Fronkenstein

I've noticed is that there are many vacuum schematics for varying years, USA/Japan versus RoW, 16V vs 32V, K vs LH... etc. There is much conjecture on those connections such as to what type of vacuum is being supplied to each port(s). On the advance side I've heard, full manifold, pre-manifold-at-the-throttle, at-the-booster, etc.

The WSM and spec guides show pictural information without any legend to the connections which is USELESS. There are MANY throttle bodies. Some look like porcupines and others, like mine, have very few vacuum ports.

Does anyone out there have any definitive information broken down by year, engine type, injection type, etc?

Thanks,

Fronkenstein

toofast928

I welded the shaft, threw away the weights and let the MSD/Haltech control the ignition map. Does this help?

Fronkenstein

Yeah that's a great thot

mark kibort

the 16 valvers , have vacuum advance on the disty, running off the port before the throttle plate...(so you get vacuum for advance timing, as more air passes over the port which happens as you give more throttle. the port on the vacuum side of the throttle plate, runs the fuel pressure reg, to pull back fuel pressure.

there is a port on the early US 928s that has a vacuum line to pull back timing off throttle, but i usually disconnect that

other vacuum lines from the intake are usually pulling air from the emission systems like the charcol canister.

the last one is from the vacuum booster that runs one to the flappy actuator, but that's on S4s.

it looks complicated but just think of the ones behind the throttle plate.(seeing vacuum at idle ) vs in front of the throttle plate, which doesn't make induced vacuum until you have throttle input.

GlenL

This is my experience.

Some time ago I got a Euro S vacuum diagram and, of course, my two '80 Euro S cars act differently. From what you say, I think I'll go back and check if the vacuum advance units are the same. And the vacuum signals don't seem to act the same. I want advance at idle but one just gives retard. Can't see well under that plenum. Another thing on the list.

Fronkenstein

Mark,

The last part of your entry was highly valuable since none of that is in the WSM, at least not from what I've seen.

There are vacuum schematics for various years, injection systems, throttle bodies, plenums, and locales, but those schematics are devoid of descriptions.

How hard would it have been to go the extra mile and document that stuff? And to really put the edge on it all, color code manifold (red) versus atmosphere (blue) side connections.

Now I'm just whining :/

Fronkenstein