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So maybe this is a dumb question, and if it is, forgive me. I'm getting ready to do brake lines and the GT3 MC on my 03 C2 w/o PSM. It sounds like I shouldn't have issues with lights etc., but my concern is the bleeding process. Will I be able to bleed the brakes with my pressure bleeder like normal after this, or will I have to track down someone with PIWIS or Durametric to enter some kind of bleed mode for the ABS pump, etc?
Undo the lines at the MC and plug them to make sure the ABS hydraulic unit doesn't lose the brake fluid inside it, then standard bleeding will work (as in no necessity to switch any valves inside the ABS or run the ABS pump to bleed the system).
If you enlarge the master piston diameter, the pressure is reduced and causes you to have to push harder for the same friction right? Why would you do this?
And sure the pedal would travel less and have a solid feel
If you enlarge the master piston diameter, the pressure is reduced and causes you to have to push harder for the same friction right? Why would you do this?
And sure the pedal would travel less and have a solid feel
1. A firmer pedal is more confidence inspiring at the height of braking demand (for me)
2. A firmer pedal that may degrade some over hard use provides better feedback of the drop off that is occurring (for me)
3. A firmer pedal allows a finer degree of modulation under hard use when inputs are generally stronger (for me)
Going to the GT3 master is right up there with the best modifications I have made for track use.
Found the difference between GT3 and PSM Master Cylinder
In case anyone still follows this, the difference is additional flow restriction in the flow path to the reservoir in the plunger in the PSM MC. The flow restriction has some spring and needle valve in it and it restricts flow significantly compared to the GT3 (I can blow in each.) For info i destructively removed the valve. See below, GT3 on top. No way to swap parts, they are all punched and pressed on. This is why the Flewis solution works, but it has the downside of restricting flow going out of the MC to the front brakes also.
Last edited by drclaw09; 06-30-2024 at 03:02 PM.
Reason: More info
In case anyone still follows this, the difference is additional flow restriction in the flow path to the reservoir in the plunger in the PSM MC. The flow restriction has some spring and needle valve in it and it restricts flow significantly compared to the GT3 (I can blow in each.) For info i destructively removed the valve. See below, GT3 on top. No way to swap parts, they are all punched and pressed on. This is why the Flewis solution works, but it has the downside of restricting flow going out of the MC to the front brakes also.
How is putting a proportioning valve on the secondary circuit restricting flow going to the front brakes? My proportioning valve is set to full flow.
Edit: Maybe I am wrong but I thought with PSM the secondary circuit is being used for that. And that it was applied to all four wheels.
How is putting a proportioning valve on the secondary circuit restricting flow going to the front brakes? My proportioning valve is set to full flow.
The pre-charge pumps into the Front brake circuit. Putting a proportioning valve on the line between it and the MC, even with the valve fully in, still lowers pressure at 1200psi, which is the purpose of a proportioning valve. See graph below from Wilwood. If your valve is fully out, you are severely restricting pressure to front brakes.
Thanks, I believe I had seen this when I put it in about 100 track days ago. I guess I should get around to installing that brake pressure sensor and see what I'm generating. Stock 996 is really a momentum car now so I would be surprised if it's that high under normal laps.
Thanks, I believe I had seen this when I put it in about 100 track days ago. I guess I should get around to installing that brake pressure sensor and see what I'm generating. Stock 996 is really a momentum car now so I would be surprised if it's that high under normal laps.
So the rear brakes are not engaged by the PSM?
PSM operates all four brakes via the Bosch 5.7 ABS unit. The pre-charge pump pressurizes to ~300psi the a) front brake circuit of the MC and because the MC is tandem, the rear circuit also, and the front brake port of the ABS unit. (see graphic below). The precharge pump does this so that PSM can work without any braking from the mush bag in the front seat and still have an effect.
01-18-2023, 09:02 PM
