Thread: Turbo Conundrums

Perhaps a seal has failed internally on the turbo and the boost is getting pushed into the exhaust stream? Maybe the waste gate has failed internally and the little arm is not connected to anything! so the wastegate is always open... As i cant find any boost leaks anywhere obvious, inlet manifold, hoses etc.

Originally Posted by Finnius

Perhaps a seal has failed internally on the turbo and the boost is getting pushed into the exhaust stream? Maybe the waste gate has failed internally and the little arm is not connected to anything! so the wastegate is always open... As i cant find any boost leaks anywhere obvious, inlet manifold, hoses etc.

Boost should be zero at idle and/or no load

Not possible for compressor to turbine bypass internally. Except via wastegate as you suggested, altho id expect if the shaft has snapped the actuator arm would fall out.

Try the IP diaphram bypass. Take for a short drive and see what happens.

Otherwise.

Ok so problem is half solved. It is now running how it is used to! I.E. The surge of power is back up at 1800RPM as it was just a RPM counter problem (alternator)! However there is still no boost! Well it gets to 4PSI at 3000RPM.

Unfortunately i have never had a reason to measure boost in the past, so i cant say for sure there was no boost before - but it drives just like it has always done - so i suspect it has never had any boost....

Is this too far fetched? To be driving around in a 300Tdi with no boost? The vehicle gets 10L to the 100km though, and i wouldn't have thought that was possible without boost?

Is there a preset spot the injection pump diaphragm is meant to be? I am only wondering this as it looks like someone before me has had the diaphragm cover off (bolt heads a bit worn) and wondering if they put it back on the way it's meant to be or if they have accidentally turned it and now it has no fuel enrichment.

The question is: Do 300Tdi engines still get 14PSI boost with no fuel enrichment from boost diaphragm on IP? I suspect they would as the boost needs to be there to push down on the diaphragm, right?

Originally Posted by Finnius

The question is: Do 300Tdi engines still get 14PSI boost with no fuel enrichment from boost diaphragm on IP? I suspect they would as the boost needs to be there to push down on the diaphragm, right?

No. They will get stuff all boost without the extra fuel, 4psi at 3k seems about right -educated guess tho.

When you take the diaphram out. Look at the eccentric cone on the end. There should be one distinct vertical line on it from where the fuel metering pin rubs. If there are 2 or more then it has been changed. Putting the diaphram in a different alignment changes the on boost fuel delivery.

Edit.
The fuel metering pin enters from the front of the vehicle, so the more distinct line is probably the original setting, align that to the front of the vehicle.

Altho i would not recommend mucking with this unless you have an EGT gauge




Also if somebody has wound the star wheel up this adds pressure to the diaphram and it needs more pressure to push it down. Pushing the diaphram down is what allows the extra "on boost" fuel delivery.

Not a very accurate measure, but if you have to push down hard on the cover to get the bolts to catch then it has been wound up.

Ok thanks for the info SSmith.

I think i have narrowed it down to that boost diaphragm. I had someone revv the engine up whilst i watched the boost gauge and by hand depressed the diaphragm with the cover off. The little pin moves out and is spring loaded and should ride on the cone no worries. But it makes absolutely no difference to the sound/running of the engine at 1800-2000RPM.

I then removed the diaphragm and so that i could see the pin physically move i rested a screwdriver against the pin and moved it in and out at 1800-2000RPM and again no difference to the engine or boost.

So i presume that whatever the little pin is connected to is stuck/not moving and not allowing extra fuel for boost? This sound right?

I am not sure how to check on this, as i can't quite see in these diagrams exactly what the sense pin interacts with? There is a plug at the end with an allen head bolt i could remove but i am not sure what to check out if i did?

Originally Posted by Finnius

Ok thanks for the info SSmith.

I think i have narrowed it down to that boost diaphragm. I had someone revv the engine up whilst i watched the boost gauge and by hand depressed the diaphragm with the cover off. The little pin moves out and is spring loaded and should ride on the cone no worries. But it makes absolutely no difference to the sound/running of the engine at 1800-2000RPM.

I then removed the diaphragm and so that i could see the pin physically move i rested a screwdriver against the pin and moved it in and out at 1800-2000RPM and again no difference to the engine or boost.

