boost lost???

[uninformed]

Hi all, well I was hoping this would be a post on what I found rather than please help me.

Truck: 98 110 CC with a 2.8tgv

last Friday night I did a quick run up to the shops. 2.5km round trip, I left the truck running whilst I ran in. On the way home, I felt a sudden reduction in power, with a noticble increase in turbo noise, mostly whistle. Not a bad turbo noise, no crunching etc.

Sat morning I looked over the various hoses I thought to be under pressure. I only found one with a little divet in it, the small short hose from turbo to waste gate, but on closer inspection it had not penetrated. I took the top hose off (I/C to plenum) looked inside and could not see any delaminating etc. I checked engine oil level, coolant level. Both 100%. As the truck was already booked in for Monday morning for a timing belt and service I figured not to much point digging deep beyond my capabilites.

The vehicle has been returned and the mechanic believes to be fine. It is not. It is definitely down on power, by the feel of my bum say 20% easy. The engine runs smoothly. starts first turn very easlily. The turbo whistle is still pronounced and louder than norm. The EGT's are higher than normal, as they also were Sat and Sunday on light small runs. Example: as I drove from mech's to truck supply store, I was sitting on 90km/h in 4th and 5th and EGT's were 400 degrees post turbo. This is no load on a light 110 ute (cut down flat bed alloy tray), normally I would expect about 200, 250 max....hell it only sits on 350 with my 1.8t trailer doing 105km/h

basicly it is still the same as Friday night after incident.

some of work done by mech:

new air cleaner
replace main serpentine drive belt
install new recored rad
replace timing belt
tensioner modified gear and idler bearing
replace crank seal and oring
replace a/c idler bearing.
cleaned I/C with kero

he did find a hole in the small hose/pipe that goes across to the injection pump. he has repaired this with a sleeve.

I was suprised that that one had a hole, as 1 it is metal and 2, to me it seem like the injection pump is getting the correct boost pressure but not the engine, thats why higher egt and less power (my guess)

I rang him when I got to the truck supplies and had the message relayed via assistant: he has asked me to bring it back in the morning, something about adjusting the timing???

now to me, its not timing. It starts very easy, runs smooth. Nothing has changed pre him working on it as regards to the incident on Friday night. Im not keen on him spending(wasting) time on the timing.

a little back history on a small issue: In the last 6-12 months something has changed in the turbo side of things: Sarting the truck first thing in the moring is normal, I usualy let idle for 30secs min, then slowly take off in 1st and low rev change into second. I go up hill a small ways to turn around then down my little hill to level ground out to a T section at main road. I just putt along to let everything get moving and oil. this is only 300m. Then when i do give it some, generally in 2nd gear that first revving of the day, you can really feel the turbo kick in, almost like a valve being half open then full open. Once it has done this the first time it doest really happen again during that first journey, yes you can still feel the turbo kick in (more than a 300tdi) but not like the initial. Now if I let the truck fully cool after the first run of the day, it is the same as described. But if I get back in it with heat, the sooner (ie hotter) the more pronounced the result is) the same "valve like" issue is happening, but it takes longer and more revs to do so...so the first 500m-1km it is underpowerd and then viola, "valve like" opening and full boost. Once agian, back to normal in said journey.....

all this was explained to mech on monday morning.


SO...What should I look for, and what should i be advising the Mech to look for. Is it maybe a stuck waste gate? or manifold gasket.

I need this sorted asap. This is my work truck and every day its down is cost me $$$$

:mad:

[harro]

I thought the 2.8tgv had a VNT not a wastegate turbo.
Have a close look at the actuator on the turbo and hose(s) make sure everything is free and working with NO leaks.
It doesn't take much to upset these turbos.

Cheers,
Paul.

[Disco_owner]

Fuel Lift Pump ?

clogged Fuel Sedimenter ?

[uninformed]

Harro, yes this is a VNT turbo (i thought that was internal shape of fins or nozzel direction????) .... is the actuator the little (40mm or so) silver round cylinder attached to the side of the turbo? it has a small hose going from it to a alloy casting directly infront of the turbo...

disco owner, the sedimenter was cleaned very well by me, new orings and tap installed and a new fuel filter installed 8000km ago. when i drained it there was pretty much zero water in it.

[slug_burner]

The VNT may have clagged up with soot. Check that the mechamism controlling the vanes moves without binding. VNT turbo's with electronic controls usually have a full range of movement built into them either at start up ot shut down to make sure everything keeps moving and nothing builds up.

If it is not a VNT turbo then the wastegate might not be shutting properly and you are leaking boost. Do you have a boost gauge that can help the diagnosis?

[rick130]

A very good point someone above raised, make sure the actuator and nozzle on the turbo have a full range of movement and soot hasn't clogged up the works. (yours doesn't have a wastegate if it's the TGV)

That might explain the sudden changes you are experiencing in boost and the higher EGT's.
At a wild arsed guess the nozzle isn't opening and closing properly.

