Two Level Boost

[kieran]

ah i see :thumbs: thanks, i was rather confussed lol :thumbs: what mani are you running?

 

[Nicely]

THS Parts.

Forgot to say. What I thought was going to be the biggest problem turned out to be fairly minor. Getting the mani out passed the ABS unit. Clearance is terrible. I have to have ali glass cloth around the unit to protect it from the heat. We are talking 1-2cm. If any one has this problem, the solution is to remove the heat shield (it has to stay off when the tubular mani goes on) and unbolt the ABS mounting bracket. The entire unit will move a few mm, but enough to get the mani in/out. It has to be, sort of, tilt-twisted...

 

[kieran]

i remeber this from mine was a pain in the rear but do able, :thumbs:

 

[A'PEXi]

not sure if this is any help, but i installed the sbc id3 myself, proceeded to set it up changing it to psi and adjusting the gain myself. have it set on 12psi with a nice gain setting around 15 (if i remember correctly) and it boosts fine, the car never spiked with different gain levels as well, just seemed to spool up a little slower.

 

[Nicely]

Thanks Ray. That's just what I needed Mine's set on 5 after following the advice here. I'll up the gain and drop the boost setting.

 

[Yakozan]

Nice :thumbs:
I havn't set mine up properly yet.
But I think I run with a set of 45 and gain 10.
However, when I up the gain it boost higher. Is it supposed to do this?
Do I just reduce the set when upping the gain?

 

[Nicely]

Follow the guide I posted on the last page. The principle is sound. It just the gain could be up a bit. Yes, higher gain means faster spool.

 

[Nicely]

B0ll0cks! B0ll0cks! B0ll0cks! B0ll0cks! B0ll0cks! B0ll0cks! B0LL0CKS!!

Its STILL doing it!!! :rant: :annoyed: :furious:

I was sure it was the turbo... Could be the tubular mani, I suppose. Is anyone else running a stable 1.1 bar with a T28BB and tubular mani?

 

[Topper]

Ah thats sh!t man, after all that. Back to the drawing board i guess

 

[Yakozan]

B0ll0cks! B0ll0cks! B0ll0cks! B0ll0cks! B0ll0cks! B0ll0cks! B0LL0CKS!!

Its STILL doing it!!! :rant: :annoyed: :furious:

I was sure it was the turbo... Could be the tubular mani, I suppose. Is anyone else running a stable 1.1 bar with a T28BB and tubular mani?

Give me your ECU and I can try it :wave:

 

[S15R]

my mate had a Starlet GT, it was overboosting at high rpm and still cant find the problem but after he changed the turbo with external wastegate, no boost spikes anymore

probably too much exhaust going out and small wastegate?

try putting it on dyno again!

 

[Yakozan]

To much flow maybe
You could try to put your cat in again to get some restriction in the exhaust.
That would slow boost down abit. Perhaps enough to stop the spiking.

If this is totally wrong feel free to flame me Just thinking out loud.

 

[Nicely]

Boost creep, I'm told. Make the wastegate bigger or get an AVCR to control to boost at specific rpms...

Tested it at lunchtime with the actuator disconnected and the wastegate tied open. Pulled 0.5 bar at peak. Should be 0...

 

[Topper]

So it could be a wastgate issue, what would cause it to open to early, or by the sounds of it, intermittently?

 

[Yakozan]

Boost creep, I'm told. Make the wastegate bigger or get an AVCR to control to boost at specific rpms...

Tested it at lunchtime with the actuator disconnected and the wastegate tied open. Pulled 0.5 bar at peak. Should be 0...

OK. So your turbo flows more air than the actuator is able to evacuate.
If you was to fit the stock cat or turbo-elbow. Wouldn't that reduce the flow in the turbo and the actuator would do it's work properly again?

