Hey i was just wondering if any of you knew what these are i am curious what it looks like and how it works...pics would be great a buddy of mine told me somethim about em but didnt know alot of detail..but he said Carroll Shelby used them, sounded interesting

 

The blades on the turbine can vary their angle to decrease spool up time by titanic amounts and then flair back out for high RPM peak flow. This is a good thing. They only work with the neccessary sensors and actuators which are ECU controlled. This is a bad thing. If you want more info on them though, do a search for "Shadow VNT" then look up "GLH-S" and find out where that spoiled brat of an SRT4 came from and still sources it's block from.

 

so the fins actually move? or does the angle just vary but still static?

 

I am assuming they actually move...heres a pic

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dornon13 &raquo;</TD></TR><TR><TD CLASS="quote">so the fins actually move? or does the angle just vary but still static?</TD></TR></TABLE>

No, it's not the blades on the spinning turbine shaft that move. There are stationary blades in the path of the air from the exhaust inlet to the turbine fan. They can turn to point almost tangentially or almost radially. Look closely at the pic above and you'll see what I mean.

 

Dornon - I'm still on "Trial User" status, so I can't respond to your IM, but to answer your question regarding: <TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">and find out where that spoiled brat of an SRT4 came from and still sources its block from."</TD></TR></TABLE>

the USDM SRT-4 has existed in Mexico for about 5-6 years now. That generation of engine is a slight evolution of the 2.2L turbo head and engines from the Turbo Dodges most specifically the R/T cars like the Daytona R/T/ and the Spirit R/T which are 16v. The SRT is a de-stroled 2.5L turbo and the internals from the old T2 2.5 mopar stuff still slaps directly in. There was some speculation that the heads were interchangable but I never found out any finalities on that one. But the reason the SRT4 is "spoiled" is because it didn't come out during the span of a fossil-fuel crisis. So they can turn the boost up and sell units. Don't worry though - another one's coming. Back to 150hp cars!!


On a more relevant note - TJBizzo is right. It's not the fins on the turbine itself that move - it's the blades directly in front of it.

 

ah i understand...my buddy has a sundance with a turbo shelby daytona engine in it and he wants one of these turbos...they sound like a good concept ...why has no one else utilized them?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dornon13 &raquo;</TD></TR><TR><TD CLASS="quote">ah i understand...my buddy has a sundance with a turbo shelby daytona engine in it and he wants one of these turbos...they sound like a good concept ...why has no one else utilized them? </TD></TR></TABLE>

They cost more. That's about the only reason, and I think it's a very poor reason considernig the long term benefits weighed against the slightly increased initial costs.

 

well damn lol

 

They came on 89 Dodge Shelby Shadow CSXs and 90 Turbo IV engines.VNTs didnt use a wastegate because of the special turbine they had.They are super expensive.

 

usually anything worth having is expensive lol

 

im bring back this topic becasue i know alot of the new desiles have these turbos.

 

more info that you ever wanted to know about VNT is below.

One thing to note, they are now coming out in a lot of desiel trucks and in the near future a lot of import cars will have them as well.

The original ones were rather small, only good for a d series because the turbo couldn't support over around 250 horses.

Also the vanes are prone to getting stuck closed unless you mod them to cylcle open and closed a lot. There are a lot of new generation turbos coming out like axial movment type where there is a shroud around the movable vanes to expose them more or less, there is also VARIABLE GEOMETRY Compressor where the compressor side ALSO hase moveable vanes, this turbo can spool up instantly but still make awesome top end. There is also a turbo coming out that has an electric motor to spool it up instantly.

EXPERIMENTING WITH THE VNT25 VARIABLE NOZZLE TURBOCHARGER


--------------------------------------------------------------------------------

By Andrew E. Johnston
Technical Support Manager
Garrett / Bendix Heavy vehicle Systems Group



INTRODUCTION

The Garrett Variable Nozzle Turbo (VNT) is one of the most advanced and interesting turbochargers that has ever been offered in production. Unfortunately the first production application of a VNT on the Shelby CSX was shorter than expected, and Garrett was left with around 1200 of these turbos. Garrett decided to make these discontinued units available as surplus at a reduced price for race and custom installations. This article discusses some basic theory and application notes for this unit.

