Turbo LS1 breaking up in boost

greetings. i have a 1999 2wd with an iron 383 and 4l80e trans and it seems to be breaking up in boost and now a bit when not in boost. i'm running a single Borg Warner turbo with the 3BAR flash and all is working well. i'm running TR6 plugs and with 2 separate wide bands they both read 12.5 ish. the truck was working rather well at 8psi so we upped the boost to around 12. it worked o.k. there and then started giving us trouble. i log this every run and see nothing going wrong. the only thing i can think is that i may need more fuel or a timing change. the last coupler tries we stayed around 18 degrees max timing. this was no help. i'm running a C16/93 octane mix and i did a little checking and i've heard a few people talking about "blowing out the spark". could this be the case even at 8psi. i'm just running too good of fuel. i've never heard of such. it doesn't seem like any more or less timing helps... this engine is 9.0:1 compression. oh yes, and i pulled a few plugs and they look absolutely brand new with over 2 hours on the dyno. shouldn't there be some hint of black? any suggestions are very much appreciated! -eli

Have you tried increasing the spark base dwell time where you see the break-up? You can find the table under engine-spark control-spark dwell. I remember having to raise the dwell at 6K+ rpm to solve exactly that problem when I used to play with turbo'd Miatas.

i was chasing a similar problem for ages on my car, i played around with different plugs, leads, dwell timing etc
I finally worked out the metal boots (that fit over leads) was shorting out the spark only while under boost. I removed all my boots and car has been running great ever since

try taking off the boots and see if things improve

it does seem like it's a spark issue. thanks for the advice. we'll see if i can figure it out shortly! i'll let you know.

Post tune and log please.

on this particular run the engine has no trouble until 5000-5200 rpm. then it sort of levels or smooths out if that makes any sense. its almost as if it hits a rev limit. it's making 600hp right now but it should rev fine to 6000. kind of weird. i wonder if its possible for some reason both widebands read lean. i pull a plug each run and they look brand new... no carbon or black at all...

here's another one where the boost is holding at 8ps1 and the dyno is showing bigtime power losses above 4k rpm. like 50 less hp. could it be the stock fuel rail or regulator? i've got an A1000 pump on this thing but the stock rail and pressure regulator. it's like when i give it more fuel it makes it worse. the fuel gauge is fluctuating 5-10 psi on the fuel rail.

i think the afr isn't correct either if you're viewing my log. it looks like it may be off one whole number according to my dynojet WB

What is the plug gap? Might be necessary to tighten it up a bit for boost.

the plug gap is .030. the problem is i've done a few of these and have never had this problem. i've also never tried to use the stock fuel rail with an A1000 pump. i think i may just need to replace the 3/8 fuel rails and line. when we were dropping power at about 4000 rpm the fuel pressure was losing almost 10psi...

well. i upgraded the fuel rail and it got a bit better. the fuel pump sounded better and no pressure drop at wot but i then replaced the TR6 plugs with some delco's for a Z06 with a .025 gap and the truck is right where i think it should be. 610@9psi/[email protected]/750@16psi. that's kind of where i wanted it.