Holding Boost Pressure

[woots]

ive just fitted a mechanical boost gauge its in(psi) fitted a hks head gasket , turbosmart mechanical boost controller. im still running stock induction system and still using the standard re-circulating dump valve. i have a bmc induction kit and hks dump valve to go on when my pipes turn up. anyway, since ive put my boost controller on, it will boost up to 18 psi then back off to around 12 psi. is there a relief valve somewhere to stop over boosting? i havent had time to check my boost valve so that is a pos. any other suggestions?

also how much psi can i run comfortabily. and how much can i boost for short bursts without risk of putting a leg out of joint?

my car is a gen 6 gt4

thankyou for your time

[GT4 BOOSTER]

did you disconnect the vsv ????

[Leeky]

Dont go above 1.2bar on the stock turbo, thats melted piston territory there.

[GT4 BOOSTER]

between 1.2 - 1.4 bar (17-20psi). = DEATH , you should hit fuel cut at overboost , but if the vsv isnt disconnected the ecu knows no better and you'll go well over safe limits.

here's some wise words from SKETCHY

Couple of point for fault diagnosis with MBC's

My boost rises and falls a little... This is fairly normal until the ball bearing seats properly into the brass body of the valve. A few hundred miles are often needed to settle it in

The boost hits my preset level, then falls, then gradually rises again up to the preset level...

This is usually caused by the small (0.7mm) vent hole in the knurled section of the adjuster being either blocked or too small. Firstly, check the vent hole is not blocked, by removing the valve and inserting a small piece of wire into the hole, then blowing through the hole. You can increase the size of the hole as much as you require, but generally, going above 1mm is pointless, as it tends to reduce the speed at which the boost level builds. Try 0.8mm

The boost hits my preset level, then creeps up slowly by 1-2psi as the revs increase...

The diameter of the hoses going to and from the BCV is too small. You need either 5mm ID Samco vacuum hose or 1/4" fuel hose from your local motor factor.

The boost rises quickly and I get a "boost spike" - this is where the boost rises above the level you need for a fraction of a second...

It is normal for the boost to spike fractionally, but the boost level should stay +/- 1psi throughout the range. If it spikes more than this, two things can be tried - 1. Move the valve closer to the actuator - ideally within 3-4" (75-100mm). 2. The input (usually taken from the throttle body) can be taken from somewhere closer to the turbo, ideally the turbo outlet. Unfortunately, this may require the turbo to be removed and a 1/4" barbed boss welded on

I cannot get the boost level low enough...

This valve, when the adjuster is backed off completely, allows free flow, so you have another problem!!

[woots]

i disconected the vsv! seems to have solved the problem thanxjust ordered some samco hose as well.

the car is allot more agessive to drive now :arrgg-matey:

i had a bit of a scare this morning. my eml light was on and had two codes stored 31 and 54. i cleared down the ecu and they both come back? i then realised my bcv was off turned it up a couple of notches, started the car the light went out cleared the codes its been fine since??

[dawesy]

tbh on the stock ct and stock ecu i wouldnt reccomend anything over 1.1 bar.

the injectors will be nearing 95% duty cycle then your nearing det teritory.

when you say mechanical boost controller do you mean bleed/relief valve? if so you are in more danger at higher boost as these (bleed valves in particular) cause the turbo to work harder to make boost, thereby increasing charge temps. save up and get an EBC (electronic boost controller) they are soooo much better

[Sketchy]

i disconected the vsv! seems to have solved the problem thanxjust ordered some  samco hose as well.

the car is allot more agessive to drive now :arrgg-matey:

i had a bit of a scare this morning. my eml light was on and had two codes stored 31 and 54. i cleared down the ecu and they both come back? i then realised my bcv was off turned it up a couple of notches, started the car the light went out cleared the codes its been fine since??

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54 is intercooler fluid level, get some coolant, take the cap of the intercooler (The big black thing on top of the engine) then start the engine, blip the throttle and you'll see the fluid level drop top it up to the neck then put the cap back on. Job done

31 is something to do with vaccum problems might need more investigation if it comes back.

You will still hit fuel cut with the vsv disabled, an you can't mistake it feels like hitting a wall. Should cut in about 17-19psi mark actually set for 4.4v on map sensor.

Fuel map runs out at 1.2bar.

[woots]

ok! thanx for all your adive im now running 1 bar of boost.

has anyone taken the dump valve off from the side of the air box! its well loud.

wot does the pipe do that enters the air box next to the dump valve? does go back to idle control as it has heavy vaccum and the engine cuts out when you block it! why i ask is im fitting my cda air box and wanted to know wot other people have done with it. i was gonna put a breather filter on the end?

[Sketchy]

ok! thanx for all your adive im now running 1 bar of boost.

has anyone taken the dump valve off from  the side of the air box!  its  well loud.

wot does the pipe do that enters the air box next to the dump valve? does go back to idle control as it has heavy vaccum and the engine cuts out when you block it! why i ask is im fitting my cda air box and wanted to know wot other people have done with it. i was gonna put a breather filter on the end?

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It's the pipe for ideal control valve etc, most ST205 specific induction kits have a bit to connect it to but if yours doesn't then a breather filter will work as well. :D