M3 Steering rack Retrofit

[DimitrisM3]

Originally Posted by Muppet

Warning long winded post.

So I think I have now got this sorted. I had a bit of a problem with the placebo effect as I would try something, restart the motor and move the wheel and think it is lighter. It is only when you turn to full lock do you feel the additional load that is required without Servotronic. In addition past 30 kph the additional weight is really not a factor.

To answer the post above they are basically the same rack. Same ratio, same fitment apart from the hydraulic pipes may be slightly differently oriented.

The issue has been whether you can get Servotronic operating on a 135i.

I have managed to get the speed adjustable assistance working in a more meaningful manner than the hit and miss that was previously the case. The weight is the same as without Servotronic in the quarter turn either side of straight ahead but the servo assistance kicks in past there and takes off the additional load as you add the additional three quarters turn. The reason for the additional weight is the amount of caster built into a 135i (approx 7 degrees stock) which means you are actually lifting the car as you are turning the wheel. It is accentuated with mine as I have 8.3 degrees.

The 135i pump is smaller than that on the M3 and 1M and I assume this means that the hydraulic pressure is less and so more human effort is required.

The new steering weight is not as light as a standard 135i and probably heavier than the sports mode on a M3 or 1M, but not un wieldy as with no Servotronic. This only really relates to parking speeds, other than that it is a little lighter up to 30 kph but faster than that feels the same as before the Servotronic function was active.

The next thing is to thank the author of NCS Dummy and the member who
posted a 1M FSW_PSW dump file on this forum. The dump file enabled me look at the difference between the instructions of a 135i and 1M and trace down the ecu other than JBBF which needed to be re coded. NCS Dummy helped find what was required in the Kombi ecu.

What came up was that the following instructions were active on a 1M and inactive on a 135i. I coded them in as active and this settled down the rather on/off Servotronic assistance I previously had. (I was aware that the Servotronic function was working after I had coded in the option as when I disconnected the wiring I would get a fault come up and there was a current running to the valve but it fluctuated wildly).

ST_MDRV_ALIVE_MONITOR
aktiv
ST_MDRV_CSUM_MONITOR
aktiv
ST_MDRV_ID_MONITOR
aktiv

So there you have it, add the option $216, recode the whole car, alter JBBF to Servotronic aktiv and make the changes to the kombi ecu as above.

It is not as assisted as a 1M but it is a lot better than none at all.

There are a host of ST_ and other instructions in the JBBF ecu which are steering related and they are the same between a 135i and a 1M. These may adjust the level of assistance but I am not sure I want to tamper to much with these. They may only relate to activ steering or electric steering. I am happy with the way it is.

I am not going to put in a big warning about doing this at your risk as I have found the ecus' to be remarkably resilient to cock ups. These are only minor changes and I also found that NCS Expert will not allow you to make alterations to instructions that are not reasonable.

Do you have the trace files for the complete coding for M3 servotronic ?

[Muppet]

You do not need trace files.

The most important issue is to make sure you have a compatible JBBF installed. You can check on Realoem the units that are compatible with a 1M. They MUST be listed as an alternative. A 135i JBBF does not have the servotronic option.

Once you have that installed the correct JBBF, code in option 216 and you are good to go.

[3k1n]

I purchased a m3 steering rack and it came with the m3 steering shaft u joint. Can anyone confirm if the u joint does in fact fit? I would rather use the u joint than have to cut the plastic tab as it came with it anyways.

[Traf]

It is perfectly usable, but then you need to disconnect the upper part, which is rly not an easy task. It is very close to the firewall.

[duder13]

Originally Posted by Solo_M_Tech

Its 100% worth the swap. The m3 rack eliminates any hand over hand action. even in the hairpins.

I guess, but, like I said, a lot of Porsches come with a slower ratio, and I haven't had many issues, at least at my frequented track or on the street. Heck, even the rack on the 997 GT3 RS is only slightly faster than the 135i's at 14.9:1 (2.6 turns.)