[uninformed]

I was sold the engine believing it was a tgv, hense a VNT. How do I check the controlling mech? what does it look like etc? There are NO electronics or computer stuff on this truck or engine

[Benny_IIA]

I was sold the engine believing it was a tgv, hense a VNT. How do I check the controlling mech? what does it look like etc? There are NO electronics or computer stuff on this truck or engine



I far as i know the vnt fitted to the tgv is a mech controlled vnt (presure).

There will be an actuator with a rod that conects on to an arm on the exhaust housing of the turbo.

Remove this arm from the actuator or the arm. then check the arm moves easily from the stop start screw to it maxium.

Also check the actuator is working just give the arm pull with a pair of vice grips attached.

also check for a small crack in the pipe running from the intake to the actuator

[rick130]

Here's some VW VNT pics.

[rick130]

http://img832.imageshack.us/img832/2088/vwgarrett143tg.gif

bugger, didn't work.
Try this

http://img90.imageshack.us/img90/2088/vwgarrett143tg.gif

[harro]

I was sold the engine believing it was a tgv, hense a VNT. How do I check the controlling mech? what does it look like etc? There are NO electronics or computer stuff on this truck or engine

The actuator will be controlled by either vacuum or pressure depending on where the small line coming from it runs to.

A vnt will have the actuator at right angles to the turbo, on a wastegated turbo it will be parallel (someone correct me if I am wrong).

Check the stop screw on the actauator rod hasn't moved (this controls max boost) and that the actuator arm can move with some encouragement:D as you are pushing against a spring. Also that the end of the actuator arm is actually resting on the stop screw.

If everything seem fine it may be internal:(.
A vacuum or pressure leak on the actuator may be the culprit but I would not expect that to affect initial spool up (boost).

Or, as you have suggested a leak in the inlet manifold or associated pipe work between turbo and inlet

There are a few tips around about cleaning out (removing the carbon buildup) a vnt with something caustic like oven cleaner but I haven't done it and I would hesitate to try it.

Cheers,
Paul.

The tip about a possible small crack in the hose to the actuator is a good one.
The same thing happened to my td5

[uninformed]

here are 2 pics of my turbo:

[rick130]

Bush65's pics showing the actuator and rod from this thread http://www.aulro.com/afvb/isuzu-landy-enthusiasts-section/82218-vnt-turbo-info.html


http://www.aulro.com/afvb/attachments/isuzu-landy-enthusiasts-section/16295d1245836046-vnt-turbo-info-actuator-2.jpg

http://www.aulro.com/afvb/attachments/isuzu-landy-enthusiasts-section/16294d1245835990-vnt-turbo-info-gt22v_1120.jpg

[uninformed]

ok, I just checked the little hose going to the actuator...I removed it, had a good look and feel, roll in fingers etc, then blew in it, then hooked up my compressor and nozzel blower and put 25 psi in one end and blocked the other with my finger....all seems good.

next I tried the actuator....I couldnt get a good go at it insitu and im thinking how can I test this thing with out recking it........DOH! hook hose up to it one end and compressor nozzel to other end of hose...15psi and it moves.

I may have found the problem! I think the little pin that goes through the bottom of the actuator arm is not located in the other end of the vnt part of the turbo....

Im going to see if I can get it in there....very very little room and I dont know how it is located, ie what stops it from popping out?

see attached pic

[harro]

ok, I just checked the little hose going to the actuator...I removed it, had a good look and feel, roll in fingers etc, then blew in it, then hooked up my compressor and nozzel blower and put 25 psi in one end and blocked the other with my finger....all seems good.

next I tried the actuator....I couldnt get a good go at it insitu and im thinking how can I test this thing with out recking it........DOH! hook hose up to it one end and compressor nozzel to other end of hose...15psi and it moves.

I may have found the problem! I think the little pin that goes through the bottom of the actuator arm is not located in the other end of the vnt part of the turbo....

Im going to see if I can get it in there....very very little room and I dont know how it is located, ie what stops it from popping out?

see attached pic

Should be a groove for a circlip, or maybe a hole for a split pin but I doubt it

[uninformed]

just took it for a spin, that didnt work. It was definitly out though, just going to see if it popped out again??

would there be a reason the moving parts inside the turbo (variable nozzels like in Ricks motion pic) would be jambed?

turbo whistle still very pronouced, egts still high and power still down

[uninformed]

yep, the little pin had popped out of the flat plate again...I suspect fairly quickly.

looking at the below attached pic, should just the little plate rotate (yellow line) or should the cast face rotate also (where red lines touch)...not the alloy compressor housing

im trying to get an understanding of the moving parts...Ricks pic has helped but cant quite tell what I should see moving from the outside

[Blknight.aus]

actuator sticking
boost compensator not functioning
Timing/valve clearances wrong
clogged muffler
sticking turbo bearings
intercooler blocked/cracked
air cleaner failed/wrong air cleanerdisregard, I left this window open too long.


I can potentially free you a slot on sunday.


The black rod from the boost actuator should move back and forth rocking the little brass arm between the second red line and the yellow one in your pic nothing else should be visably moving outside the turbo.

[rick130]

I'm guessing that pin should be fixed (peened in) where it's come out and the actuator rod pivots on it ?

