compression ratio?

[az20vt]

Right ive just added some 8.5.1 je standard bore pistons to my 1.8t engine, has rods and valvetrain done its running a gt30 at 1.8 bar when it was on standard agu pistons, now its back together and ran in its only doing 1.3 bar and feels flat above 5000 rpm checked for obvious boost leaks, timing is bang on messed with manual boost controller still no difference, im thinking its a map related problem now going to check it saturday on dyno, so my question is would the compression ratio drop cause any of these problems? p.s its running omex 600 manegment.

 

[ibizacupra]

ign would be retarded for the lower comp, and fueling would i imagine be overly rich without sufficent burn going on... you able to check your afr's?
boost should'nt drop persay, but how is it being controlled? fixed duty cycle? requested boost?

 

[az20vt]

It's running manual ball and spring controller, it's only running actuator pressure won't boost anymore, afr reading is in tens when flat out 3rd an 4th gear, it's going in dyno Saturday so will see what ignition timing is doing.

 

[ibizacupra]

10's is way rich as you know.. that aint helping spool or boost as its drowning the turbine and killing its energy

 

[Prebs]

Would 9.25: (thinking JE) be a better solution as its closer to standard compression ratio or will they also be laggy/feeling flat ?

 

[ibizacupra]

depends on the power output and boost you plan on running