Boost pressure low what could be the problem?

[coolchris]

Hi everyone i have a 2.5 and noticed today that under full acceleration my cars boost gauge goes up to 0.6 of a bar and no higher.About a year or so ago had a bleed valve(adjustable boost valve)fitted.The simple thing to do wood be to turn it up a bit and see if boost gauge reads any more but i know this could cause damage if i turn it up too high so i think i shall leave it be but what ideas have any of you got as to why the boost is reading lower than the factory setting.By the way the car seems to pull fine under full acceleration.

thanks Chris

[YellowShed]

Do you know the gauge is accurate? Is it running lower than it was? The boost actuators can be wound up a bit to raise the boost a little. Should not be a problem with the map.

YellowShed

[coolchris]

Hi Trevor not sure if the boost is accurate to be honest i know when the gauge was fitted it was running around 0.8 So it wont do any harm winding the knob up a little to see if the gauge reads a bit higher.If i got you to remap the car at some point wood you have to do away with the bleed valve.Also have open diff so with your experience wood the diff handle the extra bhp When had it on the rollers was running around 320.

Cheers Chris

[Gadgeroonie]

make sure one of the actuators has not fallen off and you are boosting off one turbo

could you have a boost leak ?

[coolchris]

cheers will check when home tommorow night just out of interest where abouts are the actuators located?what signs should i be looking for

thanks Chris

[2.5bluenob]

coolchris said:

cheers will check when home tommorow night just out of interest where abouts are the actuators located?what signs should i be looking for

thanks Chris

they are attached to the turbo

[Gadgeroonie]

follow the pipe attached to the bleed valve and it will tee into two, each pipe will go to the actuator, there is a rod that needs to be attached to a dowel on the turbo.

[Metalman]

Gadgeroonie said:

follow the pipe attached to the bleed valve and it will tee into two, each pipe will go to the actuator, there is a rod that needs to be attached to a dowel on the turbo.

The rod is held on by a tiny c-clip that often rusts and breaks off. If it has come off you can by a spare locally, even from halfords.

[coolchris]

thanks for all the help everyone will have a check and see whats what

thanks chris

[2.5bluenob]

coolchris said:

If i got you to remap the car at some point wood you have to do away with the bleed valve.

Cheers Chris

I'm shocked that youve got a bleed valve on your car. I had one on a Renult 5 back in the day and i thought they were a very crude device. I didnt know peaple were still using them.

Edited by 2.5bluenob on Monday 8th February 22:32

[hollowpockets]

2.5bluenob said:

coolchris said:

If i got you to remap the car at some point wood you have to do away with the bleed valve.

Cheers Chris

I'm shocked that youve got a bleed valve on your car. I had one on a Renult 5 back in tne day and i thought they were a very crude device. I didnt know peaple were still using them.

Someone had fitted one to my M400 to "tune it" for the previous owner, since been removed!

[Gadgeroonie]

there are bleed valves and mechanical boost controllers

bleed valves just bleed air away from the actuators so the actuator thinks you are running less boost, they are not linear and typically you see a spike in boost followed by a drop off

a mechanical boost valve is not actually such a bad tool , it opens at a pre determined level and allows the actuators to open. They often have better boost control than expensive electronically controlled devices

a bleed valve is not a great tool because people fiddle with them, electronic boost controllers can give good boost control, but again people fiddle with them

the mechanical boost controllers usually have to be taken apart to adjust boost so are less likely to be fiddled with

[YellowShed]

coolchris said:

Hi Trevor not sure if the boost is accurate to be honest i know when the gauge was fitted it was running around 0.8 So it wont do any harm winding the knob up a little to see if the gauge reads a bit higher.If i got you to remap the car at some point wood you have to do away with the bleed valve.Also have open diff so with your experience wood the diff handle the extra bhp When had it on the rollers was running around 320.

Cheers Chris

Chris,

The open diff gets killed by torque and temperature. The 3.0l produces more torque - I'm not sure if a 2.5 has killed an open diff.

As long as you have the MBE ECU and the electronic boost controller, we can map the car to the best of what it's got. Do you have any other mods?

YellowShed

[mgbond]

YellowShed said:

coolchris said:

Hi Trevor not sure if the boost is accurate to be honest i know when the gauge was fitted it was running around 0.8 So it wont do any harm winding the knob up a little to see if the gauge reads a bit higher.If i got you to remap the car at some point wood you have to do away with the bleed valve.Also have open diff so with your experience wood the diff handle the extra bhp When had it on the rollers was running around 320.

Cheers Chris

Chris,

The open diff gets killed by torque and temperature. The 3.0l produces more torque - I'm not sure if a 2.5 has killed an open diff.

As long as you have the MBE ECU and the electronic boost controller, we can map the car to the best of what it's got. Do you have any other mods?

YellowShed

My diff went on a 2.5 and I only had 260bhp at the time

Bondy

[YellowShed]

Well there you are! I stand erected/I mean corrected!

Seems like any Noble has the ability to kill an open diff.

YellowShed

[andygtt]

YellowShed said:

coolchris said:

Hi Trevor not sure if the boost is accurate to be honest i know when the gauge was fitted it was running around 0.8 So it wont do any harm winding the knob up a little to see if the gauge reads a bit higher.If i got you to remap the car at some point wood you have to do away with the bleed valve.Also have open diff so with your experience wood the diff handle the extra bhp When had it on the rollers was running around 320.

Cheers Chris

Chris,

The open diff gets killed by torque and temperature. The 3.0l produces more torque - I'm not sure if a 2.5 has killed an open diff.

As long as you have the MBE ECU and the electronic boost controller, we can map the car to the best of what it's got. Do you have any other mods?

YellowShed

is the electronic boost controler standard on the 3.0L or should I be thinking of fitting one?

[YellowShed]

andygtt said:

is the electronic boost controler standard on the 3.0L or should I be thinking of fitting one?

Not really sure on the exact introduction, but electronic boost for a some of the last 2.5s and all of the 3.0ls, plus some customer upgrades on earlier 2.5s.

YellowShed

[coolchris]

Hi Yellowshed the car has no other mods and have found the cause of the drop in boost.took car to my local mechanic turbos etc all fine then he noticed that my intercooler(standard)has split at one of the welds so looks like a re weld at my local rad refurb company.Hopefully once done the boost is back to normal level

Chris

[Gadgeroonie]

i was going to mention that !

was the car hissing on boost ?

[coolchris]

hi gadge yes pulls nice up to around 4000rpm then hissing all way to red line.So hopefully once welded normal boost pressure will be returned