So i presume that whatever the little pin is connected to is stuck/not moving and not allowing extra fuel for boost? This sound right?

I am not sure how to check on this, as i can't quite see in these diagrams exactly what the sense pin interacts with? There is a plug at the end with an allen head bolt i could remove but i am not sure what to check out if i did?

Like i said, with no load it will not generate boost, and therefore the pin will do next to nothing to the running. Rather than loading up and generating boost, it will just rev freely. Need to drive it to test.

The pin pushes against the cone, and will retract as the throttle is released, so it interacts with the throttle assembly and govenor assembly. This is about where my knowledge ends. I have a dead IP at home so can take some pics of the parts if that will help.

With the cone orientated so that the pin can come further out as it needs to it should add more fuel as boost comes in. The spring under the diaphram controls how quickly the diaphram is pushed down as boost comes on, spring too tight it will take ages and a lot of boost for it to do its job.

The confusing thing is that nothing we are talking about can really come on all the sudden, or at least not that comes to mind.

Like SSmith said, don't muck about with IP settigns unless you have an EGT gauge.
So highly recommended to get an EGT gauge setup, as they're just as important as a coolant/head temp gauge on a 300 Tdi.

You have a straight through exhaust, so almost certainly your EGTs will be pretty much ok .. but 'ya never know!

I'm just thinking re your lack of boost, could it be something as simple as waste gate just adjusted to open wayyyy to early?

I'd shorten the wastegate rod to see what changes it makes to the boost pressure.
Shorter = more boost(delayed wastegate).
Longer = less boost(wastegate opens earlier).

I've actually got an electronic boost controller that delays wastegate electronically. Works OK, feels just a bit better than without(or off) .. it minimises(or eliminates) wastegate creep.

As for the turbo enrichment diaphragm, there is supposed to be a 'preset' position, but from my reading up on the topic, it's preset for the specific engine.
It's more likely than not that this diaphragm position has been reset by someone, give the age of the engine/car.

The 'zero point' for minimum amount of fuelling under turbo pressure is when the eccentric cam at the end of the shaft is at about the 12'oclock position in it's position.
The position of the marker(usually a very faint depressed dot on the metal flange of the diaphragm) can vary as it's removable from the shaft(to allow replacement of the diaphragm .. so that's not a good indicator of absolute position of the eccentric cam.
Only the position of the eccentric cam is important. The dot marker is more as a reference point for YOUR engine.

I play with the position of mine regularly trying to eke out more power whilst minimising harm(ie. EGT!!).
So for me to tell you that at the moment my best setting for the diaphragm marker at about the 225° relative to the 12oclock point is meaningless.

remembering that the eccentric cam and dot marker may not be the same thing... like mine aren't .. that's the way mine came to me too!

I've set my eccentric cam at the 12 oclock posi for testing, which gives minimised fuelling under boost. Can't remember exactly, but I think my dot marker on the diaphragm lines up at about the 135° point.
Turbo still boosts, but I get almost zero power(ie. not rich enough) .. no smoke at all, and EGT in the 400-450 range .. max! I've driven this Pentland hills rd for testing, and car struggles in 3rd to hold 80k/h foot hard near the floor(I never use foot to the floor driving in any car!).
Not a setting I'd like to use ever(other than for testing).

I've read that with the eccentric cam turned 180°, give max fuelling. That puts MY diaphragm dot marker at the 315° point, or thereabouts. even at half throttle, ie barley any load, EGT climbs like mad, but car flies up this Pentland hills by comparison. easily at 110 and rising!
I chicken out when EGT approaches 700°C, so back right off and now have to feather throttle and drop into 3rd to help with EGT dropping back.
So after a few runs, I worked out that my most balanced point for my dot marker on the diaphragm is at this 225° point(whatever that equates too for the eccentric cam on the end of the shaft).

If I remove or turn off my GFB boost controller, I get a max 15Psi boost, I've set the GFB to give me 20Psi boost.
With no other change, (ie to fuelling) I get higher EGTs with lower boost that results with having the GFB off, than with the higher boost that it allows. More boost, more air, relatively speaking .. so slighly lower EGTs(it's not much, but about 50-ish degrees max)

Other than checking to see that the wastegate actuator moves, I've never touched it's operation in any way. I've renewed all the hoses, even tho some were pretty new anyhow(I just had a heap of hose .. so thought why not).

