Jump to content

3 L - over boost even with Dawes valve fitted


Drovers Hill
 Share

Recommended Posts

I recently had the EGR blocked and a DAwes valve fitted by a reputable company.  At steady speeds between 90 and 115 km/h (2,500 to 3,000 RPM) I get intermittent limp mode, suggesting over boost.  I took it backj to them and they reckon they can't fix it.  I will be persisting until they do, but in the mean time .... any suggestions? 

Link to comment
Share on other sites

Firstly which GU model is yours? Is it automatic transmission?
Secondly do you have boost gauge fitted and what boost you are getting?
You probably experienced the dreaded Dawes valve bounce. So wind Dawes back a bit to scale the pressure down.
Also do you still retain factory VNT solenoid control or do you have needle valve fitted and factory system bypassed?
If using needle valve than you have the spool up too aggressive.

The bit I don't like is "Dawes valve fitted by a reputable company." Most of those reputable clowns just have "NFI" while trying to ride the "gravy train" of Dawes valve boost control mods. Its not that simple.
Let me tell you that for best results you need both Dawes and needle valve fitted and in some cases more drastic action of setting VNT stop screw (highly not recommended) to reduce max turbo vanes opening to limit

turbo spool up further to reduce the chance of limp. 

As a last resort Jaycar digital voltage modifier (very complex mod) is used not only to improve performance by interupting and modifying MAF voltages (primary source of limps) but also getting rid of limp issues. Some ZD30 are simply too sensitive it seems, auto transmission equiped units especially.

 

Please supply more information about your truck type, any mods etc.

 

Cheers

Link to comment
Share on other sites

Its an 02 manual.  At this stage I haven't fitted a boost gauge.  I bought the car new and have serviced it meticulously and treated it properly.  The odometer now reads 223,000 km.  It has been a great car.  I clean the MAF sensor regularly and never notice even the slightest discolouration on it or in the cleaner that drips off.  I get great fuel economy (10 km/L).  In the eleven years I have had it the only thing I have had to replace is the battery - once.  And the radio antenna because I was reading the paper in a car wash and fogot that the radio was still on...  Obviously filters are changed as appropriate.  The car has been so good that I decided to keep it LONG term.  As insurance I decided to progressively fit the NADS.  So I started with the EGR block off and Dawes valve.  I am about to order and fit a catch can (would have done it before now but I got distracted with a dual battery system and ran out of cash).  I am now planning to do the gauges too, somewhat reluctantly.  I am not that interested in lots of information in the car as I drive - i like to relax as I tour.  By the sound of it fitting a needle valve would be very worthwhile - people say it makes for better driveability.  The odd thing with my current problem is that it only happens from 2,500 to 3,000 RPM.  It will happily sit at 120 km/h.  Wouldn't a boost spike happen above 3,000?  The big irony is that I only started experiencing problems when I started to fit the NADS.

Link to comment
Share on other sites


Oops - forgot your other question - yes, still the factory VNT control.  When I said "reputable", it was my impression because they are very concerned that it is not running properly and have assured me that they will fix it at their cost.  A colleage had his done at the same time as mine (very similar cars) and his has been fine.  He did his car on my recommendation and I am the one having problems.

Link to comment
Share on other sites

Well, there is a sequence to installing NADS and TBH at 230,000 Km its a little bit too late if you are orignal owner since new.
What is probably happening is that Dawes has been set too high (in excess 18 psi) and MAF voltages also play a part your seems like that but you wouldn't know when you have no boost gauge. All is needed is to slacken the lock nut and back the adjusting knurled end in small increments let say 1/2 turn and see what happens.
 
The ugley truth is that blocking EGR is actually main cause of overboosting and limps and Dawes is suppose to suppres those spike. The factory boost solenoid controls/affects the boost via EGR as well. When EGR opens boost is reduced by altering exhaust turbine vanes and turbo exhaust pressure increased to assist in feeding exhaust gases in, hence the turbine spool is "bled off". Once the EGR is blocked the bleed process is not there and turbo keeps overboosting or so is the theory. It is well known that EGR system can/is used to alter/limit/manipulate turbo boost.
 
As for the reputable company there you have it, they needed to advise you that in order to have EGR shimmed and boost control fitted you should have had boost gauge fitted first/simultaniously.

