Outer Limits 4x4 Board

hey guys i have put a boost guage on my zd30 and it seems to be reacting really weird. ill try explain the best i can, if im cruising along the highway at 100kph and it will be sitting on 15-16 psiwith almost no throttle should it be that high on cruising?? and if i slowly put my foot down it will with just a bit more throttle the boost drops to 7 psi then slowly build up to 16-17, same scinario but if i stomp on it it will drop to 6-7 then go to 20-22, i kow that it is overboosting so i need to adjust it but i dont think it should be dropping boost like that initally could it be a faulty boost sensor??
any help would be great
thanx

How old is the AFM. They cause boost issues when there stuffed.

Dave.

got about 150000kms on it? if ur just cruising it shouldnt be boosting should be going back to vaccume what boost guage is it? autometer or some dodgy chinese thing?

macneil wrote:got about 150000kms on it? if ur just cruising it shouldnt be boosting should be going back to vaccume what boost guage is it? autometer or some dodgy chinese thing?

firstly diesels dont create vacuum.
secondly zd30's have a variable nozzle turbo charger. completely different to a turbo with a waste gate. so it is going to boost on cruise.



now to be more helpful to rugs.
i dont have a zd30, however a quick search at patrol4x4.com has this link.
chaz is the man in the know about the zd30. so have a read what he says.
http://www.patrol4x4.com/forum/showthre ... ost+cruise
there is more info on zd30's than you can 'poke a stick at' on patrol4x4 so it would be worthwhile doing some searches there.

that boost drop is a bit of a know issue, not sure why some vechiles do and others don't.

first thing......is EGR blocked off ?

2nd....clean the MAF sensor, they get coated with oil and dust and won't work well. if still plays up then replace it. (always handy to have a spare)

http://www.patrol4x4.com/forum/ heaps of info on it. they often fit dawes valve onto it to stop the over boosting.

dave- im not sure how old the air flow meter is it has 100,000ks on it and i have only had it for 5000ks so i would imagine it has never been replaced.

macneil-- the guage is an autometer one and only has boost,

sw1-- cheers for that ill check out the sight and see what i can sort out

tweakie-- yes the egr is blocked off, ill give the afm a clean and possibly replace it, any idea on cost for one??


thanx for all your help guys hopefully will get it sorted

dave

also guys whats a dawes valve and what does it do?? where does it go??
cheers

with a blocked egr you need to make sure turbo is adjusted to suit.

dawes valve is a manul boost controller for VNT turbo's. it reduces the vac signal to the turbo acuator according to boost level.

no idea on cost of the MAF sensor. make sure you get just the sensor not the whole unit. same places are known to try and sell the whole unit at big $$$.

dads was doing the same thing, on patrol 4x4 the big book posted by nom (yom? something like that, i think it was anyway) has details on how to adjust the turbo to drop the boost.
dads was doing as yours was up around the 16psi mark etc etc, adjusted it a little and now it boosts up to 13 ish and is smoother in its boost delivery etc etc.
find that big document, think he printed it out and was 60 pages or so?
tells you all you need to know.

on the note of dropping boost when you give it a bootful, i figured it had alot to do with dumping a heap of fuel in so it drops boost a bit to keep a reign on EGTs?

cheers, andrew

but when you lower boost it makes egt's rise so it would be better to have moore boost to keep the egt's lower

Leave the turbo screw where it is unless your car is going into limp mode (too much boost).

The reason its dropping down to 7 is to compensate for the EGR valve opening.

Its normal on the zd30.

Only way around it is to block the EGR as mentioned then install a needle valve in cab or in the engine bay - this will change how the turbo spools and with a bit of tweaking will make it act like a normal turbo.

Check the link for more info - its the only way around the boost drop.

http://users.bigpond.net.au/conody/Manu ... roller.htm

Paul

i already have the egr blocked, the let me just ask this to whome has a pyro on their zd 30 if your on the highway and in 5th gear put your foot flat and hold it flat how hot will the egt's go?? i have a brand new air flow meter in it so no probs there. mine will quite quickly go 550 600 and keep going if i stay on it! its a brand new autometer guage, i have tried adjusting the screw both directions and has no affect on egt's just changes how the boost comes on, but standard screw settings, standard car will easily get to hot egt's, im at a loss guys i dont know what to do next,

doubt it would be your afm (air flow meter/sensor). If it was it would be going into limp/safe mode. (revving its tits off doing 70). To answer your question though they should be around the $200 mark. (not genuine!).

Have you thought about taking it for a computer diagnostic?

computer diagnostic? where would i get that done at nissan??

Air mass meters are a pain on these vehicles. They cause all sorts of troubles with no fault codes or limp mode problems. Best thing to do is try another unit. If it still plays up, get it to someone who knows what they are doing and adjust the vnt.


Andy

+1

as EGR is blocked you really need to adjust turbo to suit. dawes valve is ok but i still think you need to limit the turbo itself.

imho the dropping to low boost is not EGR opening up unless turbo is not able to adjust itself to suit.
most likely ecu or turbo can't adjust for some reason. typical dirty maf sensor or sticky (rusty) vanes in the turbo. also check for vacuum leaks in the control lines.

maf problems will not often bring up fault codes unless its totally stuffed.

ive have tried a new maf and no difference :( can someone who has a pyro om one of these tell me how hot the egt's will go if they hold it flat in 5th gear??

Have you read the zd30 tech doco on patrol forum. From my understanding this is what the turbo was supposed to do to prevent overboosting. Mine does the same thing, gets to 18psi then drops to <10psi. From which pipe have you got your boot guage measuring? As this can also make a difference. Mine comes from the pipe coming out of the intercooler.
I will check egt tomorrow for you, am doing a run up the hiway. My egt reads from just behind the turbo just before the first curve at the top of the dump pipe. I have a 21/2" mandrel dump pipe if this makes a difference? My temp generally sits at around 250-260 on the hiway, going uphill this can rise to 350. Highest i've had it is 550-570 towing an offroad poptop van, fully loaded, uphill going out to Landcruiser park (the Jimna range). Hope this is a bit more info for you.
Matt

EGTs going uphill 90-100k's foot flat, in 5th got to 440 degrees, at 12psi boost. Hope this helps.
Matt

thanx for the reply matt, yeah mine will easily go over that in a second cruise temps are about the same, guess i have a prob somewhere else then,
oh well keep searching,
thanx again matt