Trying To Work Out Why My Car Is Boosting At 11.5psi

[RBceffy25]

Check to see if the actuator has been modified.

Only other thing i can think of is closely inspect and or replace all your vacume lines.

[jrm]

What about a faulty / modified factory boost solenoid? (The one that would normally bleed 2psi above 4500rpm).

The fact that it went back to 5psi (wastegate pressure) at one point smells a bit fishy and points at this. I would imagine it's possible to unplug the factory boost solenoid to test this? Can anyone confirm? (Sorta opposite of the grounding trick to keep it open under 4500rpm)

[maddowse]

What about a faulty / modified factory boost solenoid? (The one that would normally bleed 2psi above 4500rpm).

The fact that it went back to 5psi (wastegate pressure) at one point smells a bit fishy and points at this. I would imagine it's possible to unplug the factory boost solenoid to test this? Can anyone confirm? (Sorta opposite of the grounding trick to keep it open under 4500rpm)

ok im sort of understanding what your trying to say !!

so if i ground the solinoid go for a run then disconnect it ans see which makes me drop to 5 psi again ??.

[maddowse]

Check to see if the actuator has been modified.

Only other thing i can think of is closely inspect and or replace all your vacume lines.

ok sorry for sounding stupid , but how would i visualy see if the actuator has been modified? would it be inside it ?

as for the vacume lines ill probably do that when i do my oil change as there not to expensive , the only question

is the vacume line going to the actuator is that a spacific size i mean does it have to be a certain part or can i use the same as on everything else ?

thanks again for your help id rather ask and sort of know what im doing other than learning after doing damage

[Rav3nNZ]

ok thanks for your help , so is there anyother why the car could be boosting higher ???

theres no controller and i checked for leaks and used another gauge to see if it was the gauge but my one is reading right !!!

is this something you would have to have a look at to know ??? is there anyone in the cranbourne area that may wanna have a look ???

its probably an r32 actuator

[maddowse]

its probably an r32 actuator

lol so there different again ???

[Rav3nNZ]

lol so there different again ???

Yeh R32 actuators are set at 10psi

Thats what alot of people have told me but on a few posts on here ive seen people say there rated at 12psi.

Either way with an exhaust and an r32 actuator you can expect to boost around 10-12 psi

Which im doing on my r33, oddly enough im boosting 13 tho lol but yeh it works a treat to get one if you can find one.

[maddowse]

Yeh R32 actuators are set at 10psi

Thats what alot of people have told me but on a few posts on here ive seen people say there rated at 12psi.

Either way with an exhaust and an r32 actuator you can expect to boost around 10-12 psi

Which im doing on my r33, oddly enough im boosting 13 tho lol but yeh it works a treat to get one if you can find one.

im sort of hopeing its not the case because as above someone said you cant go below the actuator rating

and i indend to put a front mount and a 3" split dump pipe and high flow cat on ,

this will raise my boost past the caperbility of the stock turbo , im not ready for aftermarket turbo YET!!!.

so ill need to change the actuator ,

or if its rated at 10-12 and with mods my boost goes to 13-14 can i drop it again ?

or will the turbo cope due to less pressure on the exhaust side of the turbo (due to split high flow pipe)????

or am i just looking into it too much ?

[RBceffy25]

ok sorry for sounding stupid , but how would I visually see if the actuator has been modified? would it be inside it ?

as for the vacuum lines ill probably do that when I do my oil change as there not to expensive , the only question

is the vacuum line going to the actuator is that a specific size I mean does it have to be a certain part or can I use the same as on everything else ?

thanks again for your help id rather ask and sort of know what imp doing other than learning after doing damage

some dickheads attach an extra spring to the outside of the actuator which puts physical tension on the outside of the actuator arm and poppet which in turn keeps the poppet closed for longer, making it build more boost before the poppet actually opens. For example, It’s like having a 700gram spring actuator than changing it to 1kg spring without having to actually change the wastgate itself.

Obviously this hasn’t been done as you can see from the photo.

However there is another trick by shortening the length of the arm/rod on the actuator which doesn't allow the poppet to fully open which in turn makes the turbine spin faster, making more boost. Check to see if the rod has been cut and reattached by re-drilling and re-attaching it or it may have been cut and welded.

As far as your vac lines go don't wait, just stick your ear up nice and close, with engine running and give all your vac lines (and I mean all of 'em not just the ones from the turbo) a wriggle and listen for hissing. They split very easily with the heat cycles they go through not to mention their age. Even if they appear to be in good condition, give them a flex and you may see slight cracks/splits in them. It’s almost like they become porous and spongy.

Friends, family and I have all had dramas with dodgy vac lines causing boost control issues.

[RBceffy25]

its probably an r32 actuator

Makes some sense but assuming everything else is up to scratch the stock solenoid should still be governing boost shouldn’t it? Makes sense but assuming everything else is up to scratch the stock solenoid should still be governing boost shouldn’t it?

