zd sudden loss in power

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cbadenho
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zd sudden loss in power

Post by cbadenho »

I have a Nissan ZD 30, 2003.
Have recently replaced the Turbo and injectors. Since then:
· Sudden loss of power when traveling at 110km/h, then release the accelerator and power back. If I do not release the accelerator and just press down on the accelerator no power.
· Heavy on diesel 7.5km/l as appose to 9-10 before changes.
· Lack of power when pulling away on uphill or under load. I have to wind the thing up like one of those boy racers. (turbo lag that can be measured in calendar days)
I am thinking that just maybe the variable veins are not doing what they are suppose to or getting stuck. Any one that has experienced something similar?

Patrol at Bosch for 2 weeks now: turbo pipes 100%, neutral switch 100%, throttle position senor 100%. Nissan se computer does not pick up a thing (even under falt condition). Bosch found out that their is a drastic reduction in turbo boost under falt conditions.
KOOS BEST
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Re: zd sudden loss in power

Post by KOOS BEST »

TEST IF YOUR VEHICLE IS AFFECTED BY OVER BOOST – HOW TO
To test if your vehicle is having the over boost issue carry out the following test;
• Find a nice flat piece of highway where you can coast the vehicle at a set speed without
changing speed or RPM while driving i.e. moving your foot up and down on the
accelerator.
• Get the vehicle to around 100-110 klms, not your corrected version for bigger tyres etc.
This is dependant on your vehicle; a manual GU4 sits around 2600 RPM at about this
speed. Drop gears but keep in a higher gear so that slight foot movements are minimally
registered. 4th or 5th gears are preferred.
• The important thing is to keep the vehicle at around 2600-2700 RPM.
• Coast at this for as long as you can and see if you can feel an engine twitch (bit like
being hit by a slight side wind, can take anywhere between 20-60 seconds) or if you have
a boost gauge watch the boost go to its maximum level and feel for the same twitch.
• If you feel a twitch great, don’t take your foot off the accelerator, as doing this resets
the ECU and it will happily adjust itself and lose the error. Slowly accelerate and if you
foot goes all the way to the floor with no acceleration you have just experienced a
Nissan boost safety feature, by design.
• If you have a boost gauge, on mine the boost dropped to 15PSI for about a second then to
10PSi, then to 4PSI and stayed there with no acceleration possible, foot to the floor
staying at speed.
• If you don’t feel a twitch keep coasting for about a minute then slowly accelerate if you
foot goes all the way to the floor with no acceleration you have the issue.
This Nissan designed feature is to make sure your engine does not stay at boost for long periods
of time therefore causing damage to the engine, it is an over boost safety feature that does not
throw an engine management code.
HOW I TESTED MY OWN VEHICLE
All testing was carried out on my manual Nissan Patrol Y61 ZD30TD 2005 GU4 model, build date
is June 2005, 3” mandrel bent exhaust with ceramic coated dump pipe, hi-flow CAT and vortex
muffler. I also had access to 2 other 2005 model GU4 experiencing the same issues after EGR
blocking, both with 3” exhausts. It seems that the GU4’s may not be as tolerant of modifications
as the Series 3, could be different ECU’s, more boost, new ECU code introduced, could be many
variables?
When increasing your exhaust diameter, thereby improving gas flow, or blocking the EGR and
redirecting the additional exhaust gas flow toward the turbo it will cause the turbo to spin
faster thereby giving better low down performance and faster Turbo spool up which can greatly
reduce Turbo lag, and is seen as a plus for drivability, but this also increases boost.
In the below I used the above method to test, I also tested each phase over a number of days
with a mixture of highway and around town driving. I was advised by two independent sources
that by performing the test method above my maximum boost should have been around 10-11
PSI so this is what I set the boost around (I could not find a standard same year unmodified
vehicle with boost gauge to test on).
• EGR unblocked, tested, boost was too high at around 18 PSI, so it errored as expected.
• Screwed the VNT 3/4 a turn to drop the boost to around 10-11 PSI, tested, at this point
of the test the vehicle was far more drivable even revved quicker to the higher RPMs
(3500-4000) than it had for quite a while. The engine did not work as hard and gear
Nissan Patrol Reference Document
Page 13
changes were smoother. After driving for a short period the boost would “creep up” by a
PSI or two and settle around 13-14 PSI.
• I then blocked the EGR and turned the VNT a further 1/4 a turn, tested, noticed the
boost back up around 16 PSI. So blocking the EGR increased the boost by about 5-6 PSI.
Driving around town between gear changes it felt like there was a restriction in the
engine so when you changed gears the RPM dropped quite quickly and made changing
gears jerky.
• I then turned the VNT again so that it is now 1 1/4 turn in total and the boost is now
normally back around 10-11 PSI. The vehicle is far more drivable at this level and it still
has plenty of pulling power down the highway. What it did was cause a type of power
