ZD30 stock boost behaviour...with a twist!

[timbo_1975]

Hi all... This ZD30 is in a R20 Terrano in the UK. It's a 2005 manual and I believe it has the non re-mappable Zexel ecu with NATS.

Truck is new to me, is factory stock (currently) and start/ runs good but is abit lethargic on the low to mid range. Perhaps that's how they are? It does seem to gird its loins in the 3k rpm to red line region though. Coming from a TD27 that was running 160bhp it certainly doesn't have the mid range that did.

I wanted to establish the health of the thing before improvement begins.

A boost gauge reveals a few strange things.

Revving in neutral stationary from idle, it will build boost to 15psi as revs reach 3000, after which point it drops to near zero , you can hear the turbo spool down and the engine suddenly feels 'released' from the 'load'.

https://youtu.be/kjIxWnXtrLQ


During driving; at cruise and over run it will hold 5psi boost most of the time. Presume to encourage EGR flow?

Under WOT from say 1000rpm to red line it will build boost to 8-10psi.
From a steady state cruise to WOT at 2000rpm or more it will usually spike very quickly to 15psi then drop back immediately to 10psi or so. Depends on revs when you hit WOT. The more revs the higher it will spike, but it's very fast and doesn't hold. (video was blurred )

Suspecting an ailing MAF, I have cleaned it (very dirty) and checked output volts. 1.65v at idle, almost 4v peak under load which seemed healthy.

There are no boost leaks. The VGT is pulled back against the stop at idle. Intercooler cleaned out and boost sensor o-ring checked. I have not measured output yet.

So is this normal behaviour for a stock engine? I was expecting 15-18psi at WOT, and more of a surge of torque around 2000rpm ish. To add I don't get any limp mode or check engine light.

Thanks guys

 

[tweak'e]

not much point asking here as the navara zd30 doesn't have variable turbo.
best bet is to ask on the patrol forums.

 

[Rumpig]

Second that. Probably worth fitting a dawes and needle valve and taking boost control away from the ecu like the patrol guys, mafs are a common problem as well. Lots of info here. http://www.patrol4x4.com/forum/zd30...w-old-members-data-mods-maint-gen-info-88462/

 

[timbo_1975]

Thanks so far for the input, I have posted to the Patrol forum for their input..

With a MAF, I struggle to see how exactly the ECU can control boost pressure with any accuracy, since the MAP sensor apparently isn't used 'during normal running'

 

[tweak'e]

Thanks so far for the input, I have posted to the Patrol forum for their input..

With a MAF, I struggle to see how exactly the ECU can control boost pressure with any accuracy, since the MAP sensor apparently isn't used 'during normal running'

MAF is probably a better way as its reading actual airflow rather than just a pressure. however MAF are less reliable and boost pressure is close enough.

on the topic, check the IC for leaks. thats known to upset the maf and ecu.