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  • JehTehsus
    replied
    Ok, I have tried actually putting together a calculator for comparison purposes.

    Running the numbers like this it does seem obvious there is an issue... in fact, I am kinda hoping I am buggering up my math. But I think originally I was assuming that at 70lbs pedal force, both MCs would be seeing 70lbs, whereas in reality they only see 35 (with 50/50 balance).

    Essentially, stock brakes with vacuum assist (and ignoring proportioning valve), I am getting roughly 4500lbs at each front caliper pad and 2000 at each rear caliper pad, for a total of 13000lbs. Realistically it will probably a little higher because the proportioning valve will introduce a pressure imbalance, and high front caliper pressure but lower rear caliper pressure will equal more overall caliper grip force in lbs due to larger area of front pistons. That being said, rotor diameter, weight transfer, grip etc. all come into play so these numbers are for reference comparison only.

    Now, if I run the exact same calculations with dual masters @50/50 balance, 0.75" bore, 70lbs of human effort and a 6.9 pedal ratio... I get 1515lbs for each front caliper and 675 for each rear, i.e. ~4400lbs total, or basically 30% braking force at the rotors for equivalent human effort. Sweeeeeet.

    What really sucks, is if I run the same numbers but with 0.625" MCs front and rear, and a 50% front bias, I am getting still only around half the equivalent force of the stock setup. Bringing pedal force up to 140lbs brings me into the right neighborhood, but I am not sure I am comfortable with that kind of effort repeatedly. Certainly with 0.75's front and rear I would need to be putting 200lb on the pedal. Yes, I can do a one legged squat of my 200lb fat ass, but I am sure as hell not doing that all day.

    Now, all this goes out the window once you start moving to larger calipers. With something closer to 3.5sq inch front caliper area (say, 1.5" bore dual piston wilwoods), at 70lbs pedal force and 50% bias you see 2780lbs at the calipers. If you are also running larger diameter rotors I would not be at all surprised if this translates into a really good brake feel.

    Anyway if someone wants to check my math so I can throw all those numbers out, that would be wonderful:

    https://docs.google.com/spreadsheets...it?usp=sharing

    Leave a comment:


  • JehTehsus
    replied
    Originally posted by digger View Post

    you could estimate the assist assuming the diaphragm is 10" OD and 5" ID

    Pressure x area

    7.5 psi x pi/4*(10^2-5^2) = 440 lbf (1,960 N)

    equivalent to 110 lb at pedal with 4:1

    not sure what the internal spring stiffness is this counteracts the assist




    So taking those numbers I am getting ~1000psi pressure from the stock E30 master cylinder @70lb human effort. Which is what I thought originally (used 400lbs for the booster in my estimates when selecting cylinders). I wonder then if the issue is the fact that there are now two masters, even though they are now split across the front and rear? I will take a look at the actual leverage ratios all the way to the disk using whodwhos numbers above and see what it works out too.

    I wonder if there is a comfortable set point with the stock brakes. A 0.625 and 0.7 already seem pretty small.

    Leave a comment:


  • digger
    replied
    Originally posted by JehTehsus View Post

    Do you have any idea what sort of assist the E30 brake booster provides? It would be great if I had something more definite for comparisons, random googling yields boosters providing anywhere from 400-1000+ pounds of assistance. I suppose we could try and calculate based on diameter and vacuum pressure, but I am far from an expert on whether there is more to it than that or not.
    you could estimate the assist assuming the diaphragm is 10" OD and 5" ID

    Pressure x area

    7.5 psi x pi/4*(10^2-5^2) = 440 lbf (1,960 N)

    equivalent to 110 lb at pedal with 4:1

    not sure what the internal spring stiffness is this counteracts the assist





    Leave a comment:


  • JehTehsus
    replied
    Originally posted by whodwho View Post

    Not sure on the fluid vs mechanical advantage, both will cost travel for advantage but not sure on the % each

    From notes (not 100% sure on accuracy of MC and Caliper bores)



    E30 48/33 Caliper
    E30 M3 23mm MC 54/38mm Caliper
    328 23.81/22.20? MC 54/38mm Caliper
    E36 Ti 23.81/20.64 MC 54/34 Caliper
    E36 54/36mm front to rear ratio of 2.25:1
    E36 M3 25.40/20.64 MC 60/40mm Caliper front to rear ratio of 2.25:1
    E46 330 23.81/22.20 MC 57/44 Caliper
    Do you have any idea what sort of assist the E30 brake booster provides? It would be great if I had something more definite for comparisons, random googling yields boosters providing anywhere from 400-1000+ pounds of assistance. I suppose we could try and calculate based on diameter and vacuum pressure, but I am far from an expert on whether there is more to it than that or not.

    Leave a comment:


  • whodwho
    replied
    Originally posted by digger View Post

    thanks for the clarification, so here's a dumb question is changing the effective pedal ratio equivalent to changing the bore size (assuming the % change was equal) or does one avenue provide more force advantage with less additional travel in the real world? my concern over the 5/8 was the pedal travel and it was suggested that 3/4" with 7:1 would be a decent baseline if the pressure limit valve was deleted.