band at around 2000 RPM that would make the car take off when you hit the accelerator
for overtaking etc and the boost stayed low. It is very easy too start at 2000 RPM and get
the car to over 4000RPM easily without feeling any engine restriction. However one slight
side affect was the loss of some, not much but noticeable, torque down lower. The
owners of some cars I have adjusted want to leave it this way and not re-adjust as I have
done below. If you drive a car set up like this you would understand why, you can be
cruising at 100 klms and put your foot down to overtake and the car just takes off, even
while you are towing, with no over boosting of the engine.
• After the above testing, and a few months, I re-installed my Steinbauer Diesel
performance chip. What this did was change the way the fuel is delivered to the engine
and gave it more pulling power down low. One of the side effects of installing a chip is
that it will make the engine run slightly hotter the more the chip is turned up the more
fuel, so the hotter it gets. This can also be detrimental to your engine if you do not keep
and eye on it.
• Now here’s a catch, the turbo is also responsible for cooling the combustion
temperatures in the engine. So I simply re-adjusted the turbo VNT screw back 1/8th of a
turn to slightly increase the boost to around 14 PSI while cruising on the highway. The
VNT screw is now set at 1 1/8 of a turn in total. This had the effect of dropping the
temperatures by approx 25 deg C, and gave me back some lower down torque. The
engine now has a more even power band right through the RPM range. BUT guess what,
while cruising down the highway the engine now over boost errors as it did previously.
• So final adjustment was to turn the screw back to its 1 1/4 setting to stop the over boost
error. So you can asee that only a slight 3-4mm turn of the screw can have such an
effect.
After each test I reset the ECU by disconnecting the battery(s) for 20 minutes. Make sure you
save your trip meter reading or you will lose them. This reset allows the vehicle to start back at
factory defaults and re-learn its engine set up accordingly. As a matter of course I will do this
every time my vehicle has been serviced at a dealer and it always performs smoother and
quieter than when I receive it.
IN SUMMARY
Even performing the above adjustments does not limit your maximum boost to 10-11 PSI.
Remember that at all times your boost and fuel are being determined by the ECU and it will
decide how much boost you are going to get when you need it.
When I drive around town and accelerate down the street I still get boost readings up to and
over 20 PSI with the occasional higher spike just like normal, as I should as it is a design
characteristic of the Turbo (see Glossary on VGT).
What the above does is bring the mechanical/vacuum controlled boost VNT actuator setting
down to its normal designed threshold so that while coasting along the highway you don’t over
boost your engine and cause other issues along the way, like a leaky intercooler due to higher
than normal boosts over long periods of time, or a blown engine because your MAF has failed
and the over boost just helps it fail that much sooner.
The best way to protect your engine is as a separate section in the document. So get to it, give
your engine a test and see if it happens.
Just remember, these are a great engine and Nissan to its credit has been trying to engineer out
any issues over time, in my own opinion, with the mix of power and economy and the fact that
it needs to pull a 2500 kg vehicle around it does a great job.
If you modify your exhaust, block the EGR or both you will cause the engine to over boost, it
may not boost high enough to throw a code, or even to error all the time, but it definitely will
be boosting higher than designed
Koos Best(Kosie)Mtunzini Zululand
Land Rover Discovery 3 TDV6
Patrol GU 2003 3.0d GRX (SOLD 2010)
Patrol GQ 1996 4.2d ST(SOLD 2007)
KOOS BEST
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Posts: 545
Joined: 07 May 2009 09:14
Full Name: Jacobus William Best
Nickname: Kosie
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Current 4x4: Land Rover Discovery 3 TDV6
Home Language: TWEETALIG

Re: zd sudden loss in power

Post by KOOS BEST »

Hi , your symptons sounds like a classic over boost, very common in ZD 30 engines.
Very important load down the ZD rference document from the Aus, website. It is of utmost important if you drive a ZD30.
Koos Best(Kosie)Mtunzini Zululand
Land Rover Discovery 3 TDV6
Patrol GU 2003 3.0d GRX (SOLD 2010)
Patrol GQ 1996 4.2d ST(SOLD 2007)
cbadenho
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Re: zd sudden loss in power

Post by cbadenho »

Thanks Koos
cbadenho
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Re: zd sudden loss in power

Post by cbadenho »

dit was limping weens over boost.
Maar om alles te kroon was daar 'n paar krake in die inter cooler.
toe dit reg gemaak is was daar geen turbo lag nie.
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SRXy
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Re: zd sudden loss in power

Post by SRXy »

Sounds like they swopped your engine out for a normally aspirated 4.2.... :wink:

Seriously though....I agree with the rest of the folks who've commented.
In regione caecorum rex est luscus.

Desiderius Erasmus: circa 1510
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