Differing steering setups - Standard/Servotronic/35is.

M

MACK

Veteran
 Manchester
Hi,

Over the years I've read various reviews by the motoring press (plus other sources) regarding the different steering setups that were available from the factory for the E89. Here's my understanding of what was available.

First of all its worth stating that according to Realoem all the various models use the exactly the same EPS steering rack albeit differing depending on what side your steering wheel is on. :) They also share the same track rods, track rod ends aka ball joints, tension and control arms. So are fundamentally the same in terms of hardware. However there are three different steering options offered which are all solely down to the programming of the steering control module (which is part of the rack).

STANDARD STEERING: Constant assistance independent of speed.
Driving Mode effects steering, for example, heavier in Sport than in Comfort.

SERVOTRONIC STEERING: Variable Assistance. More assistance at low speeds and less at high speeds.
Driving Mode effects steering, for example, heavier in Sport than in Comfort.
I initially thought this was standard on all UK/Euro cars (not US/Canada). But I'm now led to believe this isn't true and it was a cost option at launch and only standard on all M Sport and 35is models and then on all post facelift models. Again not 100% on this so I'm prepared to be corrected.

SERVOTRONIC 35IS MODELS: This is the one I'm most unclear on. The road tests I've read lead me to believe that the 35is has its own unique Servotronic programming that gave it sharper steering than the other models. However I'm not sure if the road testers at the time the 35is was launched were actually comparing the 35is with Standard Steering equipped models, not Servotronic equipped models. As I don't think M Sport models with Servotronic were available when the 35is was launched. So I'm not actually sure there really is any difference between a 35is servotronic programming to that of the 35i or N20 M Sport models. Once again I'm prepared to be corrected on this.

Its really difficult to find some proper information on the various E89 steering configurations so I thought I'd post this in an attempt to establish the facts.
 
Servotronic is just a piece of software, my 2009 23i didn't have the option installed.
I went BMW and asked to upgrade, they came back and said i would have to upgrade battery and alternator. So didn't bother.
My standard steering becomes heavier in sport/sport +
Overall the steering is a bit wooden and lacks any natural feel.
 
It's a real mess on information out there but you're pretty close.

Servotronic is just an option you can spec to any vehicle with EPS. I enabled it on my 2009 35i to test, just a case of setting a bit in the EPS module. It makes the steering very light at low speeds, I really didn't like how it felt. This option is on by default in certain markets but in the UK I don't believe it was available on any E89.

There's only 2 different states of programming for the EPS in the E89 Z4. One for vehicles produced in 2009/2010 and another for 2010+. The electronics are identical but the code is a little different.

- The software for 2009/2010 vehicles was only intended for N52 and N54 Z4 vehicles with settings for normal and servotronic. These are the options for steering behaviour:
Code: 
E89 with N54 without SA2VF (Adaptive M Suspension) with SA216 (Servotronic)
E89 with N54 with SA2VF (Adaptive M Suspension) with SA216 (Servotronic)
E89 with N52 without SA2VF (Adaptive M Suspension) with SA216 (Servotronic)
E89 with N52 with SA2VF (Adaptive M Suspension) with SA216 (Servotronic)
E89 without SA216 (Servotronic)

-The software for 2010+ vehicles has these options:
Code: 
E92
E93
E87
E81
E90
E91
E82
E88
E84
E92 basis
E93 basis
E81 basis
E88 basis
E90 basis
E84 basis
E89 basis with N54
E89 basis with N54 with Adaptive M Suspension
E89 basis with N52
E89 basis with N52 with Adaptive M Suspension
E89 basis
E89 basis with N54T (35is)
E89 sport with N54
E89 sport with N54 with Adaptive M Suspension
E89 sport with N52
E89 sport with N52 with Adaptive M Suspension
E89 sport
E89 sport with N54T (35is)

You can see in 2010 they basically merged all software together from other models. Previously the 1 series, 3 series and Z4 had separate configurations but they merged them together and just made it a setting to choose different steering assist between models.

Each configuration will behave slightly differently. The 2.0 models aren't named in the code but probably just use the E89_basis or E89_sport options depending if they came with MSport or not.
 
R.E92..that's very interesting thank you..

Is there a 'table(s)' that go with these parameters akin to an ECU set of maps, so that one can divine what the differences are?
 
Nobody has gone into that depth yet. People only really care about the engine and a little about the transmission coding so things like the EPS are largely ignored.

I have a steering rack from an E90 (to avoid breaking my Z4 one) that I've been playing with but haven't tried reverse engineering the code yet. It will be way simpler than ECU code. I expect it's just an assist curve that tells the motor how much steering weight to apply based on the turning of the wheel.
 
I wonder whether the code tables they use (I assume the logic is the same) explains, in part, why some people perceive a lack of feedback etc when compared to hydraulic assisted steering?

I see the E89 used a later style of EPS compared to the E85/E86..

I see from the UK 2013 brochure that Servotronic was standard on all models (S216) ..but an early E89 w/w brochure showed as optional..

