Standard boost pressure and tweaking the actuator...

[Turbodave]

Copied from the owners club where nobody seesm to want to talk to me...!

Anyways...

In the interest of curiosity, I temporarily fitted the boost gauge from my cavalier into the 850R today (auto) just to check what it was doing in terms of boost.

Thankfully, it would seem all is well. It's overboosting to 9PSi and holding around 7PSi and continues to hold until I run out of road. Idle is recording around 20 in/Hg... whatever that means and it's steady as a rock.

That all said and done, seems standard overboost for an R is 10.5PSi which means I'm down a whole 1.5PSi. Dammit. So, the question is could this been down to the actuator, ie give the nut one turn to up the pre-load and get the boost back where it should be?

I've checked all the vacuum pipes and the pipes around the turbo and all seem in good order, none perished or split and as said, the car holds around 6PSi and doesn't tail off rapidly so it would suggets it's holding boost... just not very much.

Actually quite surprised how little boost they run. I though my Cavalier was low at 11PSi overboost and holds 9PSi, though has been chipped so hits 18PSi and holds 16PSi now. Would have assumed the Volvo would be a bit more than 10.5PSi overboost standard?

Cheers

[Rnash2002]

Copied from the owners club where nobody seesm to want to talk to me...!

Anyways...

In the interest of curiosity, I temporarily fitted the boost gauge from my cavalier into the 850R today (auto) just to check what it was doing in terms of boost.

Thankfully, it would seem all is well. It's overboosting to 9PSi and holding around 7PSi and continues to hold until I run out of road. Idle is recording around 20 in/Hg... whatever that means and it's steady as a rock.

That all said and done, seems standard overboost for an R is 10.5PSi which means I'm down a whole 1.5PSi. Dammit. So, the question is could this been down to the actuator, ie give the nut one turn to up the pre-load and get the boost back where it should be?

I've checked all the vacuum pipes and the pipes around the turbo and all seem in good order, none perished or split and as said, the car holds around 6PSi and doesn't tail off rapidly so it would suggets it's holding boost... just not very much.

Actually quite surprised how little boost they run. I though my Cavalier was low at 11PSi overboost and holds 9PSi, though has been chipped so hits 18PSi and holds 16PSi now. Would have assumed the Volvo would be a bit more than 10.5PSi overboost standard?

Cheers
The actuator might do the trick but it could also be the boost control solenoid
or a perished vac pipe.

[Turbodave]

I'll tweak the actuator one turn and see how that effects the situation. One thing I have noticed, from cold it does tend to surge slightly... for eample, out my street is a long but not that steep climb. Under light load it tends to surge very slightly though the boost gauge remains steady. After a minute it's perfectly fine. Perhaps totally unrelated. I'll redo all the vac line connections and so on too... and on that note, is there any need for the standard boost gauge to have such a long vac pipe! Bloody hell, it almost wraps round the engine bay twice then §§§§§§s off through the bulkhead. Less is more!

[M-R-P]

With the boost gauge pipe length, I needed 3M to do my P2, had to go round the top of the rad, up the wing, through a gromit in the A pillar, up behind the fusebox and out the dash, by the windscreen.

[Turbodave]

The plot thickens... just went out to tweak the actuator and noted the vac pipe from the amal valve (or whatever the valve is that's attached to the airbox, 3 x vac pipes, 1 x multi-plug) wasn't looking too clever. Uncliped it and found it was perfished/cracked where it clips into a bracket near the cylinder head. So, now in the process of replacing them all with new vac pipe - however there's one goes from that valve and disappears down into the turbo, not the actuator so assume it goes into the compressor body. That looks like fun to replace. Best wait till it cools too.

Fingers crossed.

[Rnash2002]

The plot thickens... just went out to tweak the actuator and noted the vac pipe from the amal valve (or whatever the valve is that's attached to the airbox, 3 x vac pipes, 1 x multi-plug) wasn't looking too clever. Uncliped it and found it was perfished/cracked where it clips into a bracket near the cylinder head. So, now in the process of replacing them all with new vac pipe - however there's one goes from that valve and disappears down into the turbo, not the actuator so assume it goes into the compressor body. That looks like fun to replace. Best wait till it cools too.

Fingers crossed.

That will be the boost control solenoid mate,one pipe goes to the actuator one goes to the air filter pipe that goes to the side of the turbo and one goes to the housing of the turbo,pritty much underneath.

[Turbodave]

Right, it's now doing some rather odd things... your opinion folks please.

I've replaced all the vacuum pipes.

1. Tree to body of the turbo
2. Boost control solenoid to the plastic inlet pipe
3. Boost control solenoid to the actuator
4. Boost control solenoid to the pipe that disappears under the turbo.

I've also redone the vacuum pipe for the boost gauge and refitted the aftermarket analogue gauge for the time being and disabled the standard gauge.

I then turned the actuator rod in 1.5 turnes, ie towards the actuator itself.

