What happened to your Discovery 2 today?

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Originally Posted by hankdusty

did notice the wastegate modulator has been bypassed before my ownership. now to read up and see if i should get a replacement and plumb it back in, assume the modulator failed hence the bypass.. wagon drives great as is, tuned, wonder if it would be better sans bypass :whistling:

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Back when I thought I'd be smart and fit a stainless exhaust manifold off ebay ( Don't, they don't fit Discos ) I managed to snap one of the brittle little barbs for the hose on that modulator. I didn't notice any difference at all. I hadn't had the car for all that long, and didn't have the wealth of AULRO to consult back then, so I got a new one anyway. Didn't notice any difference with it back in play.

I'm sure someone like shack could tell you why you need one, or not.

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Originally Posted by Tins

I'm sure someone like shack could tell you why you need one, or not.

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Me? I'll try...

The turbo wastegate control setup on the D2 is different to the defender.
Both have the little metal can that is bolted onto the turbo that controls the wastegate, this must be functional.

The electronic modulator before it is missing on defenders, it's not completely necessary to use it, however a performance decrease will result at higher RPM/boost levels.

If you delete the electronic one on a D2, you will most likely need to lengthen the wastegate rod to stop overboost.

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Originally Posted by shack

Me? I'll try...

The turbo wastegate control setup on the D2 is different to the defender.
Both have the little metal can that is bolted onto the turbo that controls the wastegate, this must be functional.

The electronic modulator before it is missing on defenders, it's not completely necessary to use it, however a performance decrease will result at higher RPM/boost levels.

If you delete the electronic one on a D2, you will most likely need to lengthen the wastegate rod to stop overboost.

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IMO the manuals are a lot (as in heaps) nicer to drive without the modulator fitted, less all or nothing - a lot smoother linear power.

A slush box wouldn't matter - makes sense to fit it to an auto.

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Originally Posted by FNQLR

IMO the manuals are a lot (as in heaps) nicer to drive without the modulator fitted, less all or nothing - a lot smoother linear power.

A slush box wouldn't matter - makes sense to fit it to an auto.

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They should all be better with it fitted, if it's not it's either faulty or incorrectly tuned, feel free to contact me if yours isn't running properly.

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Originally Posted by shack

They should all be better with it fitted, if it's not it's either faulty or incorrectly tuned, feel free to contact me if yours isn't running properly.

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I honestly couldn't be happier with the tune, crazy amount of torque down low. 900+ k to a tank city / hwy. very rare to go over 750 egt.
(snorkle delete, air box gutted, maf gutted, silly air filter, only running 18psi max boost)

No way am I refitting the modulator. (it tested all ok and you nailed the tune)
The modulator may be needed to compensate for a restrictive intake? There's very little lag with free flowing intake. (only based on my limited experience fwiw)

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Originally Posted by FNQLR

I honestly couldn't be happier with the tune, crazy amount of torque down low. 900+ k to a tank city / hwy. very rare to go over 750 egt.

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Good to hear.

You will probably be losing a little bit of airflow at higher target boost levels, there are a couple of other "artefacts" as well, but if you are happy with it.... Go for it!

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Originally Posted by shack

Me? I'll try...

The turbo wastegate control setup on the D2 is different to the defender.
Both have the little metal can that is bolted onto the turbo that controls the wastegate, this must be functional.

The electronic modulator before it is missing on defenders, it's not completely necessary to use it, however a performance decrease will result at higher RPM/boost levels.

If you delete the electronic one on a D2, you will most likely need to lengthen the wastegate rod to stop overboost.

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ordered!

had a couple nak axle seals and a genuine expansion cap in my basket so made sense to add this and see how we go

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Originally Posted by shack

Good to hear.

You will probably be losing a little bit of airflow at higher target boost levels, there are a couple of other "artefacts" as well, but if you are happy with it.... Go for it!

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Yeah na, now you have me wanting to refit it...

Trying to get my head around the 'loss of airflow at higher boost levels'. Isn't 20psi, 20psi regardless? as in WOT 20psi sans modulator the same as WOT 20psi with modulator? (regarding airflow)


Also could one of those artefacts be mild hunting / kangarooing at medium throttle in low gears? I never thought to check this behaviour against the modulator pwm signal. (I tried everything else)

Cheers

No, 20 psi is not 20 psi!!

But for the sake of this argument, lets pretend it is.

The gt2052 setup on the TD5 defender has the wastegate actuator directly plumbed to the boost outlet of the turbo (course enough anyway).

What this means is that as boost rises and reaches the preset spring pressure in the actuator, the wastegate starts to open.

This means that whatever RPM and load you are at, the wastegate starts to open at lets say 20 psi - that's the figure you quoted.

At 2000 rpm, 20 psi is much less airflow than at 3000 RPM... But without the WGM, you are locked at 20 PSI irrespective of RPM.

On the TD5 with the above turbo, boost levels and airflow are pretty much limited by fuelling and engine size up to about 2000 RPM.

After that the engine can provide enough drive pressure to the tooth to lift boost and airflow figures far higher, that's where the WGM comes in, after 2k RPM we can allow boost to rise to a certain point - higher than the 20 psi mentioned, if we are looking for more performance... But.... After about 2800 RPM we need to start tapering boost levels ( realistically pressure ratio) to stop turbo overspeed and high EGT, until at high RPM - lets say 4k RPM, even 20 PSI may put the turbo outside of its "efficiency island"... I'd need to double check all these figures but the theory is sound.

That's what the WGM is used for. To hit target boost and airflow amounts without overspeeding at high RPM, and under boosting at low RPM.

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Originally Posted by FNQLR

Also could one of those artefacts be mild hunting / kangarooing at medium throttle in low gears? I never thought to check this behaviour against the modulator pwm signal. (I tried everything else)

Cheers

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I need to revisit your tune I think, it's probably not the missing WGM.