paulagre

Apparently this technology has been around for a while in various diesel applications, and now been brought to performance light by Porsche. Its the best thing since sliced bread, only I am not seeing really hit the aftermarket scene quite yet.

Anyone have any information regarding aftermarket sale of VTG turbos otherwise known sometimes as variable vane.

Anyone who is not familiar with this technology, do a search ON VTG. Its cool stuff.

alexdimen

iTrader: (13)

they are pretty awesome... but just reading stuff on google seems like they are very costly because of design and materials used in the mechanism, just so it can withstand the EGT's of a piston engine. used in a rotary w/ no head to cool the gasses i don't know how it would hold up.

you should see some of the turbo manifolds i've dismantled trying to get some good twin core parts! i would never subject an obscure, exotic turbo to that kind of ****.

paulagre

Yes, I have read that heat was a major concern in previous technologies. I was hoping that with the new porsche, some good news might have come to us aftermarket turbo freaks. Well, I suppose its probably a while off before it hits ground, and then a great deal longer to iron out any bugs, and especially the ones caused by a Hot Rot(ary). Thanks for your input.

I am just looking into how my build is gonna go. I got the motor out, and a world of possibilities in front of me. I hear a lot of this fight going on between twin sequential, non sequential (which I don't see the point of twin non-sequential, seems like it would be the same as a single twice the size...)and of course Single. I was thinking of going single, and then I was looking at t3-t4 hybrid, but thinking about applications they are used for, works good on a civic, but don't know about fd. And then of course I got lead into the magic of VTG's... but can't find much about application or A/M sale.

I honestly don't know if single turbo lag is unbearable on a rotory, I mean I have felt the stock lag of an FD, and sure its bad, but open up the **** pipe exhaust and I could imagine it getting a whole lot better. but now I plan on a street ported full exhaust single turbo, capable of somewhere around 400 to the wheels, with stand alone fuel and igntion and one of those tuning geniuses I figure its plausible. But having no experience with rotories and tuning them....im fishing in the dark.

And I am done ranting now.

dgeesaman

iTrader: (7)

It's been discussed before:

https://www.rx7club.com/forum/showth...&highlight=vtg
https://www.rx7club.com/forum/showth...&highlight=vtg
https://www.rx7club.com/forum/showth...&highlight=vtg

windom

iTrader: (1)

My old shelby CSX-VNT had one of those turbos. I think it was the first production vehicle to implement the technology.

rt turbo

450 Ft/lbs of torque before 2000rpms... drool.

paulagre

I Second That Drool...

CarbonR1

iTrader: (2)

I figure I'd chime in,

Variable Nozzle turbos are very robust today. I guarantee you that depending on the application, some of our VNT turbos go through much more punishment than a rotary engine could dish out. Most of them are designed for commercial vehicles that have nasty sulfur, corrosion, vibration, EGR and engine braking. The things that these turbos are designed to go through are intense. The only reason people think that it is unreliable is because they don't know how to get them to work.

They definitely have their advantages, and surprisingly most of the drive for VNT turbos and improved performance is because of emissions. And wait till 2010 when you hear about Ford using the coolest turbocharger that is in development. That's the one I'll be using.

-Kevin

dgeesaman

iTrader: (7)

That's nice, but the primary problem with rotaries is extremely high EGTs. How have the latest VNTs moved forward in that area? I've seen very few materials that can withstand sustained 1000f+ environment.

Dave

CarbonR1

iTrader: (2)

There are special steel alloys like Pluco that we use in our nozzle assemblies. In addition, on high temperature applications, our compressor side is made of iron and our compressor wheels are made from titanium. Our gas stands are constantly testing turbos with exhaust temps of over 600C. Does that answer your question?

dgeesaman

iTrader: (7)

Sort of. I forgot to ask what kind of longevity these are seeing. The nature of high temp materials is such that it's really about the rate of degradation. But I will look up those materials.

