I was just confirming what was said. Something that might not have been talked about is the TB. Being it is drive by wire, it could possibly be an issue with that - though I think it would have thrown an SES light.

 

It would have...Although a throttle body failure is not completely out of the relm of possiblities his symptoms are most common with a MAF going over voltage. Especially since part boost driving and idle are fine. The lack of a CEL further reinforces that its the MAF. Its the only failure I've seen (MAF going over 4.89 volts) that doesnt trigger a CEL but puts the car in limp mode till cycled. Boost any non-MAF voltage clamped car (350Z that is) past 12 PSI and this happens.

 

The Unichip clamps the MAF voltage so it does not do exactly what it is doing. It is seeing maximum voltage too soon, meaning he is flowing too much AIR past the MAF due to the increased boost, causing it to believe something is wrong, which trows the car into limp mode. The UNIchip should allow you to go in and modify the MAF voltage at any given parameters. By changing your exhaust you allowed the turbos to spool up much faster, which in turn flows more air past the MAF which n turn sends a higher voltage to the ECM sooner than it did prior.You need to re-tune with the new exhaust,especially watch the A/F ratio and timing...

 

Thats exactly what I figured. I haven't played or looked at a Unichip for much besides its fuel and timing curves but I figured there would be a MAF voltage adjustment based on engine speed. Couldn't you just clamp it from down low say 500 RPMS and then just alter the fuel and timing to compensate?

 

Correct, the new exhuast allowed the turbos to spool faster, therefore the clamp on the MAF need to be re adjusted lower in the RPM range. The car is seeing more CFM of air sooner than before..Causing limp mode.

 

MAF is the usual suspect.... However, a seldom understood and overlooked cause for limp mode is too high a long and/or short term fuel trim, somehting that cannot be corrected very well with piggyback, can only be done in the stock ECU. I have been having issues when boosting 12+ psi with MAF, that's because of hte overvolts. But at times, @ the initial install/tune, the car kep going into limp mode at partial throttle with hardly any boost. Sure enough the LT fuel trim for hte active bank was pegged at 25% (or 20?), whatever the max is. If BOTH short and long term trims max out, the ECU does go into limp mode.

Just an FYI