is going to be autocross, but because of the numbers I want to run and the fact that it's a DD I'm going with automatic. What's the best shift solution for an autorcross car?

The thing that concerns me is that there will be times when I need to downshift but won't be at WOT.

 

[Bender]

Go with a selectable shiftbox.

They activate full line pressure when they are turned on (yes, they are selectable so you can have the TCU still shift the car for DD duties). There is also a jack to plug in paddle shifters.

Automatic Dsm's

 

[Absit]

Huh, how about that.. I've been cruising through your site a lot but never saw that, are there any other hidden goodies? Also, what about downshifting at partial throttle with full line pressure?

 

[HighPSI TSi Guy]

What's the best shift solution for an autorcross car?

Manual transaxle.

 

[Absit]

I'm sorry I should have specified while staying automatic.

 

[definitiveno]

Bender, I need you (no h0m0)

I need your input to help figure out how to control my tc with my overdrive switch...

 

[ramsack]

An automatic is going to shift faster than any manual. You can manually choose what gear to be in, so I'd say an automatic transmission shifted manually would be better than a manual gearbox.