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993 brake booster tuning

 
Old 12-12-2018, 01:51 PM
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Sirenty
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Default 993 brake booster tuning

I recently upgraded to 993tt front / 993 rear calipers along with the 993 MC and booster. We also cleaned out the proportioning valve.

Everything feels great except we think the brakes are being slightly over-boosted. There's a very small bit of sponginess to them when boost is on. When we turn off boost, the pedal is rock hard, so we don't think there is any air remaining.

For others that have done the conversion, did you do anything to modulate the amount of vacuum to the booster, or do any other tweaks to reduce boost pressure and get brake pedal feel more like stock 964?
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Old 12-12-2018, 07:13 PM
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Spyerx
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I don’t notice this at all. Pedal feel is same regardless. Sure you got all air out? Bleed abs?
i had some inconsistent feel until i activated abs while bleeding
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Old 12-12-2018, 07:14 PM
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Bill Verburg
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Originally Posted by Spyerx View Post
I donít notice this at all. Pedal feel is same regardless. Sure you got all air out? Bleed abs?
i had some inconsistent feel until i activated abs while bleeding
Different calipers will respond differently
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Old 12-12-2018, 07:16 PM
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Originally Posted by Sirenty View Post
I recently upgraded to 993tt front / 993 rear calipers along with the 993 MC and booster. We also cleaned out the proportioning valve.

Everything feels great except we think the brakes are being slightly over-boosted. There's a very small bit of sponginess to them when boost is on. When we turn off boost, the pedal is rock hard, so we don't think there is any air remaining.

For others that have done the conversion, did you do anything to modulate the amount of vacuum to the booster, or do any other tweaks to reduce boost pressure and get brake pedal feel more like stock 964?
That's why a 25.4mm m/c is so desirable, but extremely difficult to implement

I've never tried too fiddle w/ the vacuum supply, that may help, but the basic issue is that while the 23.8mm m/c is in the acceptable range it is on the wrong end for performance purposes
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Old 01-06-2019, 04:32 PM
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tjb616
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Sirenty, did you ever figure this out? I'm about to tackle the same project.
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Old 01-06-2019, 09:03 PM
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Sirenty
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Not to my satisfaction. I’m starting to think there is still air in the system, or the shop screwed something up, which I won’t discount after other issues I had.

What confuses me me is I read old posts like this from Bill and it says the stock 964 is long and soft, and it sounds like the 993 upgrade should be less so even if not optimally sized. However, my stock brakes were high and tight (and felt awesome) and the conversion is long and soft. Opposite of what I would expect. I’m going to take it to the shop that worked on Paddy’s car when I have the RS shifter and golden rod done and see what they say.

i would’ve kept the the stock brakes, but even in current form, the big reds are much better on the track.

FYI, I had to upgrade the booster linkage housing to a 993 as well. The 993 booster would not fit in my stock housing.
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Old 01-09-2019, 08:48 PM
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Originally Posted by Sirenty View Post
Not to my satisfaction. Iím starting to think there is still air in the system, or the shop screwed something up, which I wonít discount after other issues I had.

What confuses me me is I read old posts like this from Bill and it says the stock 964 is long and soft, and it sounds like the 993 upgrade should be less so even if not optimally sized. However, my stock brakes were high and tight (and felt awesome) and the conversion is long and soft. Opposite of what I would expect. Iím going to take it to the shop that worked on Paddyís car when I have the RS shifter and golden rod done and see what they say.

i wouldíve kept the the stock brakes, but even in current form, the big reds are much better on the track.

FYI, I had to upgrade the booster linkage housing to a 993 as well. The 993 booster would not fit in my stock housing.
Hello

You could drive my 964 Turbo to see if there is a difference in the pedal feel, call me and we can plan a time time come by.

​​​​​​​Helio
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Old 01-09-2019, 11:01 PM
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Sirenty
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Thanks, Helio. I’d never turn down an offer to drive a Turbo, but isn’t your booster hydraulic and MC larger? I’m not sure it would be comparable.

Regardless, I’ll be in touch once the weather clears. Looking nasty this weekend.
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Old 01-12-2019, 01:54 AM
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Originally Posted by Sirenty View Post
Thanks, Helio. Iíd never turn down an offer to drive a Turbo, but isnít your booster hydraulic and MC larger? Iím not sure it would be comparable.

Regardless, Iíll be in touch once the weather clears. Looking nasty this weekend.
I need to do some research, What parts did you use ?

Call or text me some time
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