BASIC THEORY

Matching a turbocharger or supercharger to an engine that only runs at one speed and load would be easy. Designing a system that will achieve the optimum boost pressure under all conditions is much more challenging. Ideally, the boost could be controlled smoothly and efficiently at any speed or load. Achieving this goal requires an air compressor with a variable power source.

Superchargers are limited in this respect because they must obtain their power directly from the crankshaft.

This has two disadvantages:

1) They are directly linked to engine speed, not boost requirements, making it difficult to turn on "half way" at part load.

2) It consumes crankshaft power directly (typically 30-60 % of the engine output hp!)


Mechanical variable speed drive systems have been tried, but they are expensive, big, hard to control, and inefficient. Simple superchargers systems are typically belt driven and are controlled by a combination of on/ off switching and throttling, either of which are a compromise under part load conditions.

Turbochargers on the other hand, obtain power to drive the compressor from a small gas turbine that extracts energy from the hot exhaust. This is much more efficient than taking power from the crank directly because it is using thermal energy that would otherwise be wasted. The additional backpressure only consumes a fraction of the power that would have been required from the crankshaft The high speed of the turbine allows the use of an efficient high speed centrifugal compressor without the need for expensive gears or drive systems.

The turbine also has an important advantage because it is not directly linked to engine speed. The turbine power output tends to follow engine load, which is one of the reasons why most turbo diesel engines do not need any boost limiting controls. The compressor power, and therefore boost, can be easily controlled by changing the turbine power if desired. One way to control turbine power is with a wastegate. A wastegate is simply a valve that allows some of the exhaust to flow around the turbine instead of through it. This limits the turbine power at high speed when more exhaust energy is available than needed to drive the compressor. A wastegated system allows the use of a smaller turbine that is sized to make boost at low engine speed.(i.e. the wastegate is closed) The wastegate will prevent the turbo from overboosting at high speed as would otherwise occur with a small turbine.

This system offers smooth and simple control, but still not optimum. The exhaust energy bypassed around the turbine is wasted which is why they are called wastegates. At high speed a turbine with a larger nozzle could use all the exhaust flow and make the same power with less exhaust backpressure. The ideal system would have an adjustable turbine nozzle that acted like a small turbine for fast response at low speeds and a large turbine for maximum power and efficiency at high speeds . An adjustable turbine could also be opened to minimize backpressure when boost is not needed. This would provide the ideal boost with minimum exhaust backpressure under all conditions.



THE GARRETT VNT25

Garrett has developed a turbocharger that does this. Instead of using one nozzle to accelerate the exhaust gas towards the turbine wheel, it has a ring of 12 variable vanes. As the vanes are rotated, they change the area of the nozzles that the exhaust must pass through. The smaller the nozzle, the faster the gas velocity, the more turbine power, the more boost. At the other extreme the vanes can open fully when boost is not needed, with the resulting reduction in exhaust restriction. The concept of the VNT has been around for a while, the trick was to make one where the vanes would not stick when run for thousands of miles without lubrication in a hot exhaust environment. Garrett spent considerable time in r&d to arrive at the special combination of high temp materials and manufacturing processes for the vanes and mechanism to ensure reliable operation.



The VNT is mated with a low inertia rotating group and an efficient centrifugal compressor to achieve the goal of a truly adjustable boost system. In addition the system efficiency is improved at high speed due to the reduction in backpressure compared to a wastegated system.

CHRYSLER APPLICATION INFORMATION

From an application standpoint, this turbo was used on the high output intercooled 2.2 liter four cyl. rated at 175 hp. The Chrysler engineers utilized the engine computer to take advantage of the additional control afforded by the VNT. The computer controlled the vanes by adjusting the pressure fed to the spring and diaphragm actuator. This system used a standard catalytic converter and exhaust system. The turbo limited boost by action of the vanes and did not use a wastegate.

