yamaha_junky626
Veteran
I just put a boost gauge on my mpi stage one supercharger and i have 26 crank pulley and 22 jackshaft pulley. it should be running about 10 11 psi but i can only get 7 or 8psi at the most and this is at 1500 ft elevation. i removed my blowoff valve and blocked that off to make sure that wasn' t the problem. if im cruising at like a parking lot speed i get like 5 psi the second i pin the throttle it goes to 0 . it takes probably about 800 to 1000ft before it even hits 7 to 8 psi. i thought maybe my belt was slipping so i put on a new one and it is still the same way. the boost gauge is brand new and orinally hooked into the extra ports on the throttle body, i also tried it hooked right into my boost line from the intercooler to the controller, same thing. i double checked all my hoses on the throttle bodys and between the supercharger and the intercooler and it all looks good. i was expecting boost to be pretty much instant and its far from it. any ideas, is this normal for the boost to take this long to build.
347strokin
Expert
Although I don't really have any suggestions for you I can tell you that the S/C's do build instant boost. It should be proportional to your rpms. I'm running around 12 lbs and it's there as soon as the throttle is punched. Good luck, someone will chime in with more knowledge than myself.
yamaha_junky626
Veteran
super charger
my rpms do hit about 10800 instantly but my boost sure don't follow it.
my rpms do hit about 10800 instantly but my boost sure don't follow it.
gsxr
TY 4 Stroke Master
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Most likely the gauge , as soon as engine has rpm ( over 7000) you will have instant boost. What gauge , is it electric , digital or mechanical?
yamaha_junky626
Veteran
supercharger
its an auto meter gauge from mpi, mechanical gauge
its an auto meter gauge from mpi, mechanical gauge
Does it feel like it has boost or not. Did you change the inner belt. These strip the cogs and do that. It could also be the supercharger itself slipping.
yamaha_junky626
Veteran
supercharger
the cogs on the inner belt look good, it is a little loose, i never rode it stock, but the power feels pretty good, not quite like i would expect 240hp to feel like.
the cogs on the inner belt look good, it is a little loose, i never rode it stock, but the power feels pretty good, not quite like i would expect 240hp to feel like.
kinger
VIP Member
I just had mine out today and the boost is always there and instant. 50 mph i have 5 psi 60mph i have 8.5, any higher and i have 10 psi.
my gauge is the same as yours and runs right from the intercooler.
my gauge is the same as yours and runs right from the intercooler.
i have 26 pulley on craink and 24 on idler boost comes on instantly warming it up on trackstand blip the throttle and see 3psi
yamaha_junky626
Veteran
supercharger
i have had problems with my supercharger oil temp the last couple of years, so i'm guessing it the supercharger itself, are these a c15 blower. it sure sound like i should have full boost probably any time my rpms are over 10000. do anybodys drop to 0 right when you snap the throttle. what can actually go bad inside the blower to cause this, the compressor wheel looks good.
i have had problems with my supercharger oil temp the last couple of years, so i'm guessing it the supercharger itself, are these a c15 blower. it sure sound like i should have full boost probably any time my rpms are over 10000. do anybodys drop to 0 right when you snap the throttle. what can actually go bad inside the blower to cause this, the compressor wheel looks good.
opel
Newbie
Boost should be instant. I have the same 26/22 pulleys and as soon as I hit the throttle, mine actually snaps to 11 psi and settles down to 7 psi. I am running from 6-9,000 feet. But I clutched my rpm down to around 9900 so did'nt over rev the charger with my pulley setup.
millstreet
Lifetime Member
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same set up, mine shows 13-15 psi at WOT, settles to 10-11
boost gauge is plumbed to boots between the carbs and the head.
boost is instantaneous
boost gauge is plumbed to boots between the carbs and the head.
boost is instantaneous
slow boost
check your outout shaft on bottom. it has a dimple that is supposed to sit in the keyway of the crank. i had one that was just spinning against the flywheel until it got friction from heat, then it would make boost.
check your outout shaft on bottom. it has a dimple that is supposed to sit in the keyway of the crank. i had one that was just spinning against the flywheel until it got friction from heat, then it would make boost.
347strokin
Expert
Re: supercharger
What kind of problems were you seeing with your blower temp? Overheating?
yamaha_junky626 said:
What kind of problems were you seeing with your blower temp? Overheating?
yamaha_junky626
Veteran
supercharger
my oil temp was getting hot quite often, light would come on and could barly touch resevoir, bypass valve did help some, i will have to check my pulleys and make sure they are not slipping on the crank drive. there is a place in texas that can rebuild them, although rotrex says they are not repairable. his site is superchargerrebuilds.com if it is the charger itself i will give him a try.
my oil temp was getting hot quite often, light would come on and could barly touch resevoir, bypass valve did help some, i will have to check my pulleys and make sure they are not slipping on the crank drive. there is a place in texas that can rebuild them, although rotrex says they are not repairable. his site is superchargerrebuilds.com if it is the charger itself i will give him a try.
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