Atomic

iTrader: (42)

There are a lot of things that could be causing this, so dont give up on turbos yet!

How are you controlling boost? Just spring or using a controller?

You could have a boost leak somewhere in the cold section. Are you measuring boost at the turbo or the intake? Either way, I suggest measuring the other at the same time to check for boost leaks or a restrictive intercooler.

Cam and converter are not that great for a turbo trying to run low boost. You need to get into boost quicker without reving higher. You basically want the turbo to outrun the engine, otherwise you will be scraping by on the bottom of the compressor map.

AJII

iTrader: (7)

Thanks for the reply Richard!

I'm using a Hallman MBC. With the open downpipe and the controller all the way down I was seeing a consistent 8psi. Got the exhaust connected and saw 6psi with the same settings, cranked the controller all the way up and now see a max of 9. Usually around 7-8 though. Can my exhaust really be that restrictive? Everything I've read basically says a MBC should double my boost when turned up. Exhaust is factory piping (2.75") with a 3" Spintech (it's maybe 14" long).

I'm measuring at the intake and the boost gauge agrees with hp tuners. I'll have to drill and tap the turbo this weekend for a fitting to measure at the turbo.

Turbo seems to spool up really quick, but like I said, I have nothing to compare it to. But out of the hole it does feel sluggish if not brake boosted. No doubt it "felt" faster before with just the headers.

Timing ramps down from 30ish to 13 and Afr goes 12.3 to 11.3 in the PE settings. Only section that hasn't been tuned in well is the low 1500-3000rpm areas at 95+ kpa because i can't get much data there on the street, but even at tip in the richest I see is 10.8 which I wouldn't think would make it feel sluggish.

Thanks for the suggestions!

Atomic

iTrader: (42)

That exhaust is smaller than I would recommend. Even a basic 6.2 exhaust (3.5") would be a good upgrade and still sound good. I dont see a reason for you to need to go bigger than a 3.5" for your setup, but it will help.

How do you have the controller set up? You should be able to make the turbo make 50psi of boost with the controller maxed out.

I am thinking you have a boost leak somewhere...

Choda

iTrader: (1)

def need at least full 3 inch exhaust.

AJII

iTrader: (7)

Cutout will be about 12" from the downpipe end so I guess I'll see how that changes things and rethink the rest of my exhaust.

I have the port from the side of the intake tee'd to the MBC and gauge. And then from MBC to the bottom port on wastegate. I also thought I should be able to make more boost restrictive exhaust or not..

Not sure where I'd be leaking boost as my cold side is really simple and I cant hear/feel and leaks in the hot side.

Atomic

iTrader: (42)

The best way to check for a cold side leak is to actually pressurize the entire cold section with an air crompressor with the engine off by covering the turbo inlet and hooking up compressed air to it.

You need to add air to the top of the wastegate to get more boost than spring pressure.

AJII

iTrader: (7)

I'll do that this afternoon.

All I've read said that the top port is only used with an electronic controller. But what you're saying makes sense. So should I just tee the two ports together?

ezdaar

iTrader: (1)

use this Mr. Bubble Original Bubble & Bubbleberry Foam Soaps Or soapy water in a spray bottle, to find ya leaks.

Atomic

iTrader: (42)

Its not quite that easy...

-You have spring pressure + pressure on top keeping the gate shut (which means the turbo spins faster makes and makes more boost)
-You have exhaust back pressure + pressure on bottom opening the gate (which makes the turbo spin slower so less boost)

If you tee the ports together they will cancel each other out and it will be eactly the same as spring pressure.

Not using a bottom reference will basically double spring pressure. So if you have a 6psi spring and it makes 6psi with the bottom port hooked up to the turbo, and you remove that reference line so the gate isnt connected to anything it should make about 12psi.

Try this before adding air on top.

Just a warning, if you put the reference line to the top of the wastegate without anything connected to the bottom port this means you are forcing the gate shut as boost increase so the turbo makes even more boost. Do not do this unless you want to blow up your engine.

AJII

iTrader: (7)

Just thought about this...

BOV is also tee'd into line from intake, is it possible the bov is creating a leak under boost? Seems like the boost would force it closed, but wouldn't be the first time I've been wrong..