I would also assume (assumptions, ; ) the mother of all f**k-ups) that if your solenoid was faulty you would be getting inconsistent boost or free boosting or some sort of inconsistency

[Harey]

Makes some sense but assuming everything else is up to scratch the stock solenoid should still be governing boost shouldn’t it? Makes sense but assuming everything else is up to scratch the stock solenoid should still be governing boost shouldn’t it?

I would also assume (assumptions, ; ) the mother of all f**k-ups) that if your solenoid was faulty you would be getting inconsistent boost or free boosting or some sort of inconsistency

You cant go below the psi rating of the actuator. If its an R32 actuator rated to 10-12psi then any sort of solenoid can only increase the boost.

[RBceffy25]

You cant go below the psi rating of the actuator. If its an R32 actuator rated to 10-12psi then any sort of solenoid can only increase the boost.

exactly what i was getting at.

It is not an r32 actuator as it is impossible for it to boost at 5psi (stated earlier) if it were.

Not to mention if it were, it would be in great condition for age lol!

[Galois]

could something else have restricted the boost when the ecu went crazy?

[maddowse]

could something else have restricted the boost when the ecu went crazy?

thats what iv been thinking but iv read on this site about the ecu going into limp mode , if thats what happend to me this id assume the motor could not rev enough for the boost to build up past 5psi right ?

but then again why would it go into limp mode ? the only thing i can think of is that i acedently filled up with 95 ron fuel instead of 98 could this have done it ?

[bubba]

exactly what i was getting at.

It is not an r32 actuator as it is impossible for it to boost at 5psi (stated earlier) if it were.

Not to mention if it were, it would be in great condition for age lol!

It's not IMPOSSIBLE, but it's bloody hard.

I was having boost issues in the Stag, was very low and inconsistent around the 5-7psi range, even swapping my R32 actuator in didn't help, turned out the cat had collapsed and was blocked, causing the drop in boost. Bashed it out, got 10psi back (actuator pressure) and then dialed it back up to 15psi.

I also don't buy the "exhaust gives you 2psi" shit, pressure is pressure, just because you have a more free flowing exhaust doesn't make the actuator give you an extra 2psi. It may get there faster due to better flow which might make it briefly spike over whatever your actuator pressure is, but it's not going to hold it to redline.

[maddowse]

I also don't buy the "exhaust gives you 2psi" shit, pressure is pressure, just because you have a more free flowing exhaust doesn't make the actuator give you an extra 2psi. It may get there faster due to better flow which might make it briefly spike over whatever your actuator pressure is, but it's not going to hold it to redline.

good point i guess ill see what happens, i hope its not the cat because it will be about three months before i do the exhaust .

[Rav3nNZ]

It's not IMPOSSIBLE, but it's bloody hard.

I was having boost issues in the Stag, was very low and inconsistent around the 5-7psi range, even swapping my R32 actuator in didn't help, turned out the cat had collapsed and was blocked, causing the drop in boost. Bashed it out, got 10psi back (actuator pressure) and then dialed it back up to 15psi.

I also don't buy the "exhaust gives you 2psi" shit, pressure is pressure, just because you have a more free flowing exhaust doesn't make the actuator give you an extra 2psi. It may get there faster due to better flow which might make it briefly spike over whatever your actuator pressure is, but it's not going to hold it to redline.

Indeed, i had this exact problem in my old R34, i put in an r32 actuator and just bypassed the boost solinoid completely, it ran 10pound really nice for maybe half a day, then i heard a huuuge ripping noise like an external wastegate then a bang!

lol blew a gasket or hole in my exhaust, major exhaust leak after that and it only boosted 6-7pound after that.

I was using the stock exhaust so i reakn the cat was blocked or something not sure, but yeh 6-7 is lower than 10 last time i checked

Edited May 4, 2010 by Rav3nNZ

[RBceffy25]

I was only reffering to how a solenoid can control boost.

Ok so extreme back pressure can alter the effect of a pre determined spring rate in an actuator.

But in any case, point taken.

Back to the topic, Can anyone give any other reason as to WHY its boostin to 11.5 in an unmodified (alleged) car,

other than leaky hoses, dodgy solenoid, modified actuator, boost creep?

Edited May 4, 2010 by RBceffy25

[Rav3nNZ]

I was only reffering to how a solenoid can control boost.

Ok so extreme back pressure can alter the effect of a pre determined spring rate in an actuator.

But in any case, point taken.

Back to the topic, Can anyone give any other reason as to WHY its boostin to 11.5 in an unmodified (alleged) car,

other than leaky hoses, dodgy solenoid, modified actuator, boost creep?

Has the ecu been flashed maybe?

[maddowse]

Has the ecu been flashed maybe?

whats flashed and how would i tell?