Boost spike!!!
 

ok i have read on this on other cars but they have lots of mods. my 89 tII does not ahve alot of mods. but anyways when i punch it full throttle the boost shoots up to 10 and then goes down to 5.5 psi. i mean it doesnt do it all the time but about half the time. i was just wondering what i should do to fix this and can this hurt my engine? thanks guys

port the wastegate, if you have exhaust mods it will tend to do that

the only thing is that cat is gutted and the air pump is removed thats all that is done to the car. but will porting alone fix this problem?

I think you are either misdiagnosing boost creep, or you have a problem with your wastegate actuator.

How fast does the boost hit 10psi, and how fast does it go back down to 5.5psi WITHOUT letting off the gas pedal?

Also, what kind of boost gauge are you using, and has it ever been calibrated?

a $15 vaccum/boost guage hey it works alright. maybe i am misdiagnosing. but it hits 10 just like it normally it would hit 8. and returns at the same pace. PLEASE help me guys. spank you helpy helperton,lol

What did you do the the car in the time between when it boosted properly and the time that it began to have this problem?

not a thing at all is it really something i should worry about?

If you don't have any mods it's normal to see 1st and 2nd gear jump and then the boost start dropping because of restricted exhaust (dia./mufflers) or restrictive air intake. If you change the exhaust to bigger dia and "clean up" the intake you'll probably then experience boost creep in the higher gears. It will then be time to port the wg and add a boost controller along with electronics and fuel mods.

list ALL of your mods as far as porting/intake/exhaust
i dunno if the stock turbo will run 10psi all the way to redline with only gutted cats......im thinkiung your boost is dying off.
does it do the exact same in every gear or does it change depending on gear?

and do you have a boost controller?

no i do not ahve an aftermarket boost controller, and the only mods are the emissions removed. and the air pump removed. other than that it is all stock. help please

Make sure the wastegate line (from compressor outlet) is in good shape. A split line can cause some headaches.

Marques

10psi in itself isn't so bad, but the fact that it just started doing it for no apparent reason may indicate that something is wrong.

What is wrong with the stock boost gauge?

there's a Difference between boost SPIKE, and boost CREEP

and it's quite possible to have both at the same time too

boost spike is when u have slow wastegate response meaning it takes time to fully , (usually due to extra long vacuume hoses when running an MBC into the cockpit for example) but since u don't have an MBC u should check ur wastegate's vacuume lines consider replacing them.. maybe they're cracked and leaking or loose...

boost creep is when the stock WG is being overpowered and cannot "bleed" the extra exhaust energy fast enough

in the real world this is what it'll look like on a decent boost gauge:

(assuming WG is set for 5psi)

boost spike: u slam the gas... the boost "spikes" to 7-8 momentarily and then falls back to 5psi to redline...

boost creep: u slam the gas goes to 5.. then starts "creeping 6-7-8-9 psi as u reach redline

boost spike+creep= u slam the gas, boost hits 8 momentarily, falls Back to 5.. then starts creeping back up to 9...

Boost spkie is what is occuring. it goes all the way to 10psi(indicated).(which also brings the question, will 10 psi momnetarily cause the computer to cut fuel to the rear rotor?) then the boost goes down to 5.5 as said b4. The stock EBC is set for the fuel but off point of 8.6 as all are. so any help as to what is happening would be great, more replies please

have u checked ur vacuume lines if their lose or cracked?

over time with the heat, the rubber becomes hard and brittle.. u might consider changing them if u already haven't.. and zip tying the ends...

what is your stock gauge reading, and if you were hitting 10 i would imagin you would hit fuel cut

good point..

does ur car feel like hit a brick wall?

well today i was testing it out and floored it in 3rd. The boost bounces between 6 and 8 psi doesnt stay consistent. and no it doesnt feel like it hit a brick wall when it hits 10 psi. what is going on and how much is this gonna cost to fix?

It sounds to me like you need a new boost gauge. Is your stock boost gauge working?

yea but it also bounces, hose leak maybe?