    Do you know what size pistons are stock FR and RR stock and the M3 FR you have? numbers i found are 48.0 mm & 33.0 mm for stock but not sure.

    based on my calcs the stock pedal box ratio is ~4:1 and the Lee's linkage is 1.7:1 and 1.5:1 which gives the 6:1 and 7:1 settings. Sound about right? i figure maybe i should do some actual calculations before installing
    Not sure on the fluid vs mechanical advantage, both will cost travel for advantage but not sure on the % each

    From notes (not 100% sure on accuracy of MC and Caliper bores)

    Originally posted by Lee
    The lever in the twin MC booster delete kit (pedal box) has two positions. The mounting point closer to the 1" balance bar multiplies the original pedal ratio by 1.52 while the mounting point further away has a multiplier of 1.73

    On an e30 with the original pedal ratio being 4:1, it translates into either 6.1 :1 or 6.9:1
    On an e36 with the original pedal ratio being 4.3:1, it translates into either 6.4 :1 or 7.2:1
    On an e46 with the original pedal ratio being 3.8:1, it translates into either 5.7 :1 or 6.5:1
    Most racing pedal boxes you get from AP, Tilton, Wilwood etc have a pedal ratio of around 6:1

    19mm MCs (3/4") is a baseline when using calipers with a single Ø60mm piston or multiple 1.625" pistons
    E30 48/33 Caliper
    E30 M3 23mm MC 54/38mm Caliper
    328 23.81/22.20? MC 54/38mm Caliper
    E36 Ti 23.81/20.64 MC 54/34 Caliper
    E36 54/36mm front to rear ratio of 2.25:1
    E36 M3 25.40/20.64 MC 60/40mm Caliper front to rear ratio of 2.25:1
    E46 330 23.81/22.20 MC 57/44 Caliper

    Leave a comment:


  • JehTehsus
    replied
    Originally posted by mikey.antonakakis View Post
    FWIW, my Nuke cam gear is pretty much dead on to the cam specs (Enem Z45 turbo) when the "zero" marks are lined up.
    I don't expect to have any issues, but doing a fairly quick and rough cam profile isn't too much work so I figure I may as well check.

    Leave a comment:


  • mikey.antonakakis
    replied
    FWIW, my Nuke cam gear is pretty much dead on to the cam specs (Enem Z45 turbo) when the "zero" marks are lined up.

    Leave a comment:


  • digger
    replied
    Originally posted by whodwho View Post

    Sorry that is a bit confusing, I was running behind and a little too quick to reply. 8^(

    I meant bigger size in general, without a lot of mechanical advantage the pedal is too hard and no modulation. Even with the max leverage setting on this bracket (7:1) it was still not good for me with the .700 and .625 MCs and the stock calipers. When I went to the M3 brakes the fluid ratio of those MCs and the M3 calipers made it usable again. I ended up using a .750 and .625
    thanks for the clarification, so here's a dumb question is changing the effective pedal ratio equivalent to changing the bore size (assuming the % change was equal) or does one avenue provide more force advantage with less additional travel in the real world? my concern over the 5/8 was the pedal travel and it was suggested that 3/4" with 7:1 would be a decent baseline if the pressure limit valve was deleted.

    Do you know what size pistons are stock FR and RR stock and the M3 FR you have? numbers i found are 48.0 mm & 33.0 mm for stock but not sure.

    based on my calcs the stock pedal box ratio is ~4:1 and the Lee's linkage is 1.7:1 and 1.5:1 which gives the 6:1 and 7:1 settings. Sound about right? i figure maybe i should do some actual calculations before installing

    Leave a comment:


  • JehTehsus
    replied
    Originally posted by digger View Post
    is the input fitting to the rail a sharp angle bend like the one coming out to the FPR or a radius one?

    I knew the cast log manifold was good for something.....
    I have another 90 degree swivel fitting I am putting on the feeder end of the fuel rail. It is going to point towards where the brake booster currently is. The plan is to mount the flex fuel sensor below the brake master cylinders, of course sensor is not very big so I have a Y splitter that takes the 8-AN fuel lines down to two 6-AN, one of which goes through the flex fuel sensor and the other as a bypass. Then another Y fitting, and 8-AN hose to the fuel rail right angle fitting. All of this is fed by the fuel filter, which is just a bit after the hardline adapters. Return line is going to be running directly from the bottom of that FPR back to the hardlines.

    *edit: Wanted to note, if you are thinking fuel pressure drop due to the 90 degree bends is a major concern, I think because of the size of the 8-AN fittings I am seeing very minimal loss... I was just using an online calculator to check though (https://www.gates.com/us/en/knowledg...alculator.html) but it makes sense with my understanding, where smaller lines are much more sensitive to bends than larger lines. That said, I understand the fuel has momentum and it does not want to change direction, which certainly makes mounting my FPR directly after a 90 less than ideal, but at this point I am somewhat boned on where to put it. As LowR3vin noted, it is a bit of a piglet.

