993 brake booster tuning
12-12-2018, 12:51 PM
#1
Rennlist Member
Thread Starter
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?
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?
12-12-2018, 06:13 PM
#2
Rennlist Member
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
i had some inconsistent feel until i activated abs while bleeding
12-12-2018, 06:14 PM
#3
12-12-2018, 06:16 PM
#4
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?
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?
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
01-06-2019, 08:03 PM
#6
Rennlist Member
Thread Starter
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.
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.
01-09-2019, 07:48 PM
#7
Rennlist Member
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.
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.
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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01-09-2019, 10:01 PM
#8
Rennlist Member
Thread Starter
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.
Regardless, I’ll be in touch once the weather clears. Looking nasty this weekend.
01-12-2019, 12:54 AM
#9
Rennlist Member
Call or text me some time