[uninformed]

actuator sticking
boost compensator not functioning
Timing/valve clearances wrong
clogged muffler
sticking turbo bearings
intercooler blocked/cracked
air cleaner failed/wrong air cleaner


I can potentially free you a slot on sunday.


did you read the entire thread????

[uninformed]

I'm guessing that pin should be fixed (peened in) where it's come out and the actuator rod pivots on it ?

bonnet is up and letting cool.....it was a bit hot to touch after seeing 300+ c EGT just now....ouch

It may have a little grove for a c clip etc, I cant quite see...the litte plate it passes through seems to move freely enough and the actuator is responsive to 15 psi compressed air....

[Blknight.aus]

did you read the entire thread????

no, I opened the thread between harro and disco owner, typed up the reply (as far as I highlighted in blue) and got called away for a while, came back finished it and posted it, by then things had changed. so I edited the list into blue and added the disregard and then answered the question about what parts you should see moving.

you can test the working of the VNT internals by disconnecting the rod, wrapping some medium wire around the pin then pulling and pushing on it with the engine running, if the turbo noise changes and the actuator rod moves to try and adjust what you're doing on the VNT actuator arm then the internals of both the VNT and the actuator are ok.

[uninformed]

to recap then...... with 15psi hooked up to the actuator via a air nozzel, with a trigger to progress on and off, the actuator ROD moves up and down. The pin is still located in the end of the actuator rod with its c clip. The PIN however has come out of the little plate that has a corrsponding hole for it. This plate moves up and down fairly easy.

I just put the pin in the plate as best I could and took it for another drive. It held for 1st and 2nd and seemed to make a difference but the pin came out again....that was obvious from the drivers seat. popped the bonet and sure enough. Even with the pin in it the connection feels a little sloppy, but I have no gauge for that.

SO.....im thinking of taking the turbo off and sorting this pin out. I just cant get in there to work on it insitu.

any do's and dont's for turbo remove and replace?

[uninformed]

what are the torque values for the turbo to manifold flange bolts?

[slug_burner]

Unless the pin that connets the actuator rod to the lever that operates the VNT is able to be pushed through the lever and you can see a groove for a c clip or a hole for a split pin I'd agree with Rick and say it was peened.

You may be able to silver solder or braze the pin to the lever. You would still need some access and a torch to achieve that fix otherwise you may have to try for a partial disassembly.

[Blknight.aus]

its either peened in place or spot welded as part of the manufactureing process. You might be able to get away with crushing the arm with a pair of vice grips while the pin is in place, if you've got plenty of practice and a jewlers torch you might be able to silver solder it in place by removing the actuator and rod normal solder wont cut it due to the temps involved.

From memory the exhaust manifold bolt torque is about 50-60NM.

[uninformed]

im thinking of removing the pin and replacing with a bolt. Buy one long enough with smooth shank and cut to suit. I will just have to check the head clearance on the turbine side.

[uninformed]

Rick and The Slug were on the money, the pin was fixed to the plate by being peened or such. Not only has it broken out, it has deformed the hole it passes through in the actuator rod. :mad:

When I placed the Turbo on the bench, and since, I have been getting oil dripping from the pressure hose fitting of the actuator :confused:

now Im just waiting for my neighbour to come home. He is a Mech pluber and can help me with the welding/brazing/soldering.

I bloody hope this works!

Dave, thanks for the offer to look at it. But there was no way I was driving any distance with it like it is....EGT's just to high etc

[rick130]

I forgot to mention, close/seal/tape off all your hoses, etc.

Think clean, clean, clean.

I forgot to mention, if you are going to silver braze it you'll need a 45% silver rod and good flux as it's steel/steel.
Plumbers normally only use 3% rod for copper/copper, but if you know a fridgey they should have some 45% rod in their truck.

Bronze will work too if you are going to use that to fix the flogged out hole in the actuator rod.

[isuzurover]

Think clean, clean, clean.


You don't need to tell Serg that! His workshop is so clean you could perform brain surgery on his workbenches. I am sure the turbo will be cleaner than new by the time it goes back in.

[uninformed]

thanks Rick. Should I be cleaning the pin and plate with anything inparticualr before repair? also the rod hole?

As far as cleaning the turbo. Id be happy to if there is a correct product/procedure for it..at this stage Im not looking to dismantle it.

[rick130]

You don't need to tell Serg that! His workshop is so clean you could perform brain surgery on his workbenches. I am sure the turbo will be cleaner than new by the time it goes back in.

:D




thanks Rick. Should I be cleaning the pin and plate with anything inparticualr before repair? also the rod hole?

As far as cleaning the turbo. Id be happy to if there is a correct product/procedure for it..at this stage Im not looking to dismantle it.

Naa, just clean it as if you were going to weld it.

Don't worry about me, I'm just paranoid about pipes and hoses being open, I tape and cap as soon as things are undone, but I'm a little OCD about it too.

My neighbour is a brilliant bush mechanic, but Nev just leaves things like oil lines, turbo's and complete engines wide open for days at a time when working on them so I start twitching like Sheldon in 'The Big Bang Theory' when I walk into his shed (and I'm messy as all get out, just really OCD about some things :angel:)

[isuzurover]

thanks Rick. Should I be cleaning the pin and plate with anything inparticualr before repair? also the rod hole?

