VNT or Twin Scroll
Turbo Mini Forums

the tollerances are pretty big,

on the desils apparently they can soot up and eventually jam,
on petrols its speculated that the materials used can melt, i suspect this comes from some form of production testing....



In our world as Ive said I dont think there is too much to worry about, when on boost we'll be running rich, and thats woried about it should be running some form of overboost protection.

Edited by Joe C on 20th Oct, 2011.

On the two diesel (1749VNT) I've just had apart, soot wasn't really an issue.

The one from my own car was sticking because a couple of the guide vanes were ever so slightly bent after part of the turbine wheel came off and hit them. No soot at all, but it never did give off black smoke like some TDCis do.

The secondhand one I got from eBay was well sooted up but vanes moved fine (that one is in my Mondeo now after a rebuild and works fine, shame about the rest of Ford's engine design... (DMF failure so my starter motor is now f**cked)).

The materials of the vanes seems a high grade stainless, possibly even nimonic, as there is no sign of discolourisation etc.

I think VNT is the way forwards for us, keep up the good work Joe.

Schrödinger's cat - so which one am I ???

I'm reasonably satisfied that a VNT on a rarely used Mini turbo is going to be OK. Now that VNTs are common place and doing 100,000 plus miles on a production diesel, they have to be rugged enough to cope with extreme conditions, including short term high temperatures.

What I'm still not clear about is if they are used without a wastegate, do they impose a high TIP? Or do they just open up and generate the shaft power from more flow and less pressure?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Isnt Porsche using VNT on petrol engines

We had a tolarance issue at work yesterday, read this thread and thought I should make a remark. Would be a shame if you found out the hard way...
Nice picture Joe!

Dazed and Confused....

damn , i just remembered i have a vnt 2259 ...temptation..

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

http://www.youtube.com/watch?v=iwAFznIW_Zg

http://www.vwdiesel.net/forum/index.php?topic=19438.0

hmmm mechanical control ..
http://mercedesforum.com/forum/diesel-perf...ine-load-49672/


electronical control ...

http://dmn.kuulalaakeri.org/vnt-lda/

Edited by robert on 20th Oct, 2011.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Interesting bit about shock waves from my text book:



So this got me thinking, to prevent the shock wave, shorten the manifold i.e. hang the turbo on the back of the engine, old style, and see what happens.

Hey presto, shock waves gone from the inner cylinders and lessened in the outers, but also lost 5hp at peak :(

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Team www.sheepspeed.com Racing

Porsche do indeed;

http://www.aerocharger.com/kits_porsche_930.php

But I reckon that manifold will drop the EGT a fair bit.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Thats aftermarket. They use it on brand new ones from the factory.

Yep, just using the link to show how the manifolding is done. I assume that the factory must mount it in the same position.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Without getting too bent out of shape, it seems the average head gasket life on this forum is 1k miles. pistons maybe 2k miles, blocks not much longer when the head gasket fails and thrust bearings fail even quicker.

So 100k on a production diesel seems good - my VNT lasted 65K and that was on a Ford.

Can anyone destroy a VNT on a Mini before the rest of the engine ???

No evidence so far :) :) :)

Schrödinger's cat - so which one am I ???

The OEM Porsche setup is like this:


It's difficult to see in this picture but it's much shorter than the aftermarket setup shown above and it's also twin turbo.

Jean

http://www.jbperf.com/

bang on!

my last lump did 5-6k before its untimed demise, i defy any one to kill a VNT 's vanes before 20k on an A series.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

This was intended to be a discussion about the options to reduce the boost threshold. We seem to keep going back to the suitability of VNTs on petrol engine.

I'm satisfied that the VNT is an option on the A Series. Joe has proved his to work OK and get some miles on it. Let's face it, if anyone could bust a VNT, it would be Joe :)

My main concern is still the issue of passing all the exhaust gas though the turbine and creating VE damaging back pressure.

As for the TD04L-12T, it is a bit of an oddball, even in single scroll form. Similar compressor wheel size to a GT1548 and a turbine wheel similar to a GT2052. Wheel size does not tell the whole story, but I would imagine it to be slow to spool and that's why they have upgraded it to a twin scroll.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

OK, back to the point....

You're either going to have to measure the pressures or try to do some calculations but without any benchmark from any engine, calculations are going to be marginal.

One thing that does occur with respect to their dominance on diesels, there is another big difference apart from temperature..... diesels generally consume the maximum amount of air they can physically flow irrespective of required power output, and regulate power by altering the fuel flow only.

So for maximum power the limit is essentially air flow in both cases but at low power the diesel exhaust gas flow will be more than the petrol (probably why they deliver boost at lower RPMs). For that reason alone I don't think the manufacturers would tolerate a design that was particularly restrictive.

Schrödinger's cat - so which one am I ???

The rev range of a diesel will mean that they do not run much or even any overlap on the cam. Hence a bit more back pressure can be tolerated. A petrol engine at 7-8k is a different matter.

I expect, but need data to confirm, that the VNT nozzles work both sides of the "normal" nozzle size i.e. they open up bigger as well as close down to bring boost in early. Much like the VVT in my Fez where I see as much benefit at 2k as I do at 7k.

I wonder if Joe could get some TIP data? Where's he gone?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Schrödinger's cat - so which one am I ???

LOL, been fixing my hangover this morning... oooff!

Ive got a gauge (that Ive had for well over a year!) to connect up, I best get on the case and get some fittings on order.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Schrödinger's cat - so which one am I ???

If anyone like me has no idea about the twin scroll turbo i found a great article.
http://www.modified.com/tech/modp-0906-twi...gn/viewall.html