Porsche Releasing Antilag Turbo ...

[Coupe-This]

Hey guys, was just reading a guys magazine at work the other day (forgot the name, will have to find out tho)

But apparantly porsche are making a turbo that has a changing a.r

This would initially mean that the a.r would be something tiny on idle, say .10 for arguments sake, once revs, and boost climbs the a.r would open up to well, the possibilities are endless ... 1.26 ?

This would give awesome low end, mid end and top end.

Apparantly they have been running these on deisels for a little bit of time now. Now getting onto the petrol scheme, i cant remember the name of the actual company that developed it with/for porsche.

Would be great to see in the flesh !!!, just wondering how exactly they would do it.

But then again, its another part to fail, damn cars !

hehe

anyone know any more info/truth to this, will try and find out the magazine it was in tomorrow

[Johnny Cash]

Yeah, I agree with the another-part-to-fail idea.

Sure, Porsche will make it good, but they'll charge for it too.

And the cheap kits that end up on eBay will fail in a week.

Aand we'll have to wait for the locally produced compromise...

[paulr33]

garrett have on the shelf turbocharger that uses vanes that change their flex size i think it is during run time to decrease lag in the low rpm range and to open up when on full song. i think the t04z uses it, not sure. looks very good

[caminperth]

They're called VAN turbos - or Variable Area Nozzle turbos I think. It's a great idea that no-one seemed to want to develop. Great to hear a manufacturer is doing it as the flow down effects over time will be handy for us...

[Josh]

They are also known as a variable geometry turbos.. not sure if we have them at work yet tho

[scathing]

They're called VAN turbos - or Variable Area Nozzle turbos I think. It's a great idea that no-one seemed to want to develop.

Except for pretty much any OEM that makes a turbo diesel. Few modern turbodiesels don't use it - I know one of my mates was considering putting a variable vane turbo off a diesel Patrol onto his petrol motor....not sure how far he got before he got rid of the car the engine was meant to go into.

An article on the 997 Turbo's new snails can be found here.

[ellie]

Saab of all manufacturers have been using variable turbos for donkeys years and the reason that these turbos have been in diesels for ages and hadn't transfered to petrol is because up until recently (1-2 yrs) the basic design had been pattented to a couple of truck compenies but now its a free for all so now citreon,BMW,audi,saab,porsche etc are developing the turbo for petrol application. I know audi have had electic servo motor controlled variable vain turbos for about a year and they hoot! ! ! Where as BMW have been using electrically switch vacuum actuated variable vain turbos on their diesels for a few years now and apparently a twin turbo 3L 6cyl using these turbos is in the pipeline. Should haul arse!

[Warpspeed]

VATN turbos have been around for over twenty years. They work wonderfully well on diesel engines, but are not terribly good on petrol engines. I know because I have run one on my DOHC Laser turbo engine for about four years.

A VATN will give you very low lag, a very low boost threshold, and very low top end power. The problem is that ALL the exhaust has to go through the turbine, there is no wastegate. That means very high exhaust back pressure which limits top end power.

The only way around this is to use a wastegate as well as adjust the exhaust vanes but it is very complicated to control. I tried for four years and eventually gave up.

It is a bit like sequential turbos, a brilliant idea that does not work terribly well in practice.

VATN turbos have been available for twenty years, where are the really fast drag cars and fast street cars using these turbos ?

I bought a brand new VATN from Nissan as a spare for a Nissan Patrol diesel. It was rated at 150Kw on a four liter diesel, so figured I should be able to get 150Kw from my 1.6 litre petrol Laser. I could never get it working to my satisfaction.

If these things are so good, why did Nissan not use a pair of them on the GTR ? Nissan used them on their diesels around that time, so why not on the GTR ? Porsche do a lot of funny things, and they have obviously made it work somehow. But I very much doubt if the technology is readily transferable to other engines.

Edited March 8, 2006 by Warpspeed

[666DAN]

The new 911 turbo does 0-100 in 3.9...so the system can't be all that bad

[Warpspeed]

The new 911 turbo does 0-100 in 3.9...so the system can't be all that bad

I am sure it works great. But that probably has much more to do with engine management, and control and integration of the movable vanes and wastegate (if used), rather than the turbo itself.

Don't expect to get similar performance from just a bare VATN turbo, without the fancy software control system to go with it.

Garrett are pushing their GT series ball bearing turbos for high performance OEM petrol applications, and their VATN for high performance OEM diesel applications. There are reasons for that...........

[PHaT MR30]

I think Audi and Mercedes use these on their diesels

[discopotato03]

Variable Area Turbine Nozzle exhaust housings are still being developed but will probably be specific to a set state of tune . The theory is to keep the exhaust gas speed up over the engines total operating range and be able to achieve a large enough effective a/r to prevent the VATN turbo from overboosting at the redline . I think its another gimic (sp?) to get around the I want /need positive pressure from idle all the way up . The ones I've seen in bits have small turbines in relation to their compressor and the turbine housing is always a bulky cumbersom heavy thing .