 

[yewei]

nicely :wave: did u replace ur mani by urself? as in DIY? i'm having problems with my car, it sounded jus like a tractor n lost a lot of power. i think i got a cracked mani? could u guys give me some pointers? is the mani + dump pipe from ss auto-chrome or xs-power recommendable?? thanx for replying :thumbs:

 

[Nicely]

Hey yewei. Sounds like its more likely the turbo to mani gasket. Regardless, you'll need to replace the gaskets when you take everything off to get to the mani. It'll be pretty obvious if the gasket's gone, as it'll have a section missing out of it

I did it myself (with the help of a mate). If you would like a guide, take a look at this one

I wouldn't recommend either of those manis :no: The quality is rubbish. They tend to crack more easily and are very untidy inside. If you don't mind paying a bit more, get the Tomei one off Greenline :nod:

 

[Nicely]

Looks as though its boost creep. Its taken a year, but I finally got a diagnosis off one of the SXOC Mods

Disconnected the actuator arm from the turbo and tied the wastegate flap open. This should ensure that zero boost can build. Floored it in 5th and 6th over the usual peak power points where the problem usually occurs. Boost started building as the revs increased and peaks at 0.5 bar. With the wastegate fully open...

This means that the wastegate isn't large enough to allow the boost pressure to escape quick enough to keep up with the flow of the exhaust.

Three options:

1. port the wastegate slightly larger. This is a documented and proved process.
2. fit an external wastegate. Expensive and a ball ache.
3. fit a smaller turbo elbow/dump pipe to increase the amount of back pressure and slow the flow.

Now, Meddy had a near identical spec to me and never encountered boost creep. The only major difference in spec is that he still had the standard manifold. I've got to think about it, but I'm seriously considering fitting a standard main back on...

To those with a tubular mani, you may well find you have the same problem once you try to boost over 1 bar if you have a T28BB...

 

[Yakozan]

Looks as though its boost creep. Its taken a year, but I finally got a diagnosis off one of the SXOC Mods

Disconnected the actuator arm from the turbo and tied the wastegate flap open. This should ensure that zero boost can build. Floored it in 5th and 6th over the usual peak power points where the problem usually occurs. Boost started building as the revs increased and peaks at 0.5 bar. With the wastegate fully open...

This means that the wastegate isn't large enough to allow the boost pressure to escape quick enough to keep up with the flow of the exhaust.

Three options:

1. port the wastegate slightly larger. This is a documented and proved process.
2. fit an external wastegate. Expensive and a ball ache.
3. fit a smaller turbo elbow/dump pipe to increase the amount of back pressure and slow the flow.

Now, Meddy had a near identical spec to me and never encountered boost creep. The only major difference in spec is that he still had the standard manifold. I've got to think about it, but I'm seriously considering fitting a standard main back on...

To those with a tubular mani, you may well find you have the same problem once you try to boost over 1 bar if you have a T28BB...

I would fit the stock manifold.
It's free

Edit: What about fitting a racing cat?

 

[Meddy]

Looks as though its boost creep. Its taken a year, but I finally got a diagnosis off one of the SXOC Mods

Disconnected the actuator arm from the turbo and tied the wastegate flap open. This should ensure that zero boost can build. Floored it in 5th and 6th over the usual peak power points where the problem usually occurs. Boost started building as the revs increased and peaks at 0.5 bar. With the wastegate fully open...

This means that the wastegate isn't large enough to allow the boost pressure to escape quick enough to keep up with the flow of the exhaust.

Three options:

1. port the wastegate slightly larger. This is a documented and proved process.
2. fit an external wastegate. Expensive and a ball ache.
3. fit a smaller turbo elbow/dump pipe to increase the amount of back pressure and slow the flow.

Now, Meddy had a near identical spec to me and never encountered boost creep. The only major difference in spec is that he still had the standard manifold. I've got to think about it, but I'm seriously considering fitting a standard main back on...

To those with a tubular mani, you may well find you have the same problem once you try to boost over 1 bar if you have a T28BB...

Sorry but thats not correct mate. With the wastegate fully open it wont mean your not going to build any boost it just means the boost will be slower to build and will ultimately be a bit lower in level. The max exhaust flow a wastegate can bleed off is only about 30-35%.