I'm not saying anyone should or shouldn't do this mod. Just pointing out that the standard 135i ratio isn't exactly slow.

[bbnks2]

Originally Posted by duder13

I guess, but, like I said, a lot of Porsches come with a slower ratio, and I haven't had many issues, at least at my frequented track or on the street. Heck, even the rack on the 997 GT3 RS is only slightly faster than the 135i's at 14.9:1 (2.6 turns.)

I'm not saying anyone should or shouldn't do this mod. Just pointing out that the standard 135i ratio isn't exactly slow.

Uhm 14.9:1 @ 2.6 turns is massively different from 16:1 and needing 3 complete turns. The M3 12.5:1 rack takes that 3 turns down to 2.5 or so which would put it more in-line with feeling the same as your Porsche.

There are also track width and wheelbase considerations that need to be factored in to just how well the car turns with x or y steering ratio.

If you think 16:1 isn't that bad on a bmw then you've never autocrossed lol. You need 2x as much hand movement as an FRS/BRZ, Miata, or even older BMWs that got quicker racks like the Z4.

[duder13]

Originally Posted by bbnks2

Uhm 14.9:1 @ 2.6 turns is massively different from 16:1 and needing 3 complete turns. The M3 12.5:1 rack takes that 3 turns down to 2.5 or so which would put it more in-line with feeling the same as your Porsche.

There are also track width and wheelbase considerations that need to be factored in to just how well the car turns with x or y steering ratio.

If you think 16:1 isn't that bad on a bmw then you've never autocrossed lol. You need 2x as much hand movement as an FRS/BRZ, Miata, or even older BMWs that got quicker racks like the Z4.

I’ve never seen anyone say 3 full turns. C&D called the 135i rack 16:1, 2.7 turns. R&T called it 15.3:1. Automobile Mag called it 2.5 turns.

I never had a GT3 RS. I wish! My 911 and Cayman were both 16.9:1. I did AX some, but, yes, I prefer a track.

FWIW, E46 M3 was 15.4:1. I’m not saying E92 M rack isn’t cool. I’m just saying 135i rack isn’t that bad, so I’d personally spend my money elsewhere.

[bbnks2]

Originally Posted by duder13

I’ve never seen anyone say 3 full turns. C&D called the 135i rack 16:1, 2.7 turns. R&T called it 15.3:1. Automobile Mag called it 2.5 turns.

I never had a GT3 RS. I wish! My 911 and Cayman were both 16.9:1. I did AX some, but, yes, I prefer a track.

FWIW, E46 M3 was 15.4:1. I’m not saying E92 M rack isn’t cool. I’m just saying 135i rack isn’t that bad, so I’d personally spend my money elsewhere.

I've seen plenty of people (including my own steering wheel) say 2.9 turns. I also see a lot of 2.7 numbers. The 15.3:1 and 2.5 turns is probably from European cars with EPS (variable electronic rack) . 1M is put at 2.2 turns. I think it's more like 2.3-2.4 for a 135i with a 1M/M3 rack swap so sorry for saying 2.5... Gotta remember that suspension kinematics differ slightly between these cars as well.

Regardless, steering ratio is just the relationship between steering wheel input and resulting steering angle at the wheel. Modified suspensions and wheels change this relationship and not all makes and models of cars have the same range of steering angle to cover. Wheelbase, track width, and suspension kinematics need consideration also if you want to compare car-to-car. The rack ratio itself doesn't mean much if you still need to do k-turns to turn your car. 30* of steering in a Porsche can produce significantly tighter actual turning radius than 30* of steering on a BMW. Believe it or not, Porsche cars generally have significantly shorter wheel bases than BMW's. 97." wheelbase vs 105" wheelbase...

On a track the M3 rack makes a difference too. You go from crossing arms in tight turns to only needing half as much movement. Is it a NEEDED mod to get a round a track? No. But, it's a welcomed difference.

