ZD30 - Vacuum to Boost control

[LostBenji]

G'day all,
I am fairly new to these forums but have been dirty and greasy long before my peaches grew fur. I have a small following who is already keen on these hence I decided to start a fresh thread rather than hi-jack another.

As some would know, I have a fairly stout ZD30 that does well considering the competition. I have already done the basic mods like induction, boost control, exhaust, suspension height and shocks.
However, I do have a area that bugs me, the Dawes Valve & Needle Valve all rave about! More on this at bottom.

Now I fully understand the logic that Nissan had with using a vacuum control on the VNT with regards to safety (line breaks, boost is dumped. Actuator breaks, boost dumps. ECU panics or solenoid shits its pants, boost dumps) however, this leads to poor control unless you have a good EBC and solenoid. Unfortunately, we all know the factory ECU and solenoid are crap at boost control.

Now step in the Boost Actuator:

Attachment 66974 . . . . . Attachment 66975

This was an eBay find after seeing a few YouTube videos of some Diesel Performance mobs selling kits and parts. Now when watching, I noticed the very similar looks and designs of the actuators and figured that the local mob was just buying them in and machining off the labels.

http://www.ebay.com.au/itm/MAMBA-Adj...kAAOSw--1WriRq

Now, these ones are good quality, come packaged well (no grey-box shit) and have 6 springs for various boost settings. Now, the smart lookers will realise these are for the Hitachi HT-12 turbos that are wastegate controlled (Navara) rather than VNT like the Patrols. The arm is quite long and bent so no good for the VNT turbo at all. So, the tools are out and new rod/arm is being turned up. I was asked by Westy about the travel/stroke of these, I can assure you, there is over 20mm of travel in them, twice whats needed to go from full-fine pitched (high boost) to fully feathered (boost dumped).

The next part to come will be the use of an EBC, Electronic Boost Controller or simple two-stage control. An EBC will allow fine control of boost over the entire range however, I don't need that much control and would be more inclined to run a simple switch (mounted on gear shifter) and simple solenoid to flick between low boost (13-14PSI) and high boost (18-20PSI) when needed. I will explain this more shortly.

The idea of keeping it simple is reliability rather than complexity.

I will come back as the mods progress with updates.


Dawes & Needle Valves suck with VNT!
The reasons why as anyone who has used them is simple, they are rude & crude, that simple. When the boost rises slowly, the ball will lift out of seat and roughly the defined pressure and start to flow positive pressure air in the vacuum line on the VNT actuator. This can in normal cases catch the boost level and keep it steady to a point. However, if you are getting up it a little, boost rises very quickly. The Dawes opens alright but does so very rudely dumping big blast into the actuator which then blurts open and feathers the vanes. The result is usually and quiet sound of a turbo stall as the boost pressure on the pressure side then reverses into the now stalling turbo which on a petrol car would result in a flutter. Yes, I go off at light and people quickly here a diesel that blows-off (the sound, not really a blow-off (external boost dump)). The needle valve is a controlled leak of the vacuum into the VNT actuator and can dampen the issue but also leads to slow ramp of the turbo which results in lower performance and same effect as wastegate creep.

So why is this bad, well this is a symptom of the crudeness of the Dawes on these setups. I now have boost spikes and boost creep like you wouldn't believe. This is also why I have mentioned in the past that my boost is not a set point. Dawes is set for 16PSI but depending on the needle valve and how I bring on the power, 12-19PSI is common which then gives me the shits when the ECU fun-stops when it sees high boost/air flow under part loads. I will do a video on this soon showing the current setup and its joy on the open road.



P.S With factory ECU and fueling, around 16PSI is the max boost that is useful as there is no more fuel to be added. On the highway, 13-14PSI keeps the turbo off full scream while keeping the EGT's under 300 while crusing @ 110Kph. Any more boost over 16PSI isn't doing much and just robing power with exhaust back-pressure.

[BigRAWesty]

Keen to follow this one..
So you are modding the rod I see..

Also electric controlled boost levels.
I wouldn't be chasing dual level setup, I'm more after a plug and play, set and forget setup.
Can you run just a single setting and forget it?
18psi seems to be the magic number with the 3ltr engines so was thinking an adjustable boost controller with a 8 psi spring just incase..

[LostBenji]

Keen to follow this one..
So you are modding the rod I see..

Also electric controlled boost levels.
I would be chasing dual level setup, I'm more after a plug and play, set and forget setup.
Can you run just a single setting and forget it?
18psi seems to be the magic number with the 3ltr engines so was thinking an adjustable boost controller with a 8 psi spring just incase..

Pretty much. Low boost will be done with spring while high boost will be done with solenoid and controlled leak (needle valve).

I found power and pull rolled off by 16PSI (mine is measured post turbo, pre-intercooler). Anymore boost didn't deliver anymore grunt as I would the point of diminishing gains has been passed along with increased intake temps. Remember, still on stock intercooler for now.

