Can I change the Servotronic relay (controller) to lighten the steering?

[baka]

Hi, I know most people want the opposite effect but due to a crash years ago I need a car with light steering.

The A4 B7 2.0TFSI Quattro S-Line I just bought is amazing, but I could do with the steering being a little lighter. It's got the 640 in at the minute.

My old A4 B7 2.0TFSI SE had lighter steering, but I guess this could have been down to the narrower rubber and lighter wheels (215 on 16" vs 235 on 17")? Foolishly I didn't think to check the relay before I sold it.

[Rulty]

Believe the relays for the s4 and rs4 give the steering a sportier feel. Unfortunately I think this is as light as you will get with out changing tires and such

Sent from my Pixel using Audizine mobile app

[canadianA4B7]

I believe there is a difference in racks from A4 to s4 and rs4, just installed the S4 rack from a b6 S4. The relay from the rs4 is 628, which I have not yet tried. But the new rack makes a noticeable difference in feel, from what I've been told the rs4 relay wil make mine feel like the rs4.

I think your not able to do what you would like. I believe it's as light as your gonna get.

[Rulty]

You'll need the steering rack to make it feel like an rs4 too

Sent from my Pixel using Audizine mobile app

[baka]

Thanks guys! I shall explore other options.

[Steve Bassen]

629 from a B6 A4 (not S4) should get you the lightest (most overboosted) steering wheel, FYI.

[Rulty]

Honestly you can probably use a number of relays in that slot the higher will give you more steering boost but may wear out the servo faster.

Sent from my Pixel using Audizine mobile app

[canadianA4B7]

You'll need the steering rack to make it feel like an rs4 too

Sent from my Pixel using Audizine mobile app

I'm gonna have to disagree. As I researched the shit out of the steering rack b4 I upgraded

There is no RS4 rack. Been confirmed a hand full of times. The S4 and rs4 racks are the same. The rs4 has a servo relay that is 628.

The only thing I did not confirm is the unit that the car plugs into on the rack. I have the A4 one removed, the S4 unit is in the car, the rs4 cars could have a different revision for this part. Wish I had taken a better look at the replacement rack. If so the relay in the car + the unit (controller maybe) on rack as a combo could be the answer to how the RS4 rack is the lowest ratio rack available.

Ratios (these are likely incorrect as I don't have the actual data in front of me)
A4 is 14.1:1
S4 13.2:1
RS4 12:1

S4 is noticeably tighter, more feel to it and it seems to be much more responsive in and out of turns. This coupled with coilovers, 034 sway bar links, adjustable upper control arms may all be factors which have changed my car. But it's crazy how responsive it is.

[Okedokey]

Im trying to understand how a relay can make any difference, it is either on or off.

[Rulty]

Wait how are they the servo rack then if they have different ratios?

Sent from my Pixel using Audizine mobile app

[Van Black]

Im trying to understand how a relay can make any difference, it is either on or off.

Doesn't the servo have a controller, not a relay?

[Okedokey]

Yeah it does, but I am talking about relay to relay changes, not servo changes. I cannot see how a relay that is the same voltage and current can modify anything with the servo beyond on / off.

[Charles.waite]

Im trying to understand how a relay can make any difference, it is either on or off.

Well its not a basic relay. Thats why it costs $120 not $10...

It has some sort of logic that alters the voltage going to the assist servo so alter the amount of assist it provides based on either wheel speed or gear/rpms. It would be interesting to see one disassembled.

[canadianA4B7]

Well its not a basic relay. Thats why it costs $120 not $10...

It has some sort of logic that alters the voltage going to the assist servo so alter the amount of assist it provides based on either wheel speed or gear/rpms. It would be interesting to see one disassembled.

When I buy the rs4 relay I'll gladly do this. To both the 640 and the assist device on rack.

[Rulty]

http://www.rowand.net/Shop/Tech/AllAboutRelays.htm nice write up on relays and how they work in cars. Will give some insight as to why the 640 relay is different to the rs4 relay (forget the value) and that changes the way the servo responds.

Sent from my Pixel using Audizine mobile app

[Okedokey]

Well its not a basic relay. Thats why it costs $120 not $10...

