300tdi Boost adjustment - Thoughts?

[megz]

Hey fellas


The manual for the 300tdi suggests a boost of approx. 1.0 bar @ 2500-3000 rpm, in 3rd gear travelling up a slight incline.


I replaced my turbo 2 years ago and installed a boost gauge and since then have never managed to peak above 0.75 bar.


Today I pulled off the manifold and shortened the actuator rod 7 full turns, resulting in a boost of just below 1.0 bar.


Tomorrow I plan to pull everything off again and install new gaskets - I didn’t want to put a new one on yet in case I had to pull everything off again - as I understand it the manifold gaskets are meant to be single use.


So my question is this: when I pull everything off again, should I shorten the rod a little further? What happens if I continue to shorten the rod too far?


Thanks in advance!


Dave

[rick130]

Yep, factory should be 15.5-16.5 psi otherwise EGT's will be too high and the Tdi needs as much help as it can get.

I'd go higher, 18-20.
Over about 20 the composite head gasket may not take it, and you'll be moving off the conpressor map anyway.

[megz]

That's great thanks Rick. I'll keep tweaking.


Yep, factory should be 15.5-16.5 psi otherwise EGT's will be too high and the Tdi needs as much help as it can get.

I'd go higher, 18-20.
Over about 20 the composite head gasket may not take it, and you'll be moving off the conpressor map anyway.

[donh54]

You haven't mentioned what your EGT's are currently.
I would strongly recommend you do some test runs up a suitable hill, before locking in the changes.

[megz]

I hear your point Don.

Prior to adjustment the EGT would typically read:

400ºC cruising at 100km/h ("cruising" defender style - about as quiet as a single engine cessna [bighmmm])
600-620ºC struggling up a long incline in a headwind

I haven't seen the gauge read any hotter than 620ºC. This might change in the summer months of course.

Following Rick's advice above I adjusted the rod another 4 turns (11 in total) and this has effectively shortened the rod 10mm overall. The boost now reads 1.0 bar (originally 0.75 bar) @ 3000 rpm, 3rd gear up an incline, and temp still sitting below 600ºC.

Due to current restrictions in Victoria i'm unable to get to any decent roads to really test it out but will do and report back.


You haven't mentioned what your EGT's are currently.
I would strongly recommend you do some test runs up a suitable hill, before locking in the changes.

[Red90]

There is really no point in increasing the boost unless you are also going to increase the fueling. You will have less power now than before.

[megz]

Really? I think the boost was underperforming from when the new turbo was installed and I thought shortening the rod would at least return it to spec?

And yes, next step is to adjust fuel.


There is really no point in increasing the boost unless you are also going to increase the fueling. You will have less power now than before.

[Red90]

Adding more air only robs power unless you add fuel with it. You might have gotten a bit from the boost compensator but probably not much. If you are not getting much more than 600 EGT your fueling is quite low.

[megz]

A little update for anyone following this thread...

On the actuator rod there were originally 13-14 threads visible, and I was getting 0.75 bar (10.9 PSI) @ 3000 rpm (EGT cruising temps of approx. 400ºC).

I then shortened the rod so there were 4-5 threads visible, and this brought my boost to 1.2 bar (17 PSI) @ 3000 rpm (EGT 400ºC).

I figured this might be putting a little too much pressure on an engine that's approaching 400,000kms so lengthened the rod to 5-6 visible threads. This now creates a max boost of 1.0 bar (14.5 PSI) @ 3000 rpm.

Since making the adjustment I've given the FIP screw a quarter turn and EGT remains sitting just over 400ºC (450ºC if I really push it).

Performance wise I haven't noticed much of a change around town but was able to get on the freeway today and definitely noticed an acceleration difference when travelling 80 - 100kms.

When the restrictions ease I'm looking forward to trying it out on some long and steep highways. This is where the old boy has really struggled in the past.

Thanks again AULRO for all the advice and feedback!

Dave