weird dyno graph
 

hello everyone, last week my brother and I dynoed his camarobut we notice the hp graph after 5000 stayed flat... and couldnt make it go up.
mods: stock ls1 bottom end, 243 heads, t6 gt45 turbo, 60lbs injectors, 45mm turbosmart wastegate, 273xer cam, bbk intake, 4l80e , circle d converter, walbro 255 (edited post), even on the street it feels like it gets stuck.... with the supercharger it didnt have that problem, there are no knocks, no boost leaks and afr was a little lean at wot 12.1 but nothing else, boost @8.5 psi


https://cimg9.ibsrv.net/gimg/ls1tech...134a391777.jpg

and with a lot less timing and boost it would keep doing the same... boost @5.7 psi


https://cimg4.ibsrv.net/gimg/ls1tech...3dc8463e62.jpg

What kind of fuel system are you running ? Stock pump?

stock fuel rails, and walbro 255, planning on a walbro 450 and external fpr

#1 put both the torque and power graphs together into 1 graph
#2 do not scale them differently, it makes looking at it difficult
#3 include the A/F graph below the hp/tq graphs so we can see it
#4 always use smooth: 0 for diagnosis of dyno output graphs

#5 the torque is falling off after a peak, as if you had a stock cam/head on a stock engine. Either raise boost, or help the engine breath to bring it back up, as it passes that point.

#6 i see you have run files in the 50's. did you make 50 passes on a dyno in the same day?
if there was a #7 it would be:
#7: Generally, Do not make more than 10 or 12 passes on a dyno in a single day/event. If you needed more tuning you should have done it before you got there.

we had some troubles with the dyno not logging the a/f but with the recordings from our wideband, the afr was steady 11.8 until 5200 wich started to lean out to 12.1

heads are 243s and cam is a comp cam 273xer , with the vortech supercharger it made 516 whp without that flat graph and with the same fuel pump

there are 50+ passes, because they stored them all since it was NA in the 2012, we only were there for an hour

so its got some cam. Not sure what the head flows (I am not an LS guru) but when you have the head/cam for a flat torque curve to redline, and you arn't getting one, and you ALSO happen to have a turbocharger, you must now investigate the dynamics of the exhaust system/turbine. Perhaps your exhaust route is restrictive.

Aside from exhaust gas pressure problems, you could be losing boost pressure. More boost as the RPM rises will "fix" the issue if the compressor has anything left in it, but it will compound an exhaust restriction problem (you might get too hot, make sure to have an EGT gauge). You really want to watch the EGT for setups with convoluted/ugly exhaust routing, homemade situations.

Typical turbo with a Auto graph.

But it is not just on the dyno, on the street you can feel the car doesnt run well past 5200

My engine ran out of fuel pump (single 255) at about 5psi. I know your AFR weren't reading excessively lean but you may wanna get more pump before doing anything else.

in the lower power graphs, you can see the power start to came back in.

Id be looking in the drivetrain