Single set spring would be bad as the engine would easily be on max boost on the highway which is not ideal.

[threedogs]

Not 100% but I think Guest 4wd in Fairfield Vic convert the ZD30 from
a vacuume system to a boost operated turbo, Pricing is under $1000 and
includes vdo boost gauge.

I think 16 psi would be the magic number as far as high boost is concerned,
with all my fiddling any higher really didn't achieve much more. Time to start playing
again I think lol

[LostBenji]

Ouch, a grand.... Fark me.

[BigRAWesty]

Pretty much. Low boost will be done with spring while high boost will be done with solenoid and controlled leak (needle valve).

I found power and pull rolled off by 16PSI (mine is measured post turbo, pre-intercooler). Anymore boost didn't deliver anymore grunt as I would the point of diminishing gains has been passed along with increased intake temps. Remember, still on stock intercooler for now.

Single set spring would be bad as the engine would easily be on max boost on the highway which is not ideal.

The crd sits on 14psi on the highway at 110 anyway. So I don't think it would matter to much..
I have read a couple of folks who have ditched dual dawes setups because a lower boost on the highway increased fuel usage and higher egt's..

Maybe 15 psi is the compromising number for a single setup..
Stock boost is read after cooler..
So if your running 16 pre cooler it could be 14 psi post cooler...

[threedogs]

Ouch, a grand.... Fark me.

I think there is a bit involved in it, $700 was the price,
but you would need to ring and find out some details.
Guests 4Wd do great work,, another shop that has a spotless
workshop and great 4x4 knowledge

[Rumcajs]

Now I fully understand the logic that Nissan had with using a vacuum control on the VNT with regards to safety (line breaks, boost is dumped. Actuator breaks, boost dumps. ECU panics or solenoid shits its pants, boost dumps) however, this leads to poor control unless you have a good EBC and solenoid. Unfortunately, we all know the factory ECU and solenoid are crap at boost control.

G'day,

I'm sorry but above is not correct.

Do you even understand why variable geometry turbocharger is actually used? It is used to control the incoming air but not for safety or power but to control emissions. EGR technology doesn't work (simple laws of physics) if the turbo is pumping fresh air in at higher pressure then the exhaust gases will ever come out! Retarding turbo at will and increasing exhaust back pressure will drop the amount of fresh air coming in and push exhaust gases in instead in the simple explanation. It gets even worse as buterfly like shutters are introduced in the intake to close or restrict the incoming fresh air even more....

So what came as brilliant answer to control if not elimminate turbo lag (variable geometry turbocharging) become a nightmare of emission shackles....

It is not very accurate or quick to control fixed geometry turbo once the turbine is spinning..... btw on heavy truck engines (non EGR) they use compressed air to fully control waste gate via air PWM valve to choke the turbo at will to keep emissions under control. (The compressed air is coming from the brakes system so cheap implementation again, it is already there essentially same as in cars vacuum is already there in the intake or via vacuum pump on diesel engines equiped vehicles)

The only reason they use vacuum control in cars is because it is cheap and easily available. (The brake booster works on vacuum too so why not utilise the existing tech uh?)

Car makers will use the cheapest method available to them at the time....

If they use electric steeper motor now in VGTs it is only because it allows even greater and finer (read faster) control over the turbo charger boost and exhaust back pressure interaction as the emission fraud is advancing to lower levels.

With the Dawes/TILIX/NV mod or your mod all you are doing is simply converting variable geometry turbocharger in to essentially fixed operation where the variability is used as a safety mechanism only aka waste gate like operation. While effective still primitive use of VGT IMHO!

Regards

[LostBenji]

Morning Rum,
This is where we are going to have to disagree I think. My responses in red.

G'day,

I'm sorry but above is not correct.

Do you even understand why variable geometry turbocharger is actually used? Yes, I very much understand VNT, VGT, VVT and VAT (Variable Aperture Turbo/Tech).

It is used to control the incoming air but not for safety or power but to control emissions. EGR technology doesn't work (simple laws of physics) if the turbo is pumping fresh air in at higher pressure then the exhaust gases will ever come out! Retarding turbo at will and increasing exhaust back pressure will drop the amount of fresh air coming in and push exhaust gases in instead in the simple explanation. LOL, For the engine to see back-pressure, the vanes need to be pulled closed/tight thus creating back-pressure but also boost as the exhaust is now moving at higher velocities and pushing on the turbine wheel. The ECU would normally control the solenoid (which is PWM by the way) to regulate the the VNT to control boost into the intake. Nissan chose Vacuum in this case as it was cheap and available (as you have mentioned) but also gave an extra side benefit for which I mentioned in OP and you have zeroed in on without thinking that I may have extensive backgrounds in these areas. I didn't feel at the time I needed to go fully technical in it's total operation. Just for the record while on it, the pressure on the turbine side is usually close that of the boost pressure. Exhaust while very hot is low density - high velocity, on the compressor side, air is colder and denser. The higher velocity gas flow is the differencing factor, not pressures ....

