Whorse
12-24-2005, 06:49 PM
http://www3.telus.net/braun/16v.html - I'll try to add updates to this link on my site and add some pictures as I get them done.
I've toyed with this idea a lot, but never looked that seriously at it because of money. I'm curious how cheaply this could be done, while still maintaining a solid setup with some reliability.
The Problem:
1990 TIV 2.2L Engine: 160-175hp depending on who you talk to, and 210-225lb-ft depending on who else you talk to.
The actual theory behind the VNT is terrific, but the final product released in 1989 and 1990 by Shelby and Chrysler isn't ideal for tuning and upgrading. As most of us know, the 2 limiting factors are the size of the VNT housing (smaller than a T1 Mitsubishi), and the restrictive flow of the head and exhaust, which is somewhat necessary on a VNT to prevent overspooling in milder and colder weather.
Unlike the comparable Turbo II application, the VNT does not use a wastegate to control exhaust flow. Taking advantage of the nature of the VNT, the computer uses a similar looking device, an external vane controller and actuator. Using pressure supplied to the diaphram in the vane controller, the actuator moves, opening and closing the vanes accordingly, to limit boost.
Herein lies the ebb and flow of the VNT's success. The VNT turbo, being small and quickspooling, power was easy to come by, and came earlier than other turbo applications. However, to limit overspooling the turbo, boost was kept low, to about 12 psi, by means of a restrictive exhaust.
Overboost cutout is at about 14.7 psi, but doesn't cut out immediately. I've spooled my VNT to over 18psi in the cold and not cutout because I let off the throttle quickly.
Due to its size, the stock VNT25 is limited to about 200hp, topping out around 230hp in free flowing, high spooling setups (this drastically shortens the life of the turbo).
Running an open exhaust and ported head on the VNT allows for more flow, and more power, but also more overspooling. The solution is to simply install a wastegate, or run a controlled amount of boost to the vacuum side of the vane actuator to help control the boost.
By now, you've either spent a lot of money on increasing the flow and then controlling the VNT from the extra exhaust flow, or realized that the VNT just isn't made for tuning. There are two other VNT turbos available for TIV cars.
The most common is the VNT28, which has the same turbo housing and is a bolt on upgrade, using a larger compressor wheel to allow for safe boost up to about 18psi (VNT25 is safe to about 14.5psi).
The S60-VNT which uses the super60 turbo compressor is good for over 25psi, and provides more flow at 12psi than a VNT25 supplies at 16psi, hence more power at lower boost.
Both turbos are expensive, hard to come by, and require aftermarket or custom ECU calibrations to run effectively. An upgraded VNT turbo with the appropriate calibraion, a flowing head and less restrictive exhaust will cost you in the range of $1000, and might only net you an extra 50hp if you're conservative, which leads to my idea: 16 Valve Twin-Turbo VNT 2.2L 4 Cylinder.
The Plan:
Most people by now are probably bored and scoffing at me for using Twin Turbo in the same sentence as 4 Cylinder. Fair enough, it's not common, and requires a lot of custom fabrication, but could allow for much higher net results, and more HP per Dollar than simply upgrading an existing VNT.
The Dodge Turbo III cars sport a hefty 220hp stock, and benefit from two main advantages (and others, like distributorless ignition) over the slightly older Turbo IV setup: 16V DOHC Head, and a larger Turbo. An upgraded Turbo IV car with the stock VNT25 probably won't be competetive with a TIII car as it just can't meet the HP numbers easily. However, a Turbo IV car coverted to Turbo III status, while maintaining it's Turbo IV wiring and vacuum setup, should yield better driveability and more power than a modified TIII.
The VNT25 is rated for 150-200 horsepower, so two of them should be able to provide 300-400 horsepower, while spooling faster than a conventional turbo.
Converting a TII engine to TIII almost always means a custom intake manifold, which is beneficial to the twin turbo idea, as we'll have 2 sources of boost, but only one intake manifold to receive it.
