Boost dropping

Hi guys I'm hoping someone can shed some light on my little problem, the boost on my 300tdi raises to approx 15psi but then seems to drop off prematurely leaving a cloud of black smoke till I change up and get boost again, the pump has been turned up abit. The wastegate moves but has spring tension, all pipes seem ok, would it help turning up the turbo slightly?
Cheers Dan

the problem is you mucking around with the pump.

wastegate is meant to open at that pressure.

you could adjust the wastegate so it opens up at 16/17 psi, but the risk is yours!

Mines set around 20psi, I'm carefull with it don't drag heavy loads and don't use full throttle for any extended periods

It was only tweeked a little bit as it seemed to struggle while off-road in certain areas but it's not the wastegate opening that's the problem it how premature it opens, seems low in the revs, I'm goner try and turn up the turbo slightly to see if it helps but I don't really give it any hammer, mostly steady local drives and occasional off roading.
Cheers for replies
Dan

If it's building pressure at 15 psi the turbo is ok, I think your waste gate is not holding up. Boost drops, she then runs rich hence the black smoke.

If all of your clamps are tight and you have no burst charge air hoses then your waste gate might have issues. First thing to do is to look for leaks in the charge air route.

Had a look around and a listen can't find any leaks, is it worth adjusting the wastegate or do I need to do something else?
Cheers Dan

Dannyboy444 said:

Had a look around and a listen can't find any leaks, is it worth adjusting the wastegate or do I need to do something else?
Cheers Dan

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You cannot listen for leaks if it's leaking under boost. You have to physically checks clamps, bend hoses and look for cracks, you have to work here Dannyboy.

Remove the charge hoses and check them properly, clean them if needs be and then tighten the clamp.

Also check the compressor wheel to look for shaft play....you could also loose boost of the turbo wheel is rubbing the housing but I am sure you would hear that unless you have music cranked up or you running straight pipes.

Do not play around with the boost and pump if you do not have a boost nor EGT gauges.

Some things you can dick around with but this can cost you an engine by experimenting.

Ok lol and not got loud music lol only 1 speaker in full truck haha and standard pipe, but I will have a really good look over the pipes the next few days and see what that brings as for the tweeking I do have a boost gauge fitted to check boost, the pump on the other hand only had a very slight adjustment,
Thanks again for the help
Dan

Dannyboy444 said:

Ok lol and not got loud music lol only 1 speaker in full truck haha and standard pipe, but I will have a really good look over the pipes the next few days and see what that brings as for the tweeking I do have a boost gauge fitted to check boost, the pump on the other hand only had a very slight adjustment,
Thanks again for the help
Dan

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Lol OK. I realized that you had a boost gauge since you said you were boosting to 15 psi.

Readjusting the pump really won't help your boost drop situation. Be careful not to dial the pump down too much, you will damage the engine. Hope you documented the changes you made to the pump from its original setting.

Cheers.

Dannyboy444 said:

It was only tweeked a little bit as it seemed to struggle while off-road in certain areas but it's not the wastegate opening that's the problem it how premature it opens, seems low in the revs, I'm goner try and turn up the turbo slightly to see if it helps but I don't really give it any hammer, mostly steady local drives and occasional off roading.
Cheers for replies
Dan

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if it's hitting 15psi, why do you think it's opening up prematurely?

afaik, and i'm no turbo expert, the wastegate actuator will open up the wastegate to keep you max at 15psi(standard) under full boost.

are you saying that your gauge reads to 15psi and then drops down to zero?

if so, it sounds to me like your wastegate is sticking or the actuator isn't working correctly (maybe weak spring).

if you unclip the actuator rod, does the wastegate move freely?

Removed the actuator rod and the wastegate is free,
Cheers Dan

So it picks up to 15psi, what pressure does it drop to when you are at high revs? Could be that pump max fuel delivery is set too high rather than you loosing too much boost pressure if it drops to say 13/14 psi.

Drops down to between 5 and 10 psi,
Cheers Dan

You could try disconnecting and plugging the wastegate actuator pipe so it cant open then take it for a spin keeping an eye on your boost gauge. At least that will tell you if it is the wastegate dumping the pressure or the turbo failing to produce it

I removed the wastgate pipe and blocked it, now it boosts off the clock but still drops off prematurely, It used to boost right through the revs, but now dies at about 2.5-3k revs, It also used to do 80mph with plenty of spare go! Now it gets to about 60 boost drops and struggles to 70.
What do you all reckon?
Is it turbo rebuild time?
Cheers guys
Dan

Dannyboy444 said:

I removed the wastgate pipe and blocked it, now it boosts off the clock but still drops off prematurely, It used to boost right through the revs, but now dies at about 2.5-3k revs, It also used to do 80mph with plenty of spare go! Now it gets to about 60 boost drops and struggles to 70.
What do you all reckon?
Is it turbo rebuild time?
Cheers guys
Dan

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don't over boost it, you'll do damage!

your turbo sounds like it making enough boost and your wastegate sounds like it's working well.

you'll always have a bit of boost tailoff btw, but dropping to 5 is low. i'd be thinking the wastegate actuator is duff, say weak spring.

pull the pipe coming from it to the t piece and blow down it, if you can keep blowing then the diaphragm is gone, but it's opening fine, so i doubt it is.

part number is STC3084, but for the price of them, you could pick up a good used turbo.

might be worthwhile seeing if you can buy a knackered turbo very cheap and swapping the actuator over to see if it is that.

or wait for someone with more knowledge of turbos

Haha cheers bud and I try not to overboost anyway very rarely give it any beans, I only tweeked it for sticky situations/times that I need it off road.
if the actuator was duff would it still tail off with the actuator blocked off?
I will have another look at it lol,
May need an inhaler lol
Gets out of breath too early lol
Cheers
Dan

Dannyboy444 said:

Haha cheers bud and I try not to overboost anyway very rarely give it any beans, I only tweeked it for sticky situations/times that I need it off road.
if the actuator was duff would it still tail off with the actuator blocked off?
I will have another look at it lol,
May need an inhaler lol
Gets out of breath too early lol
Cheers
Dan

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say you nipped the pipe so the actuator didn't get any pressure to push the rod down, then it wouldn't open the wastegate and it would overboost.

inhaler trick.. might as well

Where is your boost gauge connected to, is it the turbo wastegate pipe or at the intake manifold? If its at the manifold then you may have a case of pipe delamination causing a partial blockage at high flow rates?