Supercharged Phazer odd boost issue

stingray719 · Dec 2, 2013

MPI Supercharged Phazer after sitting for a long time will boost to 9lbs for one or two time hammering throttle. Then it goes to 3lbs boost for rest of the day. Have checked everything I can think of, wondering if fuel pressure regulator might be the issue even though sled has a little over 300 miles on it. Can low fuel pressure cause this? I thought a supercharger would boost no matter what the amount of fuel was? Thoughts?

P.S. dual GEMS controllers (stock):face-icon-small-dis

1madbird · Dec 3, 2013

Hey stingray after we talked about fuel pressure issue I remember that my AFR gauge was running right around 12-13 all the time so I don't think I have a fuel pressure problem. I would recommend that you install one that will tell you if you are running out of fuel which would cause it to go lean.

TRUEBLUEMAX · Dec 3, 2013

Sounds like an issue with the blowoff valve to me. If it is getting stuck open or the spring is weak then it won't hold enough pressure.

stingray719 · Dec 3, 2013

1madbird said:
Hey stingray after we talked about fuel pressure issue I remember that my AFR gauge was running right around 12-13 all the time so I don't think I have a fuel pressure problem. I would recommend that you install one that will tell you if you are running out of fuel which would cause it to go lean.

Not sure I trust my AFR guage as it says 15-16 all the time no matter if I turn GEMS up so far it bogs from being rich.

stingray719 · Dec 3, 2013

TRUEBLUEMAX said:
Sounds like an issue with the blowoff valve to me. If it is getting stuck open or the spring is weak then it won't hold enough pressure.

MPI supercharger doesn't come with a blow off valve....that was my first thought though.

Called MPI and the tech I talked to did not have an answer. Very odd that when cold it hits 9 pounds boost and is a rocket but after a couple runs drops to 3 pounds and stays. Checked all charge hoses too.

irondave86 · Dec 3, 2013

Can you fell the loss of power? Maybe your boost gauge is bad too?

stingray719 · Dec 3, 2013

1madbird said:
Hey stingray after we talked about fuel pressure issue I remember that my AFR gauge was running right around 12-13 all the time so I don't think I have a fuel pressure problem. I would recommend that you install one that will tell you if you are running out of fuel which would cause it to go lean.

After talking to Matt at MPI I think I may have a crack in my airbox. Does your Phazer make a blow off valve sound? (even though they didn't come with one) Mine makes a sound just like the blow off valve in my turbo truck does and it didn't come with a blow off valve.

stingray719 · Dec 3, 2013

irondave86 said:
Can you fell the loss of power? Maybe your boost gauge is bad too?

Can definately feel the diff between 3lbs and 9lbs on guage. When it hits 9lbs it is a match for an 800 sled in a drag race.

1madbird · Dec 3, 2013

Does your Phazer make a blow off valve sound? (even though they didn't come with one) Mine makes a sound just like the blow off valve in my turbo truck does and it didn't come with a blow off valve.

yes mine does that. If your AFR doesnt seem to move i would replace the sensor. If you are running race or AV gas it kills them pretty fast.

1madbird · Dec 3, 2013

Could be the intercooler also i would lean more toward this since this see's the heat from the boost first and the heat would open up a crack. Also the mounting on the intercooler is not very good so one may have ripped and hole in it or something.

n2otoofast4u · Dec 3, 2013

stingray719 said:
Can definately feel the diff between 3lbs and 9lbs on guage. When it hits 9lbs it is a match for an 800 sled in a drag race.

Off subject but this is 100% true. My turbo phazer at 12psi would out run all of the late model 800 2s sleds. It was a heart breaker for sure. Hope you get your issue figured out.

BigFish BC · Dec 3, 2013

1madbird said:
yes mine does that. If your AFR doesnt seem to move i would replace the sensor. If you are running race or AV gas it kills them pretty fast.

if running av or race gas get yourself some of this & you wont have sensor probs again.
decalin
http://www.aircraftspruce.ca/catalog/appages/Decalin.php

sifton · Dec 4, 2013

stingray719 said:
MPI Supercharged Phazer after sitting for a long time will boost to 9lbs for one or two time hammering throttle. Then it goes to 3lbs boost for rest of the day. Have checked everything I can think of, wondering if fuel pressure regulator might be the issue even though sled has a little over 300 miles on it. Can low fuel pressure cause this? I thought a supercharger would boost no matter what the amount of fuel was? Thoughts?

P.S. dual GEMS controllers (stock):face-icon-small-dis

I had one couple years ago- check your intake boots, had to recamp mine once.

stingray719 · Dec 4, 2013

sifton said:
I had one couple years ago- check your intake boots, had to recamp mine once.

Yep, did find one hose loose. Still thinking it is air box just have not been out to get it off yet.

stingray719 · Dec 22, 2013

ANOTHER PULLEY WENT BOOM!!!!!!!!!!!!!!!!!!

I say another because I had one go boom on my supercharged Nytro with 1800 miles and now this one on a Phazer with 435 miles. Very strange that it would slip enough to lower boost but not blow until 127 miles later?

MATT, this heating new pulley in an oven to install really doesn't give me warm fuzzies either. Did MPI ever come up with a better solution to the pullies?

Now I have to accept some of the blame here as I knew these pullies could have issues if not installed in a very odd way, but this one was built by a dealer in Utah so I assumed all was well as the sled had less than 300 miles when I got it. So, my bad for not checking the pullies out.

roughrider99 · Dec 22, 2013

I diagnosed a nytro with the same issue, it would be fine at the start but a couple hard pulls and that pully would give and slip once it slips it then gives out way easier till it cools down and develops an interference fit again. Heating up the pulley then slipping on the shaft is a good way to do it, I deal with heating and freezing bearings and races to slip on for an interference fit when rebuilding power trains for large dozers and huge mining haul trucks.

When you replace the pulley your gonna need a new shaft as well to get the proper fit, your old shaft has been spun and will most likely happen again if you don't have a new matching shaft and pulley. Also depending on how tight that interference is, you have about 5 seconds to get that pulley from the oven to being seated properly on the shaft

stingray719 · Dec 23, 2013

Thanks to Matt @ MPI for calling me back and helping round up the parts I need.

.

stingray719 · Dec 26, 2013

Thanks to MATT @ MPI I will have parts needed and have the girlfriends Supercharged Phazer back together for our big yearly trip!

Thanks again Matt!

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