bmwe21.net forums

Hi

Does Anyone know the best ignition settings for a 6 cylinder m20 engine 79 bmw 520. I have had reset the distributer position. So I lost the setting. Using a timing light I set the timing to 22 btdc z mark at 1500 rpm according to haynes manual. With vacuum hoses disconnected and blocked.
The car seems to be slow to accelerate on unleaded petrol. Has anyone better ignition sitting

I have advanced the ignition timing from 22 Degrees to 24 Degrees at 1500 revs. Pickup accelaration is not noticebly better.

The reason why I went at the distributer in the first place was, The engine was hunting at idle.
I found slight leak on the vacuum retard side of the vacuum capsule. Replaced the capsule so there are no vacuum leaks on the car now. When I had the distributer out I noticed small amount of play / back lash bewtween the drive helical gear and main distributer shaft. I removed the roll pin and inserted a tapered dowl pin. This took up the backlash.

My distributer is a electronic point types. I stripped it down, mechanical advance and retard is working correctly, observed no wear or broken springs. Light and heavy spring are present.

So with Unleaded do we need slight more advance does it burn faster than unleaded?

22 degrees at 1500 rpm is the right setting. If you made sure there are no more vacuum leaks, you may want to have a look at the CO %

Thanks for the info, there are no vacuum leaks. I have solex 4a1 carb fitted. so the co% at idle I dont think would effect the acceleration or pickup. The mixture screws I think only have an effect at idle and part throttle. When more of the little holes are uncovered with the trottle plate opening. I believe the idle circuit then is out of action. These two mixture screws have not being adjusted.

When I refitted the distributer and set the dynamic timing. My idle speed went up to 1000 rpms from 800 rpms. So I had to back off the idle speed screw to bring the revs back down to 800rpms. This leads me to believe the car was originally a little retarded on the timing. But I don't know how much of an effect the back lash in the drive helical gear and the vacuum leak retard side on the timing.

I phrased the question in the previous post wrong.

Does unleaded petrol have a faster burn time than Leaded petrol?

Regards Eddie