As far as cleaning the turbo. Id be happy to if there is a correct product/procedure for it..at this stage Im not looking to dismantle it.


Whatever you do - don't use brake cleaner! It turns into a toxic gas if you try welding or brazing!!!

You need to make sure the joint you will braze has been cleaned to bare metal and is free of oil. So good degreaser followed by sandpaper will be fine. After that, the flux your neighbour will have will do the rest.

As for the turbo, the turbine side will be well and truly cleaned every time it gets to high EGTs. For the compressor (inlet) side, have a look for oil/soot deposits. Cleaning these off will improve turbo life. You will need to a solvent or degreaser that won't harm aluminium.

You could also flush the oil galleries in case there is any coking, but if you use good oil and change it regularly then there probably isn't much point...

[rick130]

Whatever you do - don't use brake cleaner! It turns into a toxic gas if you try welding or brazing!!!


[snip]


Shouldn't it all have evaporated by the time you get a torch near it ?

[isuzurover]

Shouldn't it all have evaporated by the time you get a torch near it ?


Brake Cleaner = Phosgene Article (http://www.brewracingframes.com/id75.htm)

[uninformed]

NO BRAKE CLEANER EVER!!!!!!!!!!!!!

I was already aware of that one. (thank god!) I just use acetone and let dry. The pin-plate was done using 45% silver rod and ezy-flow flux. First attemp did not work. The silver did not want to take to the pin, the plate yes, but the pin no. so I popped it out and we cleaned again and put some flux on the pin not just the rod this time. Second time is better and will have to do, but we both got the distinct feeling that it didnt take 100%...the silver was pooling over to the side on the plate rather than going do in to the hole....the pin is not moving independant of the plate. Only time will tell :(

The rod was just cleaned with acetone and filled completely with manganize bronze flux coated rod. Now I just have to drill and file it flat, hook it all up and check the function

[rick130]

You'll possibly find there was some plating left on the pin.

Overheating will also oxidise the base metal and kill things quickly, and it's really easy to do with steel as it retains heat so well compared to copper or even brass.

45% rod capillaries very well when things are clean and fluxed well, as well as with the right heat.

It's also difficult sometimes with two distinctly different masses to get the heat the same on both pieces, in this case I'm guessing you could overheat the rod easily without getting quite enough heat into the pin.

It's tricky at times.

[uninformed]

ok so it was the pin into the plate. Plate is about 2.5mm thick, maybe 3 at max. The pin is of various dia, up to about 9mm at max, 7.5 where the actuator rod slips over it, then a c clip groove and of coarse the little nib end that went into the plate. From what you are saying Im guessing the plate was hotter than the pin? The smallest tip I had was a #8...would have been nice to have something smaller but you have to make do with what you have I guess.

Actuator rod travel: so now I can put it back together. I had to take the rod end/fitting off to braze it. It was seated up against a lock nut which I have tried not to move (tried). When the actuator is in the retracted position the little plate is up against a stop. That part is fine...atm if I put it back together I have to put a little pressure in the actuator to extend it so the rod will fit over the pin/plate...once seated it is fine. At approx 18psi the actuator rod is extended, but not to the extent that it is moving the plate its full range of movement...now its not far off it, say only 2-3mm but im wondering if I should adjust the rod fitting down so it slips over the pin/plate with zero pressure thus not loosing any shaft travel??? should I be using the full range of the plate (vnt adjuster)???

a variable that may have come into play is where I drilled the hole in the rod fitting. As I had to completely weld/fill the hole I had no indication as to how close to the end of the rod it was....I just used basic engineering and said that if the hole has 3mm of material left on each side then it only needs 3mm left on the end...this would be close to where it was but I cant say for sure how accurate???

looking at the below pic that Rick posted earlier. If this is the same model Turbo as mine (it looks the same in the actuator area) it has the lock nut(yellow) at the top of the rod fitting sitting just a few mm below the theads of the small mounting bolts(red). Currently mine is about 1mm higher than the bottom of the threads....IS that anything to go by???

[slug_burner]

ok so it was the pin into the plate. Plate is about 2.5mm thick, maybe 3 at max. The pin is of various dia, up to about 9mm at max, 7.5 where the actuator rod slips over it, then a c clip groove and of coarse the little nib end that went into the plate. From what you are saying Im guessing the plate was hotter than the pin? The smallest tip I had was a #8...would have been nice to have something smaller but you have to make do with what you have I guess.

Actuator rod travel: so now I can put it back together. I had to take the rod end/fitting off to braze it. It was seated up against a lock nut which I have tried not to move (tried). When the actuator is in the retracted position the little plate is up against a stop. That part is fine...atm if I put it back together I have to put a little pressure in the actuator to extend it so the rod will fit over the pin/plate...once seated it is fine. At approx 18psi the actuator rod is extended, but not to the extent that it is moving the plate its full range of movement...now its not far off it, say only 2-3mm but im wondering if I should adjust the rod fitting down so it slips over the pin/plate with zero pressure thus not loosing any shaft travel??? should I be using the full range of the plate (vnt adjuster)???

a variable that may have come into play is where I drilled the hole in the rod fitting. As I had to completely weld/fill the hole I had no indication as to how close to the end of the rod it was....I just used basic engineering and said that if the hole has 3mm of material left on each side then it only needs 3mm left on the end...this would be close to where it was but I cant say for sure how accurate???

looking at the below pic that Rick posted earlier. If this is the same model Turbo as mine (it looks the same in the actuator area) it has the lock nut(yellow) at the top of the rod fitting sitting just a few mm below the theads of the small mounting bolts(red). Currently mine is about 1mm higher than the bottom of the threads....IS that anything to go by???