On a side note, I killed my stock rack at 70k miles and now the replacement M3 rack is also leaking fluid at 115k miles. Anyone else destroying power steering racks? I am not lowered excessively. Around 4" of ground clearance so like 1" of lowering maybe.

[duder13]

Originally Posted by bbnks2

I've seen plenty of people (including my own steering wheel) say 2.9 turns. I also see a lot of 2.7 numbers. The 15.3:1 and 2.5 turns is probably from European cars with EPS (variable electronic rack) . 1M is put at 2.2 turns. I think it's more like 2.3-2.4 for a 135i with a 1M/M3 rack swap so sorry for saying 2.5... Gotta remember that suspension kinematics differ slightly between these cars as well.

Regardless, steering ratio is just the relationship between steering wheel input and resulting steering angle at the wheel. Modified suspensions and wheels change this relationship and not all makes and models of cars have the same range of steering angle to cover. Wheelbase, track width, and suspension kinematics need consideration also if you want to compare car-to-car. The rack ratio itself doesn't mean much if you still need to do k-turns to turn your car. 30* of steering in a Porsche can produce significantly tighter actual turning radius than 30* of steering on a BMW. Believe it or not, Porsche cars generally have significantly shorter wheel bases than BMW's. 97." wheelbase vs 105" wheelbase...

On a track the M3 rack makes a difference too. You go from crossing arms in tight turns to only needing half as much movement. Is it a NEEDED mod to get a round a track? No. But, it's a welcomed difference.

On a side note, I killed my stock rack at 70k miles and now the replacement M3 rack is also leaking fluid at 115k miles. Anyone else destroying power steering racks? I am not lowered excessively. Around 4" of ground clearance so like .75-1" of lowering maybe.

I absolutely hear what you're saying. My point was simply that I wouldn't characterize the 135i standard rack as particularly slow. The E46 M3 rack was about the same, and the E36M rack was slower (both longer wheelbases.)

It should also be mentioned that faster ratios aren't necessarily better, depending on usage, due to loosing precision, as well as the so-called "sneeze" factor at high speeds. A rally car, like an STI, makes more sense with a super fast ratio vs. a 911 GT3 RS, which is going to be doing very high speeds on a track. I guess, our BMWs are somewhere in between.

Either way, the M3 rack surely adds "twitchiness" to the 1M, which many love. If my standard rack goes, I'm not sure which I'd pick.

I'm surprised you've blown two racks already. That does seem a little odd.

[amg6975]

The ratio of the rack doesn't matter at all, it's the motion ratio of the wheel to the steering wheel. The motion ratio of the 135 is quite slow, so the faster M3 rack makes it closer to what you'd experience in a Porsche with a "slower" rack but faster motion ratio. It's all about the "lever" at the upright.

I can tell you without a doubt that M3 rack is one of the best upgrades I've done to the car. It actually feels like a sports car now. Sneeze factor is still perfectly fine.

[duder13]

Originally Posted by amg6975

The ratio of the rack doesn't matter at all, it's the motion ratio of the wheel to the steering wheel. The motion ratio of the 135 is quite slow, so the faster M3 rack makes it closer to what you'd experience in a Porsche with a "slower" rack but faster motion ratio. It's all about the "lever" at the upright.

I can tell you without a doubt that M3 rack is one of the best upgrades I've done to the car. It actually feels like a sports car now. Sneeze factor is still perfectly fine.

I’m not sure what you mean. The steering ratio is the ratio between the turn of the steering wheel and the turn of the wheels, whether it’s a BMW or Porsche.

Now, the 135i steering is heavier than my Porsches, probably because of the engine placement, but the Porsches I’ve owned have been similar when it comes to ratio and lock-to-lock.

[amg6975]

Originally Posted by duder13

I’m not sure what you mean. The steering ratio is the ratio between the turn of the steering wheel and the turn of the wheels, whether it’s a BMW or Porsche.

Now, the 135i steering is heavier than my Porsches, probably because of the engine placement, but the Porsches I’ve owned have been similar when it comes to ratio and lock-to-lock.