CUSTOM APPLICATIONS

So, What engines are candidates for a VNT 25? The answer is not so much engine size, but power. This turbo should work on an engine that can produce 150-200 hp with 8-15 lbs of boost. I am aware of a 1600cc VW installation that is very responsive. Twin VNT's on a 400 hp Porsche should be outrageously more driveable than the stock big single turbo. Another candidate for a twin would be a Buick 3.8 liter V6. This turbo should also work on high rpm 1 liter motorcycles, but the turbine housing is fairly large from a packaging standpoint. Remember that these application suggestions are just that, not guarantees. These units have standard late model Chrysler turbine and compressor housing connections and use standard Chrysler gaskets. As far as using the VNT on a custom application, the flange dimensions and bolt patterns are not the same as any other turbo, but adapters can be made with the dimensions shown

OIL SUPPLY

This turbo needs .3 gpm of oil @ 30 psi. minimum at full power. Any oil that you can use in the engine will work for the turbo. The oil drain uses one bolt and seals with an O ring. A flat flange with a gasket will also work. A .5 inch minimum inside diameter oil drain is recommended and must be within 30 degrees of vertical with no "sink traps" that will allow oil to puddle.

CARBON SEALS

The unit uses a carbon seal and therefore be used with a carburetor upstream in a draw through installation,although the Chrysler was fuel injected. Except for the VNT turbine, this unit is very similar to a standard Garrett T25. The compressor, bearings and seals are interchangeable with T25 turbos.

WATER CONNECTIONS

The water cooling is intended for passenger car applications where the turbo is bolted to a heavy cast manifold withlittle airflow and many miles of stop and go service. The water cooling is not needed on a race car that isn't driven daily. Likewise, the water is not needed when the turbo is mounted on headers that don't store heat like a casting can. The water fitting is designed to mate with a steel tube flare nut. These can be removed and a different adapter can be threaded directly into the pipe threads and in the housing. Remember that the water is only for cooling during shutdown, the oil cools the bearings when the engine is running. When the engine is shutdown the heatstored in the cast exhaust manifold "soaks back" into the turbo causing the water in the center housing to boil.

When this happens it is important that the bubble that forms can escape upwards causing water to flow in from below and allowing the cycle to repeat itself. The upper hose should connect to the engine at a higher point than thelower water connection. The water flow direction while the engine is running is not important. It is when the engine stops that the boiling occurs.

TEST INSTALLATION AND VNT CONTROL

To determine the ease of controlling the actuator and to discover any installation problems in general, the author installed a VNT25 on his sandrail (Dunebuggy). The engine is a 2 liter German Ford. To keep the installation assimple as possible, the turbo was mounted on an old Roto-Master cast iron manifold that was intended for a T04B. Drilling the bolt holes out to 9/16" allowed the turbine to fit 3 of the 4 bolt holes and sealed acceptably for the test. The turbo pressurized a Motorcraft 121 two barrel carb in a simple "blow through" configuration. The pressure side (small tube) of the VNT actuator was connected to the hose fitting in the compressor housing.

The results were instant boost and easy wheelstands in 1st and 2nd gear. The vanes were closed at idle and it was very quiet, even without a muffler. The VNT limited the boost to 12 psi without any further controls during thequick " around the block" bonzai runs. (This control point is a function of engine size and flow and may be different for your application.

The addition of paddle tires and some steep dunes, however, changed things. The engine was not fully loaded onsuch a light vehicle on flat pavement. On a steep incline the boost would rise to over 20 psi as the engine became fully loaded. The solution was to install a conventional wastegate to control boost when the flow range of the VNT was exceeded. This is recommended for all VNT applications.

BOOST CONTROLS

Chrysler did not need a wastegate because the backpressure of the stock exhaust limited turbine power. TheSandrail used a very low backpressure 2.5" exhaust system. The Sandrail installation simply ran a hose from the compressor housing to the pressure port of the actuator. Do not make the mistake of assuming that the larger 1/4" port is for pressure because it is the same size as the fittings on the compressor housing. The 1/4" port is for vacuum. The smaller 3/16" port is for pressure. Pressurizing the vacuum port forces the vanes closed at all times.

