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Thread: E36 LS swap: need smaller diameter brake booster

  1. #1
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    E36 LS swap: need smaller diameter brake booster

    I have an E36 M3 with LS installed using Vorshlag kit. I recently pulled out the 5.7 LS1 and installed a built LS2 6.0. I'm running Jesel shaft mount rockers which require taller valve covers or valve covers spacers.

    As many of you know valve cover to brake booster clearance is only about 1/4inch with the stock valve covers.

    With the spacers or taller cover I have not clearance and interference issue.

    Which smaller diameter booster have you all used with success?
    I plan to retain ABS function.

    I see the Merc. E190 booster has been used. What year?
    Any other options?

    Also I have considered moving the stock booster over and up but then pedals would move with it or would require a good bit modifications to move booster and retain factory pedal location.

    Thanks

  2. #2
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    My $.02 on the E36 LSx booster options from my first hand experience and research for greater valve cover to booster clearance. I have spent a great deal of time and effort and some money looking into and trying alternatives. I’ll outline the basic pros and cons with each.


    1) Moving the booster/pedal assy over;
    a) Pros; Adds clearance to the valve cover while retaining the OE booster, ABS travel sensor if equipped doesn't require relocation.
    b) Cons; Requires quite a bit of work/fabrication due to the impact this modification has on other systems/items.

    2) Smaller Booster;
    a) Pros; Gains considerable clearance to the valve cover, allows a little more room under/near the booster for other items to fit if relocated in that region, also adds just a little more room under/near booster if cramming the ABS module up under Master Cylinder if the headers allow.
    b) Cons; For those with the ABS pedal travel sensor in their booster, this mod requires relocating the travel sensor to under the dash, or deleting the ABS all together.

    3) Hydra/Hydro boost; I have no experience with this system. As I understand it, the clearance gained is considerable at the expense of added hydraulic plumbing for the system and a little bit of fabrication, a viable alternative for sure, others input that have gone this route would be appreciated.


    Moving the booster over requires quite a bit of modification and fabrication. Due to the design of the booster, firewall and pedal bracket assy, the entire package must be moved in whole, the booster can not be moved without moving the pedal assy as well. We have looked into this extensively including modifying a bracket assy and mocked up. JTR may still offer this as an option in their kit for those interested. Work involved in this mod; modifying the bracket assy, modification of the firewall penetrations for the booster, the clutch M/C penetration, and clutch reservoir line. Pending on how far the booster is moved, relocating the BMW EFI and DME relays that reside next to the booster to allow the move and also relocating the X6031 connector (if retained/used) to clear the clutch reservoir hose.

    Smaller booster requires sourcing said booster, Mercedes is the source I found that has the same exact “footprint” as BMW, (BMW and Merc sourced boosters from the same manufactures, footprint dims are exactly the same: booster face to pushrod, bolt C/L spacing, clevis extension, etc), even their pedal bracket assembles designs are amazingly similar. Merc used a few different diameters in their boosters, even offered some in aluminum. I have not tried the Aluminum booster myself, it is light weight and small diameter though not sure how much “pushing” effort it can take without deformation as it is has no through studs like the steel versions, (I have a few of both on hand having mocked them up). The smaller diameter steel boosters and Aluminum Merc boosters require opening up the hole for the M/C by approx. .050” and the Merc clevis that attaches to the brake pedal itself is tighter with a smaller clevis hole, both mods can be performed by a competent machine shop or fabricator, (I offer this service to those interested). For those retaining the OE ABS with the ABS travel sensor, (some earlier 3 channel ABS systems do not have this travel sensor protruding out the face of their brake booster and are therefore exempt from having to deal with this aspect), relocating the travel sensor from your OE BMW booster to under the dash so it retains its function as BMW designed is imperative for the ABS to function and not set trouble codes. JTR is working on the parts for this ABS travel sensor relocation for use with the smaller booster.


    BMW alongside the Merc aluminum and steel dual diaphragm booster;





    BMW booster has approx 1/8" valve cover clearance in this position, note Merc booster clearance.