The future will tell but I see the next turbos having more modern turbine and housing forms and wider ranging compressors as well . The diesel turbo is heading into higher pressure ratios and the turbine sides that can drive double sided compound compressors to achieve it . The manufacturers are screaming for higher outputs without greater engine capacity which well developed diesels with better engine controls can do .

The VATN turbo is a problem for petrol engines because their higher exhaust gas temperatures do nasty things to the VATN housings intricate vanes and if they lock up overboost can kill . Even if they can get round this its debatable if the compressor can make serious boost over a wide airflow range read engine rev range . The sad fact of life is that the rotary compressor is not a perfect thing , when it works over a variable speed range its pumping efficiency also varies and this has to be lived with . The turbochargers chief limitation is that it has to balance out exhaust energy against a rotary compressors limitations and turbine efficiency/flow against compressor efficiency/flow neither of which is linear .

Cheers A .

[LBR33]

*Imagines a VAN T88-34d Turbo with the response of a gt2530*

[Josh]

It's still gotta know when to change its area, needs a bit of software...

I am sure holset haven't released their Variably geometry turbos in aus yet, they arte supposed to be different to others available at the moment.. will check tomorrow at work..

[Warpspeed]

Discopotato sure knows his stuff !

Yes indeed, diesel engines are fundamentally quite different. Diesel engines use no throttle body, and the flow through the compressor and turbine is always fairly high.

Diesels also produce massive low end torque that always rapidly falls off as Rpm rises, and they never develop high top end horsepower (for their engine size). As a result diesel engines don't have the high top end air flow requirements that petrol engines have.

Have you ever noticed that large diesel engines never use wastegates ? The TO4 range of turbos were all originally designed for large diesels, which is why none of them have internal wastegates.

VATN turbos work really well over limited airflow ranges, and as Disco says, much lower exhaust gas temperatures. Turbo applications for diesel engines are totally different to turbo applications for petrol engines.

Garrett have developed the VATN to the point now where any new high output diesel engine is almost certain to use a VATN turbo, they are that good. But the problems of applying these same turbos to petrol engines are fairly formidable and not to be underestimated.

Porsche have made it work, and good luck to them. But don't think you can just buy a Porsche VATN turbo and bolt it onto your Skyline and get similar results, not without the sophisticated fully mapped software control system to control the movable vanes anyhow.

I am not trying to put Porsche down, just let you guys know that this is not some magic new turbo that is about make everything else obsolete. Not for us petrol heads anyway. But if you are a trucker, they are absolutely great.

Edited March 9, 2006 by Warpspeed

[discopotato03]

Corky Bell in his book Maximum Boost shows pictures of the "Aerocharger" which is no longer made . From memory the Aerocharger used an actuator not unlike an integral gate actuator which could work with boost signal pressure , though not quite the same as electronic control .

Cheers A .

[Warpspeed]

I am familiar with those actuators. They use two diaphragms, a small one driven by boost pressure, and a larger one in front operated from manifold vacuum. Each diaphragm has its own spring, and there is a push rod inside to decouple the rear diaphragm from the front one.

The system holds the vanes in the fully open position at small throttle openings (high vacuum) and closes the vanes when you floor it. The vanes then open again when the desired boost pressure is reached. I had a homemade system exactly like that, but it still left a lot to be desired.

A much better idea is to use a stepper motor, and fully map the vane position against Rpm and load.

The biggest problem I had was that moving the vanes into the fully open position would certainly limit turbine Rpm and control boost, but it did nothing to reduce increasing turbine back pressure with flow. Fitting a larger turbine wheel would then unacceptably reduce the boost threshold and response. I played around with this VATN for four years, and it was NEVER anywhere near as good as a decent modern ball bearing turbo. It was better in some respects, and a lot worse in others, but on balance the whole thing was a mess.

When HKS bring out a VATN with a suitable control system for petrol applications, that is superior to a straight high performance ball bearing turbo, that would really be something. But it just won't happen.

There is far more scope for twincharging petrol engines. Use a supercharger and turbo together. The latest 2006 VW 1.3 litre Golf GTI just released in Europe sets new standards for power, engine flexibility and fuel efficiency. That is the way I see things progressing if you want something better than a ball bearing turbo.

I had a twincharge system fitted to my car before the VATN. My satisfaction score out of a hundred:

Twincharge system 100 points

VATN 30 points

Ball bearing turbo 75 points

My next car will definitely be either supercharged with a screw supercharger or twincharged. Either should easily beat a straight turbo for on the road performance.