T5 boost levels - standard, safe and bleed valve plumbing.

[Turbodave]

I've had a look online but there seems to be a fair amount of conflicting advice out there regarding boost levels on a 'standard' T5. I gather they should run at 9.6PSi / 0.65bar as standard and they do not have an overboost facility? So, on a standard, healthy car should they hit said boost pressure and hold it or do they overboost to 9.6PSi / 0.65bar then drop back and hold a slightly lower value?

Reason I ask, I have a T5 which may/may not be mapped (no way of telling) and it also runs a bleed valve. I don't have an aftermarket gauge in it (yet) however it'll boost to about a 3rd of the way into the white zone and hold it. Last night, I tweaked the bleed valve by roughly 3/4 of a turn and the car was then boosting up towards the end of the scale but there was no boost cut or fuel cut.

So, issue I have is a) I'm unsure what a standard T5 will do boost wise before the ECU shuts things down and b) what are the safe limits of a mapped car? Appreciate there will be differences depending on the map and fuelling, however mine was happily boosting to the end of the scale without any issues - which makes me wonder if it is mapped or if the standard ECU map will be ok with a modest increase in boost before it throws the towel in.

Also, bleed valve plumbing - mine is currently in the vacuum from the actuator to the boost solenoid, the latter of which is still fully plumbed in but I gather there are ways of doing away with the boost solenoid completely when running a bleed valve? Any thoughts on this? Is the solenoid a fail safe and thus should really be left connected up or are there no benefits?

Whilst I'm not after big power, though oddly the car actually seemed smoother to drive when the boost was increased. With the bleed valve closed off (or at least wound in) the car seems a bit hesitant and farty. Hence, again... wonder if it's been mapped and thus actually needs a bit more boost. Appreciate it has a rising rate FPR however mapped and standard boost could possibly create crappy running. But, on the other hand I don't want to go dialling in more boost and then be left picking up bits of conrod from the M90.

Cheers

[LiamT4]

Think 14psi is about the max boost a standard car will run before the ecu will cut it.

[960kg]

I've had a look online but there seems to be a fair amount of conflicting advice out there regarding boost levels on a 'standard' T5. I gather they should run at 9.6PSi / 0.65bar as standard and they do not have an overboost facility? So, on a standard, healthy car should they hit said boost pressure and hold it or do they overboost to 9.6PSi / 0.65bar then drop back and hold a slightly lower value?

Reason I ask, I have a T5 which may/may not be mapped (no way of telling) and it also runs a bleed valve. I don't have an aftermarket gauge in it (yet) however it'll boost to about a 3rd of the way into the white zone and hold it. Last night, I tweaked the bleed valve by roughly 3/4 of a turn and the car was then boosting up towards the end of the scale but there was no boost cut or fuel cut.

So, issue I have is a) I'm unsure what a standard T5 will do boost wise before the ECU shuts things down and b) what are the safe limits of a mapped car? Appreciate there will be differences depending on the map and fuelling, however mine was happily boosting to the end of the scale without any issues - which makes me wonder if it is mapped or if the standard ECU map will be ok with a modest increase in boost before it throws the towel in.

Also, bleed valve plumbing - mine is currently in the vacuum from the actuator to the boost solenoid, the latter of which is still fully plumbed in but I gather there are ways of doing away with the boost solenoid completely when running a bleed valve? Any thoughts on this? Is the solenoid a fail safe and thus should really be left connected up or are there no benefits?

Whilst I'm not after big power, though oddly the car actually seemed smoother to drive when the boost was increased. With the bleed valve closed off (or at least wound in) the car seems a bit hesitant and farty. Hence, again... wonder if it's been mapped and thus actually needs a bit more boost. Appreciate it has a rising rate FPR however mapped and standard boost could possibly create crappy running. But, on the other hand I don't want to go dialling in more boost and then be left picking up bits of conrod from the M90.

Cheers

As LiamT4 says the cut out is about 14/15psi and it will feel like hitting a brick wall when the boost is suddenly reduced to 10psi.

A re-map will allow you more psi without cut out.

I don`t know if you really have a Bleed Valve fitted or a MBC (Manual Boost Valve) as they are different and our motors react and are controlled better with the MBC.

The Boost Solenoid or as Volvo call it TCV allows boost in 1st gear to about 5psi and 2nd gear to about 8psi after that in 3rd 4th 5th you will get the standard max of 9.6/10psi after 3000revs.

Before you tamper with any boost fiddling you would be a fool to without a proper boost guage the white area is only a guide!

It is the R model that allows overboosts for about 7 secs. and not the standard T5 model

Read the pics. for more information especially the Adaptive Functions which tell you about fuel/air ratio and the learning of the ECU to adapt.

The pic. with the boost figures are 130 = 18.8psi / 140 = 20.3psi Absolute Max. Running with standard Turbo

159 = 23psi / 173 = 25psi Absolute Boost with standard Turbo

[T5frankie]

right at the end of the white scale is about 14.5 psi which is a safe amount pre-mapped