    Steel Merc smaller booster installed in my car;


    JTR ABS Travel Sensor Relocation solution installed in my car;



    I went with the smaller steel Merc booster and ABS travel sensor relocation, now have 30,000 miles on conversion with no issues.
    Last edited by BRAAP; 10-23-2012 at 11:17 PM. Reason: Adjusted pics to include dual diaphragm.

    '97 Sedan, Cosmos Meconium, Click ME for the build thread.

  3. #3
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    BRAAP excellent info, thanks for posting that.

    It looks like the Merc booster only has two mounting bolts on the firewall side? It that right?

  4. #4
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    Quote Originally Posted by Demon Speed View Post
    ...It looks like the Merc booster only has two mounting bolts on the firewall side? It that right?

    That is correct.

    '97 Sedan, Cosmos Meconium, Click ME for the build thread.

  5. #5
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    Quote Originally Posted by BRAAP View Post
    That is correct.
    Did you weld two additional studs to the booster or just use the two that we there for mounting the booster to the firewall?

  6. #6
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    Just used the 2 studs.
    When I first ran across that I was slightly skeptical of the 2 stud vs 4 stud design, decided to trust it as Merc did since the Merc pedal bracket assy is identical to the BMW in design, side by side are similar visually, (they were clearly very much aware of each others work and design) FWIW I have stood very hard on the pedal a few times, (much harder than I would in panic stop, thats probably what broke my seat back frame), prior to the first drive just to be sure the 2 stud arrangement would be OK, inspected my bracket assy for stress issues at approx 20,000-25,000 miles, all looks fine.

    Here are a few shots of the BMW pedal bracket assay, firewall surface of bracket is 5/16" thick, raised bosses around the booster through-studs adds another 1/16"-1/8" in thickness.




    Last edited by BRAAP; 10-23-2012 at 11:00 PM. Reason: Automerged Doublepost

    '97 Sedan, Cosmos Meconium, Click ME for the build thread.

  7. #7
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    If you look at an E46, the brake booster has two studs, just like the Mercedes booster.

  8. #8
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    This should be a sticky post.

    Excellenty post. Thanks for all the information. This car is primarirly used for track days so that's why I was concerned with the two stud mounting. Also I hope the stiffness of the booster and mounting is at least equivalent or better than stock.

    I'm ordering the booster today.

  9. #9
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    That looks sooooooo clean! Damn it, Mike, sell it!!!!!!!!

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  10. #10
    M5Hunter is offline Still has a E39 Supporting Vendor
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    Good info, added to the conversion sticky thread!

  11. #11
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    Is there a noticeable change in brake pedal feel with the Mercedes booster?

  12. #12
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    I didn't notice a change, then again there was quite long time period between the conversion so my perception of any change could be skewed. Many others have driven the car and the only comments regarding any differences from stock is the additional power. No one has mentioned anything regarding the brakes or pedal efforts, only how refined it is and how it feels, ride,s and drives like stock but lots more torque, everywhere.

    FWIW, my car is a '97 M3 sedan, has a Brembo big brake kit and stock M3 MC. With the brake pads that came with that kit, (previous owner installed), pedal effort was light, felt good. I recently installed "The Brake Man" street compound pads in these brakes and noticed a slight increase in pedal effort from that, nothing that is obnoxious or draws my attention.

    Best friends car is a '98 M3 coupe, bone stock brakes, his pedal does feel lighter than mine, we both agree that in comparison his feels too light and mine feels just right, nice balance between throttle, brake and clutch. Fwiw as avid Autocrossers over the years we both are discerning in a cars feedback to the driver.

    Another aside, in theory the smaller booster should deliver less boost due its reduced surface area the vacuum acts upon, (read higher pedal effort). The valving internally has an effect on the amount of "boost" delivered for a given pressure input as well, I have no idea what that is for the BMW or Merc boosters, sorry, just have dealt with differences in the how reactions disc responds with more less aggressive "boost" in the old Datsun Z cars, just throwing it out there.
    Also, the LSx with stock cam is going to develop more vacuum, (lower MAP), at idle vs the 4 valve BMW engine it replaces which will produce more "boost" from the booster as well. Adding a large cam typically reduces idle vacuum and one side effect is reduced brake booster "boost".

