RyanPerrella

No 928 has any form of traction control. They have an electronic rear Diff, called PSD, but thats by no means a traction control or stability control system.

docmirror

Tomay to, Tomah to. You decide by the definition from Porsche(including the tortured grammar):

"PSD is an aid to driving off on road surfaces with varying degrees of traction and serves to improve the driving stability when cornering with high lateral acceleration .

Acceleration out of corners The PSD cuts in over the entire speed range whenever the control unit recieves a high lateral acceleration signal when accelerating our of corners and the inside wheel shows signs of slipping .

The PSD(sic) lock transmits the non-transferable driving force of the inside wheel to the outside wheel.

Deceleration in corners If the control unit recieves a high lateral acceleration signal at speeds over 60km/h a limited slip torque is also built up when decelerating in corners to counteract any slewing of the vehicle."

The system uses individual wheel speed sensors, vehicle sensors, engine speed sensors, and two rate-motion G meters to determine velocity and direction. a central control unit(PSD) decodes all that **** and changes the traction applied to the driving wheels.

If it flys like a duck and it quacks like a duck........

Doc

RyanPerrella

I disagree, a PSD is not a traction control or stability control device in the modern sense of the word. Those devices on anything from Domestic's to Ferrari's use either individual wheel braking, throttle cutting ,or other means to keep a car from getting sideways.

A PSD is an electronic traction device for acceleration. Its not nearly as advanced or as intrusive as modern stability control systems. Its an electronic rear diff, NOT A STABILITY CONTROL SYSTEM TO KEEP A BAD DRIVER ON A BAD ROAD OUT OF TROUBLE.

RyanPerrella

They use yaw sensors, there is no such sensor on the 928. Although the 928 may have a steering angle sensor but I am not sure.

Anyway, the PSD came about in the 1990 model year, for those wondering on its availability, It was standard on all 1990 and post year cars. a traditional mechanical LSD was no longer available.

John Veninger

Your not remembering right........

docmirror

Well, let's go to the source, namely Porsche again and see what they say:

"In spite if this aid to safety, it still remains the responsibility of the driver to adapt his style of driving to the prevailing road and weather conditions, as well as to the current traffic conditions. The higher degree of safety afforded by this system(sic - PSD) must not be regarded as justification for taking greater risks."

Additionally, the 'yaw' sensor that supposedly doesn't exist on your 928 is about 10cm under your butt. The schematic representation is on sheet 9, grid K73, and the discussion, diagnosis and testing of the accelerometer is in the WSM beginning on D39-201. It is shown and clearly labelled on D39-202a

The only correct statement in your post Ryan is that modern traction control uses throttle or engine torque limiters on drive-by-wire sytems. However, traction control has been around for decades before there was any type of power limiting system. One of the first, if not the first was pioneered by Jensen for the model FF. Later, in the early 70s GM got into the game with 'MaxTrac', Toyota, Mercedes, Porsche, Ford, and all the rest of the players had systems through the late 80s, none having any type of power limiting control, all used torque modifiers either at the brake hub, or the differential.

Doc

brutus

I would agree with Ryan that in TODAY"S world when someone says traction control the meaning is it hits the brakes or cuts engine power. Simply transfering the power from the wheel that is spinning or might be about to spin is far less than what people have come to expect. Step on the gas pedal too hard in a wet corner and the PSD the GTS and you all end up in the weeds. Friend's Vette will not even do a burnout until he pushes the button and turns OFF the traction control . Was Porsche trying to make the PSD sound like it was a modern traction control ? I test drove an SRT 8 Hemi and it would just chirp the tires and in a tight corner it would not power oversteer now that is traction control just not as much fun.

zekekid

Great post.... it gives me lots of info to work with on my 1980 16V

6mil928

Best novel I've read in years:-)

Brett928S2

Hi

Good post (that must have been hard work)

You got a fair amount of the Euro stuff wrong though...as an example, my S2 (UK) 1986 (made for 1 year only as the transition model between 16v and 32v ) has the most powerful 16v motor in it (4.7) and its 310 hp with a 2.35 diff (auto) there were also a very few S2 manuals as well. It also had S4 brakes and suspension.

In the UK we never had a 5.0 ltr 16 valve either....

All the best Brett

SharkSkin

Nice post -- I must have missed it first time around.

I have one correction, and a couple of observations that are more subjective.

First off, the change to blade-style fuses happened beginning with the 85.

Secondly, IMHO the 78/79 electrical is a lot easier to troubleshoot than later models, first because it is simpler, second because it's easier to make sense of the wiring diagrams. (the diagrams go to the newer, more confusing style after 83)

Third, IMHO the CIS cars have much better throttle response than all later cars. This is very subjective -- YMMV.

Iwanna928

I am looking to buy a 928 in the next few month's. This was a thread that I read through my searching. Very informative for a newbie! Now I will have to wait and see what come my way!

Stephen

Lopez

Is this really true vs. a '78-79? Because if it is I would like to know what "drivetrain" components I can swap out and save 200 lbs... The registry says they actually gained about 75 lbs. from '79 to '80.

dprantl

Hmm, I've never heard of this. The 16V Euros were lighter, but AFAIK the US models kept steadily rising in weight as more features were added.

If you want the best value 928 that is a great driver and is fast, you want an early 32-valve, '85 US model. Borg-Warner synchros on the 5-speed, over 300lb.ft of torque below 3k RPM stock, and can easily and cheaply be tweaked to 300rwhp. $5k will buy you a nice one these days if you look long enough.

Dan
'91 928GT S/C 475hp/460lb.ft

GRTWHT

Thats a really interesting read on the 928 to a potential buyer of the car.
I'll have to refer to this when I'm out looking for my second car sometime.

Glenn
'81 928
4.5L M28/10 3 Speed Auto 2.73:1
and loving it
Australia.