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Go Back   TDIClub Forums > VW TDI Discussion Areas > TDI Power Enhancements

TDI Power Enhancements Discussions about increasing the power of your TDI engine. i.e. chips, injectors, powerboxes, clutches, etc. Handling, suspensions, wheels, type discussion should be put into the "Upgrades (non TDI Engine related)" forum. Non TDI vehicle related postings will be moved or removed. Please note the Performance Disclaimer.

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Old October 4th, 2003, 21:57   #1
KERMA
 
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Default adjust auto transmission line pressure

Here is an easy, free mod you can do when you service your auto transmission for fluid and filter change, or whenever you have the pan off. I found this while developing my new plug-in "tuning box" for these transmissions (an ugly but functional working prototype is in my car right now)

Here is a picture of the valve body from underneath the car, with the pan and filter removed:




Here is a closer view of the area around the adjustment:



The funny cap srew with the "star-shaped" notches is what you will turn to make the adjustment. Here is a picture of the hex wrench in the appropriate location:



About the only "special" tool you need is this shortened 3mm hex wrench. I ground mine down to about half the length onthe short end so it would fit. The fitting is actually for a T-20 torx, but it is a very tight fit unless you want to remove the valve body from the transmission, not recommended. 3mm hex works in a pinch if it is shortened.


***Warning***

DO NOT TURN THIS "SCREW" IN THE OUT DIRECTION TO TRY TO LOOSEN IT. YOU WILL BREAK THE LOCKIING TABS THAT LOCK IT IN PLACE.

Here is a fuzzy closeup picture of the star-shaped adjustment, from the valve body on my workbench. Note the locking tabs are broken.... Here's your chance to learn from my mistake, do not try to loosen them, only turn this in the righty-tighty direction.



How far do you turn it? On the workbench I got about 30 "clicks" out of it- you will see what I mean. In the car only about 20 clicks. Maybe I could get more if the wrench was ground a little shorter to get in there better, but it was enough.

The result: much more positive shifts. you need to see for yourself. [img]/images/graemlins/cool.gif[/img]
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Old October 4th, 2003, 22:14   #2
KERMA
 
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Default adjust auto transmission line pressure

BTW just a reminder, reset the basic settings for the transmission again after you do this, to reset the fuzzy logic.
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Old October 4th, 2003, 23:07   #3
NYTDI
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Default adjust auto transmission line pressure

Very interesting!

Do you think a torx screwdriver bit would fit in OK, then I would turn it w/one of those little side handle rachet bit drivers?

I'm really interested in your up coming tweaker box for the tranny.
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Old October 5th, 2003, 16:10   #4
will360655
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Default adjust auto transmission line pressure

You can't do this just from the outside of the vehical. I don't even have 20k yet, so I'm not even close to a fluid change or anything.
Will
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Old October 5th, 2003, 19:55   #5
NYTDI
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Default adjust auto transmission line pressure

Yeah I understand that the pan has to be dropped to get to the screw. I've done 2 F/F changes so far.

I was just asking if KERMA thought that a side rachet drive bit could be successfully used in there.

Hey KERMA I have a spare TCU. Would that be any use to you for futher development?
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Old October 5th, 2003, 20:57   #6
KERMA
 
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Default adjust auto transmission line pressure

NYTDI:

If I could "borrow" the TCU for a while, it might help. MOstly I want to look inside and get a feel for some of the components they mount on the board.

Right now I want to run my box on my car and see if anything blows up before I risk anyone else's. Feel lucky? I could send you a prototype, if you don't mind cutting a few wires inside the harness...

So far, so good, but it will definitely need a few internal adjustments in the valve body for the most benefit. For starters, the main pressure reg valve needs to be re-worked to allow more flow to the TC. It is amazing that the TC works at all as restrictive as that thing is. It's also kind of strange because if it opens up TOO far it just dumps pressure back to the sump. It's like there is a fine balance that has to be maintained between no TC flow and dumping all the pressure to the sump. There can definitely be more flow if the valve is machined a little different. A nice side benefit will be more cooling flow because ALL the flow to the TC goes through the cooler first. Maybe if I have time I will work up a simple schematic diagram for the hydraulic circuits to help explain what I am doing.

I would say, based on my experience with this simple adjustment the last couple days, that it is definiely worth doing if you have the pan off. The car responds much better to the throttle and it is obviously better coupled to the wheels, more power getting down. Max the main pressure and lock the clutch and it is like a rocket through 2nd and 3rd gear- right in the fat torque band no more revving aimlessly to 4k and staying there. That is no doubt hard on the equipment though. But what a hoot. I am using the torque for the first time. As a side benefit: the controller seems better behaved after all this.

The problem now is getting something together in a user-friendly package, as long as it won't blow anything up. I had to slice into the transmission harness cut some wires and solder the gadget in place, and run wires thru the firewall. I want so find or make the round plug for the valve body on the transmission so it is more plug it in and go type of thing, but as far as I can tell the plug is not available. The other alternative is to unplug wires at the TCU.

There is less than 2 cm gap between the transmission case and the adjustiong point, no standard socket wil ever fit. Even the shortest little replaceable screwdriver tips are too long. It is tight. This may be a job for... METALNERD!!! a really short t-20 is the ticket, maybe bent like a typical hex wrench so you can turn it.
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Old October 5th, 2003, 21:10   #7
NYTDI
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Default adjust auto transmission line pressure

email or IM me your address, I'll get it in the mail to you Mon. or Tue.
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Old October 6th, 2003, 20:30   #8
GoFaster
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Default adjust auto transmission line pressure

Hey Kerma,

I gather that your response to a "No User Serviceable Parts Inside" sticker is the same as mine.

[img]/images/graemlins/laugh.gif[/img]
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Old October 7th, 2003, 11:51   #9
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Default adjust auto transmission line pressure

[ QUOTE ]
GoFaster said:
Hey Kerma,

I gather that your response to a "No User Serviceable Parts Inside" sticker is the same as mine.

[img]/images/graemlins/laugh.gif[/img]

[/ QUOTE ]


Sorry, man. I can't help it. It's my nature. To me, that that sticker means "Tinker with me, please" [img]/images/graemlins/grin.gif[/img]
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Old October 28th, 2003, 15:07   #10
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Default adjust auto transmission line pressure

Update?

How's this working? Tranny explode yet? Does it shift harder (ie is it any less smooth when you're not floorin' it)?
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Old October 28th, 2003, 21:21   #11
KERMA
 
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Default adjust auto transmission line pressure

WOrks great.

Crisper shifting, lower rpm shifting.

I recommend this mod to everyone. Do it when you service your transmission. Quick, easy, and FREE.
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Old October 29th, 2003, 05:46   #12
Occams_Razor
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Default adjust auto transmission line pressure

[ QUOTE ]
KERMA said:
WOrks great.

Crisper shifting, lower rpm shifting.

I recommend this mod to everyone. Do it when you service your transmission. Quick, easy, and FREE.

[/ QUOTE ]

"Lower RPM shifting"? [img]/images/graemlins/eek.gif[/img]

My transmission already short shifts from 1st to 2nd as it is! [img]/images/graemlins/confused.gif[/img]

Is that lower rpm shifting under normal acceleration or lower rpm shifting under wot?
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Old October 29th, 2003, 19:35   #13
KERMA
 
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Default adjust auto transmission line pressure

I think maybe the power mods change the way it shifts. Mine was shifting too high for my liking, and had a hair-trigger downshift more or less. This tightened it up a bit. Not dramatic, but definitely noticeable.
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Old October 30th, 2003, 05:55   #14
Judson
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Default adjust auto transmission line pressure

So, does doing this just make the shift crisper, and
not change the shift points?

AFAIK, the two biggest complaints against this auto
are:

1) revving and revving instead of shifting and getting
back into the torque zone

2) shifting way too early and lugging the bejeesus
out of the poor motor

I'm actually more concerned about fixing #2. I figure
more power will help #1, as an upsolute chip didn't
help #2.

Jud.
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Old October 30th, 2003, 08:13   #15
KERMA
 
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Default adjust auto transmission line pressure

Actually, rev and rev problem is worse with higher line pressure. That's where forced TC lockup comes in. You can lock that thing up in all gears once you get rolling. I do sometimes when I want to punish some poor unsuspecting ricer. This part I implemented after the racing season was already done, no way to test it at the track, but feels like good for at LEAST a good 3/4 sec in quarter mile ET.

This line pressure mod does change the shift quality some. For the better I would say.

Wish someone else would do it so I'm not the only one with first-hand experience.
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