A buddy of mine has a whipple supercharger on his 03 Yukon Denali. Its all stock exept for the whipple and a flowmaster 40 series with a single 23/4 inlet and dual 2.5 outlets. Here is the problem. With the stock whipple pulley he is seeing 10psi, I drove it for quite awhile today and there is no way that thing is seeing 10psi, the guage says so but by the way it runs i would say more like 3psi max. My mostly stock sierra denali will stay almost dead even with his supercharged yukon till about 80. Thats all the higher we went. Now in my opinion I think that his exhaust is killing him. Stock manifolds, into y pipe, into single 2 3/4, to muffler. I feel the single 2 3/4 from the y pipe to the muffler is whats hurting it. However i dont really know. Any help would be great.

 

i say check the by pass too see if it is hooked up right, if that puppy stays open then no pressure will build up for boost.

 

I am open to any ideas, I just hate to see him not make full power because of somthing stupid. Especially when you drop 4 Grand on a supercharger.

 

When my converter broke apart I was hitting 12 psi untill the pieces blew out it went back down to 8 psi.

 

Also check the boost guage, that could be acting up. Could also be all the whipple craptronics. What size pulley is it? You said stock size but what size is that? Has he always been seeing 10psi or is this just something new? Hopefully our Twin Screw Director will chime in here.