On the exhaust side, running 2 custom headers, from cylinders 1/3, and 2/4, allows for 2 downpipes, and therefore, 2 turbos. Even a ported 8V head won't be able to flow enough exhaust to spool even the tiny VNTs quickly when using half the exhaust ports. However, a 16V head would provide ample flow to spool the VNT turbos, which are suited for slightly smaller engines than standard turbos of the same size.
Using 2 headers, 2 downpipes, and 2 turbos, leads to the obvious conclusion of using 2 exhausts (:thumb: Dual Exhaust), which will eliminate some of the backpressure in the system, and allow the turbos to spool more easily.
Intercooling will only help our purpose here, and our choice of intercooler will depend greatly on how we choose to supply boost to the intake manifold. Unlike a true Twin Turbo, like the Stealth R/T or Nissan 300ZX, we only have one intake manifold, so running 2 throttle bodies to it poses the problem of keeping the boost consistent on both turbos.
Running a large Front Mount Intercooler (Think Custom Welded Multicore) with large inlets and outlets on the endtanks should provide enough flow and cooling for the entire application.
Since both turbos will be facing the same direction, it will be easier to "Y" both turbo outlets to the same inlet on a single intercooler. Since we're using stock VNT25s (or VNT28s if you want to upgrade a bit for some extra power), it makes sense to use their stock turbo outlets, and Y them into a larger, 3" intercooler inlet. This setup is space efficient, and cost efficient as it eliminates the need for an extra intercooler, throttle body, intake manifold port, and a lot of front end custom fabrication to fit it all.
Running the intercooler outlet to whichever choice of intake manifold you choose should be no different than a normal 16V conversion. Since we're already doing so much custom work, it won't be much more to tie in some extra boost control, vane actuator control, and maybe even a boost bleed for some extra fun along the way.
Obvious roadblocks and drawbacks:
Custom Calibration will be necessary
Boost Control will be more difficult than with a single turbo
The fuel system will need to be upgraded
Engine internals will also need to be upgraded to handle these boost levels.
A great amount of custom work is involved, as this is no longer bolt-on work.
This is obviously a job for someone who loves custom work and wants to try something a bit different. I thought about this idea for a while, and being a VNT guy, I think it's the ideal turbo for this setup on our engines, as it's one of the only turbos that will spool quick enough to be effective in a Twin Turbo application, and it's small enough that it won't be as difficult to find room for it.
I'll try to add replies with some drawings if I can get any done before things get really busy around here. Very curious to hear some input on what will and won't work with this idea.
Whorse
I've toyed with this idea a lot, but never looked that seriously at it because of money. I'm curious how cheaply this could be done, while still maintaining a solid setup with some reliability.
The Problem:
1990 TIV 2.2L Engine: 160-175hp depending on who you talk to, and 210-225lb-ft depending on who else you talk to.
The actual theory behind the VNT is terrific, but the final product released in 1989 and 1990 by Shelby and Chrysler isn't ideal for tuning and upgrading. As most of us know, the 2 limiting factors are the size of the VNT housing (smaller than a T1 Mitsubishi), and the restrictive flow of the head and exhaust, which is somewhat necessary on a VNT to prevent overspooling in milder and colder weather.
Unlike the comparable Turbo II application, the VNT does not use a wastegate to control exhaust flow. Taking advantage of the nature of the VNT, the computer uses a similar looking device, an external vane controller and actuator. Using pressure supplied to the diaphram in the vane controller, the actuator moves, opening and closing the vanes accordingly, to limit boost.
Herein lies the ebb and flow of the VNT's success. The VNT turbo, being small and quickspooling, power was easy to come by, and came earlier than other turbo applications. However, to limit overspooling the turbo, boost was kept low, to about 12 psi, by means of a restrictive exhaust.
Overboost cutout is at about 14.7 psi, but doesn't cut out immediately. I've spooled my VNT to over 18psi in the cold and not cutout because I let off the throttle quickly.
Due to its size, the stock VNT25 is limited to about 200hp, topping out around 230hp in free flowing, high spooling setups (this drastically shortens the life of the turbo).
