Can't Exceed 14psi Of Boost

[Glennno]

Hi,

Recently took my R33 to my tuner after recently purchasing the car for some tuning as it had cold start issues. Other than this, it ran well for me.

Tuner called to say car is making less power than I mentioned was on previous owners dyno sheets.

Facts:

- car hits 14PSI and then drops off as car revs increase (tuner said this indicates a flow issue).

- cat converter is s high flow and looks brand new when looking through it.

- cam timing is perfect

- removed boost line to try get turbo to free spool - no increase in boost. Boost still lowers as revs increase (also indicates flow issues?)

Car specs:

- 97 R33 manual

- Haltech platinum pro ECU with MAP sensor and 02 sensor disabled and unplugged but left in dump to act as a bung.

- K&N pod filter with custom alloy intake pipe

- GT3071 with .86 housing low mounted

- 3" dump and front pipe combined (single piece) - high flow cat in new condition. 3.5" HKS Hi Power silent catback with 2 x hot dogs.

- Blitz return flow intercooler.

- Plumb back turbo smart BOV. (Car is fluttering, so isn't leaking)

- Profec B Spec II boost controller with dual stage. Setting 1 is rather mild, setting 2 is the 14PSI setting and makes 310-330HP

- Has typical supporting fuel system and mods etc.

I'd love some help in things to try looking for... Is it worth looking at the waste gate actuator? Pulling the intercooler piping apart to find something restricting it? Pulling the exhaust apart? Running it with no pod filter? Removing and inspecting the turbo itself?

All mods were made in 2012 with brand new parts by original owner and installed and tuned by a performance workshop. Motor was compression tested then and was fine. Motor seems to run well and sound good other than the cold start issues that I sill have. Hunts for revs for 2 seconds and stalls. Second start is perfect. Going to get s brand new tune performed but also want to fix this not boosting issue.

Thanks

[89CAL]

Its free to pull the intake pipe off and check the turbo. Its also free to drop the exhaust (well need to buy a new gasket). Personally I would drop the exhaust pre-cat

[KiwiRS4T]

Dropping the exhaust is simple - sounds like you might have a fairly restrictive system.

Test for boost leaks (make up a plug and apply air supply)

If you are keen you could put a nipple either side of the intercooler and measure pressure drop.

And yes maybe your turbo has failed.

[Glennno]

Thanks guys... Couple questions

1. Where does my MAP sensor live? how much of the intake can i remove and still run the car?

2. With removing the intake pipe to check the turbo, is this to check shaft play?

3. I can leave the dump and front pipe connected and remove the cat and the catback. Would i then take it for a quick drive and see if i can exceed boost? if this fails, remove actuator boost line and test again?

Thanks guys, would be a shame if the turbo had failed but i guess anything is possible.

[Glennno]

Another question

4. Could the actuator for the turbo's wastegate be too low of a spring and actually have the wastegate open at around 14PSI if it were too weak? Could i be bleeding all my pressure out the ass end due to a failing or too-low of an actuator spring? Was just a thought on an R33 Facebook page.

[Glennno]

Another question

4. Could the actuator for the turbo's wastegate be too low of a spring and actually have the wastegate open at around 14PSI if it were too weak? Could i be bleeding all my pressure out the ass end due to a failing or too-low of an actuator spring? Was just a thought on an R33 Facebook page.

"If the spring is too soft, even with no pressure signal to the actuator, the valve will open if there is enough exhaust back pressure, which will limit the amount of boost produced by the turbocharger." - Turbosmart Website.

[XGTRX]

If you have no leaks then you can do a few things.

Block if the BOV and see if it allows higher boost.

Find out the waste gate spring rating. I assume its internal waste gate.

[Glennno]

The BOV is a turbosmart Plumb back and the car flutters when i let off the accelerator.. I have a feeling the BOV wouldnt be leaking?

Is there any way to find out the waste gate actuator spring rating? it is indeed internal. Couldnt see any model or marking on it with it installed. Someone suggested getting a compressor or bike pump with inline gauge to pump into it but, this seems like a lot of mucking around. I'd be happy enough to replace the actuator if i knew what exactly to purchase. End of the day, could sell it if it makes no difference at all.

[XGTRX]

Just a gauge on the waste gate hose and use a pump connected to a t piece. 5 minute job

[Glennno]

This would achieve working out at what pressure the wastegate opens. It may or may not prove that the wastegate is the culprit though? I guess if it opens at 6PSI, its likely to be the issue.. If it opens at 10PSI or higher, then likely not going to be the issue?

[conan7772]

my brand new gt3076r internally gated didn't boost more than 16 psi with similar set up to yours on rb25/30

stuck on an 18psi large can actuator- fixed

minimum boost now 14 psi

for some reason Garrett fitted 7 psi actuators, I guess so they don't come on like a sledge hammer

Edited June 13, 2016 by conan7772

[Glennno]

Wow awesome.. thats lifted my spirits a little knowing that it could definitely be the issue.

If you put an 18PSI actuator on, wouldnt the minimum boost be 18PSI, not the 14PSI?

Also, got a link to an actuator that might bolt directly to my GT3071R? Im not sure what will and wont fit, if it needs to be turbo-specific etc.

[Glennno]

After a little thinking, i think my idea will be as follows - Disconnect the actuator from the wastegate flap and figure out a way to wire the wastegate flap shut... This should then allow me to boost higher than 14PSI and if not, i have another issue.

[admS15]

After a little thinking, i think my idea will be as follows - Disconnect the actuator from the wastegate flap and figure out a way to wire the wastegate flap shut... This should then allow me to boost higher than 14PSI and if not, i have another issue.

Sounds like a plan[emoji106]

[Glennno]

So i dont need to open another topic that has likely been covered.. It seems theres a vacuum line at the back of the intake manifold and the front.. What would be better for tapping in for my boost gauge? (Getting a digital one)

[89CAL]

Any vac source that comes from the manifold

Doesn't matter which

Pressure at all points should be equal and undiminished. Or something like that

[Glennno]

Beautiful, champion. Something else someone might be able to help with (Yes, i have a list of things to sort)... The white strip under my rear left hand tail light leaks and i get water in there.. Can this strip be replaced or must the entire rear left tail light unit be replaced?

[89CAL]

Which strip are you talking about? Not the strip in the middle of the boot underneath where it opens?

I'm not real sure what you mean here. Photo?

[Glennno]

Ah sorry, should have explained a little better. In the photo below, im talking about the individual white light strips directly under the 2 x round brake lights. The white strips where the indicators live. Mine on the left hand side is filling up with water from rain.

http://www.skylinespares.com/wp-content/uploads/2013/06/IMAG0764.jpg

[XGTRX]

Pull out the whole light assembly and reseal them with windscreen sealant. Its a common problem because the sealant goes hard. 2 hour job.