 

Sequence order is

 

1. Boost and EGT (pyro)gauges so you can actually see what is happening and react to it first. Low boost+ high EGTs= engine failure later so you can back off/change how you drive.

2. Catch can (to stop oil mist from crankcase breather mixing with EGR gases and carbonising/depositing in the inlet manifold and inlet ports restricting airflow)

3. Dawes, needle valve and EGR fix to remove that idiotic boost control of factory setup and have more responsive vehicle

(caution fuel consumption can be affected at higher speeds)

4. ......

5. .........

 

So far you have been lucky especially cause ZD30s are lottery some last for a long time some blow up at earliest opportunity (stock one). What  kills them are long cruises down the highway at 100 km/h when EGR opens boost drops off and EGTs skyrocket.

 

If you don't wanna know what is happening to your truck while driving than don't bother with NADS. Deal with the grenade problem when it happens eventually if ever.

 

I'm sorry but not wanting to know what is happening especially in case of ZD30 is gonna come back to haunt you eventually Patrol with ZD30 is probably a wrong car/truck to own in that case.

 

When comparing similar cars unfortunately some are just more sensitive and react with limps when settings don't agree. No one car is alike. You are not the only one with this problem.

 

Cheers

Edited by Rumcajs
Link to comment
Share on other sites

The car is back at the workshop.  They took the Dawes valve out (but not the EGR block) and the problem still existed.  Driving the car with a scan gauge showed no meaningful error codes.  The boost pressures are all over the place - don't seem to be controlled at all.  Hopefully the cause can be found and resolved soon.  Also, there is a lot of blow by gas; when you take the oil fill cap off there is a lot of pressure.  Maybe a blocked PCV valve? 

Link to comment
Share on other sites

  • 1 year later...

hi gents, i am having a similar problem so i figured i might reply to this original thread rather than start a new one. on my drive home from work today my CRD was boosting up rapidly to 15-16psi, then dropping down, and then up again, and basically boost all over the place. it used to boost up to 15psi, drop down to 12, and then gradually creep up to 14psi in a very controlled manner. it was making a weird noise so when i got home (10mins) i popped the bonnet and the hose from the catch can back to the intake had come loose. the hose clamps are pretty weak and the ends are not flared so it's not hard to pull them off, but still - strange.

 

there was a fair bit of oily residue on/around the catch can so i pulled it off and gave it a clean - not sure if this is just from the hose clamps being useless, or some other thing. the catch can drains back to the sump and there wasn't much oil in it. i checked all the boost/intake connections for leaks and they all seemed ok. there is a bit of oily residue around the turbo, not sure if this from the turbo, is overspill from the catch can or poor aim filling up??

 

i have owned the vehicle for about 9months/5,000km and this is the first time it's played up. any ideas?? perhaps a dawes valve that has suddenly decided to crap out?? turbo seals??

 

some specs

2010 CRD manual, 59,000km

3" exhaust, EGR blanking plate, dawes valve, boost/egt guages, snorkel, cross country catch can 

std turbo, intercooler, turbo timer

 

thanks for your help lads

Edited by dan
Link to comment
Share on other sites

I'd dismantle Dawes to check it for faults (jammed spring/ball or debris) first.

As far as catch can is concerned I stick to ones made/designed by professionals (Provent) not backyarders business with penchant for copying ideas and a bit of 'ally' welding skill.....

Cheers

Edited by Rumcajs
Link to comment
Share on other sites

thanks for the tip, i pulled the dawes apart and there didn't seem to be any obvious faults - no debris/oil/etc, lines clear, no jams. i couldn't hear any leaks from the vac/boost lines either, but the engine is fairly noisy so hard to entirely tell. the line between the intake and dawes is in poor condition but not cracking yet - i will try replacing it, but after that i am out of ideas - MAF maybe? i would have thought the dawes would keep things under control. i have it wound all the way out so i was expecting it'd limit me to 5-10psi, not the 20psi it is spiking to??

 

i share your sentiments on the catch can, but it was already in the vehicle when i bought it and i don't reckon it's worth the $$ to change over.

Link to comment
Share on other sites

TBH it doesn't compute! Is it connected properly? The T piece end connects to vacuum lines and boost goes on the opposite. To me this looks like the boost line side to Dawes valve is leaking or is restricted so Dawes doesn't get full pressure hence no vacuum drop to retard the vanes. Usual problems with Dawes are opposite, it internally leaks hence no boost unless the ball seizes shut.

