Why my 16g wouldn't reach 20psi until 5K

[LumpyVR4]

Funnily enough with new throttle seals I had to adjust my idle down A LOT. Just done a quick tuning trip atm. I'm working tomorrow at 6am, so I thought I'd save checking out the performance improvement until then.

Preaching to the choir but, do regular boost leak checks people!

 

[4piknup]

Did you put them in the way they were?
I flipped mine over so the boost pushes the seal lips harder to the shaft.
Im not so worried about the vacuum leaks

 

[LumpyVR4]

Hmm didn't think of that. It's the first time I've done this so I was obsessing over getting everythying exactly the same as what I took off. Good point though. A little Googling taugh me that 25 in Hg is only about 12psi, and I rarely see 25 in Hg.

Raining and foggy this morning so I didn't give it the beans. I can report 20psi at around 4.5k at part throttle. The best I used to be able to do at part throttle was 7 or 8psi.

 

[Benzo4gT]

I flipped mine over so the boost pushes the seal lips harder to the shaft.

Nothing better than flipping something over to get the lips to seal harder on the shaft.

 

[CLuTZ]

Are you running a Cyclone intake?? Im seeing 21psi at around the 3600rpm mark.

 

[LumpyVR4]

Aus spec ECI multi manifold. That 20 psi at 4.5k was on partial throttle. Not sure exactly how much, say half. If I can see where the hell I'm going on the way home from work I'll bury it to see where my boost comes on and peaks under full throttle.

 

[croket]

i see peak boost at 3800 with same manifold and a 20g , i would be guessing you should see peak by 3500 at the latest

 

[LumpyVR4]

It was better, but still leaky. Full boost at 4300. It spools from about 2200 then boost stops building at about 10 psi at 3k, then sits there until just below 4k. Then it builds to 20 psi. Presumably the turbo is pushing so much air by then that it can cover the leak and the waste gate pressure. I've put the leak tester on again and found a couple of little leaks at 20psi. The big one though I think is the turbine seal. In a quick test it leaked from 15 psi to 5 psi in 2 minutes.

 

[4piknup]

I should watch some utube on leak testing. Your results sound ok for 15psi boost. Mine leaks down at a similar rate.
Are you using bubbly water to find leaks?

 

[LumpyVR4]

I haven't needed to yet. All my previous leaks have been totally obvious. Better break out my squirty bottle full of detergent.

Update:
My vacuum system was such a hodge podge of different bits of hoses, I ripped it all out and started again with new hose and brass joiners instead of plastic ones. After that I kept losing pressure through the turbo while testing, so I took a suck it and see approach. Gained another couple of hundred RPM but it's still acting the same way, boosts to about 10psi, then stops there, then builds to full boost around 4k.

Next up is taking the turbo out of the mix and attaching the tester to the turbo out hose. I hope it's something simple like the standard hose clamps aren't up to it and I need T-bolt clamps on the cooler piping.

 

[croket]

Be sure to check injector seals mate , when i last did a leak test only soapy water would pick them up. T clamps are a bit over the top unless running high boost. I can pump 1.8 bar into mine now with only a tiny leak from a bad clamp behind the bumper one day ill get around to replacing it

 

[CLuTZ]

Try a different actuator

 

[LumpyVR4]

Try a different actuator

I still need to go around with my soapy water, but you have me thinking. Is this cenario plausible?

The guy I bought the car off told me it had a 20psi gate. Maybe he assummed that becuase the car peaks at 20psi. Is it possible it has a 10psi gate and seeing as it is 3' off the o2 housing that once the revs come up the stock waste gate can't pass enough air and it creeps to 20psi?

 

[4piknup]

Pin the wg open and run it up. This will test for creep.
When you leak test, bypass the solonoid and you will see when the gate opens or is fully open

 

[LumpyVR4]

Be sure to check injector seals mate...

Seeing as the rest of my vacuum system was stuffed I worked on the assumption that my injector seals would be too. I stopped at Meek on the way home today and grabbed some new ones. I didn't bother to test the old ones, I just pulled the injector rail. Not that I has to pull at all, it just lifted out. Number 1 seal was completely stuffed and the rest weren't great either. I know I should keep testing but I'm just going to test drive it tomorrow.

 

[croket]

Good stuff for the price of them and the ease of doing the job its well worth it i think

 

[CLuTZ]

Is it possible it has a 10psi gate and seeing as it is 3' off the o2 housing that once the revs come up the stock waste gate can't pass enough air and it creeps to 20psi?

That's exactly what I was thinking. What boost control do you have? If you are running wastegate pressure i'm guessing you're hitting 10psi and creeping to 20psi, higher in the rev range.

 

[LumpyVR4]

There is no external boost control. Once again because the guy I bought it off said it ran 20psi and the turbo had been changed, I assumed that the waste gate had bee changed to 20psi. The more I tihnk about this the more I'm thinking it's just creeping to 20psi.

 

[4piknup]

The creeper.

 

[GeoKez]

Try what Jack said and wire the gate open. See if it gets to 20psi, results will tell you lots of things.