Weird exhaust/fuel cut question?

[DJ23GSX]

My mods are Ported 16g with 34mm flapper,Ported 2g exhaust man and o2 housing, 3" turbo-back exhaust, 3" intake pipe with K&N, ACT2600 SS line, MKIV i/c, 2.5" upper and lower i/c pipes, Magnecor's, bpr7's, Fluidyne radiator, Walbro 255lph pump on a Fully balanced motor with 4 layer metal head gasket and ARP head studs and all brand new internals and a brand new ported head with 3 angle valve job. Now here's the deal i have my manual boost controller set for 13psi and it creeps to 16psi and i hit fuel cut and thats understandalbe but when i put the silencer in my muffler (n1 catback) i can run 16psi all the way to redline without hitting fuel cut. WHY when the silencer is out i hit fuel cut in the higher rpms at 15psi but with it in i can run 16psi through all gears right up to redline??

 

[mitsutuner]

The silencer causes increased exhaust gas backpressure, meaning the exhaust gas stays in the system a little longer & burns cleaner & more completely, which is detected by your O2 sensor. With your mods you have ample gas & less restricted flow thru your motor & too much unburned gas at the O2 sensor triggers fuel cut.

 

[DJ23GSX]

Is there a cheap fix for this or is a SAFC needed?

 

[mitsutuner]

the cheap fix is to leave the silencer installed. The expensive fix might be the safc, but before doing that I think you should hook up a pocketlogger & datalog your motor to find out exactly what is going on--there's always a chance you could tweak the timing or something to reduce your problem.

 

[DJ23GSX]

Well with the silencer in my logger numbers look great i hold between 19-21* timing 0-3 counts of knock and my o2v's are usually between .8 and .84. This is all the way to redline no fuel cut. With the silencer out my timing is a little bit lower maybe 18* in the top of 3rd knock is sometimes around 7 counts and around 6000rpms my o2v's drop to 0 my timing drops to around 9 and knock shoots up to 35+ and i hit fuel cut. My o2's are around .8-.82 all the way to about 6000rpms when i get the pop and they drop to 0. My next mods are going to be a safc and some 680's but i just want to be sure that will resolve this problem and its not something else i should be looking for.