A UK 2010 brochure states 'electric power steering' as standard but shows no option for Servotronic?
 
flybobbie said:
Servotronic is just a piece of software, my 2009 23i didn't have the option installed.
I went BMW and asked to upgrade, they came back and said i would have to upgrade battery and alternator. So didn't bother.
My standard steering becomes heavier in sport/sport +
Overall the steering is a bit wooden and lacks any natural feel.
Click to expand...

I've update my original post to reflect what you said about the standard steering getting heavier with Sport.
 
Pbondar said:
I wonder whether the code tables they use (I assume the logic is the same) explains, in part, why some people perceive a lack of feedback etc when compared to hydraulic assisted steering?

I see the E89 used a later style of EPS compared to the E85/E86..

I see from the UK 2013 brochure that Servotronic was standard on all models (S216) ..but an early E89 w/w brochure showed as optional..

A UK 2010 brochure states 'electric power steering' as standard but shows no option for Servotronic?
Click to expand...

I think what you said about the brochures highlights the confusion. Early cars seem to lack Servotronic, certainly as standard where as later ones it appears to be standard. A vin check of my 04.12 car shows that it has Servotronic and the brochure I've seen from the same time period states it was standard across the board. I do still wonder if there are two versions of the Servotronic programming one for the run of the mill models and a sportier one for the 35is. Or if the reality is the Servotronic cars are in fact all the same and road testers and BMW's own marketing was comparing the 35is Servotronic with standard steering from earlier models etc.

R.E92 said:
It's a real mess on information out there but you're pretty close.

Servotronic is just an option you can spec to any vehicle with EPS. I enabled it on my 2009 35i to test, just a case of setting a bit in the EPS module. It makes the steering very light at low speeds, I really didn't like how it felt. This option is on by default in certain markets but in the UK I don't believe it was available on any E89.

There's only 2 different states of programming for the EPS in the E89 Z4. One for vehicles produced in 2009/2010 and another for 2010+. The electronics are identical but the code is a little different.

- The software for 2009/2010 vehicles was only intended for N52 and N54 Z4 vehicles with settings for normal and servotronic. These are the options for steering behaviour:
Code: 
E89 with N54 without SA2VF (Adaptive M Suspension) with SA216 (Servotronic)
E89 with N54 with SA2VF (Adaptive M Suspension) with SA216 (Servotronic)
E89 with N52 without SA2VF (Adaptive M Suspension) with SA216 (Servotronic)
E89 with N52 with SA2VF (Adaptive M Suspension) with SA216 (Servotronic)
E89 without SA216 (Servotronic)

-The software for 2010+ vehicles has these options:
Code: 
E92
E93
E87
E81
E90
E91
E82
E88
E84
E92 basis
E93 basis
E81 basis
E88 basis
E90 basis
E84 basis
E89 basis with N54
E89 basis with N54 with Adaptive M Suspension
E89 basis with N52
E89 basis with N52 with Adaptive M Suspension
E89 basis
E89 basis with N54T (35is)
E89 sport with N54
E89 sport with N54 with Adaptive M Suspension
E89 sport with N52
E89 sport with N52 with Adaptive M Suspension
E89 sport
E89 sport with N54T (35is)

You can see in 2010 they basically merged all software together from other models. Previously the 1 series, 3 series and Z4 had separate configurations but they merged them together and just made it a setting to choose different steering assist between models.

Each configuration will behave slightly differently. The 2.0 models aren't named in the code but probably just use the E89_basis or E89_sport options depending if they came with MSport or not.
Click to expand...

Do you think if your car was a later model, say 2014 there would be more options in the coding? Hence some of the confusion around this
 
I think the coding for all N20s were the same, apart from the M Sport vs non...

Without a standardised test of two N20s , msport vs normal or N20 vs 35i who knows?
 
Pbondar said:
I think the coding for all N20s were the same, apart from the M Sport vs non...

Without a standardised test of two N20s , msport vs normal or N20 vs 35i who knows?
Click to expand...

It's a bit annoying not knowing. If a 35is specific servotronic software exists thats gives then a bit of a sportier feel, it could potentially be a useful upgrade on the N20 and 35i models

Although I'm actually inclined to think that all the servotronic cars have exactly the same coding
 
I’m not sure what sportier is / could be in this case.. :tumbleweed:

For me personally, I think I’ve got to a point where the handling set up on my car where it’s as good as I need it... :driving:

I guess what you / we could do, if we could master the BMW factory tools, is load the 35 variants and just see?

Feel free to go ahead and try it please :thumbsup:
 
Pbondar said:
I’m not sure what sportier is / could be in this case.. :tumbleweed:

For me personally, I think I’ve got to a point where the handling set up on my car where it’s as good as I need it... :driving:

I guess what you / we could do, if we could master the BMW factory tools, is load the 35 variants and just see?

Feel free to go ahead and try it please :thumbsup:
Click to expand...

I'm good with the spanners not so with the software. So I will pass😁
 
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