Dave

BLUE TII

iTrader: (9)

My EGT probes placed at the turbo rotary exhaust ports show 800-900 C at cruise and I am managing to keep it a bit below that under load w/ very conservative tuning.

Some rotary tuners at the bleading edge of HP run 1200+ C under load for max power (yes, off the scale of most performance EGT gauges).

Do you think the current crop of VGT would do OK with these temps? I have a Ford 6.0 VGT turbo in the garage I was interested in trying.

MR_Rick

iTrader: (7)

I think there was a company that tryed this for performance application a while back. I think it was called Aerodyne.

CarbonR1

iTrader: (2)

It's difficult to group a set of turbos from different applications and across different manufacturers as a crop that would handle your specific needs. If you are serious about doing it, then you can make it work. Whether or not it'd be worth it to you is up to how deep your pockets or how much you know about VNT turbos/electronic control.

alexdimen

iTrader: (13)

is variable nozzle the same as variable geometry?

windom

iTrader: (1)

Yes

dgeesaman

iTrader: (7)

How do you tune the VNT to work with the ECU? Is it a piggy-back, completely independent, or must it be all in the ECU so that it can adjust fuel injection in anticipation of the extra load?

I guess I'm thinking that the hard pieces would only be half the battle.

Dave

CarbonR1

iTrader: (2)

Without getting into too much detail, there is something called

AVNT Advanced Variable Nozzle turbocharger, and this is controlled with a single axle vane, and is usually oil pressure controlled, so it essentially opens up the vanes more as oil pressure is increased.

DAVNT Dual Axle Variable Nozzle Turbocharger is controlled with an REA "rotary electric actuator" which is basically a small rotary box controlled with a PWM or CAN electric signal. It is flow calibrated before we send the turbos out so that each turbo has the same closed flow turbine flow rate. If you are good with electronics, it is not difficult to get it controlled, and you can change vane position with load, oil pressure, or whatever parameter best suits your needs.

fritts

iTrader: (5)

All these VNT's except for a few have all been designed for diesels. Diesels are only putting out 800-1000 F. I have a hard time believing that at the rotary exhaust temperatures they would survive. That's why from what I understand we don't seem them used widely on gas engines today.

CarbonR1

iTrader: (2)

Maybe you don't see them on gas engines as often right now, but I assure you that you will see it in the near future. As we speak I am developing the new GT17V, GT20V, and GT22V for passenger car vehicles. The reason they are used in Diesel, is because Diesel motors are more efficient, are friendlier to boost and have greater longevity. Longevity of these turbos? Commercial Trucks are designed to last over a million miles, do you think that these VNT's blow out at 50k miles? Over the last 5 years or so, the reliability of VNT's have increased dramatically. It's ironic that we are talking about the turbos taking too high EGT, when most of our warranty claims right now are due to LOW egt corrosion.

-Kevin

dgeesaman

iTrader: (7)

Right now it's clear that the vast majority of VNT implementations are on low egt applications, so the vast majority of warranty claims will be the same.

As for lasting a long time on diesels, well that's precisely the point. When you push materials toward their temperature limit, the lifespan goes down rapidly. Just because it lasts 1,000,000mi at 800-1000f doesn't mean much when you put it into service at 1000-1200f. The way that strength, corrosion cracking, and creep properties change, you might find that a 200f increase in temp reduces component life to 1/10th or 1/100th. So as they hurdle the increase in EGTs associated with going from diesel to gasoline, then there is yet another increase to get into rotary applications. And I don't think there will be much automotive market pressure to make that last jump.

I have no argument that good things are coming and this technology may truly the Next Big Thing for performance and race cars. It's not something to put off that single turbo upgrade, and if you managed to install the 997 turbo on their rotary it will probably cook in a hurry.

I expect VNTs are a ways off from affecting the mainstream rotary aftermarket, sad as it is to say that.

Dave

CarbonR1

iTrader: (2)

If tuners are really getting EGT's to 1200C, then that's way too hot for the VNT nozzle assemblies. The nozzle assembly can take around 800C/1500F and be reliable, any more than that, who knows.