PSD hose now available
#1
The Parts Whisperer
Rennlist
Site Sponsor
Rennlist
Site Sponsor
Thread Starter
PSD hose now available
We are now offering a PSD replacement hose made by Greg Brown. The system works at a very high pressures and nearly 20 year old hoses may be doing some swelling by now.
http://www.mailordercentral.com/928i...944 355 081 01
http://www.mailordercentral.com/928i...944 355 081 01
Last edited by Mark Anderson; 12-13-2012 at 08:23 PM.
#4
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
#7
Rennlist
Basic Site Sponsor
Basic Site Sponsor
The PSD system works from pressure sent from a pump/reservour to a slave cylinder, which pushes on the "fork" which increases the "limited slip" action of the differential. After initial activation, the system continues to "look" at the percentage of slip and continues to "adjust" the pressure until the "speed differential" of the rear tires is within design specs.
The faster the system responds, the better the system works. Having a "spongy" rubber hose in the system is actually a very bad idea...especially as the hose ages. These hoses get so soft and "balloon like" that many times the required pressure to control the speed differential of the two rear tires is not achieved until the vehicle is actually all the way past the corner that caused the system to activate. The time from "zero lock" to "required lock" gets so long (in terms of time) that the differentials slip way too much and the oil turns black very quickly, due to slippage.
The PSD system is a very, very clever engineering marvel. It is a very high quality system, which when working properly, is one of the better ideas that came from Porsche. However, it is extremely overlooked and generally works very poorly. Many systems haven't had the fluid changed in years. Many are so filled with "old dirty fluid" that the filter in the reservour is completely clogged. We found that changing the fluid, installing a new filter, and bleeding the system isn't satisfactory, in most cases. Getting rid of the "expansion" of this hose can reduce "lock" time by over 50%...and that makes the vehicles faster, safer, and more fun to drive, through corners.
__________________
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
Trending Topics
#8
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
#11
Archive Gatekeeper
Rennlist Member
Rennlist Member
How do you know if the PSD is functioning properly?
#12
Rennlist
Basic Site Sponsor
Basic Site Sponsor
#13
Rennlist Member
Join Date: Jul 2002
Location: Deep in the Heart of Texas!
Posts: 3,267
Likes: 0
Received 5 Likes
on
4 Posts
Good explanation Greg, thanks. Now, out of curiousity, where does the hose go exactly ... I'm thinking the hard line goes all the way to the slave on top of the diff, so hoping the hose isn't buried so far up underneath something that you have to take the whole car apart to change it !
#14
Archive Gatekeeper
Rennlist Member
Rennlist Member
Tom-
Here's a shot of the flex hose , it connects to a check valve that sits inside that half box-y bracket on the left rear of the diff. ('Scuse the filth, this is the GTS when I got it. Note the rust milkshake dripping from the line...) It bascially goes between the hardline from the pump and the hardline around the top rear of the diff:
You can sorta see the hardline from the pump, dangling in front of the battery box heatshield- it is normally bolted to the floor of the rear deck in a its little 'U' bracket:
Here's a shot of the flex hose , it connects to a check valve that sits inside that half box-y bracket on the left rear of the diff. ('Scuse the filth, this is the GTS when I got it. Note the rust milkshake dripping from the line...) It bascially goes between the hardline from the pump and the hardline around the top rear of the diff:
You can sorta see the hardline from the pump, dangling in front of the battery box heatshield- it is normally bolted to the floor of the rear deck in a its little 'U' bracket: