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Not getting full boost in first gear

jhjones

By jhjones,
in Engines & Forced Induction

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jhjones Rising Star

jhjones

Posted
Posted (edited)

Hey, got this problem, I'm not getting full boost (18psi) in first gear, only getting 15psi. When I switch it to low boost (15psi) I only get around 12psi in first gear. I can hear the screamer pipe from around 9 psi on the high boost setting.

The wastegate spring is 1 Bar, Ive pressurized the intercooler piping up to 24psi and there are no leaks.

I can't remember if it was like this when I got the car tuned as I don't really drive the car.

Mods:

RB25DET Neo

GTX3071R

Link G4

50mm Turbosmart wastegate

6Boost low mount twinscroll Manifold

Edited by jhjones
KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

 You know that 1 bar is only 14.5psi?  Have you got a boost controller or is boost controlled by the Link via a Mac Valve? I'm not sure that full boost in 1st gear is all that important. 

Shoota_77 Veteran

Shoota_77

Posted
Posted

I'd be worried if you can hear the wastegate venting at 9 PSI.  Seems to indicate it's bleeding off too early.

You need to get one of these-

handpump.jpg

Remove the wastegate from the manifold (so you can see when it starts to open) and then disconnect the vacuum/pressure hose at the engine (so you're including all hose between engine and wastegate which may identify a leak somewhere) and then apply pressure (not vacuum) to the wastegate actuator.  In theory it should not crack open AT ALL until you reach what is supposed to be the wastegate spring pressure.  If it's opening before the target pressure then you either have a weak spring, a leaky diaphragm or a leak in the vacuum/pressure hose.  That's my evaluation anyway!!

Good luck.

 

jhjones Rising Star

jhjones

Posted
  • Author
Posted

Boost control is done by the link using a mac valve.

If there was a leaky diaphragm wouldn't i hear it leaking out the port on the mac valve when i pressurized the intercooler pipping. Same with a leak in the vacuum/pressure hose except i would hear it leaking from the hose.

In the high gears boost shoots up the 15psi then slowly creeps to 18psi. Normal?

R_34 Community Regular

R_34

Posted
Posted

Right, bigger turbo and getting full boost in 1st gear doesn't come along because of inertia of the CHRA and available energy on the turbine wheel.

I wouldn't be too worried about getting full boost in 1st gear but more by your creeping issue. What size your gate is ? Which manifold do you use ?

menthol369 Collaborator

menthol369

Posted
Posted

How old is your wastegate, and does it hit the track often? 

The wastegate springs get weak over time with continued heat cycling, i had 1 bar gate springs that ended up opening around 6psi due to the heat. This was after a couple of years on the track however.

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