I did surch on this issue but didnt get an answer...

we did a rebuild on my FC 13B engine with a half bridgeport... after a 3000 Miles "break in" period i started to push it but there comes the problem...

at full throttle and higher rpms boost will rise over 14 psi and higher... there is no more boost control but the complete turbo setup is stock... stock wastegate works and all hoses are connected proberly... if boost reaches numbers above 7 - 8 psi the engine starts to "choke"... BUT if i accelerate and hold the throttle so boost wont go higher than 8 psi the engine runs smoth and powerfull till 7k rpms.

i got installed a wideband O2 sensor but the numbers are ok even when the enginge starts to "choke" so its no question of leaning out or running to rich...

id be really thankfull if anyone of you could give me some suggestions on this...

oh and sorry for my poor english...

 

I assume you have ported the wastegate and installed an FCD? What have you done with the exhaust?

 

no the wastegate is stock... and not ported... as far as cutting out both cathalytic converters the exhaust is stock too... oh and no FCD as im running a standalone...

i was told since we ported the engine it would have a higher volumetric effency and at a certain point of throttle opening and RMP'S the turbo begins to some kind of "overspooling".... this would mean i have to get a bigger turbo... ??!!

 

im currently running my 1/2 bp'd fc with thr stock turbo. its runs great. it just spools SUPER fast. almost full boost (8psi) before 3k rpms. its an s5 motor though.

 

as far as i know there are diffrences between S4 and S5 turbo units... thats was i was told.... did you port the wastegate ?

 

I run my HB on stock twins at 7psi, runs ok but I have a few problems regarding the fueling.

At 6k the powerband really kicks in.

 

well like i wrote the engine runs great if i just push the pedal down so boost may not rise above 8 psi.... thats about 50 % of throttle opening... if i push harder boost goes up like cracy and the enigne starts to choke... i even replaced the connecting hose between turbo and wastegate with new ones to clear theres no leak or something... the twinscroll system is driven by a spare channel at the standalone and works great too....

but there is just no more boost control.... things were all ok before the rebuild... but we didnt make any change at the turbo unit... i just cant figure out what the problem is all about...

 

Stock turbo is WAY too small for a half-bridge. You are choking the engine and there's no hope of boost control with a ported stock wastegate. Upgrade....