As I have not set up a turbo little less a VNT I am only speculating and cannot speak from experience.

I think that as long as you can idle the engine and it has no trouble starting then you can probably go for the full range of travel on the rod, If the vanes are closed up too much then I'd expect that the back pressure on the exhaust will make it harder to idle and may need an increase in fuel to get it to idle. May run a bit warmer as a result of the extra fuel and additional back pressure. If it does not idle I would open the vanes up a bit more instead of adding fuel. You may give up a bit of travel on the control system but it will be more efficient by dropping the back pressure on the exhaust.

[Blknight.aus]

it depends on which way your vanes are setup to swing but if your rod moves out under pressure then you want the arm to just not quite hit the stops when you have the rated boost pressure applied to the waste gate

ideally you want to achieve with the rod adjuster near the middle of its travel.

if the turbo response is too slow (assuming correct fueling rates) then shorten the rod. to delay the actuation of the vanes.

[uninformed]

thanks Slug...but I think you may have it backwards??? (or I have miss understood you) I dont really know much about turbos.....

when the actuator is in the retracted postion (ie minimal boost = idle) the rod is up and the plate against the stop on the cast iron housing. This stop has not been touched, so whether I leave the adjustmant on the rod as is, or wind it out 3mm, it will not change this stop point and the plate will still sit against it. The actuator has a spring inside it so it takes more than 1 or 2 psi to get it to move....

what im looking at is if I have to use 2-3mm of rod movemnt just to get it to seat at the stop postion, I loose this in full extended position.

what is this controling other than the vane angle? ie does the actuator control max boost??? I dont want to run more than stock, which I believe upto 20psi.

[uninformed]

it depends on which way your vanes are setup to swing but if your rod moves out under pressure then you want the arm to just not quite hit the stops when you have the rated boost pressure applied to the waste gate

ideally you want to achieve with the rod adjuster near the middle of its travel.

if the turbo response is too slow (assuming correct fueling rates) then shorten the rod. to delay the actuation of the vanes.

the stop mounted in the cast iron housing is a crub screw with a lock nut. I have not touched this and cant see how the plate DIDNT touch it....im pretty sure it did.

I will check whether the amount im taking about, will either way have the plate open to its maxium. I can clearly see the point where the soot stoped above the lock nut on the actuator rod. And going off the pic I took of the wollowed out rod fitting I think I have my new hole pretty close to original....+ or - 1mm from the end.

[Blknight.aus]

the external stop is the limit for the actuation mechanism, If you have the acutator pushing the arm into that too early the extra pressure in the diaphragm can cause it to rupture. the clearance only needs to be minisucle 1 thou of an inch is enough.

the other side of that is...

if you have the arm pushed into the stop too early the extra force generated by the actuator will eventually twist the pin out of the arm.

[uninformed]

the rod/actuator is not PUSHING the plate into the external stop...It is PULLING it...hence that is why it is against it in the pic I posted (ricks) and why I was saying that it was against it under minimal boost(idle) as it hasnt enough to actuate the rod off it

[harro]

thanks Slug...but I think you may have it backwards??? (or I have miss understood you) I dont really know much about turbos.....

when the actuator is in the retracted postion (ie minimal boost = idle) the rod is up and the plate against the stop on the cast iron housing. This stop has not been touched, so whether I leave the adjustmant on the rod as is, or wind it out 3mm, it will not change this stop point. The actuator has a spring inside it so it takes more than 1 or 2 psi to get it to move....

what im looking at is if I have to use 2-3mm of rod movemnt just to get it to seat at the stop postion, I loose this in full extended position.

what is this controling other than the vane angle? ie does the actuator control max boost??? I dont want to run more than stock, which I believe upto 20psi.

Max boost is controlled by the stop screw, this sets the minimum amount the vanes can be closed, remember you don't have a wastegate so this has a major impact on your EMP (exhaust mainfold pressure).
The actuator rod length sets the rate of boost.
it is a fine line to balance the two and i think this is referred to as the duty cycle.
I have never set up a VNT but to my understanding it is best done with a boost gauge and of course someone who knows how.
Hope someone here can steer you in the right direction;).

Cheers,
Paul.

[Blknight.aus]

it depends on which way your vanes are setup to swing but if your rod moves out under pressure then you want the arm to just not quite hit the stops when you have the rated boost pressure applied to the waste gate

ideally you want to achieve with the rod adjuster near the middle of its travel.

if the turbo response is too slow (assuming correct fueling rates) then shorten the rod. to delay the actuation of the vanes.

tail end around... your stop looks to be the retraction limit, Id set it so that it just starts to clear at about 1PSI....

