Engine won't rev past ~4200 - Turbo SBC

[turbostang]

I spent about 6 hours on the dyno today to get pretty much nowhere, lol. It was only 105* outside.

The MS details are MSII, V3, 2.891

Engine details: SBC, Turbonetics T70, 80# injectors, VR sensor, NO HEI module, direct high current coil driven

The problem is seems to be a replay of what I've seen over and over searching through threads on this subject - and it's possible I may be facing TWO problems.

First, I can't seem to find a definitive answer on WHAT the max dwell setting should be (or at least start at) and what the max spark duration should be (or at least start at).

Second - I'm getting what appears to be tach signal drop out that starts just before the engine begins misfiring like crazy. (see datalog starting about 3.604s)

(*this tuneup and dyno datalog may not go together as far as VE/spark/AFR tables are concerned - so don't be alarmed there. The rest of the tune should be identical and ALL of the pulls today netted nearly identical results, flatlining at ~4200 or so)

[Matt Cramer]

The dwell settings depend on the coil, and at high RPM, you usually don't have time to fully dwell the coil anyway. You can increase the high RPM dwell by decreasing the Max Spark Duration setting a little, but if the coil really needs 3.6 ms of time to fully charge, you may not be able to gain enough dwell. (I see it's dropped off to 1.8 ms at 4800 RPM). Usually, distributor + inductive ignition system + V8 + high boost is not a good combination; I would consider upgrading to an MSD box, EDIS, or some other ignition upgrade.

[turbo-brooks]

I don't think the coil really needs 3.6Ms to charge fully, that was more of a test, hence the disclaimer on I wasnt' sure if this was the tune I ended up with or not near the end. I did some comparisons on tunes and took some notes, and two of the pulls in the middle of the day actually netted 5500 or so, but it was still banging pretty bad.

I'll post those results tonight when I get home.