ANF

Hi guys,

Going through my newish 928 S (1983 ROW) slowly and catching up on maintenance and fixing things as I go.
There is a vacuum line coming out of the distributor that has been blocked off. Firstly should it be connected and if so where to?
I will be replacing all vacuum lines and fuel lines along the way.



Many thanks

Mrmerlin

looks like all of the hoses should be replaced and a new set of ignition wires fitted

SwedeInSiam

The advance side should be plugged on Australian and Swedish M28.11/12 cars as it is on yours but not with a bolt :-)

9two8

That vacuum line goes immediately to the back of the throttle body , Iv'e just replaced every vacuum line on my car with silicone and the difference to the car is amazing, everything associated with vacuum performs so much nicer on the car, just do it ! They will all be rock hard and just snap like a twig, and also be leaking air.

GlenL

Here's a vacuum diagram for the Euro S with CIS. Takes a bit of head scratching itself, but the vacuum lines are all shown.

ANF

Thanks guys. Yes replacing all the vacuum lines is on the list, along with fuel lines and spark plug wires and a bunch of other stuff, catching up on some maintenance takes some time and $$

Cheers

WallyP

Vacuum line on the the outer side of the advance can is advance; line on the inner side is retard.

ANF

Thanks, looks like someone has blocked off the advance line....!

ANF

You are correct SwedeInSiam! 928s to Sweden and Australia had the vacuum advance deactivated for emissions reasons.... not sure what it was for exactly, but wondering now if it could be re-connected for any gain.....

waynestrutt

In that drawing are the bottom vacuum connections at the throttle body on the filter side of the throttle body and the top single vacuum line on the engine side of the throttle body?

Dave928S

The advance was plugged on Oz cars because petrol at the time (Super which was 96 RON), was not up to the required octane rating specified by Porsche (98 RON). Advance increases the timing by up to 6 degrees, but higher in the rev range, when it's not 'lugging' and is less likely to knock .... the retard reduces timing by 3 degrees, but only when the throttle is fully closed, to reduce idle.

If you run premium (98 RON), and you connect it, you can set the advance to 26 degrees BTDC @ 3000 RPM (up from 23 degrees), and you should get improved throttle response and economy. With those settings you are safe with 98 RON Premium, but with normal unleaded you might get knocks, and have to back the timing off.

I recommend replacing the fuel lines running over the RH cam housing with Greg Browns versions, which are a major improvement over the originals, in that very hot location. Get them direct from Greg, or Roger at 928'sRus also stocks them.

In the pic I can see your coil cover is missing ... stops water dripping on it from the bonnet/guard gap.

ANF

Thanks Dave. I am going to connect back up and adjust timing to suit, I always run 98 fuel.
Will look into the fuel lines, they will all be replaced along with just about everything else in there.....
We should get together someday, virtually in your back yard.
Will look for a coil cover too, the jump post cover is missing too....

Cheers

SMTCapeCod

I think you'll notice quite a difference, timing and fuel adjustments made a discernible difference on my (former) 83 S/ROW.

You want to makes sure that vac port and hose to the WUR (item 3 in schematic) is tight as well, for accel enrichment.

Note also that the factory image shows a WUR with both an upper and lower (accel and decal) vacuum feed and I'm not seeing it on yours.
They both originate at throttle body, one above and one below the throttle plate.
The single feed WUR is less costly..so it raises the question-- fuel curve aside-- if there was a swap how was the line capped/terminated and is it still holding good vacuum.

ANF

Both vac hoses on the WUR are there and appear to be good. It is quite difficult to see all that happens under the spider and it looks like the only way to replace all lines is to remove it!! Which I will do soon.......

Cheers

Dave928S

Removing the spider is worthwhile doing, as it doesn't take long, you can see everything, and it's piece of cake to lift out the whole plenum/throttle assembly. Once out you can clean the V and the whole assembly, replace the rubber mounts which I guarantee will be shot, and with everything easy to see, get the rest perfect.