2jzgte not holding boost

[RZTT]

Hey guys got a problem with boost hope someone can help me out. Had the car on dyno last night and we set the boost at 17psi. It goes up to 18psi the drops back to between 14-15psi. It seem likes something not letting the boost to hold steady. Cant work out what causing the boost to drop. Could it be my actuator that not letting the boost to hold?

When i was running JDM twins i had the same problem and never actually got around to fix it cause I did USDM turbo conversion. And now the same problem after completing the conversion.

Mods on the turbo side:
USDM twins
Power Fc
Greddy Ls intercooler
Ported manifold
Ported egcv
Apexi Avrc boost controller
kakimoto catback exhaust with hiflow cat
3"custom mid pipe
3" custom dump pipe

Here is my old dyno graph was done when i was running JDM twins. As you see it hits 1.35 bar then starts to drop off to 1.05 bar.
Will get new dyno graph next week

[wilbo666]

Are you sure the 'peak' isn't a result of the sequential system putting the second turbo online?



What are you using to control boost? And how is it installed?

Cheers
Wilbo

[RZTT]

Are you sure the 'peak' isn't a result of the sequential system putting the second turbo online?



What are you using to control boost? And how is it installed?

Cheers
Wilbo

Hey mate, The 2nd turbo definitely comes online and reaches its max RPM then it starts to drop instade of holding the boost.
I'm running Apexi Avrc boost controller its the blue screen one.
It was installed by professional mechanic

[bungs]

You using the stock bov? i've heard the seals stop sealing after a while and cause boost leaks..

[RZTT]

You using the stock bov? i've heard the seals stop sealing after a while and cause boost leaks..

sorry i should have mentioned, Im using HKS SSQ bov

[Norbie]

An exhaust restriction could do this. Can you try dropping the exhaust after the dump and go for a quick (and loud) test drive?

[RZTT]

An exhaust restriction could do this. Can you try dropping the exhaust after the dump and go for a quick (and loud) test drive?

The exhaust is 3" all the way and 4.5 inch tip. Only running 1 highflow cat. The USDM Egvc is massive compare to JDM Egvc. I think the JDM is around 2 inch and USDM 3 inch. I could drop the exhaust and go from a quick spin but its gonna sound so loud like top fuelers lol. Will give it a go

[Mr_Flawless]

could be your tuner? (no offence) the avcr is a good boost controler, but if not set right they can spike, peak and drop off, rather than hold, i had problems with this in my silvia with this boost controler, took it to my dyno tuner, and it never had a problem after that.

[Phoenix01]

Forgive my ignorance, but just wondering. I remember it not being a good idea to go above 1bar with the JDM ceramic turbos, for reasons relating to the ceramic wheels self destructing... But how much more boost can you realistically make with USDM twins? As they might peak at 18psi shortly after the 2nd one comes on, could the issue be infact that the turbos themselves are becoming the restriction at higher engine RPM?

I might be way off the mark, but it was just a thought that occured to me.

[RZTT]

Forgive my ignorance, but just wondering. I remember it not being a good idea to go above 1bar with the JDM ceramic turbos, for reasons relating to the ceramic wheels self destructing... But how much more boost can you realistically make with USDM twins? As they might peak at 18psi shortly after the 2nd one comes on, could the issue be infact that the turbos themselves are becoming the restriction at higher engine RPM?

I might be way off the mark, but it was just a thought that occured to me.

You are right about the JDM twins going bang over 17psi but i've seen JDM twins being pushed up to 20psi and still going strong. The reason my JDM twins was spiking up to 19psi due to having full 3" turbo back exhaust setup without cat with 4.5 inch tip. And i didn't have restriction ring in the dump to keep the boot down however it still should hold atleast 17psi after the spkie.

And with the USDM twins it can handel quiet a bit of abuse. I've seen guys in the US pushing these twins up to 22psi and daily 20psi without any issue. At this point I'm thinking my wastegate Acuator might be weak and causing it to open up at high RPM/peek. We going to do Wastegate spring mod to see that fixes the problem.