    Hopefully that doesn't muddy the waters too much more than they already are. In short, if the smaller booster does increase pedal effort, it's sublet enough that it doesn't stand out to me or the others that have driven my car with the smaller Merc booster.

    '97 Sedan, Cosmos Meconium, Click ME for the build thread.

  13. #13
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    Quote Originally Posted by Wideopentuning View Post
    Is there a noticeable change in brake pedal feel with the Mercedes booster?
    I wanted Braap to use the dual diaphragm booster, but he fell in love with the single diaphragm booster. Less weight, and a cleaner looking installation.
    Since he had an M3, which has larger brakes than the standard E36, his pedal effort is reasonable.
    I have concerns that if the small Mercedes booster was used in a non-M3 E36, the pedal effort would be significantly greater.

    The BMW 5 series dual diaphragm booster is similar to the Mercedes dual diaphragm booster. I believe the same booster is used in the E46 M3. The primary difference between the BMW and Mercedes dual diaphragm booster is the vacuum fitting.

  14. #14
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    Quote Originally Posted by MikeJTR View Post
    I wanted Braap to use the dual diaphragm booster, but he fell in love with the single diaphragm booster. Less weight, and a cleaner looking installation...
    True enough, mocked up both the Merc Dual and single diaphragm, Mike wanted me to run the dual, begin stubborn I went with the single.

    I updated a couple of the above pics to also include the Merc Dual pictured next to the Merc single and BMW.
    Here are a few shots of the Merc dual diaphragm booster mocked up in my car during that phase of the conversion.

    For those with the X6031 connector, you will want to move that connector as the dual diaphragm places the M/C forward enough creating a clearance issue with the clutch reservoir line. Not a big deal, some cars don't have this connector, those that do can move the connector.





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  15. #15
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    Quote Originally Posted by BRAAP View Post
    I didn't notice a change, then again there was quite long time period between the conversion so my perception of any change could be skewed. Many others have driven the car and the only comments regarding any differences from stock is the additional power. No one has mentioned anything regarding the brakes or pedal efforts, only how refined it is and how it feels, ride,s and drives like stock but lots more torque, everywhere.

    FWIW, my car is a '97 M3 sedan, has a Brembo big brake kit and stock M3 MC. With the brake pads that came with that kit, (previous owner installed), pedal effort was light, felt good. I recently installed "The Brake Man" street compound pads in these brakes and noticed a slight increase in pedal effort from that, nothing that is obnoxious or draws my attention.

    Best friends car is a '98 M3 coupe, bone stock brakes, his pedal does feel lighter than mine, we both agree that in comparison his feels too light and mine feels just right, nice balance between throttle, brake and clutch. Fwiw as avid Autocrossers over the years we both are discerning in a cars feedback to the driver.

    Another aside, in theory the smaller booster should deliver less boost due its reduced surface area the vacuum acts upon, (read higher pedal effort). The valving internally has an effect on the amount of "boost" delivered for a given pressure input as well, I have no idea what that is for the BMW or Merc boosters, sorry, just have dealt with differences in the how reactions disc responds with more less aggressive "boost" in the old Datsun Z cars, just throwing it out there.
    Also, the LSx with stock cam is going to develop more vacuum, (lower MAP), at idle vs the 4 valve BMW engine it replaces which will produce more "boost" from the booster as well. Adding a large cam typically reduces idle vacuum and one side effect is reduced brake booster "boost".

    Hopefully that doesn't muddy the waters too much more than they already are. In short, if the smaller booster does increase pedal effort, it's sublet enough that it doesn't stand out to me or the others that have driven my car with the smaller Merc booster.
    Very good infor from both BRAAP and JTR. Would you happen to have a part number or Year/Model etc that the dual diaphram Merc booster is off of?

    I just got in the Merc 85' 190D booster yesterday. I haven't installed it yet.

    My car has a StopTech 4 piston kit up front with stock calipers in the rear. I run PFC06' all around.

