1982z28with18s

I've sanded down all the ground connections once already.

No signs of coolant leaking, coolant level stays the same and no white smoke out the exhaust at all.

Ultra_Dog

Is your Knock Retard kicking in and pulling timing out?

1982z28with18s

Knock retard can't pull any timing, my knock sensor is bad, has been for about 8 months, so it can't pull any timing at all.

Sparkz28ss

Have you pulled the valve covers yet?

1982z28with18s

Just pulled them again today, everything checked out fine.

dookie454

dont mean to beat a dead horse here...

To rule out fueling plot your injector pulsewidth vs RPM see if by chance it spikes or dives in the area of power loss. You should be able to connect an AFR with pulsewidth vs RPM.

If that's coming up different from good run to bad run check your Baro make sure it's not changing on you (should always be around 50-53kpa on a 2 bar, ~100kpa on a 1 bar) from when it's running good to running bad.

If you really want to get involved now would be a good time to either clamp to the header primaries or loosen the headers and install some thermocouples (ideally one for each cylinder) and see whay cylinders cool down more than others during the problem.

Aside from this.. I had 3-4 bad optis in a row (kept getting strange high rpm cutouts, misc popping, overall strange running). 2 were MSD pro billets. Dissasembled and Locktited the last pro billet and all has been fine since.

And BTW, yes they can be installed out of sync and still run (my first opti).

1982z28with18s

Here is a pic of the graph from the dyno a few weeks ago, finally got a hold of it.



That doesn't look like it's valve train related.

cause4panic

What was the a/f ratio thru all of this? To me it looks fuel related. Or your blowing the spark out. Obviously with a/f ratio u see it get real rich when u blow out the spark and you lean out if there is a fueling issue.

How much timing are you running?

1982z28with18s

18-19 degrees timing, AFR stays FLAT in the low/mid 11 range.

Ultra_Dog

belt slip. does your boost continue to climb thruout the RPM or taper off at 5K?

DirtyDaveW

Belt Slip? It's a Turbo, not a supercharger.

rskrause

Wow, I know how frustrating these things can be. I suspect the ignition system, as you do. But you seem to have looked into just about every aspect of that. One thing that was already mentioned was knock retard. Make sure that isn't what's happening by simply programming it out. If that doen't work - try running it off boost. If it runs ok off boost, I would go back to igniton. When I have seen vavetrain problems causing high rpm power loss it's usually consistent. But if it's an HR, I'd make damn sure the valves were adjusted right and aren't too tight..If it's an HR it COULD be lifter pump up, though this does tend to be pretty consistent.

Rich

1982z28with18s

Here is the graph vs engine speed, you can see the engine speed DROP at wot.



I have the two dyno jet file if anybody wants them to play around with. :thumbup:

RPM VS TIME...

speed_demon24

Here's what my dynograph looked like with a lose rotor in the OPTI FWIW.

David94TA

Are you sure that 18 degrees of timing is enough in the higher rpm range? It seems that there was another board member who was having a similar problem and it turned out that he just needed a little more timing.