Recent boost issues.....

[850T5 Jason]

Hello everyone, havnt been on in a while so hope everyone is well !, and the cars too!!

Right.............

Ive got a few issues with the T-5 recently that are becoming annoying an worrying, i apologise in advance if this subject has been covered a million times before but it would be good to have a "live chat" about it so to speak

The car was all good a few months ago, it made 250bhp and 260lb/sf @ 12.5psi of boost tailing off to rest at around 10.5PSI @ 6000K using a MBC, de-catted 2.5" exhaust and a panel filter but things have changed a little recently.

The boost itself has dropped to around 10.5-11psi and after around 5000RPM the boost drops rapidly down to around 7psi at 6-6200RPM. I Also plumbed back in the stock solenoid and i get a spike to 6PSI the it drops to around 5PSI...
The car has also now become overly sensitive to fuel cut even at 11psi when accelerating from low down or accelerated up hill etc (high load) both on light throttle and full throttle.

Naturally ive been playing to sort the issue out for example ive tried -

1. replacing the diaphragm in the recirculating valve in the turbo
2. checked all the boost hoses for leaks etc
3. checked the T.B and vac tree for leaks
4. checked the PCV system
5. checked the intercooler
6. tried another boost solenoid
7. Changed the MAF sensor
8. checked and changed vac lines

etc etc.....

I would appreciate a few ideas on other things that may be causing the issue, ive heard of cracked turbine housings causing the boost drop and tailing off at high revs......sound familiar??, but then why the increase in fuel cut at lower boost levels??
Also ive heard the actuators can some times become weak leading to the boost drop and tailing off ??, but again you would not imagine this to cause fuel cut more often??

Its worth mentioning a few things such as - even if i wind in the MBC (22psi) i still get no more than around 11PSI of boost and it still tails right off without any evidence of any boost leaks etc :/
And the car still feels fairly rapid aswell !!, i have a boost gauge in the car aswell as the stock rubbish gauge confirming the drop in boost and tailing right off at high RPM's etc so its definitely happening

Anybody suffered this before?, im guessing the flow from the turbo is going somewhere but im stumped as to where as there is no apparent leaks to be found externally on the boost system.....

Any help would be very much appreciated, thank you in advance

Jason

[dtp]

Test the recirc valve with a vac pump it might be split.

[claymore]

Sounds like a boost leak somewhere, even if you say you've checked everything, have you tried winding up the wastegate a couple of turns

[850T5 Jason]

Test the recirc valve with a vac pump it might be split.

Thanks for the response..

I tested this after replacing it with a new diaphragm using a mitivac, i pumped it upto 20 inHg and it held for a satisfactory amount of time so im as confident as i can be that its not split.

thank you

Jason

[oblark]

I had a problem a while ago with low boost on my 1996, 855 t5, replaced all the rubber hoses from turbo to intercooler and intercooler to throttle body this brought the boost back up to 10psi

Do away with the MBC and have it remapped,

[850T5 Jason]

Sounds like a boost leak somewhere, even if you say you've checked everything, have you tried winding up the wastegate a couple of turns

Indeed there seems to be a leak somewhere, i have yet to try the actuator but ill make it one of my next jobs and see how the car responds to that

Thank you

I had a problem a while ago with low boost on my 1996, 855 t5, replaced all the rubber hoses from turbo to intercooler and intercooler to throttle body this brought the boost back up to 10psi

Do away with the MBC and have it remapped,

Im fortunate to have access to second hand parts so i have literally swapped the entire boost circuit to see if any of the hoses are leaking but this made no difference at all
I will be doing away with the MBC in time, i would love to have gone straight for a remap but funds where an issue at the time, im hoping to go for a brand new 16T i have access too through work so once i obtain the new turbo ill go for a map...... But i will be sorting out this issue firstly

thanks

Jason

[oblark]

I`m running a 16T, blue injectors, RIP kit and a RICA 304 and the old girl goes like a rocket.......

[850T5 Jason]

I`m running a 16T, blue injectors, RIP kit and a RICA 304 and the old girl goes like a rocket.......

Thats what i like to hear ill be there one day when i get it running okay again

Jason

[glock19]

Is your wastegate flap broken or dislodged ?
Next, is your MIL lamp working ? Maybe you're on LIMP but just didn't realised it without a working indicator.

[850T5 Jason]

Is your wastegate flap broken or dislodged ?
Next, is your MIL lamp working ? Maybe you're on LIMP but just didn't realised it without a working indicator.

Hello, thanks for your comment

I think i am being forced into the turbo area as you say, over the past couple of days ive conducted a few tests -

Removed and tested the stock actuator (opened at 3psi), diaphragm tested okay so i turned the rod a few turns until it opened at 4-5psi. This made no difference (still ran 5psi tops using the O.E solenoid) and still wouldn't run any more than 11 psi using the MBC wound right in!, and once again boost tails off rather quickly at higher revs.

Next i pressure tested the intercooler - tested OK, boost pipes - OK and once again checked the recirc and it isnt leaking at all.....never something simple right ha

As for the MIL lamp, i cannot say 100% if its working or not but either way the ECU is free of codes ....

I think it must be waste-gate related as you say, or maybe the compressor housing seal maybe??

