Thread: td5 disco boost set ups?

How much boost are you planning to run? What have you setup to measure it and how is it plumbed in?

It is not just the MAP sensor that limits the boost. It is the MAF sensor as well, especially when you start on the bigger numbers.

Alive Tuning and BAS both sell a turbo boost box to trick the MAP sensor. This is fine for most setups. These turbo boxes work by allowing the signal through up to a certain value (a predetermined value which is less than that which would cause the cut out), once the signal gets to that value the box's output remains at that value regardless of the input signal being higher (so the signal that the ECU actually receives is always less than the figure that would cause cut out). The effect of this is that in low boost driving the ECU is getting the proper and accurate signal (as it's less than the cut out value so the box allows the signal to pass straight through), but when your in high boost it outputs the signal that will prevent cut off.

But if your running more boost, in my case I have a peak of 23psi in my inlet manifold, you'll need to sort out the MAF sensor too. There are two options for this:
IRB developments dual stage turbo boost box - unlike the Alive Tuning and BAS units, it tricks both the MAP and MAF - it is also fully adjustable for tuning.
Alive Tuning MAF

Originally I ran the Alive Tuning Turbo Boost Box and MAF combination, this was fine, everything worked properly and fixed the overboost issues. The MAF sensor quality is low, cheap plastic.

I then replaced this with a IRB Developments units and an OEM MAF sensor. This was even better as the MAF effects the automatic transmission and the OEM has the best shifts.

However, IRB are hard to deal with as they are so busy that they're slow to respond and e-mails seem to be far down the list. I actually got through to them via their Facebook page in the end.

Also of note is that the TD5 in the Defender does not run the ECU controlled actuator. When you install a VNT into the TD5 Discovery, you also disconnect this.

There's plenty more threads on all this, a fair few by myself as I was having this issue and learning/working through it. They may be interesting reading for you.

Yes I know electronic limitation. Maf and map sensors clamping at 4.75 volts.

I got one on the map already. Putting one on the maf will be next.

My question was more to with what is controlling the limited boost on the turbo itself?

Is the wastegate actuator limited by a diaphragm rating?

On the defender setups what actually controlls the max boost?

My understanding of turbos came from my patrol. Increasing boost on that was done by simply putting a vacuum override controller. And just turnung the boost set put up as fair ad you want. 40 50psi was high amounts of boost but easy to set.

With out the boost controller override the diaphragm in the waste gate actuator was set by spring rating. 15psi.

Hence the question for the td5 waste gate actuator? Is it limited in the same way?

The vacum signal to the diaphram on the wastegate controls boost. The more pressure the more the wastegate opens slowing the turbo down to reduce the boost. The boost pressure pushes on the wastegates diaphram which moves the rod which mechanically opens up the wastegate proportionally.

I do not know how much pressure the standard diaphram can handle before you blow it.

But, just like you Patrol if you fit a boost controller in the vacum line (e.g. something like http://www.gfb.com.au/products/boost...troller-by-gfb which you'll often find on ricer vehicles) that will increase the boost pressure - this is because the wastegate is not getting the full pressure to tell it to start opening up (i.e. you might be running 30psi boost pressure, but the boost controller is only allowing 15psi past to activate the wastegate). It's just a form of tricking the wastegate.

The modulator in the vacum line on the TD5 Discovery (Defenders don't have them) essentially is an electronic ECU controlled one of these.

However, it's much easier on the turbos fitted to the TD5 to just adjust the length of the rod on the wastegate which similarly effects the effectiveness of the wastegate opening from the pressure. Requires no cutting, fitting anything or any costs.

Generally 18psi is considered the same limit to increase the standard turbo.

Remembering the vane of the turbo is designed for efficiency in a rpm range. Exceeding that rpm often results in greater wear, shorter turbo life and decreasing gains due to inefficiencies.

Most with VNT's run around 18 - 23psi.
There is a larger VNT special order and Alive Tunning's hybrid turbo's for higher boost levels.

I'm I understanding you right. The rod adjustment with the electronic modular fitted will fool the boost up higher. Is it the same result as bypassing it with one of those vac controllers?

Or do you mean adjusting the rod will only created a slower opening of the waste gate but still starting from what the ecu has set for opening?

Originally Posted by scottsride

The rod adjustment with the electronic modular fitted will fool the boost up higher. Is it the same result as bypassing it with one of those vac controllers?

Or do you mean adjusting the rod will only created a slower opening of the waste gate but still starting from what the ecu has set for opening?