[uninformed]

Max boost is controlled by the stop screw, this sets the minimum amount the vanes can be closed, remember you don't have a wastegate so this has a major impact on your EMP (exhaust mainfold pressure).
The actuator rod length sets the rate of boost.
it is a fine line to balance the two and i think this is referred to as the duty cycle.
I have never set up a VNT but to my understanding it is best done with a boost gauge and of course someone who knows how.
Hope someone here can steer you in the right direction;).

Cheers,
Paul.

so as the engine revs up, the boost increases and the actuator rod extends....this extention and its limit is what limits max boost???

im not sure which way the vanes are positioned at idle with the actuator rod retracted...

[harro]

so as the engine revs up, the boost increases and the actuator rod extends....this extention and its limit is what limits max boost???

im not sure which way the vanes are positioned at idle with the actuator rod retracted...

With the actuator retracted and engine at idle the vanes are as closed as the stop screw lets them. this is maximising ehaust flows to the turbine.
This is what makes a VNT so much better than a wategate turbo as there is much less energy being wasted.
With the actuator fully extended the boost will be at it's LOWEST.
The overall operation is in some ways similar to a wategated turbo but much more complex and efficient.

Paul.

[uninformed]

thanks Paul, so do you think it would be safe to say, that if the rod fitting is set within 2mm of original postion and either way it was against that set stop, I should be ok...as I said I never touched this set stop and I dont think anything would have changed with it. My major concern was over boosting, but I think that max boost wont have changed. I think I will leave the rod set up so I have to put a small amount of pressure in the actuator to fit it up...that means at rest/idle the actuator spring is already compressed a little and should move off a touch quicker...the rod travel length lost here will only affect minimum boost at full extention


clear as mud :confused:

[Blknight.aus]

with VNT its the fueling from the pump that sets max boost, the VNT controlls how it shapes on.

[uninformed]

with VNT its the fueling from the pump that sets max boost, the VNT controlls how it shapes on.

how so?

[c.h.i.e.f]

let it warm up then hold it flat in most gears

[c.h.i.e.f]

or..... you could pull turbo apart and clean veins

[harro]

thanks Paul, so do you think it would be safe to say, that if the rod fitting is set within 2mm of original postion and either way it was against that set stop, I should be ok...as I said I never touched this set stop and I dont think anything would have changed with it. My major concern was over boosting, but I think that max boost wont have changed. I think I will leave the rod set up so I have to put a small amount of pressure in the actuator to fit it up...that means at rest/idle the actuator spring is already compressed a little and should move off a touch quicker...the rod travel length lost here will only affect minimum boost at full extention


clear as mud :confused:

Provided the stop screw for minimum vane gap postion has not been moved (max boost) you should be able to adjust the rod length to achieve the original boost curve you had.
Err on the side of caution and start with the actuator rod resting on the stop and no pressure on the actuator (lengthened) then drive it and test loads (boost rate) if to much lag shorten the rod. The effects are much more dramatic than a wastegate adjustment so about half a turn at a time until you reach the boost rate you had (hopefully).

Cheers,
Paul.

[Blknight.aus]

how so?

with an old school turbo you were limited by the boost actuator opening the wastegate and how much fuel you could pour down its neck. the more boost it tried to make the wider it opened the wastegate.


with the VNT there is no wastegate turbine speed is controlled by where on the turbine wheel the gasses are directed by the vanes. VNT turbocharger cutaway animation - YouTube here, more or less is the mechanical layout of your VNT in action. (this is a vacuum actuated unit)


at low exhaust pressure the vanes direct the exhaust gasses to the outside of the wheel where they can exert the most torque on the compressor wheel spinning it up. As the flow rate increases the gas is directed towards the center of the wheel

turbo de geometria variable - YouTube (http://www.youtube.com/watch?feature=endscreen&NR=1&v=iykU0qZSp8Y)

heres a demo of what happens inside the turbo at varying exhaust flow rate.

once the vanes are all in, it comes down to how much fuels going in.\
]

[uninformed]

thanks Dave, I kinda got that part, it was the "fueling from the pump that sets max boost" part I was lost with???

Cheif what part were you replying to :confused:

Paul, I have just returned it to where I believe it was originaly. Going by the clear line of soot above the lock nut on the actuator rod (it is clearly clean thread then black sooted thread). This was pretty close to where the nut had been left, Im pretty certain I hadnt moved it more than half a rotation either way during dismantling. I also feel I have the new drilled hole in the end of the actuator rod fitting pretty close to original. I dont have a boost gauge in the truck. Nor one to use for testing. I will go by the seat of my pants and EGT's....hell I dont think it is going to be worse than after last friday night when the pin must have finally broken free. Seeing this and how wollowed out the actuator rod fitting was, I think that may have lead to the lag "valve like" feel I explained in the begining of the thread.

Tommorrow will tell :eek:

[slug_burner]

You will be ok, it is not as though you have to set ip up from scratch.

The vanes I belive to be used to vary the size of the passage that the exhaust goes through, this in turn causes a higher gas speed when the vanes are towards the closed end of range of movement, higher gas speed causes turbine to turn faster.