It gets even worse as buterfly like shutters are introduced in the intake to close or restrict the incoming fresh air even more.... I hope you are not hinting at the main throttle butterfly and the swirl butterfly which are purely open of closed, not used for EGR purposes...

So what came as brilliant answer to control if not elimminate turbo lag (variable geometry turbocharging) become a nightmare of emission shackles....

It is not very accurate or quick to control fixed geometry turbo once the turbine is spinning..... btw on heavy truck engines (non EGR) they use compressed air to fully control waste gate via air PWM valve to choke the turbo at will to keep emissions under control. (The compressed air is coming from the brakes system so cheap implementation again, it is already there essentially same as in cars vacuum is already there in the intake or via vacuum pump on diesel engines equiped vehicles)

The only reason they use vacuum control in cars is because it is cheap and easily available. (The brake booster works on vacuum too so why not utilise the existing tech uh?) Car makers will use the cheapest method available to them at the time.... Correct, Vac VNT control was cheap and also, was all that was around at time of the ZD30 VNT design.

If they use electric steeper motor now in VGTs it is only because it allows even greater and finer (read faster) control over the turbo charger boost and exhaust back pressure interaction as the emission fraud is advancing to lower levels. Yes, the tech came along later after stepper motors became strong and fast enough.

With the Dawes/TILIX/NV mod or your mod all you are doing is simply converting variable geometry turbocharger in to essentially fixed operation where the variability is used as a safety mechanism only aka waste gate like operation. While effective still primitive use of VGT IMHO! No, I am using boost pressure to do the work normally done by Vacuum. While no or low boost due to low revs or low power, the vanes stay closed thus allowing quickest spool when needed. When boost starts to rise to the spring pressure (in my case will be likely 13-14PSI) then the actuator will start to push out opening the vanes thus reducing the angle of vanes/nozzles and thus effort on the turbine. The only time that boost will be raised will be when I open the solenoid and introduce a controlled leak of the boost going to the actuator thus raising boost pressure.

Regards

As I said in the OP, I will update this as I go and complete the project with its gains.

[Rumcajs]

Morning Rum,
This is where we are going to have to disagree I think. My responses in red.



As I said in the OP, I will update this as I go and complete the project with its gains.

Indeed,

The higher velocity gas flow is the differencing factor, not pressures ....

Err, I suppose should have explained that better, but you are correct there .....

I hope you are not hinting at the main throttle butterfly and the swirl butterfly which are purely open of closed, not used for EGR purposes...

Nope, wasn't referring to ZD30 operation at all e.g. LR Defender Ford based 2.2L Puma engine does that among others.

No, I am using boost pressure to do the work normally done by Vacuum. While no or low boost due to low revs or low power, the vanes stay closed thus allowing quickest spool when needed. When boost starts to rise to the spring pressure (in my case will be likely 13-14PSI) then the actuator will start to push out opening the vanes thus reducing the angle of vanes/nozzles and thus effort on the turbine.

Using positive (boost) or negative (vacuum) pressure is irrelevant, you're still doing exactly the same what is done on fixed geometry turbochargers with the waste gate by reducing efficiency of the turbine as the boost raises in this case backing off vanes in VNT unit or in waste gate scenario of fixed unit bleeding of exhaust gases through a by-pass channel.

Therefore I will stand by my comment

turning variable geometry turbocharger in to essentially fixed operation where the variability is used as a safety mechanism only aka waste gate like operation.

while not saying it is a bad thing to do.

For the argument sake positive pressure curve based on the actual boost is/might be more efficient/desirable then relying on vacuum pressure which is subject to variation based on the demand. That part is probably more desirable however to get truly fully variable geometry turbo charging you would have to design a system which maintains boost pressure across the rev/load range and not backing off based on boost pressure only that's "dumb" waste gate operation.

So, having custom PWM electronic controller taking inputs from TPS, RPM, Airflow/MAP for example would be perfect but that is kinda self defeating cause engine ECU can and does that, trick is to change its mapping to work as one expects or wants for maximum power output. So ECU re-mapping is much smarter and better way then bumming around with recreating waste gate effect. Doable but very difficult for the average punter indeed I'm trying to decipher ZD30 ECU maps and it is a headache for sure especially when I know I won't be able to do anything easily with it because of non erasable chips used as well as the NATS chip.

Indeed all thing considered we are lucky that Nissan has chosen such simple and primitive design which can be so easily tampered with for really desired output to overcome the artificially imposed limitations.

On Di iZD30 engine ECU starts backing off the turbo vanes at around 14% TPS and at full TPS or WOT they're fully backed off if we can call PWM duty cycle of 18% fully off and 55% fully on.

BTW, I always thought that backed off vanes are closed and fully expanded are open but I suppose it is matter of interpretation.

Cheers