On idle, I'm still getting between 18 and 20 in.HG

Now, when driving in 'D' and in 'Sport' mode (not that that changes anything) flooring the throttle from around 2000rpm (ie so it doesn't kick down) will see the gauge hitting around 6 or 7PSi on the gauge and holding.

As the speed increases, the boost also starts climbing to around 10PSi however when the auto box changes up, it spikes the boost to around 13 or 14PSi then it drops back down to around 9 to 10PSi.

Not being too familiar with how these things boost, I'd have expected the car to overboost to around 10PSi then settle at 8PSi under prolonged and heavy load regardless of gear/speed... ie, soon as the throttle is floored and the car is loaded up, overboost then settle to held boost.

Mine seems to be relauctant to overboost and instead is hitting and holding around 7PSi and then if you keep the pedal floored, the boost then starts to climb to around 10PSi and as said, when the autobox changes up it spikes up to 14PSi then drops back.

I've rechecked all the vac pipes and so on and all appears fine. The car pulls well, but sometimes feel quite as quick as it should be. Then again, they're not the quickest things from say 30mph up but over 60mph it seems to start pulling much harder... when does tie in with what the boost gauge is telling me.

Any thought chaps?

[Turbodave]

Right, to update that...

Volvo 850R is now running Volvo S40 T4 boost control solenoid and duringt he short roadtest, it would appear nothing has changed.

Still boosts to around 7PSi under heavy load then as the speed climbs, the boost rises to circa 10PSi and spikes to 14PSi momentarily when it changes up a gear and then drops down again.

So, can't be a boost control solenoid issue but again, perhaps I'm looking for an issue that isn't there?

[T5frankie]

your car doesn't have an over boost mate lol, it should be around 10.5 psi though, run the proper bcs though mate mine wouldnt run right with a v70r one, just tighten the actuator until it gets to where its supposed to be

[Turbodave]

your car doesn't have an over boost mate lol, it should be around 10.5 psi though, run the proper bcs though mate mine wouldnt run right with a v70r one, just tighten the actuator until it gets to where its supposed to be

Hmmm, that'll be that then.

I was always under the impression the R's were the same as a normal T5 aside for the fact they had a slightly higher overboost which in turn gave them the slight power increase.

If that's not the case, then my boost seems even more erratic. I'd have expected it to load up to 10PSi under load, mine won't hit 10PSi until it's really started to gather speed... ie, sort of 60mph and beyond with the foot buried in the carpet.

The other odd trait is the sudden and brief spike up to circa 14PSi when the auto box changes up, again at sort of 60mph and above speeds. Is that normal? It's a really sensitive gauge I'm using but then again, I'm also basing my experience on Vauxhalls so perhaps the above is all pretty normal for a T5?

Bloody cars...

[T5frankie]

Hmmm, that'll be that then.

I was always under the impression the R's were the same as a normal T5 aside for the fact they had a slightly higher overboost which in turn gave them the slight power increase.

If that's not the case, then my boost seems even more erratic. I'd have expected it to load up to 10PSi under load, mine won't hit 10PSi until it's really started to gather speed... ie, sort of 60mph and beyond with the foot buried in the carpet.

The other odd trait is the sudden and brief spike up to circa 14PSi when the auto box changes up, again at sort of 60mph and above speeds. Is that normal? It's a really sensitive gauge I'm using but then again, I'm also basing my experience on Vauxhalls so perhaps the above is all pretty normal for a T5?

Bloody cars...

sounds pretty normal to me its harder to set autos up than manuals it should peak at 10 psi then tail off a little in all but 1st gear, only the original t5-r's had the overboost for 30 secs to take them from 225-240 bhp, the 850r just had the permanant 1.5 psi extra over the t5 so is a permanant 240bhp, expect the odd boost spike mine does too, better to set autos up with the in car boost gauge, it needs to be in the middle of the white to be standard, just give it a little extra though with tightening the actuator, the end of the white on the gauge is about 14.5 psi so anywhere up to there is safe

[T5frankie]

my map was boosting at 26psi mate

[Turbodave]

Spot on buddy.

I've put one more turn on the actuator and it's doing pretty much as you describe. Given they don't have overboost, that certainly explains why it doesn't hit circa 10PSi as soon as it's loaded up but will then climb to where it should be once it gets going. The spike is still there when it changes up, that's a bit odd but if they all do that sir, then that'll do for me.

26 miles on £15 of V-Power... light's back on! No more roadtesting today!

[glock19]

For the autos, you won't release the pedal during upshift - so at 6000 rpm with 0.8 bars suddenly dropping to 4000 rpm (during gear shift), it will cause an excess build-up of boost since the engine is running slower (not comsuming the air). The ICV is not open to release the boost pressure too as there's no vacuum like the manual where you lift-off the throttle.

For your earlier question on the lower boost pressure issue, check is the hose from the intake manifold-to-ICV is good, along with the ICV diaphragm. These helps the system to hold a better pressure.