Rb25det Boost Tappering Off.

[RicsR33]

Hi Guys/Gals

Ok so ill start from the start.

Took my car in to get the following mods tuned.

t04e - plain bush bearing (I KNOW) (wastegate port has be honned out)

Aftermarket low mount manifold

Bosch 040

SAFC

blocked bov (yes stalls sometimes- so there was no fabrication to the intake pipe)

3inch intake pipe

catch can (yes hooked up correctly - so there was no fabrication to the intake pipe)

3 1/2 inch exhaust

Apexi Pod

$22 ebay boost controller

Was hoping to see around 200-220 kw atw (with my stock ecu and average turbo)

When my tuner did a few base runs, we saw the boost spike to 14psi and the ecu chucking a mental, even losing a 100 hp through the midrange the car still made a top of 269hp atw running rich.. As we were searching for the problem for the spike saw and felt the actuator rod not opening the wastegate fully, once i adjusted the tension on the actuator rod the car was no longer spiking but would hit 11 psi and fall off to around 6psi by redline which was only making around 230hp. we came to the conclusion that it was the crappy dual port 4 psi actuator. so he tuned the car quickly with what we had to work with, took some fuel out since it was still running mega rich.

next week i shot down to MTQ and bought a garret 8psi actuator, put it on and went for a quick run around the block before the tune, from what i saw on the boost gauge it seemed to be holding .6 bar fine. we put it on the rollers and did a base run, boost was around 10-11 psi but tapered off to 7 psi, checked the tension on the rod and there was enough spring tension to hold the wastegate shut also the car was down 10kw from what it was a week ago. and lost quite abit of power in the mid range also was running a little leaner then a week ago, we tried winding the boost controller right up, it only added 1 psi and still lost boost to 7. We the turned the boost controller completely opposite way it made a constant 4psi right across the rev range?? souldnt it be 8psi since thats what the actuator is? we also tried a GFB controller on it as well with same results. We then checked the part number stamped on the actuator and it is indeed a 8psi. No matter what we tried the boost was leaking off..

Now could this be a restriction in the exhaust? (was thinking of droping the exhaust from dump and see how it runs, then maybe from exhaust housing if it made no difference from there) its a JJR Turbo back exhaust with a split down pipe and "high flow cat"(not actually to sure how high flow lol)

What are some of your idea's? bellmouth? i cant see why it could spike and build to 14psi but now it cant even hold 11psi?

sorry for my life story just wanted to try and explain fully to you guys.

Thanks Richard

[RicsR33]

Today i tightened the rod even more and its spiking back to just under 1 bar but still tapering off to .7 bar i dont understand why i cant keep my boost stable.

[mosquitocoils]

It could simply be the manual boost controller... I think they don't hold boost well in the upper rev range. Have a search here on SAU, it's well documented.

You kind of have to weigh up the pros and cons - $30 for a controller that holds pretty well, or $500 for an EBC.

I'm happy with the turbotech manual controller hahaha.

And if I didn't understand the problem properly, I apologise

[Ultimategtr]

Get a EBC, other borrow or buy, otherwise you could spend years trying to fix this.

[RicsR33]

i do have a profec laying around at home, just not 2 sure how to install it, might look at the greddy install instructions and have a go at putting it on.

[R31Nismoid]

It could simply be the manual boost controller... I think they don't hold boost well in the upper rev range. Have a search here on SAU, it's well documented.

Say what? Any links to where such a statement is well documented?

I've never read such posts...

Properly setup, boost control, will work fine regardless of if it has flashy lights and buttons or a screw top.

I've never used anything other than a bleed valve. Made over 370rwkw, 24psi @ 8000rpm.

So it comes down to installation 9 times outta 10.

[RicsR33]

nismoid i know you know quite abit what are your idea's or solution? ive checked the vac lines, my controller comes off the cooler pipe to the boost controller then to the actuator. the vac's are brand new and the actuator is brand new, tension seems correct. I did also mention we tried a gfb controller on it as well with the exact same result. hmm

[R31Nismoid]

drop the exhaust first, see what happens.

also when the internal gate was ported, was a new end cap used, larger one so that air does not go past?

Why was the rear ported anyway? They flow enough for the turbo they are.

[RicsR33]

yer when i got the turbo the port was only at 20mm, i was told this causes spiking on alot of these shit turbos so i got my fitter and turner at work to port it out to around 29mm, hyper-gear then built me a rear flange with a 33-34mm wastegate flap, im almost 100% sure that it overlaps the port by atleast 1mm all round, yea the exhaust will be the first thing to drop tommorow when im back at work with access to a hoist.