continued l-jet M20B23 troubles

[LJ851]

I thought so. :up:

[kronus]

yup! there is success!

Retimed it yesterday. Ended up giving it a lot more advance than it had, and now it's great, chirps 225s, accelerates up hills, etc. It's still not fast, but it's good now. Still runs hot, though, so I think either I have an air bubble, the radiator is done, or an HG leak pressurizing the coolant. The temp gauge and/or sender might also be going - it will be steady midway between middle and the mark to the right of it, and then randomly rise up to the mark and come back down without much of a change of engine load.

[LJ851]

Any news?

[LJ851]

I was just thinking of a way to see if you can find your missing horsepower at full throttle. Yeah, it could still detonate at part throttle with vacuum hooked up and another potential drawback could be that you are moving the entire timing curve up so you are changing the timing at idle as well.

It might not be an issue or you may need a dist that has a longer advance curve (or you could modify yours)

[kronus]

I will approach it with the carbed-M10 approach to distributor tuning, i.e. advancing the piss out of it. However, if I'm advancing until the detonation point with just mech advance, wouldn't that put it solidly past that point with vacuum hooked back up?

[LJ851]

roger, will try. pinging as in detonation, right?

Correct.

I just did some research and saw some #s like you are talking about. Is your dist on this list ?

http://forums.bimmerforums.com/forum/showthread.php?836299-79-323i-M20B23-Timing-Specs&p=16931083#post16931083

The only reason i could imagine such a low advance # would be for emissions, not for performance at all.

[kronus]

roger, will try. pinging as in detonation, right?

[LJ851]

I would leave the vacuum advance off and keep advancing it until the engine pings and then back off 5 degrees or so.

Turn it up 10 to 29 degrees and see what happens.

[kronus]

I see. It was pretty consistent above 3k after I set it.. maybe 5 more degrees?

[LJ851]

you keep saying total mechanical.. do you mean total of vacuum + mechanical?

No, just the advance provided by the centrifugal weights inside the dist with no vacuum assist. Assuming the vacuum pot advances, vacuum would add additional timing on top.

Typical total centrifugal advance is high 20s to mid 30s. Vacuum advance will add 10 or 15 degrees on top of that for a total of high 30s to high 40s at part throttle (high vacuum)

Total centrifugal advance could be all in by 3k or might not be all in until much higher like 5k+.

Since i used most of the internals of an e21 323 dist when i built my 911 dist i am fairly intimate with them. The advance springs are very light and i would be surprised if you got much more advance past 3k.

[accident]

du.

[ak-]

i like air injection

[kronus]

you keep saying total mechanical.. do you mean total of vacuum + mechanical?

[LJ851]

I'll play with it, but the 19 degree spec was confirmed by a few different sources, and there's a very obvious mark on the damper..

I wouldn't doubt that mark is how BMW checks it, i'm just saying it needs to go higher and it would be worthwhile checking total mechanical adv.

[accident]

Jetronic is not fuel injected, it's caca.