348 - Rear brake valve and regulator.. what they do? | FerrariChat
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348 Rear brake valve and regulator.. what they do?

Discussion in '348/355' started by luckydynes, Jul 1, 2023.

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  1. luckydynes

    luckydynes F1 Rookie

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    #1 luckydynes, Jul 1, 2023
    Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Hello,

    I’m installing a wilwood adjustable brake bias. Attached are the graphs of how it controls rear brake pressure. Anyone know what these two devices do in the existing brake hydraulic circuit?

    The reason I’m doing this is I have no rear abs sensors and the rears are locking under hard braking. I don’t really want to play with brake compounds.. luv having knobs to mess with (that sounds bad but u get my drift :)).

    Thanks for any info!
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  2. luckydynes

    luckydynes F1 Rookie

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    #2 luckydynes, Jul 1, 2023
  3. m.stojanovic

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    #3 m.stojanovic, Jul 1, 2023
  4. m.stojanovic

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    #4 m.stojanovic, Jul 2, 2023
    Looks like you would need to set the Wilwood proportioning valve at "notch 1 / fully out" to have similar ratio of 50% of the input pressure acting on the rear brakes. However, the start of proportioning will, at this setting, be at 150 psi which is considerably earlier than the 360 psi (25 bar) of the 348's original proportioning valve.

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  5. luckydynes

    luckydynes F1 Rookie

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    #5 luckydynes, Jul 2, 2023
    Thank you! Priceless info in the thread you referenced and you already crunched the numbers.

    Sounds like the new valve I’m thinking of installing will not have the “delay” function that the “hexagonal” part creates.

    On the proportioning side I read a great description of the valve acting as a sort of a master cylinder “resize”. As you’ve concluded, to get the same 50% overall brake pressure reduction I’ll need to be all the way out. Seems the relative piston diameters in the device create the slope of the curve.

    This is such great info.. the other thing I may consider is keeping the stock unit and adding this device in series. I’m not sure if graphing the characteristics of the Ferrari valve will help further understand the net effect… having two valves in series doesn’t seem like a good system but if it helps without going to a new pedal box for now that is the goal…. thank you for sharing this excellent info!
     
  6. luckydynes

    luckydynes F1 Rookie

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    #6 luckydynes, Jul 2, 2023
    There was a graph in the manual so I inputted and converted to psi. Thanks again for mentioning this info is in the manual. A buddy helping me suggested we put pressure gauges on the calipers and check it’s doing what it’s supposed to be doing before worrying about changing things… great advice I think.
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  7. m.stojanovic

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    #7 m.stojanovic, Jul 5, 2023
    The hexagonal "Delay Valve" seems to be integral part of the Teves system, required to compensate for its operation where the "boost" fluid pressure is applied to the master piston for the front brakes and applied directly to the rear brakes. I believe it is there to prevent locking of the rear brakes in certain circumstances. In the case of Teves on Jaguars, the hexagonal thing (same as the 348's one, 8.5) is just below the MC:

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    It is probably better to keep the hexagonal thing and experiment with replacing only the existing Proportioning Valve (cylindrical thing, 5!25) with an aftermarket one.
     

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