    The new engine in the car is 6.0 LS2 with cam duration 242/248 110LSA. (similar to "TREX"). So it will be interesting to see if I have a vacuum/brake boost issue. This is why I'm interested the dual diaphram booster too.

  16. #16
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    Quote Originally Posted by MikeJTR View Post
    I have concerns that if the small Mercedes booster was used in a non-M3 E36, the pedal effort would be significantly greater.
    Has anyone with non-M3 brakes used this booster? Any feedback of pedal effort?

    I'm not really sure what I'm looking at (in the above photo) with regard to relocating ABS travel sensor. What exactly is involved?

    What Mercedes vehicle(s) are viable donors for these boosters?

    Tipsy

  17. #17
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    Quote Originally Posted by TipsyMcStagger View Post
    Has anyone with non-M3 brakes used this booster? Any feedback of pedal effort?
    ...
    Tipsy
    Percentage of increase should be same. The difference is small enough that if you haven't driven your car for say a 6 months cause you were giving it an LSx infusion, you may not even notice.


    Quote Originally Posted by TipsyMcStagger View Post
    ...
    I'm not really sure what I'm looking at (in the above photo) with regard to relocating ABS travel sensor. What exactly is involved?
    Tipsy
    A= Bracket and pivoting clamp that captures the ABS travel sensor, bolted to the brake pedal arm.
    B= Pocket that seats the ABS travel sensor piston rod.
    C= ABS Travel sensor itself.




    Quote Originally Posted by TipsyMcStagger View Post
    ...
    What Mercedes vehicle(s) are viable donors for these boosters?
    Tipsy
    Mercedes 190E Diesels have the smaller steel booster which I prefer, the aluminum version can be found in other various 190E models, haven't been able to narrow down a pattern as to which cars came with what other than Diesel had the small steel version.

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  18. #18
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    How much "clearancing" can be done to the stock BMW brake booster without compromising its function? I am running into substantial clearance issues with the stock unit w/ Vorshlag motor mounts

  19. #19
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    Quote Originally Posted by sivart173 View Post
    How much "clearancing" can be done to the stock BMW brake booster without compromising its function? I am running into substantial clearance issues with the stock unit w/ Vorshlag motor mounts
    Are you running tall valve covers? Have you spoken with Vorshlag?

    I'm pretty sure I've read that keeping the frame mounts a little loose while installing the engine can help to align things properly, but I have no first hand experience (yet).

    Tipsy
    Last edited by TipsyMcStagger; 10-21-2013 at 10:02 AM.

  20. #20
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    Does anyone offer an ABS sensor reloction kit to buy or have measurements to make the bracket? Im running into some serious issues trying to clear the booster with my intake so the 190 booster looks promising

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  21. #21
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    Bumping this up. Apparently JTR had been working on a pedal travel sensor relocation kit to compliment swapping on a smaller booster. I sent them an email inquiring about it fairly recently but never got a response.

    Anyone know what the story is, if that made it into production? Trying to weigh my options whether I want to go with a smaller booster or just shift the entire pedal assembly slightly.

  22. #22
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    Why do you need to move the pedal assembley over? Are you using their kit?
    - 96 328is 6.0L. (LS1 to LS2 build thread: http://forums.bimmerforums.com/forum...ad.php?2098938)
    - 96 328is 5.7L. (LS1 build thread: http://forums.bimmerforums.com/forum....php?t=1289987)
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  23. #23
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    thread is a few years old, any consensus on the best "smaller" brake booster? A part number would be great! Not sure if I will even need it for my build but would like to be prepared

  24. #24
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    I have the 85' Mercedes 190D booster installed. It required opening up the center hole on a lathe to fit the master. It also requires relocating the brake travel switch to the pedal. The pedal effort is noticeable higher. It would be nice if can find the boost factor value for each booster then you would know the difference in the pedal effort.

    If I didn't have to run tall valve covers I would have kept running the stock booster.

    Sent from my SCH-I545 using Tapatalk

  25. #25
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    I know this thread is very old but I’m wondering if anyone has access to the jtr kit for the pedal travel sensor relocation. I have a hydroboost setup for my ls swap and I am set on retaining the original abs functionality. Thanks!

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