When I first got my D1, I flet it had even less go that with the boost fuelling to a minimum. Took it to my mechanic he took it for a spin and utter simply change the muffler. Did, and made a massive difference. (that was pre EGT and pre boost gauge for me).
After that i got the gauges and started to muck a bout a bit here and there, and more so to learn more about the Tdi.

THIS Ian Petersen PDF about tuning the Tdi's IP is very good.
Worked well for me so far. 40K klm later and it's still going .. so I'm thinking I haven't done anything wrong.
if you have it, my apologies for wasting bandwidth. If you don't have it.. it's one of those resources that make tinkering easier to do.
Note in that PDF he makes reference to the 12'oclock mark for the diaphragm dot mark. This may have no bearing on the position of the eccentric cone. This can't be stressed more than enough. Mine was totally different.
I assume mine has had work done, or tweaked, or whatever, but it wasn't as per his explanation .. so don't assume that yours may be either.

One other question: do you have a 300 Tdi or 200 Tdi. Dunno if it makes any difference, but if it does in any way .. it'd be good to have that cleared up too.

But from everything explained so far, I'd be looking at pressure loss via the inlet manifold(ie. gaskets, or whatever else could do that .. split in the intake hose or something). You may not be hearing it with the engine running, so I'd be looking to inject compressed air into the inlet manifold.
And also look into the position of the wastegate.

Something that could be giving you 'false readings' :
Boost pressure with the engine revving, but not under load(ie. measuring the boost with the car revving but sitting there with the bonnet open) won't give you much boost!
Engine needs to be under load.. driving .. uphill, higher gear = better.
So if you've been measuring the boost with the car stationary, then extend the gauge you have and get the gauge into the car and drive it .. or if you can safely secure the gauge to the outside but still readable.
You don't need a lot of road to see boost rise up to 15Psi. just a few revs, under load(hill or higher gear, not lower gear).
Think of it as: boost comes with the foot pressed down hard, back off and boost drops.

Sorry for the long post, hope it helps.

Originally Posted by AK83

One other question: do you have a 300 Tdi or 200 Tdi. Dunno if it makes any difference, but if it does in any way .. it'd be good to have that cleared up too.

But from everything explained so far, I'd be looking at pressure loss via the inlet manifold(ie. gaskets, or whatever else could do that .. split in the intake hose or something). You may not be hearing it with the engine running, so I'd be looking to inject compressed air into the inlet manifold.
And also look into the position of the wastegate.

Something that could be giving you 'false readings' :
Boost pressure with the engine revving, but not under load(ie. measuring the boost with the car revving but sitting there with the bonnet open) won't give you much boost!
Engine needs to be under load.. driving .. uphill, higher gear = better.
So if you've been measuring the boost with the car stationary, then extend the gauge you have and get the gauge into the car and drive it .. or if you can safely secure the gauge to the outside but still readable.
You don't need a lot of road to see boost rise up to 15Psi. just a few revs, under load(hill or higher gear, not lower gear).
Think of it as: boost comes with the foot pressed down hard, back off and boost drops.

Sorry for the long post, hope it helps.

Yup it's a 300Tdi, you and SSmith are lifesavers.
The problem is sorted now i hope. I tested the boost whilst driving with the new wastegate disconnected and it looks fine. Like up to 15PSI. I never took it over that as i don't have the wastegate to release it. I have to get a brass tee tomorrow and then test the wastegate again and hope it holds pressure and releases. *fingers crossed*

You wouldn't believe it but the beginnings of this problem were caused when i swapped out the alternator (of all things!) and the new one had a pulley which was slightly larger than the old one and it threw the rev gauge off! Had to swap and modify pullleys from the old one Then there was a wastegate actuator that was full of rust or debris. And to top it all off i did some other work at the same time - new harmonic balancer turbo hoses etc! It has been a steep learning curve as this is my first diesel disco.

That info on the eccentric position is great - I have learnt so much in the last couple of days about the turbo and fuel side of the 300Tdi! I will drive around with the boost gauge connected for a while. I wouldn't mind an EGT gauge, just in case someone before me has fiddled with fuel settings. Are they expensive? I welded a bung in my V8 exhaust for a wideband sensor is fitting similar?