Erratic boost 04 liberty gt

[Ej20mick]

Hi guys new to this forum and find it great

Not sure if I'm posting in right topic
03 my04 liberty gt auto
I recently fitted a new ultrex dump and catback exhaust. Avo tmic. Apexi panal filter and replaced all header, up pipe, dump, exhaust gaskets at the same time. I then had it dyno tuned and the guys were pretty happy with the tune and how it responded. I've noticed that the boost is all over place if I put my foot into it at low rpm the boost comes up to 16psi instantly then slowly tapers off to 13psi back up 15psi then down again before finally deciding to steadily hold boost once reaching higher rpm. Seem to be midrange rpm. if I accelerate while in the midrange rpm it doesn't spike to 16psi it goes to 13psi stays for a few seconds then slowly up to 15psi. Car never had this issue and made good power down low and through the mid range before mods. Not sure if it was like this before I had it tuned after doing mods as I drove it to tuners trying to stay off boost

Thanks Guys and keep up the good work

[Yowie]

Two thoughts (not necessarily solutions):-

1. A tune often targets different boost under different conditions. Eg a quick spike to get the turbo moving, peak boost in the midrange and tapering the boost downward towards the redline (especially for a smaller turbo beyond its efficient limit at high revs). Don't assume you should be seeing the same boost hold steady all through the rev range at wide open throttle.

2. Check your vacuum hoses between the turbo, boost controller and wastegate. I had uncontrollable boost for a bit before i discovered that the rubber vacuum hoses connected to the turbo had swelled and become useless:-



(now replaced with silicone vacuum hoses)

[Ej20mick]

Yowie
Have had a quick look at vac lines all appear good but will have a better look

Seems to be lacking power when boost comes down and slow to build rpm

[norbs]

Fark me how can they (tuners) be happy with that !! Something doesn't sound right to me. Could be many things. Hope you get it sorted.

[Ej20mick]

Norbs
Thanks mate I'll have to call tuner this week and check if maybe they pulled timing or boost due to pinging. I'll try put a pic up of dyno sheet

[bigBADbenny]

Have you done some health checks?

Its not unusual to have leaking or popped hoses after a tune.

So eg pressure test the inlet tract.

Here’s a starter:
Pressure test the inlet tract, key on acc.

Eg block inlet tube after the airbox.
Remove brake booster hose and blow into it or connect it to a low pressure source < 1psi.

Listen for hissing or use soapy water spray, look for bubbles.

The test encompasses everything including injector seals, inlet manifold gaskets, fuel purge returns, plenum, pipes, hoses etc.

Be persistent, you might have more than one leak.

[bigBADbenny]

Sounds like a dynamic leak, prime suspect is the stock throttlebody hose.

Replace it with the avo or Kobe silicone hose with quality Norma clamps.

[bigBADbenny]

Here’s another starter, other suspects include fpr ref hose (pops off nipple at the lower end of cyl4 inlet manifold runner to a vertical down nipple under the FPR, map sensor hose (goes brittle and cracks) and the two fuel purge returns (one to the inlet pipe, the other to the front of the inlet manifold)...

Vacuum and boost checks.
It will help to be able to id all the hoses.

Ziptie everything without a clamp.

Engine off, key on acc.

Going clockwise around the engine bay:
Inlet to turbo (rots underneath)
Wastegate to compressor outlet, tee’d to boost control solenoid
Turbo compressor outlet to intercooler gasket/s
Blow off valve gasket
Blow off valve vacuum reference hose
Blow off valve return hose to inlet
Intercooler to throttlebody hose (stock hose has a gasket that causes leaks that may vary according to boost/vacuum)
Fpr vacuum reference hose to lhs rear inlet manifold runner (backfire under boost)
Front of inlet manifold: left to right
Fuel purge solenoid, check the hose is not cracked before the solenoid and after it at the return to front of inlet manifold or the other return to inlet manifold.
MAP sensor
Boost control sensor, from wastegate tee, return to inlet manifold.
Around the top of engine: head breather balance tube and head blow by and crank case breather returns to inlet pipe
Injector seats.

Don’t forget that for this test supposed to block the inlet tract post maf.
Note that for this test the engine should not be running.

The idea is to pressurise the entire inlet tract at no more than 1psi, after the maf.

Usually if doing a high pressure test, you’d isolate eg inlet tract from the throttlebody to prevent blowing out your cam seals.

[Ej20mick]

bigBADbenny
Thanks mate for the good advice will give it a go over weekend. I've already changed the intercooler inlet and outlet to silicon hoses as they came with avo intercooler

[bigBADbenny]

A small tuna can or jam jar lid with masking tape around the circumference is a good plug.

then pull the brake booster vacuum hose off, key on acc, blow into hose, listen for air leaks and or use soapy water spray everywhere, especially the plenum.

Step 2 is add a hole to the plug, insert rubber tyre valve, remove schraeder valve, add air or air & smoke.

Add the valve with some rtv on the inside to seal it.

Little compressors are noisy so turn it off to gear the hiss.

As described a healthy car will exhale for at least a few secs when you release the pressure source.