They will eventually plug up with carbon, causing the " potato in the tailpipe" effect. If your engine runs poorly or won't start again after your first test run, check the actuator hoses. The boost setting can be mechanically adjustedwithin a limited range by shortening the rod length. Make sure the diaphragm does not bottom out before reaching the full stroke. It can also be adjusted with an electronic adjustable boost control system that is designed to control a conventional wastegate.

A pressure regulator can also be used as a "boost over boost" control to raise the actuator pressure control point just as it is used on a wastegate. In a nutshell you run a controlled amount of boost to the "wrong" side of theactuator to cancel out part of the pressure on the boost side. Each psi put on the back of the diaphragm raises the boost setting by 1 psi and so on. This is plumbed by hooking up the actuator pressure port to a boost signal (i.e. the fitting on the compressor housing) directly as usual. Then hook up a second from the same boost signal to a pressure regulator and then to the vacuum side of the actuator. Setting the pressure regulator to 1 psi raises the boost `1 psi etc...

In an off road or race only application this simple system will suffice. As a minimum a " part throttle open" controlcan be easily achieved by connecting manifold vacuum through a check valve to the vacuum side ( big tube) of the actuator. The check valve is to block boost. To prevent any pressure from being trapped between the check valve and the actuator, a .030" bleed orifice to atmosphere should be used. This will open the nozzles when vacuum is present at idle and part throttle.

This has some important benefits:

1. It cycles the vanes every time the throttle is depressed which helps them stay free of carbon.
2. It prevents excessive EGR due to higher then normalbackpressure which affects idle quality.
3. It improves fuel economy by eliminating backpressure caused by the turbo.
4. It prevents part throttle boost which heats the intake air unnecessarily.
5. It provides a more linear feel to the throttle pedal position.


GENERAL INFORMATION

There are a few very important points concerning these turbos:

1) A common question is: Do you have one with a different compressor wheel, or A/R? The answer is no We only have this particular unit available. ( p.n. 465599-6)

2) These turbos have been discontinued and once the 1200 are gone that is it. Chrysler reportedly has quite a few for the Shelby's, but they may cost more when purchased through a dealer.

3) As far as emissions are concerned, this turbo is only legal on the 89 CSX, 90 Shadow, 90 Daytona, & Lebaron


another good site with pics and stuff
http://www.thedodgegarage.com/....html

 

I actually wrote a term paper on VNT's or VGT's .... whichever you prefer.... i'm not going to post it, its 25 pages, but if anyone would like more info, i can definatly accomodate...... the main reason they aren't used on smaller sports aplications is due to the fact that a properly sized "normal" turbo can function just as well as a VNT, without the added cost, and control mechanisms.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by spoolinlude &raquo;</TD></TR><TR><TD CLASS="quote">I actually wrote a term paper on VNT's or VGT's .... whichever you prefer.... i'm not going to post it, its 25 pages, but if anyone would like more info, i can definatly accomodate...... the main reason they aren't used on smaller sports aplications is due to the fact that a properly sized "normal" turbo can function just as well as a VNT, without the added cost, and control mechanisms.</TD></TR></TABLE>

thats the answer i was looking for, i was wondering why no one has tried one yet? its seems like it would be very helpful if you were using a larger sized turbo though, like a t67. what size turbos do the new desiel trucks use?

 

very intresting thread... technology is so great.

this reminds me of the hydracharger design that changed hands a few times... with the fluid driven design.

