so i was wondering if my fuel pressure may be the reason for my engine rpm's dropping and rising at higher boost

my fp gauge at idle says 46

i have 270cc injectors in place of the stock 235's

what should i be looking at with the vacuum line on the fpr on and off with those injectors

ok let me put this another way

at 46psi idle pressure my pocketlogger said that the short term fuel trim was constantly -10
when i turned the FP down to 36psi at idle

the short term trim goes between -1 to +1
does that look better

or should it be around the -10

come on guys
does anyone have an answer on this

oh and i did find a vacuum hose that had fallen against my egr pipe and melted a hole in it so i am sure that was causing some issues

boost leak test
so many holes so much hissing

you want your short term trim to ba as close to 0 as possible. +1/-1 is fine.

Terry

wierd
i am finding one more leak
it sounds like it is coming from the turbo itself
i at first wet the wastegate actuator on my hrc kit and saw some bubbles coming from where the actuator bolts to the turbo housing so i used some thread sealer to close up the threads but i still hear a leak

finally no hissing anywhere else
but right there

and it is proving to be the hardest one at all

your rpm is droping and rising at higher boost? What exactly are you talking about? What is your fp at whatever psi?

If you have vac leaks, that can cause f*cked idle.

Nick
97RS


THX KAPTAIN MYKE FOR HOSTING! www.kaptainmyke.com

exactly what it says

if i try to boost more than 5psi when i put the pedal to the floor
it hits about 4500 rpms
then drops back to 4K
the boost drops down to about 5 again
and then the rpms build back up
along with the boost
and then fall off again

my dyno sheet looks like a sin wave

but like i said i found a vacuum line with a huge hole in it
so that was probably the problem
i havent got a chance to run it again to find out


at idle my fp is 36psi
but with the vacuum leak it was reading 13psi of vacuum
when it is normally 24 psi of vacuum

What does the vacuum line that goes to the FPR look like?

i am not sure what you mean
but it comes out of the intake manifold
T's into my greddy profec boost controller and then goes into the fpr

Originally posted by baxsom
so i was wondering if my fuel pressure may be the reason for my engine rpm's dropping and rising at higher boost

A vacuum leak(s) will affect idle and acceleration under load. When you accelerate, it sometimes hesitates like a bad misfire, and idle rpm will be up and down.

i was hoping this was my problem but i did a boost leak test
and although i did find a leak and fixed it my engine is still screwy
i dont get this in lower gears but in 5th
when i hit about 5k the rpms' drop down to about 4000 rpms then build back up to 5000 again
then drop again

could it be my profec B acting up
i have my limiter set at 11 psi and the peak boost has never said it hit higher than 9.5

the only thing i can think of is it is spiking to the limiter on the boost controller and that is what is lowering the rpms but it is happening so fast that it is not registering

i am going to unhook the profec and just run the vacuum line straight from the wastegate to the turbo and see what happens

Originally posted by baxsom
i am going to unhook the profec and just run the vacuum line straight from the wastegate to the turbo and see what happens

That's a good idea. Also, make sure your bov is holding boost. Do you have a fuel pressure gauge? If your in-boost fuel pressure is high, it's possible that could cause a hesitation. What about your air/fuel reading? Is it also erratic when the rpm fluctuates? Is your ignition in good order?

ignition is stock with a msd coil

i need to make sure and check wot fp
it is 40 psi at idle

and i do know that when i had it on the dyno it was 10:1
which seems pretty rich to me


i think that i will get the aermotive a little sooner and dump the cartech quicker than i thought
that may help

i tightened my BOV a little
it was fluttering a little anyway
so it may not have been tight enough to hold higher boost

If your WOT fuel pressure is 10:1 at only 10-12psi of boost, you are definitely running way too rich. I think a/f of ~12.5:1 should be the target range under 17-18psi boost on premium pump gas.

so in my case should i raise my boost setting to lower the a/f
i know the engine has been built to handle it
or lower the wot fp screw
i am still using the cartech so so correct me if i am wrong but believe this screw is the spring loaded one on the side right
counterclockwise to lower

It's not a good idea to raise the boost level until you're sure of the problem. Try lowering the wot fuel pressure (that copper-toned knob) a little at a time. This is when you'll want to hook up a fue pressure gauge. Did you get a mechanical fp gauge with your kit?

i took the mechanical gauge off and put an electric sender in its place to go inside the cabin

at idle with the vacuum line on
i get 45 psi on the gauge

there is another thread going discussing the same topic almost
so lets close this one off since many of the questions being asked here are there also