It has some sort of logic that alters the voltage going to the assist servo so alter the amount of assist it provides based on either wheel speed or gear/rpms. It would be interesting to see one disassembled.

Nope. Its just a switch the only logic is on or off. The control module does what you describe. Thus my difficulty understanding how a relay could do anything different.

[Charles.waite]

The relay IS the control module though. If t were a dumb on/off relay there couldn't be any difference between that and your average $5 fuel pump relay. I'm assuming the servotronic relay has some sort of PWM output to the steering rack servo or pump or wherever the assist is generated.

I'm not sure how many stages of variable assist there are, but I would assume maybe 4 or 5 dependent on vehicle speed. Ask anyone who has swapped in an S4 or rs4 servotronic relay and the differences aren't in their heads.

[Okedokey]

The relay IS the control module though. If t were a dumb on/off relay there couldn't be any difference between that and your average $5 fuel pump relay. I'm assuming the servotronic relay has some sort of PWM output to the steering rack servo or pump or wherever the assist is generated.

I'm not sure how many stages of variable assist there are, but I would assume maybe 4 or 5 dependent on vehicle speed.

Nope, its just a relay, the servo is the motor that will be controlling the torque rate. A really cannot be PWM. The only thing I can think of is that the relay crossover voltage (coil impedance) may be different allowing it to engage earlier/later.

[Charles.waite]

That's the solenoid. Maybe I was confusing your terminology?

Are you saying that solenoid differs based on the car (a/s/rs)? Is that solenoid mounted on the rack?

[Okedokey]

Thats a servo, a motor.

[Charles.waite]

Oh jeeze. I guess I'm clueless about how servotronic works then, haha. I'll shut up!

[Okedokey]

Nah man, I don't know either, could be completely wrong. I just cannot see the real benefit of the relay changes. It would be good to have some wiring schematics of the different relays including specs hey.

[Okedokey]

So I just read the training manual, the relay activates the ECU which controls the servotronics... again, not sure how this changes anything.

[Okedokey]

Ok, so I had a look at ElsaWIn. See below.

Power is connected via the ignition switch to the Servotronic Control Unit (the relay - as you said).
The relay then outputs to the solenoid valve (again, what you said)
This would be a standard 12V on off except for the input from the ABS control unit speed signal.
What I think is happening is that the final voltage that the solenoid sees is the net difference between 12V on the relay and the speed signal. (e.g. 12V +/- voltage from speed signal).
So if the speed signal is outputting 6V, the potential difference on the solenoid would be 18V.
However all of the above information goes into the ECU via the K line so I still believe that the ECU is doing the changes not the relay.

Again, this still doesn't tell me how the relay would make a difference UNLESS there is a different resistance on the output side of the relay.

[Charles.waite]

I didn't know ELSAWIN had wiring diagrams. I really need to acquire said software, my hardback Bentley is woefully out of date. In addition to being somewhat useless.

[Rulty]

There are a lot of types of relays the most basic is on off switch controlled by the current. I'm not sure what the values on the relays are actually signifying but there are lots of relays. I imagine this type of relay controls the voltage based on the vehicle speed input...more assist at lower speeds....higher speeds change the voltage for less assist

Sent from my Pixel using Audizine mobile app

[Okedokey]

There are a lot of types of relays the most basic is on off switch controlled by the current. I'm not sure what the values on the relays are actually signifying but there are lots of relays. I imagine this type of relay controls the voltage based on the vehicle speed input...more assist at lower speeds....higher speeds change the voltage for less assist

Sent from my Pixel using Audizine mobile app

Except for the fact that relays don't do that and the wiring diagram doesn't allow for that anyway.

[Charles.waite]

Some good info here. I believe it applies to the b7 system:

http://www.audiworld.com/forums/a6-s...relay-1650870/

And pictures of the circuit board inside one of them here:

http://forums.quattroworld.com/s4s6/msgs/157312.phtml

[Okedokey]

Well well, I stand corrected. Sorry about that.

[Van Black]

I didn't know ELSAWIN had wiring diagrams. I really need to acquire said software, my hardback Bentley is woefully out of date. In addition to being somewhat useless.

I can help you with that if you'd like