 

good to see some 2.2 knowledge being passed around. the old chrysler turbo's were just as much a pain to everyone else as the srt-4 is now. kinda funny.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Nobody Special &raquo;</TD></TR><TR><TD CLASS="quote">
the USDM SRT-4 has existed in Mexico for about 5-6 years now. That generation of engine is a slight evolution of the 2.2L turbo head and engines from the Turbo Dodges most specifically the R/T cars like the Daytona R/T/ and the Spirit R/T which are 16v.</TD></TR></TABLE>

yes, the 2.4t has been in mexico for a while now. but, it isn't a slight evolution of the 2.2 the 2.2 is very similar to the ol' slant 6. the R/T cars are plain' ol' 2.2's with fancy lotus heads on them. oh, and beefy(er) guts.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Nobody Special &raquo;</TD></TR><TR><TD CLASS="quote">The SRT is a de-stroled 2.5L turbo and the internals from the old T2 2.5 mopar stuff still slaps directly in. There was some speculation that the heads were interchangable but I never found out any finalities on that one.</TD></TR></TABLE>

not really, because the 2.5 is a stroked 2.2. i forgot what magazine did a tear-down on a SRT-4 motor, but it's TONS more beefy than the strongest 2.2. the cylinder heads do fit on the old 2.2 blocks, in fact any 2.0-2.4 head will fit. from dohc's to single slammers.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Nobody Special &raquo;</TD></TR><TR><TD CLASS="quote">But the reason the SRT4 is "spoiled" is because it didn't come out during the span of a fossil-fuel crisis. So they can turn the boost up and sell units. Don't worry though - another one's coming. Back to 150hp cars!!</TD></TR></TABLE>

indeed. thats what killed the american chrysler turbo's in the early 90's. they could have kept them going, but they would have to use 'exotic' materials (now they're not so exotic) to keep the cylinder temperatures consistent, etc. i'm glad they kept them going in mexico.

 

i was just noticing your name correct me if i am wrong i may have misunderstood this and took it serious instead of a joke but doesnt GLHS mean "Goes Like Hell Somemore" or somethin along those lines

also how much power were these turbos good for on the daytonas? my buddy has a 2.2 sundance he always talks about getting one but i dont see it getting too much hp


Modified by dornon13 at 4:27 AM 5/30/2005

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by downeyballz &raquo;</TD></TR><TR><TD CLASS="quote">thats the answer i was looking for, i was wondering why no one has tried one yet? its seems like it would be very helpful if you were using a larger sized turbo though, like a t67. what size turbos do the new desiel trucks use?</TD></TR></TABLE>

The new fords/dodges/chevys all use around (and i say that loosely) the same size turbo, 60 to 80 a/r housings and 80 to 1.14 hot sides, this is just a guess, i have no confirmation.....as for t67's, you have to remember the efficiency ranges of the COMPRESSOR side...... and with t67s its up and over 1bar, all the way to 3.5bar...... wow, 3.5 bar......

and to those who care, yes i've been drinkin since 3:30 pm

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dornon13 &raquo;</TD></TR><TR><TD CLASS="quote">i was just noticing your name correct me if i am wrong i may have misunderstood this and took it serious instead of a joke but doesnt GLHS mean "Goes Like Hell Somemore" or somethin along those lines</TD></TR></TABLE>

yes. the original 86 GLHS was based on the omni GLH (goes like hell). the S is for "S'more" according to shelby, but there are some that think it's shelby instead. of course, chrysler will never admit to any of it, but shelby himself is on record saying so. thats good enough for me.

i had an 87 GLHS, those were the same car, same chassis etc, just a different body. i really should change my username.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dornon13 &raquo;</TD></TR><TR><TD CLASS="quote">
also how much power were these turbos good for on the daytonas? my buddy has a 2.2 sundance he always talks about getting one but i dont see it getting too much hp
</TD></TR></TABLE>

if it's got a 2.2, it could be fast, but it takes a bit to get it over 250. and if it's an 89+, you have to change the turbo as it's a teeny mitsubishi turbo.

 

well we are pretty close friends he is my roomate actually so i know its pretty fast...he is running 20 psi but i cant recall what the turbo came off of...i know its not the stock one...he is actualy down right now because we cant figure out any kind of fuel managemant you have any suggestions for that?

 

go to http://www.fwdperformance.com and look at their custom calibrations. or, go here:

http://www.turbododge.com/foru...?f=21