Boost is anaemic - Am I too demanding or looking at rebuild

[Cody]

1991 TD Syncro Transporter with the 1.6l swapped out for a 1.9l AAZ.
the manifolds, IP  and Turbo (K-24) are from the original engine.  A TDI Intercooler was plumbed in.

Does the following intake manifold pressure sound like a problem?

Turbo boost is pretty slow to come on (at least in my opinion) nothing until about 2500rpm and then it is about 2.5psi and then it'll peak around 5 unless I'm flooring it up a hill in which case I'll get about 7.5psi.

I was wanting more and so I turned the wastegate screw all the way in (it was almost there already or things were just seized - the screw is completely free-threading and then just stops completely I guess I was expecting to feel like it was pushing against something)

On the first run after that up the test hill it very briefly jumped up to about 10psi but immediately dropped back down to the usual 7.5 psi.

I plugged the BOV vent (3/4" coolant hose clamped onto vent and a blanked 3/4" steel pipe clamped into the othe rend of the hose)  and there is no improvement.

You can hear the turbo whine pretty good, so it's spinning just that the resulting boost seems anaemic.

Smoke screw has been adjusted a bit but there is no smoke whatsoever.

Any suggestions as to what to approach next.

Some have suggested a K-14. Would that spool faster?  How about a VNT?
Does a K-14 plumb right in with the 1.6l manifolds?

[vanbcguy]

Sounds like you might have a boost leak somewhere... Make sure everything upstream of the turbo is good and tight and not leaking anywhere.  Also make sure your exhaust manifold is sealed tight to the block - mine was a TINY bit loose and it cost me about 1.5 PSI and 500 RPM more till boost came on.

[Vincent Waldon]

Stock spec, up a hill in 3rd with your foot to the floor and 3000 RPM is around 10 psi, according to the Bentley.  The stock BOV pops at 12psi, so you can see what the wastegate was dialed into, from the factory at least.

So, you're not that far off actually... but you should be able to see that 10  psi whenever you mat it and get the RPMs up.

Vanbcguy makes some great suggestions... look for boost and/or exhaust leaks that are costing your precious psi.

Failing that, the most usual cause of low boost is a leaky wastegate... not much you can do there except remove and repair.

[jtanguay]

sounds to me like you need to go VNT, K14, or get a taller transmission  :wink: a little pump tuning should make it more driveable.  on my 1.6TD i could get 10 psi @ 2500 rpm in 3rd with the K24.  it will definitely lag, but it flows a lot of air so you have a higher power potential.

with my mTDI and same turbo, its difficult to get 10 psi @ 2500 rpm because the damn clutch wasn't holding the torque  :twisted:

a VNT turbo (properly installed) will be the best in terms of driveability, but is much more complicated to install (the vanes need tweaking etc).

[gigaz2]

my exhaust housing was cracked right across the wastegate seat..

high EGTs and very poor boost

[Smokey Eddy]

i dont have any fancy fueling and my T3 will do huge boost at WOT... I never ever put my foot to the floor because my hoses come apart at 25psi.

no BOV or waste gate... the boost is directly proportional to where your foot is. up a huge pull i can go 80 at 10psi very comfortable. No thick smoke...

I just recently (yesterday) did 300 km.

EGT's were 1,100 at their peak.

[vanbcguy]

Maybe I'm nuts, but my K24 seems to make way more boost low down than others around here...

I'm usually hitting 10 PSI just past 2K RPM in second... by 2.5K RPM getting 15 PSI is no problem whatsoever (that's where I have my wastegate set)...  I haven't done ANYTHING other than block off the BOV and put a 'tee' in to my wastegate line.

Highway cruising is usually in the 4-6 PSI range at 120 km/h or so on flat ground...

[jtanguay]

Maybe I'm nuts, but my K24 seems to make way more boost low down than others around here...

I'm usually hitting 10 PSI just past 2K RPM in second... by 2.5K RPM getting 15 PSI is no problem whatsoever (that's where I have my wastegate set)...  I haven't done ANYTHING other than block off the BOV and put a 'tee' in to my wastegate line.

Highway cruising is usually in the 4-6 PSI range at 120 km/h or so on flat ground...

what kind of tranny do you have?

[Smokey Eddy]

with my t3 i find i find the same.  2-4psi at 120 on flat  ground.

[anto]

i dont have any fancy fueling and my T3 will do huge boost at WOT... I never ever put my foot to the floor because my hoses come apart at 25psi.

no BOV or waste gate... the boost is directly proportional to where your foot is. up a huge pull i can go 80 at 10psi very comfortable. No thick smoke...

I just recently (yesterday) did 300 km.

EGT's were 1,100 at their peak.

Smokey eddy are you saying you have blocked off all wastegate hoses and running maximum boost basically and the only control you have is when you let off the accelerator?
How has the turbo stood up to this?

[Smokey Eddy]

That's exactly right.


WELL,

I don't drive with my foot to the floor all the time... so ... it's fine? it's only done 25psi maybe ... 4 times? The most it will ever really see in normal driving is like ..15psi...


I just like to be able to lay the power down if i need to...
you really don't need any kind of boost control on a diesel. Unless you have a problem with driving with your foot on the floor alllllll the time.

on a smaller turbo i could see having a waste gate being beneficial. but outside of racing conditions my set up does me just fine. I'm comfortable with the turbo making 20psi max on normal driving.

I plugged this fitting with JB weld

and i use an ALH tdi intake, so there is no BOV.

[anto]

Cool!
Ive a k14 which i might block off then.
Im normally pretty relaxed with day to day driving so the car doesnt see much boost at all....

What advantages does this bring over it being controlled by the wastegate? Ive the wastegate set to roughly 21psi max on my k14 at the minute....
Obviously the capability of more boost, but does it spool up a lot quicker?

[anto]

Also is it the sustained high boost pressures that would kill a turbo or would one run of high boost possibly kill it as well?

[vanbcguy]

Maybe I'm nuts, but my K24 seems to make way more boost low down than others around here...

I'm usually hitting 10 PSI just past 2K RPM in second... by 2.5K RPM getting 15 PSI is no problem whatsoever (that's where I have my wastegate set)...  I haven't done ANYTHING other than block off the BOV and put a 'tee' in to my wastegate line.

Highway cruising is usually in the 4-6 PSI range at 120 km/h or so on flat ground...

what kind of tranny do you have?

I THINK it's an ATH, I'll have to check again... That's the appropriate one for my chassis though and the gear ratios line up with reality...

[jtanguay]

Maybe I'm nuts, but my K24 seems to make way more boost low down than others around here...

I'm usually hitting 10 PSI just past 2K RPM in second... by 2.5K RPM getting 15 PSI is no problem whatsoever (that's where I have my wastegate set)...  I haven't done ANYTHING other than block off the BOV and put a 'tee' in to my wastegate line.

Highway cruising is usually in the 4-6 PSI range at 120 km/h or so on flat ground...

what kind of tranny do you have?

I THINK it's an ATH, I'll have to check again... That's the appropriate one for my chassis though and the gear ratios line up with reality...

3.67   3.45   1.94   1.29   0.91   0.75

not too bad!  fairly tall.  so in 2nd @ 2000 rpm you're doing roughly 30 km/h.  some oils help lubricate the turbo better too, so you get less lag that way.