The modulator allows the ECU to delay the opening of the wastegate if it wants (it cannot open it, it can only prevent it from opening or reduce it's ability to open) - I don't know what parameters it does this at though. Basically, it's an electronic version (controlled by the ECU) of the manual boost controller that I linked before - the advantage is though that it can be turned on and off as required by the ECU, where the manual ones are set and forget, so they are always in application (and therefore always reducing the boost pressure level flowing through them).
As I mentioned before, Defenders don't have this component, it's also removed when fitting a VNT onto a Disco.
If you were to remove it from your vehicle, it would still run fine.

Originally Posted by scottsride

The rod adjustment with the electronic modular fitted will fool the boost up higher.

Depending which way you adjust the rod depends on the effect on the boost. < http://www.alivetuning.com/alive-bou...tion-Guide.pdf > Adjusting the length of the rod increases or decreases the effect of the movement in the diaphram in opening the wastegate.
Essentially if you lengthen the rod, when the diaphram moves it will increase the effect on the wastegate operation, thereby opening earlier and decreasing your boost pressure.
If you shorten the rod you decrease the effect. So the diaphram will move and it will push the wastegate open less. This will increase the boost pressure.

Originally Posted by scottsride

still starting from what the ecu has set for opening?

The ECU doesn't directly control the wastegate and it certainly cannot open it (it can only prevent the boost pressure getting through and thereby prevent/reduce it from opening). The boost pressure through the vacum line to the diaphram controls the wastegate.

The modulator is controlled by the ECU. The modulator can prevent the boost pressure from reaching the wastegate, which indirectly controls the wastegate, only in stopping it or reducing it's opening.

Originally Posted by scottsride

Is it the same result as bypassing it with one of those vac controllers?

If you fit one of the manual boost controllers they restrict the flow of the boost pressure through them. They will therefore allow less boost pressure through them to reach the wastegate. So you may be running 30psi of boost into the engine, but if you've set the manual boost controller it's only allowing 15psi through. So the wastegate is only opening at the level of 15psi.


If you disconnect the vacum line off the wastegates diaphragm and go for a drive (I don't recommend this) you'll find the turbo keeps spinning up. My silicone line rubbed through once and the turbo was pushing out 30psi very quickly. This is because without the vacum line providing the boost pressure signal the wastegate doesn't open.


There's a few other issues to consider:

turbo's vane design - they're designed to be efficient in a certain RPM range, exceeding this will providing diminishing returns. You'd be better off upgrading to a replacement turbo designed for the rpm that your looking to operate in.

Fuelling - if your tricking the MAP and MAF sensors into believing that there is a lower boost pressure (in order to avoid the overboost) then your only getting fuel into the engine for the lower boost level and the engine is running lean. Whilst the lean condition is not an issue for the diesel engine, your not really getting the best power out of it with a very lean air to fuel ratio.
A smart tuner can probably retune the vehicle's ECU mapping to suit, but I imagine that it may then be overfueling and running rich at low boost levels - which is an issue for heat.

This is why the best option, for drivability and low down grunt/torque (rather than outright power) is a VNT. This will provide you with 18 - 23psi constantly throughout the rev range (from idle to redline).
50psi is useless in a vehicle like these if you have to rev up to 4,000rpm before you start making it.

Ok its sounds like Murphy's law bitting down on this. From what your saying its better to keep the maf and map reading true sensors to keep the fuel supply correct at the top.

And keep the max boost down to before overboosting kicks in.

You got me interested in the vnt turbo now. You say it provides steady boost accross most of the rev range from idle. That sounds like what a turbo should do.

So the standard td5 turbos are optimised to work at a specific rpm. Or is it that they designed to spool up on lighter exhaust pressures but don't give much extre boost past a curtain point.

I have in the making the larger torque convertor v8 mod for next week. I'm excited to see how the auto drive with a lower stall speed. Larger lock up cluch too.

Ill go and read those threads you linked in now. Thx for the information too.

Just saw that twr covered this as well sorry



While I just had a really good read of this thread I failed to see one thing mentioned
First off clamping voltages is a ricer thing to do I know as I have clamped my fcd (fuel cut defender) on my supra the reason I clamped it is there is a 80% fuel cut on the map resolution for fueling now in my case I removed the cut but added a 2-1 rising rate regulator to compensate for the poor fuel map beyound that 80% mark

Not sure but from what I saw yesterday with my old boys d2 td5 (nice place for injectors and injection pump btw) that being electronicly controlled injectors that the reason for the what you would call low boost cut off would be poor map resoltion beyound that point

Safe bet would be to enhance the map while driving that boost level into the clouds

Hope this made sense and hope you can see the angle that I coming from.

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