[uninformed]

any ideas on what torque value to do up the 10mm(OD shaft/thread) banjo bolt fitting that goes into the top of the turbo between the compresor and turbine?

[rick130]

Theoretically you should use two new copper washers (or whatever is used there) and at a guess the banjo bolt should be 25Nm or thereabouts.

It might pay to pull the connector off the IP solenoid and crank it till you get oil pressure, just to ensure the turbo has oil, then reconnect the solenoid and fire her up.

[uninformed]

Theoretically you should use two new copper washers (or whatever is used there) and at a guess the banjo bolt should be 25Nm or thereabouts.

It might pay to pull the connector off the IP solenoid and crank it till you get oil pressure, just to ensure the turbo has oil, then reconnect the solenoid and fire her up.

yes but....thats all I had so the 2 copper washers have been reused. I will keep an eye on it.

good info on the start up procedure.....should I do it now after I already started it :angel: (should have checked in first doh!)

off to give its first run :eek:

[rick130]

I've annealed plenty of copper washes over the years too for re-use when I didn't have any new ones on hand.

Take her for a run, she'll be fine. :D

[rovercare]

yes but....thats all I had so the 2 copper washers have been reused. I will keep an eye on it.

good info on the start up procedure.....should I do it now after I already started it :angel: (should have checked in first doh!)

off to give its first run :eek:

It will still be oily, it will be fine, dry bush on the turbine shaft is bad, but seeing as you've just removed it

VNT, will make less boost, high EGT's with non operational vanes, or no boost and higher EGT's depending on action of control and where it fails to, as you have found, also the whistle is awseome, when in the open position!!

[uninformed]

Ill have to learn how to do that annealing trick one day.

well a definite improvemnet. feels pretty much like normal, maybe a little better than pre Friday's event. I would put that down to excessive play between the actuator rod fitting and the external plate. EGTS are much closer to normal with only getting up to 250c Post/T on a hard excelleration up to 80km/h through the gears and in to 4th, with it starting to fall a little when leveled out 80km/h. The more destinctive turbo whistle has now gone back to normal as well. This was only a 2-3km short run. I will do some more with inspections today.

nothing seems to be leaking at this stage. I will keep an eye on that banjo fitting. The turbo to manifold did not have a gasket??? and as for the 3 studs/nuts, well if it wasnt for my beautiful Snap-on Hi-po 0 offset ring spanner, I think I would still be trying to get those undone. Torque was set at FT!

the hardest thing for me doing this, was self-doubt. Not having the "feel" for certain things like bolt tightness etc...and it is always hard to tell when getting in for that first drive as being a bit worried, emotion comes into play and the senses are hightend, which is hard to remove that from logical judgment of the small things

thanks to all that chipped in a helped. Especially Rick for putting up with my phone calls :angel:

[rovercare]

Ill have to learn how to do that annealing trick one day.

well a definite improvemnet. feels pretty much like normal, maybe a little better than pre Friday's event. I would put that down to excessive play between the actuator rod fitting and the external plate. EGTS are much closer to normal with only getting up to 250c Post/T on a hard excelleration up to 80km/h through the gears and in to 4th, with it starting to fall a little when leveled out 80km/h. The more destinctive turbo whistle has now gone back to normal as well. This was only a 2-3km short run. I will do some more with inspections today.

nothing seems to be leaking at this stage. I will keep an eye on that banjo fitting. The turbo to manifold did not have a gasket??? and as for the 3 studs/nuts, well if it wasnt for my beautiful Snap-on Hi-po 0 offset ring spanner, I think I would still be trying to get those undone. Torque was set at FT!

the hardest thing for me doing this, was self-doubt. Not having the "feel" for certain things like bolt tightness etc...and it is always hard to tell when getting in for that first drive as being a bit worried, emotion comes into play and the senses are hightend, which is hard to remove that from logical judgment of the small things

thanks to all that chipped in a helped. Especially Rick for putting up with my phone calls :angel:

For a dude who seems to raze people on the interweb often about being wrong, I'd of thought it would of been a doddle, I can understand the diagnostics can be a little daunting, but those repairs?

Anyhow, turbo to manifold should be fine, so long as there has been no deformation, its quite common to surface grind heads and manifolds and all things similar and run no gasket

[uninformed]

For a dude who seems to raze people on the interweb often about being wrong, I'd of thought it would of been a doddle, I can understand the diagnostics can be a little daunting, but those repairs?

