Mpi SC nytro shows lean

[Xcdhracer15]

Have a 13 nytro mtx with mpi SC running 28/28 pulleys at -1000ft elevation. Has gems controller and prologger with wide band 02 just before tunnel dump muffler.

It seems to run lean, 14-16:1 cruising at low throttle and only 13.5-14.5 wot. Shows 12.5-13.5 at idle.

Almost wondering if it's the wideband sensor acting up. Tried adding fuel on the GEMs controller but it didn't seem to change anything.


Thoughts?

 

[sshewchuk]

MPI told me to run a 26T bottom pulley to reduce boost at 1000'. The say the air is too thick and increases compression too much.

 

[Krummy]

I am not shocked to see this with those pulleys. That is too much boost for a stock sled. I am running a 27 bottom and 28 top with AFR at 12.4 WOT. The GEMS is cranked to the max and both Ulmer and MPI believe my fuel pump is the weak link. 28/28 should be around 7.5 psi boost at that elevation which should not be run on pump gas without a head shim or ECU Modification. My best bet is your fuel pump cannot keep up to those levels of boost. I have a 26 Bottom gear if you need one to lower your boost levels.

 

[full tilt viper]

Just tested 28x28 ( 7.0-7.8lbs ) with the exact same outcome . On stock fuel pump and compression @1000 27bx28t is the ticket and no more. The sled runs perfectly at 6-6.5 with low 12's at WOT .

 

[kinger]

Go larger fuel pump, my apex did that same thing initially.