 

Any loss of vacuum should retard the turbo vanes and drop boost. If at idle you crimp/disconnect the line to VGT actuator piston does the vane actuator lever drop down?

 

MAF sensor is unlikely culprit and in any case CrD ZD30 uses both MAF and MAP (boost) sensors to coordinate fuelling control.

 

Regards

Edited by Rumcajs
Link to comment
Share on other sites

yep it does seem a bit strange!! thanks for all your suggestions mate. dawes valve is definitely connected as you suggested. removing the vac line from the actuator causes the lever to drop as you suggested it should.

 

i pulled the intercooler off today, gave it a clean and put it back on again tightly to look for any vacuum/boost leaks and think i may have found the problem - i can hear an air leak coming from around the cold/drivers side of the intercooler. not sure if it is the hose or cracked intercooler, couldn't really feel any air. took it for a short drive and could also hear a leak noise when boost gets up. would a cracked intercooler cause the boost curve to be uneven?? it sounds likely to me??

 

also - uneven boost curve aside, i would have thought the dawes valve would still stop the overboost problems?? it spiked up to 20psi after cleaning and reassembly. have i got the dawes setup right for low boost - to raise the boost pressure i thought you use the lock ring to extend the length of the valve?? so i have the valve adjusted so it is as short as possible, was expecting it to cutout at 5psi??

 

fwiw, there was a bit of liquid oil and black grime inside the intercooler and pipes. i would have thought the catch can would stop that?? but i am not sure how long its been since the intercooler was cleaned (if at all), or if it was ever cleaned after the catch can was installed.

Link to comment
Share on other sites

G'day mate, I think you've got it wrong, that is why you have 20 psi boost spikes. ===>

it spiked up to 20psi after cleaning and reassembly. have i got the dawes setup right for low boost - to raise the boost pressure i thought you use the lock ring to extend the length of the valve?? so i have the valve adjusted so it is as short as possible, was expecting it to cutout at 5psi??

fwiw, there was a bit of liquid oil and black grime inside the intercooler and pipes. i would have thought the catch can would stop that?? but i am not sure how long its been since the intercooler was cleaned (if at all), or if it was ever cleaned after the catch can was installed.

To "shorten" or screw Dawes valve in means increasing its unloading pressure so you want to lenghten the valve or unscrew it to reduce the unload pressure. It simply affects the spring inside the valve and the tension of it, the pressure required to unseat the ball will be higher when tension is increased, reduce the spring tension, lower the pressure required to overcome it.

Loosen the lock nut and then unwind or back off the valve couple of turns (mark to position) to check where you stand.

As for the "catch can" it just proves the point, it doesn't work properly because if it did you wouldn't have any oil residues in the intercooler.

If you hear "boost" leaks and can't find obvious culprit the chances are that you have warped or blown/cracked exhaust manifolds or its gaskets or split EGR tube all very common on crD ZD30, the exhaust manifold warped and gaskets stuffed especially.

Regards

Edited by Rumcajs
Link to comment
Share on other sites

hi mate, you were bang on with the dawes valve. have it set to about 14psi now, and the boost curve is a lot smoother. still get the occasional spike of a few psi higher, but i think it is back to normal. when i originally started playing with the dawes valve the locking ring wasn't tight, so i am guessing that it had just came lose and readjusting/tightening it has fixed the issues. after having the dawes set incorrectly at a very high psi where it did nothing, i can now see why people install these!! thanks for all your help, if you are ever around brisbane i owe you a six pack.

 

so now that the boost curve is smoother and the spikes are almost gone -- is there any consensus on what is a comfortably safe boost level on a CRD?? i am happy with the power at 14psi, but if i can reliably run it a bit higher then why not?? opinions would be welcome please mate.

Edited by dan
Link to comment
Share on other sites

It can be safely pushed to 18 psi. That is the limit on non CrD so safe for CrDs for sure. Mine (non CrD) spikes to 18 psi when pushed and generally keeps around 14-16 psi. I do find that higher boost is not always the better, generally fuel consumption increase follows. I have set dual Dawes where I keep it to low boost (11 psi) for eco and higher (14-16 psi) for power when pushed.

 

Regards

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...