    I could mount it on the other end of the rail (*maybe, there is not much more room there), but I would have to flip the feeder end around. That said I don't expect I will see issues; if I do I can certainly move it at that point and cut a couple new hoses.
    Last edited by JehTehsus; 05-25-2020, 08:43 AM.

    Leave a comment:


  • digger
    replied
    is the input fitting to the rail a sharp angle bend like the one coming out to the FPR or a radius one?

    I knew the cast log manifold was good for something.....

    Leave a comment:


  • LowR3V'in
    replied
    daym that fpr is cartoony big.

    Leave a comment:


  • JehTehsus
    replied
    Mostly stuck working on the chicken coop this weekend, but I did manage to rough out a fuel pressure regulator mounting bracket and get the coils all mounted. Coil mounting panel still needs a few adjustments (probably going to bolt on a strap to keep it under tension, right now it will likely 'flap' a bit which I obviously don't want. Also need to redo the plate-to-engine bay mounting holes, I need it about an inch further back).

    I also almost managed to get to degreeing my cam... feel like every time I get started something comes up. Soon. Catch can also arrived, so I am at the point now where I need to pull the booster, get the Massive pedal kit in, then mount the E85 sensor, fuel filter, catch can (going to try and plumb both coolant overflow and valve cover vent to this), new power steering fluid reservoir, and somewhere to stick some relays. Will also need to get the electric fan mounted and then go through the joys of measuring, cutting and getting connectors on the fuel lines.

    Finally, need to figure out a solution for a few last little bits. Primarily running AN-4 for all my vacuum lines (hopefully less of a pain in the ass at 30PSI) and I need to get some BSPP 'G' fitting to AN adapters, as well as a couple of bosch M10x1.5 to AN adapters. Of course I found a company in Australia that has literally everything I need, and at a great price to boot, but they are only shipping stateside at the moment due to the pandemic, so I will likely need to figure out a US-to-Canada mail forwarding setup of some sort. Also need a couple electrical connectors, but digilkey has me covered there.

    Fuel pressure reg with a rough bracket I put together (still needs some cleanup and paint). I suck at bending metal, maybe because I just have a bench vise, but overall could have been a lot worse:

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    I am almost completely happy with how coil packs turned out. Once again, using a vise and angle grinder to cut steel is not a core component of my skillset, but for now it looks okish enough I can live with it:

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    I came so close to actually degreeing the cam today... friggen chickens. Probably a waste of time at this point, but I figure it is a good exercise to do regardless.

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    Attached Files

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  • whodwho
    replied
    Originally posted by digger View Post

    i'm confused the stocks MC is 0.875/0.690 so which bigger size ones didnt you like?
    what did you settle on?
    Sorry that is a bit confusing, I was running behind and a little too quick to reply. 8^(

    I meant bigger size in general, without a lot of mechanical advantage the pedal is too hard and no modulation. Even with the max leverage setting on this bracket (7:1) it was still not good for me with the .700 and .625 MCs and the stock calipers. When I went to the M3 brakes the fluid ratio of those MCs and the M3 calipers made it usable again. I ended up using a .750 and .625
    Last edited by whodwho; 05-23-2020, 07:29 AM.

    Leave a comment:


  • JehTehsus
    replied
    I ended up picking a 0.75 for the fronts and 0.625 for the rears - they actually just arrived today. I think I probably went to big on the fronts, looking over it again.

    Also, quick build update before dinner:

    Plan B for fuel pressure regulator will work well I think. Going to cut and fab up a little bracket to mount to that stud on the IM this weekend.





    Throttle body modifications are not quite there yet. I am pretty much perfectly happy with how the intake air temp sensor worked out (little copper tube with protective heatshrink boot on the tip). Ended up tapping throttle body for 4-AN and getting a 4-AN smooth hex plug, which I then tapped to 1/16NPT. I know the o-ring is visible in that picture, I am actually relying on red loctite to make the seal. The IAT itself will be sealed into the 1/16 NPT with blue loctite. Came out as well as it could have, not perfectly straight but I don't have a drill press.

    The right angle 4-AN to 6-AN fitting is too big by a friggen hair, which figures. Need to find a different 4-AN fitting I suppose, but not the end of the world. That fitting will be providing manifold vacuum/pressure reference to the vacuum station, which will feed the MAP sensor and probably get tied into some turbo goodies later on down the road.



    And yes, I know throttle plate screws are missing.

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    These are the sensors: 2 combination pressure/temperature and the air intake temp/ IAT shown above. The PTS's will be going on oil and coolant respectively, another is already present on the fuel rail.

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  • digger
    replied
    Originally posted by whodwho View Post
    The fluid ratio of the stock brakes and bigger masters made for a very hard pedal with minimal travel. It probably would be ok for a track car but on the street I was not very comfortable with it especially if I needed to panic stop.

    Looks like many the pics are down today, hopefully they were working when you viewed that thread? Photobucket sucks with their bandwidth limitations, I will have to recreate the thread here with re-hosted pics.
    i'm confused the stocks MC is 0.875/0.690 so which bigger size ones didnt you like?
    what did you settle on?

    Leave a comment:

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