Anyhow, turbo to manifold should be fine, so long as there has been no deformation, its quite common to surface grind heads and manifolds and all things similar and run no gasket

yep, I will give a raze or 3 with things like opinion or if I feel miss information, but I dont remember giving anyone a hard time about having a go or doing mech stuff themselves, especially those that arnt trained. I normally take my truck to a LR mech as it is my only, AND work vehicle. I dont have the time nore want to miss somthing or do damage due to something silly like over/under tightening a nut/bolt etc. 50% of this stuff is principle and 50% feel from PROPER experience. I dont have anyone local that can really help me with this stuff especially a LR. I have 2 mates that are youngish ex mech's they can be helpful and then sometimes not know stuff I would. You may find it funny, but the LR mech of over 30 years, with a very good reputation didnt even pick up the problem after I was very clear about it, then when I informed him that it hadnt been resolved he wanted to adjust timing....clearly he felt the turbo system was fine. I doubt he checked the actuator at all. Hell it didnt take me long to find it with some internet help....and I thought it was a wastegate hahahaha

I was never around anyone mechanical growing up and never had someone tinkering etc

[Bush65]

Sorry, I've only just got to this thread.
Of the 2 turbo pics that Ric posted above, the 1st turbo is mine. It is a genuine VNT (variable nozzle turbine, also known as variable geometry turbine) turbo for the same 2.8 litre engine that Serg has. That pic was taken before I fitted it to a 300Tdi in my old rangie.
To suit my application the compressor cover (housing) has been rotated a little to chage the angle of the outlet. Otherwise it is identical to the turbo that Serg has.
I still have the turbo (the rangie and 300Tdi have gone), but unfortunately it is in storage a lot of km's from where I am now, so I have to go from memory.
Reading the posts from the beginning my 1st thought was carbon/soot jambing the vanes or the vane adjustment mechanism.
To clear-up some matters in some posts:
These particular VNT turbos, as fitted to the 2.8 litre International engine, use a boost pressure actuator (same design as a wastegate actuator) to adjust the vanes (variable nozzle). A boost pressure signal from the compressor outlet is supplied to the top of the actuator can. The pressure acts apon a diaphram and as boost pressure increases to a preset pressure it will start to extend the rod below against a spring below the diaphram in the lower section of the actuator can. When these Garrett VNT turbos are fitted to most other engines the vane/nozzle actuator uses vacuum, which is easier to control by engine management computers. The modern diesels with VNT turbos and engine management computers also control the vane geometry to allow greater recirculation of exhaust gasses to reduce NOx levels, something not easy to do with a boost pressure actuator. No computer was ever used with the 2.8 International engine that Serg has.
The pics that Rick posted above showing the vanes and the mechanism that changes their angle is just as it is with these particular Garrett VNT turbos.
When boost pressure is low, the actuator adjusts the angle of the vanes so the turbine can produce more torque from the lower energy in the exhaust gas. Greater torque drives the compressor impellor faster so boost pressure increases (being a dynamic compressor, pressure is a function of impellor tip speed squared).
As boost pressure increases, and if the driver still has his/her right foot down, the fuel injection pump will increase the fuel injection rate and the increased mass air flow through the engine (from higher charge air density and engine speed) the energy in the exhaust gas rises significantly. In this state the turbine increases speed and the actuator will start to open up the vanes to control the turbo speed and reduce drive pressure (EMP - exhaust manifold pressure).
Now to the problem of adjusting the linkage from the boost pressure actuator. From memory, with this turbo, the spring in the boost actuator pulls the nozzle control lever against the stop screw. Also from memory, the length of linkage between the actuator and control lever is adjusted so that the lever is held against the stop, but starts to move away when boost increases (I don't know what this pressure should be for the 2.8 International engine).
If the length of the linkage is too short, more boost pressure will result, but there will be greater restriction in the turbine nozzle, resulting in greater EMP and turbine speed.
I would drive it as is, then if boost pressure is significantly less than it was before the control lever failed, I would shorten up the link from the boost actuator (knurled adjustment nut with lock nut).
If boost pressure is normal (or greater than before) and EGT is higher than normal, I would lengthen the link to reduce the exhaust flow restriction in the turbine (lower EMP).
The above assumes no other problem such as leak in the boost signal line between compressor and boost pressure actuators on fuel injection pump, and turbo.
Hope this helps.

[uninformed]

thanks John, regarding the actuator setting in my situation, I was either setting it where it was or lengthening. both postions would have it against the stop at rest. I eneded up setting the lock nut where I could see a distinct soot mark above it, stoping cleanly on the thread. If I got my hole drilled in the actuator rod fitting, the same postion as original, then it should be the same as it was set up at factory. Currently it has the actuator with a little "pre load" on the internal spring (say 1 or 2mm) at rest. Unfortunately I was unable to get the factory/original set up due to the problem at hand. By the "seat of my pants" Dyno, it feels pretty close.

Hoses have been checked and all seem ok.

currently running ok.

[c.h.i.e.f]

sorry uninformed my previous statements was in regards to the vanes clogging with soot if not driven hard sometimes but john has explained in much more depth anyways :D
im mainly going off what happens on the larger diesels with vnt's and when they first came out it was a common problem with stopping full movement of the vanes and causing all the problems the same as low boost would...

john awhile ago there was talk about the vnt's being weaker and having problems if asked to put out high boost levels i remember dougal showing some interesting pics and info then you posted borgwarners new range of vnt's.are they a good option these days for high power levels but still be reliable? or is it more feasible to go compound setup if room permits?

oh and uninformed a thing i have seen done to clear the system out was get a spray bottle make sure its on a fine mist and take engine to half revs and spray water into the intake it makes engine run ruff for a bit but it cleans everything out.this was also recomended by performance diesel companys in USA and dont hold me to it but i swear i seen Gale banks suggesting it too!