Is it? I thought it was the ratio of the gears in the rack itself, and then the motion ratio was dictated by that ratio and the geometry of the upright?

[duder13]

Originally Posted by amg6975

Is it? I thought it was the ratio of the gears in the rack itself, and then the motion ratio was dictated by that ratio and the geometry of the upright?

Yep, and then you can use the maximum angle of deflection to calculate lock to the lock.

Again, the 1M rack is a great upgrade for a lot of people. I’m just saying the standard 135i rack isn’t what I’d consider slow and is inline with a lot of other sports cars.

[amg6975]

Originally Posted by duder13

Yep, and then you can use the maximum angle of deflection to calculate lock to the lock.

Again, the 1M rack is a great upgrade for a lot of people. I’m just saying the standard 135i rack isn’t what I’d consider slow and is inline with a lot of other sports cars.

I'm still not totally convinced. The 135 rack felt way slower than many other cars I've owned with "slower" racks. Color me skeptical.

[duder13]

Originally Posted by amg6975

I'm still not totally convinced. The 135 rack felt way slower than many other cars I've owned with "slower" racks. Color me skeptical.

I wonder if it's just because it's heavy? The 135i steering seems pretty heavy compared to most cars from its era.

[juld0zer]

The hydraulic assist is not as strong as on other cars. I mean, for argument's sake an E70 of the same era has lighter steering yet turns 275's using pinky pressure - even without the active steering option.

Could we just fit the active steering version of the pump and call it a day or would we risk blowing something up from the additional pressure? Or a 1M pump?

An E90 or E82 running 205 runflats on the front axle steers quite well (light and feels quicker than my 135i ever did).

[amg6975]

Originally Posted by juld0zer

The hydraulic assist is not as strong as on other cars. I mean, for argument's sake an E70 of the same era has lighter steering yet turns 275's using pinky pressure - even without the active steering option.

Could we just fit the active steering version of the pump and call it a day or would we risk blowing something up from the additional pressure? Or a 1M pump?

An E90 or E82 running 205 runflats on the front axle steers quite well (light and feels quicker than my 135i ever did).

Later cars can have the variable assist retrofitted with the M3 rack. I fully intended to do it until I drove it without it, and it really isn't so bad. My wife has no troubles with it. The pump on the 1M/M3 is larger, I believe but I don't know what affect that would have.

[ngtrix]

Originally Posted by Mmike

plz help if u have any idea

I have the same problems. temporarily using dc/dc Converter, manually adjusted the voltage on it for a comfortable steering

[Muppet]

Originally Posted by ngtrix

I have the same problems. temporarily using dc/dc Converter, manually adjusted the voltage on it for a comfortable steering

See my post #134.

You must have a Junction Box that is compatible with a 1M.

[frontside0815]

Any one here now did the swap coming from a car with active steering?
Im still not sure if i would want to try it.

I like the speed of my steering, but i don´t like the feeling of connection you have- it somehow feels like a electrical steering not mechanical because of the active steering.

[S54ca]

For all of you with active steering who are interested in this swap:

The hardware is a direct fit, although I would recommend swapping the supply / return pipes from a rack with some from a non A/S car. Specifically, the line which attaches to the front of the rack with the rubber isolators is bent differently, which strains the rubber isolators.

Coding wise, these are the steps that I took to get rid of the A/S lights on the dash / iDrive and get rid of DSC related A/S errors:

1. Change VO (remove $217); FA_write to CAS and NFRM (make sure the NCS profile being used is able to modify & write, it didn't take if the AL module is still showing in ISTA or INPA)
2. Change any mention of 'AFS' in the KOMBI man file to nicht_aktiv
2. Update DSC ZB# to the latest contained in E89 datens
3. Calibrate DSC module using ISTA/D

That should be all - good luck!

[ShocknAwe]

Hopefully someone can help.

Trying to figure out if I need to put the 1m tie rods on my build

M knuckles, M arms, nonM rack.

Is the rack for the M vs nonM different length?