Pulleys for low elevation?

[Heflerrx1turbo]

hey guys bought a nytro with a mpi supercharger on it and currently has 28/28 tooth pulleys on it mpi told me that it's at 8-9 psi at 450-1400 ft I live in Iowa so it's around 1000ft am I safe with this set up or do I need to drop the bottom pulley to 26t (5-6psi) pulley I'm fine with losing some power and lowering the psi I just want it to be safe for the motor. And is it recommended to run race fuel with psi set at 5-9? With out a head shim?

Thank you in advance! Any info is great

 

[Jory]

hey guys bought a nytro with a mpi supercharger on it and currently has 28/28 tooth pulleys on it mpi told me that it's at 8-9 psi at 450-1400 ft I live in Iowa so it's around 1000ft am I safe with this set up or do I need to drop the bottom pulley to 26t (5-6psi) pulley I'm fine with losing some power and lowering the psi I just want it to be safe for the motor. And is it recommended to run race fuel with psi set at 5-9? With out a head shim?

Thank you in advance! Any info is great

A few hundred feet wont make a difference and the ecu/map(s) will compensate for that anyway. I'm sure you took it for a test rip so it will act and run the same at your current altitude.

 

[waldo1]

i ran 28 on bottom and 26 top in michigan 1000 feet or so - ran 8 pounds - perfect set up - no fuel pump, gems yamaha controller, apex gearing and clutching, no intercooler 93 octain. perfect safe set up,

 

[sshewchuk]

I'm at 750' and MPI recommended 26t bottom and 28t top for pump gas.

 

[waldo1]

I'm at 750' and MPI recommended 26t bottom and 28t top for pump gas.

Thatll be like 4 pounds of boost - 86 octain - super slow mpi yamaha safe - 10 k miles - 7-9 pounds of boost 93 octain. perfect, stock mpi everything, no gages. put on a 25 29 with a splash of 110 if u have some - other wise - just stay off the wide open stuff for long.

 

[sshewchuk]

So my worry of having to put 87 in while somewhere remote isn't an issue? Just put it in and drive her?

 

[waldo1]

yep - just dont doo a wide open shot up a big hill for a mile - probally could tho anyway.

 

[sshewchuk]

"Big hill" lol, it's Manitoba. I'd say we are good then! Thank You!

 

[full tilt viper]

Just back from testing my old 29bx28t @sea level. Watched gauges and 9000 RPM closely -10 hard packed groomed fast conditions. Makes a solid 8-8.3 lbs with AFR's creeping up into the 14's fast at WOT. My 27bx28t Makes 5.2-6 and is getting plenty of fuel. Waiting on my 28b to arrive which I hope gets me to 6-7.3. Also I hope I can fuel it properly at that boost level. Running cold air , inter cooler and stock fuel pump.