boost

rtebeau

Registered User
i just got my car back from getting the tranny rebuilt and now when i go WOT i only get around 8 PSI of boost (i use to get around 11 or 12) and i feel like my car has lost alot of power, any ideas what happen?
its a 1990 tbird sc
all stock
 
check your vac lines. when they where geting the top bolts on the trany something probly got lose or came off.
 
sorry i dont know to to much about cars but my father use to be a mechanic, is checking these easy enough i can do or should i just wait and see if he doesnt mind helping
 
can u keep the car running without pressing the gas ?
if u can, let it run while u go around all the vacuum lines spraying them with carb cleaner. spray around all the joints, including the intercooler and tubing. when and if you find a leak, the rpms will raise and the idle of the car will kinda smooth out.

thats my easiest explanation, hope you understand it.
 
can u keep the car running without pressing the gas ?
if u can, let it run while u go around all the vacuum lines spraying them with carb cleaner. spray around all the joints, including the intercooler and tubing. when and if you find a leak, the rpms will raise and the idle of the car will kinda smooth out.

thats my easiest explanation, hope you understand it.

thanks, ill try it out sometime tomorrow
 
when its in park its about 18 or 19 and im not sure if this has anything to do with it but i thought i read somewhere that when the car is off the gauge should read 0, mine stays around 1 or 2 vac
 
just the gauge off it happens all the time, your porobably still hitting 10psi of boost just the gauge is reading -2 at 0 so at 8psi its really 10


or perhaps its reading accurately according to your butt dyno
 
just the gauge off it happens all the time, your porobably still hitting 10psi of boost just the gauge is reading -2 at 0 so at 8psi its really 10

thats what i thought at first but i really feel like iv lost that initial jolt that sends you into your seat, it feels like it slowly climbs to speed, if that makes any sense
 
i sprayed the vacuum lines (not sure if i got them all) with the carb cleaner and...nothing.. and my boost has gone down a little too now at WOT it doesnt go past 6 or 7, and the car has definitely lost power, i cant even get the tires to spin anymore
any help would be awesome
 
ouu

check to make sure your belts aren't slipping, give the tensioners a tug and see if they give any.

is your air filter clean?

check the valve on the inlet plenum by the act sensor, it should be closed with the car off and opens with vaccum when the car starts

do you have any codes?
 
most all times when rebuilding a tranny(auto) the torque converter gets replaced, direct cluch from engine will give you around 8lbs boost. im betting the new converter has no stall. most sc's will reach with a 10% od sc pulley and good exhaust around 13-15lbs at 4k rpm. id say get a stall converter. around a 3800 should make you happy but keep in mind to get a bigger tranny cooler as well, stalls get hot.
 
On our cars because we make so much torque down low, a 3800 would not be ideal. I would say around 2600 because thats about where our motors are starting to make really great torque numbers.

Frit
 
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