Tripster

On a 78 Euro the Distributor only has one line going to it, (vacuum retard). How does this retard work and when does it work? I know it retards the timing at idle and advances after throttle, does it come back into play and retard again on Boost?

Tripster

I know someone here has the answer to this question, please input.
The car makes vacuume at idle and when getting on boost the vacuum goes away and in turn retards the timing? Correct?
What is a safe level of timing when on boost???????? 78 Stock CR .8 Bar

I have set my total timing @ 28 @ 4000 , but when the car idles at 900 rpm the timing is aroung 5 BTDC NOT ATDC as the fan shroud states. When I pull the vacuum hose off at idle the motor only changes 3-4 degree timing

RarlyL8

Mark - I will bring you my copy of the 930 workshop manual Friday morning.
I went back and re-read the chapter (28) concerning vac advance and retard. Like I said before the curve depends on the engine type or model number for the dizzy. California has the most conservative graph while the Euro models had the most agressive, as expected.

Tom F

The vacuum retard units only function when there is vacuum, as far as I can tell. They don't have any provision for boost. Did you try connecting a pump to it, to see what it does with 0.5 bar pressure on it?

LeonardZ

Look on the back side of the vacuum diaphram on the distributor at the bottom of the diaphram. Is there a vacuum line coming off the back of the diaphram?
You might have to look up from underneath through the engine tin near the turbo to see it.
Leonard

nathanUK '81 930 G50

I too would love to know this information too. My car is a ROW euro '81 930. It might have a later engine in the car though. The dizzy has two diaphragms.

I noticed that when I sucked on either diaphragm there was movement inside the dizzy. The field coil moved. When I blew on either of them I could not get any movement. IIRC sucking on a different unit made the coil move a different direction.

I hope Stephen will answer this for us.