continued l-jet M20B23 troubles

[kronus]

(continuing from http://www.r3vlimited.com/board/showthread.php?t=291366)

situation: very low power being produced by my l-jet M20B23; runs hot and overheats at high load.

diagnostics:
compression is good (~170ish all around)
timing belt is on right
timing is set to 19 degree mechanical advance at 3K rpm with vac advance disabled
mechanical advance works
vacuum advance works
plugs are new
injectors are freshly rebuilt
fuel pressure is in spec (2.5bar)
smoke tested extensively, no vacuum leaks
no obvious signs of oil and water mixing

any ideas on things I should check at this point? It feels like it's producing about 60 horsepower..

[Silverdogz]

ECU corrosion?

[LJ851]

What is the total mech advance ?

[kronus]

19 degrees, there was a convenient mark on the harmonic dampener for it already.

[LJ851]

That cannot be enough advance. Even air cooled engines run way more than that. Rev it up to 5k and see if it keeps advancing. That thing needs at least 30 degrees total mechanical advance.

[accident]

Convert to fuel injected and electronic timing. Problem solved.

[kronus]

That cannot be enough advance. Even air cooled engines run way more than that. Rev it up to 5k and see if it keeps advancing. That thing needs at least 30 degrees total mechanical advance.

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..

Convert to fuel injected and electronic timing. Problem solved.

it's already fuel injected. converting to air injection soon.

[accident]

Jetronic is not fuel injected, it's caca.

[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.

[kronus]

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

[ak-]

i like air injection

[accident]

du.

[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.

[kronus]

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

[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.