Hi Everyone,

I have an issue
my 04 G35 Built shorblock, Vortech S/C with only 1,500 miles on it, 2.87 pulley.

I just rebuilt my engine and finish my break in of about 1,500miles, and the S/C is new as well with only 1,500m

I went to tune my car and am hitting 11psi at 5500rpm on the dyno and then my boost will drop to 7psi , just snaps from 11 to 7psi.
we tightened the belt down and it is extremely tight and still lost psi.

compression test & leak down test are good.
we smoked it and did a boost leak test, system is tight.


i am stumped at why my boost drops down and my power is lost,



any advise is greatly appreciated,
thanks.
Jim

 

my bvp leaked, but the boost just never peaked, rather than peaking than dropping like yours. doesn't sound like belt slippage bc of boost would flatline rather than peaking and dropping. I'd say check the bvp if you haven't. Maybe it's able to hold boost up to 10lbs then breaks loose.

 

i would test the MAF and the coilpacks, and fuel pump as well.... as well as he said.. a faulty bypass valve could be the culprit

 

we did check the bypass valve and even shut it, you can hear that sucker when its releasing air it was shut, vehicle is getting plenty of fuel.

he did tune it and the MAF was working , i have the uprev system.

out of curiosity how would the coilpacks cause me to loose boost ?
i do get a p0300 at startup every other day.

thanks for the replies.

 

i believe p0300 is multiple misfires.... was the intake plenum gasket removed recently? id replace those just in case there is a leak/leaks..... if air is getting out before going into the cylinders, that would cause boost loss cuz thats just like a vacuum leak i think.... gaskets are cheap so its a painless diagnostic... i guy i used to work with had an f/i Z and had issues with it sucking the gasket into the plenum... you never know.. it usually is something stupid simple though

 

nvm.. that is most likely not the issue... i looked at your dyno and noticed your AFR is steady to redline.... although i guess it wouldnt hurt to double check... i dunno if ignition break up would cause a boost leak or not.. also spray water on the regular vacuum lines around the plenum and TB and see if they have bubbles when on the throttle at high rpm... you'd s*** yourself if it was fixed by a $2 rubber hose i bet. lol

 

i rebuilt the whole engine and all the gaskets are new,
we pressurized the system to 19psi and smoked it, saw no leaks,

were stumped we dont think its a vacuum leak ,
i was thinking that my valves are floating but the leakdown test came back good.

so stumped at this

 

Have you figured out what was going on yet?

 

Could the misfire code cause the ecu to retard timing, in return dropping fuel, causing boost loss? I'm just throwing out ideas til one sticks to the wall

 

Hmm...could it be the belt slipping? That would explain a sudden decrease in boost. I've heard that even if the belt is tight, it could slip when using a smaller pulley...especially with the 2.87. I just purchased a GTM pulley mod, that is basically an idler pulley that is installed next to the supercharger pulley. It helps prevent belt slip. I too have a built engine, and I'm still breaking my engine in. My tuner wants me to use a 3.12 pulley instead of the 2.87. He said that the 2.87 will boost too much. Strange, considering my engine is built as well. What compression ratio are you running? Is 1500 miles what your builder recommends for an adequate break-in? Keep us posted. Interested to know the issue actually is.