Either way ive taken delivery of a brand new 16T yesterday so time will tell if its the turbo or not, however i didn't purchase the 16T as an attempt to cure the issue. I bought it because the current 15g is an old timer! and by that i mean its a 265000 mile unit taken from a scrap T5 at a moment of desperation , the oil seal leaks a little on over run but both the thrust bearing and the journal bearings are perfect! but ive wanted to re-con/change it for some time ready for future power levels etc

many thanks

Jason

[960kg]

So what has happened the last 20 days?

I am interested as i had a problem after my 304 remap with boost varying all over the place.

I did everything just as yourself and no results.

I have just bought a brand new BCS from Volvo £51 and all ok now. Boost comes in earlier than on the old faulty BCS and much smoother then POW! up to 15psi

Keith

[oblark]

So what has happened the last 20 days?

I am interested as i had a problem after my 304 remap with boost varying all over the place.

I did everything just as yourself and no results.

I have just bought a brand new BCS from Volvo £51 and all ok now. Boost comes in earlier than on the old faulty BCS and much smoother then POW! up to 15psi

Keith

I`ve been running a 304 RICA for the last few weeks and all has been OK until Tuesday of last week when it will only boost to 7 psi instead of 15 psi, the boost peaks at 4000 rpm. As well as the boost problem it also over revs when changing gear. Ive replaced ALL the vac hoses, checked the waste gate which opens at 4 psi, cleaned the idle control valve.

Any ideas please....

Thanks

[craigoodwood]

I`ve been running a 304 RICA for the last few weeks and all has been OK until Tuesday of last week when it will only boost to 7 psi instead of 15 psi, the boost peaks at 4000 rpm. As well as the boost problem it also over revs when changing gear. Ive replaced ALL the vac hoses, checked the waste gate which opens at 4 psi, cleaned the idle control valve.

Any ideas please....

Thanks

yours lasted longer than mine did then, take the blues out and reset the codes, apparently they are the wrong impedance and the ecu dun like them....

[glock19]

@oblark : Your BCS/TCV is damaged, it's allowing the full force of air from the turbo snail to the wastegate actuator

@craig : Injectors from the M4.3/4.4/ME7 has the same impedance.

[oblark]

[QUOTE=glock19;477724]@oblark : Your BCS/TCV is damaged, it's allowing the full force of air from the turbo snail to the wastegate actuator

Thanks for pin pointing the problem, to comfirm the BCS was damaged I fitted a MBC that is set to 1 bar and boost was back to normal. So a new BCS needs to be ordered.

[oblark]

@oblark : Your BCS/TCV is damaged, it's allowing the full force of air from the turbo snail to the wastegate actuator

@craig : Injectors from the M4.3/4.4/ME7 has the same impedance.

Fitted a BCS that I got from "theflyingbrick" today and went out for a drive, No change, only 7 psi of boost at 4000-5000 rpm. So I fitted a MBC and 16 psi at 3500 rpm and goes like a rocket.

Could the fault be with the waste gate actuator ( which starts to open at 4 psi ) or could the fault be with the remapped ECU ?

Thanks

Rob

[960kg]

Fitted a BCS that I got from "theflyingbrick" today and went out for a drive, No change, only 7 psi of boost at 4000-5000 rpm. So I fitted a MBC and 16 psi at 3500 rpm and goes like a rocket.

Could the fault be with the waste gate actuator ( which starts to open at 4 psi ) or could the fault be with the remapped ECU ?

Thanks

Rob

This is only my opinion but why put secondhand parts that are vital to performance on your motor when you have a problem. The BCS apparently should be changed around 100,000. Mine is on 158,000 so i just bit the bullet and bought it. How do you tell if it doesn`t work correctly! You may of taken on someone elses problem.
It must be a faulty BCS as without it and the MBC fitted it flies!!!

[mitchyboy01]

This is only my opinion but why put secondhand parts that are vital to performance on your motor when you have a problem. The BCS apparently should be changed around 100,000. Mine is on 158,000 so i just bit the bullet and bought it. How do you tell if it doesn`t work correctly! You may of taken on someone elses problem.
It must be a faulty BCS as without it and the MBC fitted it flies!!!

Secondhand parts are cheaper and often work great for thousands of miles. Hence the huge demand for used parts. Not everyone has the money to run to the dealer every time they need a part!

[glock19]

FYI, the diagram from Volvo on the vacuum/boost hoses to the BCS is wrong. I've repeated this statement many times but references are still being made to the Volvo diagram (for M4.3). The M4.4 is correct though.

@oblark :

FACT : With the condition that the interlocking spring clip for the BCS connector is facing upwards, then if you look from the top, the highest port coming out from the BCS, goes to the wastegate actuator. The middle port is back to the intake tract. The bottom port is going to the turbo snail.

FALSE : The volvo diagram shows the opposite for the top and bottom port. They could not be fully blamed though as they did not state which way the electrical connector is facing.

[oblark]

FYI, the diagram from Volvo on the vacuum/boost hoses to the BCS is wrong. I've repeated this statement many times but references are still being made to the Volvo diagram (for M4.3). The M4.4 is correct though.

@oblark :

FACT : With the condition that the interlocking spring clip for the BCS connector is facing upwards, then if you look from the top, the highest port coming out from the BCS, goes to the wastegate actuator. The middle port is back to the intake tract. The bottom port is going to the turbo snail.

FALSE : The volvo diagram shows the opposite for the top and bottom port. They could not be fully blamed though as they did not state which way the electrical connector is facing.

Have I got hold of the wrong end of the stick or Iam I thick, are you saying that this diagram is wrong.