overboosting,,, tell me why

RBSX · Post by **RBSX** » Sat Dec 01, 2007 10:27 pm

hi guys
ive just installed a bigger FMIC and a 76mm exhaust
standard downpipe
my car is boosting over a Bar and hitting the fuel cut off
why would it suddenly do this ?
prior to all the upgrades it was boosting 0.6 bar
gauge is fine pipes are ok

Any ideas guys
thanks

ChemCool · Post by **ChemCool** » Sat Dec 01, 2007 11:06 pm

Is there a boost controller fitted?

Chem

Daniel · Post by **Daniel** » Sat Dec 01, 2007 11:51 pm

are you sure the pipe that goes to your actuator on the turbo is on properly or that it has no cracks?

Iv had a minor split on mine before just where the clamp holds it on, it looked fine until i took it off.

Installing a fmic should give 2-3psi more boost ova the more restrictive wmic

Phinx · Post by **Phinx** » Sun Dec 02, 2007 12:20 am

Its the exhaust, The increased diameter is taking away the back pressure so the exhaust gasses are going through the turbine instead of the wastegate.

The Turbo is having a hard time managing its boost

you will need a boost control but unless its electronic you will still suffer spikes

veecee · Post by **veecee** » Sun Dec 02, 2007 7:47 am

dude - its boosting over a bar and normal is 0.6. the mods he mentioned cannot do that to a normally operating system!

so RB - check for induction leaks! specially on the actuator vacuum pipe, as dannieboy said!!!

i installed a bigger exhaust and nothing changed.

the only time i had problems is when i installed a crappy manual boost controller, then my boost control was all over the place.
if you're gonna get a boost controller, then rather splash out and get a decent electronic one!

Phinx · Post by **Phinx** » Sun Dec 02, 2007 9:19 am

Well check the actuator piping agreed but I suffered huge pikes when the exhaust was changed

How are you holding the boost at 0,6 bar ? Do you have a boost controller?
Does the actuator open all the way ?

My moneys is on the exhaust if all checks out

Vlade · Post by **Vlade** » Sun Dec 02, 2007 6:08 pm

if it sounds like the turbo is gonna bite your passengers feet off, my money is on a boost leak

veecee · Post by **veecee** » Sun Dec 02, 2007 6:33 pm

sweet - bets are on!

whats the prize phinx!!!???

thats phinx for exhaust (I didnt know that could happen!)

and myself and vlade for boost leak (i know all about this one).

ChemCool · Post by **ChemCool** » Sun Dec 02, 2007 9:34 pm

If it is a boost leak, wont the sx idle crappy like up and down the revs?

veecee · Post by **veecee** » Sun Dec 02, 2007 9:48 pm

you're right and wrong, depending on where the leak is. vacuum pipe leaks might not cause this problem, but a boost pipe leak will. so its a bit difficult to tell! the easiest way to tell if its a vacuum pipe leak is to check the level of vacuum under idle on a vacuum/boost gauge!

i've had a vacuum pipe leak before and nothing really changed other than higher boost than normal.

also i once had a clear vacuum pipe leak on the way back from durban. my car has never run so strong before. i was able to hit about 240km/h on the n3 about 250km's from durban. i've never been able to hit such high speeds again - although i've never tried again. hahaha - i was just showing off to the wifey!!!

MyPRodOL · Post by **MyPRodOL** » Tue Dec 04, 2007 7:37 am

Exhaust, i agree

Have experienced this myself, got a greddy profec b spec 2 prob solved...

Doctor G · Post by **Doctor G** » Tue Dec 04, 2007 1:35 pm

My vote is on the vacuum pipe at the actuator. Pulled mine deliberately the other day and it boosted about 1.125bar consistantly. Normally around 0.5bar.

In fact, it boosted so nicely that it blew some other vacuum pipes out of place too. Idle was a bit nasty but once everything was plugged back up it was cool again.

RBSX · Post by **RBSX** » Tue Dec 04, 2007 4:46 pm

Thanks Guys

just to clear up a few things

Ive got a stock turbo and manifold and down pipe, its a 76mm from the flange at the bottom all the way back

There is no boost controller, just the standard actuator with the pipe going in the compressor

Bigger cooler with 63mm from turbo to cooler and 76mm from cooler to
intake
Dumpvale is just after the turbo before the cooler,
Pipes are secured an doesnt seem like there is any leaks

Making boost from just under 3000rpm but hits over a bar as soon as i apply throttle

As Far as i know the olny thing that controlls boost will be the acutaor so im going to try and get it tested or replaced

any thoughts......

Oh any i checked the vacuum pipe to the actuator, its fine

The thing i dont under stand is that every thing was fine before the changes

veecee · Post by **veecee** » Tue Dec 04, 2007 7:41 pm

yes - i think we overlooked that.

who did the changes - what did they break???