Running an open exhaust and ported head on the VNT allows for more flow, and more power, but also more overspooling. The solution is to simply install a wastegate, or run a controlled amount of boost to the vacuum side of the vane actuator to help control the boost.
By now, you've either spent a lot of money on increasing the flow and then controlling the VNT from the extra exhaust flow, or realized that the VNT just isn't made for tuning. There are two other VNT turbos available for TIV cars.
The most common is the VNT28, which has the same turbo housing and is a bolt on upgrade, using a larger compressor wheel to allow for safe boost up to about 18psi (VNT25 is safe to about 14.5psi).
The S60-VNT which uses the super60 turbo compressor is good for over 25psi, and provides more flow at 12psi than a VNT25 supplies at 16psi, hence more power at lower boost.
Both turbos are expensive, hard to come by, and require aftermarket or custom ECU calibrations to run effectively. An upgraded VNT turbo with the appropriate calibraion, a flowing head and less restrictive exhaust will cost you in the range of $1000, and might only net you an extra 50hp if you're conservative, which leads to my idea: 16 Valve Twin-Turbo VNT 2.2L 4 Cylinder.
The Plan:
Most people by now are probably bored and scoffing at me for using Twin Turbo in the same sentence as 4 Cylinder. Fair enough, it's not common, and requires a lot of custom fabrication, but could allow for much higher net results, and more HP per Dollar than simply upgrading an existing VNT.
The Dodge Turbo III cars sport a hefty 220hp stock, and benefit from two main advantages (and others, like distributorless ignition) over the slightly older Turbo IV setup: 16V DOHC Head, and a larger Turbo. An upgraded Turbo IV car with the stock VNT25 probably won't be competetive with a TIII car as it just can't meet the HP numbers easily. However, a Turbo IV car coverted to Turbo III status, while maintaining it's Turbo IV wiring and vacuum setup, should yield better driveability and more power than a modified TIII.
The VNT25 is rated for 150-200 horsepower, so two of them should be able to provide 300-400 horsepower, while spooling faster than a conventional turbo.
Converting a TII engine to TIII almost always means a custom intake manifold, which is beneficial to the twin turbo idea, as we'll have 2 sources of boost, but only one intake manifold to receive it.
On the exhaust side, running 2 custom headers, from cylinders 1/3, and 2/4, allows for 2 downpipes, and therefore, 2 turbos. Even a ported 8V head won't be able to flow enough exhaust to spool even the tiny VNTs quickly when using half the exhaust ports. However, a 16V head would provide ample flow to spool the VNT turbos, which are suited for slightly smaller engines than standard turbos of the same size.
Using 2 headers, 2 downpipes, and 2 turbos, leads to the obvious conclusion of using 2 exhausts (:thumb: Dual Exhaust), which will eliminate some of the backpressure in the system, and allow the turbos to spool more easily.
Intercooling will only help our purpose here, and our choice of intercooler will depend greatly on how we choose to supply boost to the intake manifold. Unlike a true Twin Turbo, like the Stealth R/T or Nissan 300ZX, we only have one intake manifold, so running 2 throttle bodies to it poses the problem of keeping the boost consistent on both turbos.
Running a large Front Mount Intercooler (Think Custom Welded Multicore) with large inlets and outlets on the endtanks should provide enough flow and cooling for the entire application.
Since both turbos will be facing the same direction, it will be easier to "Y" both turbo outlets to the same inlet on a single intercooler. Since we're using stock VNT25s (or VNT28s if you want to upgrade a bit for some extra power), it makes sense to use their stock turbo outlets, and Y them into a larger, 3" intercooler inlet. This setup is space efficient, and cost efficient as it eliminates the need for an extra intercooler, throttle body, intake manifold port, and a lot of front end custom fabrication to fit it all.
Running the intercooler outlet to whichever choice of intake manifold you choose should be no different than a normal 16V conversion. Since we're already doing so much custom work, it won't be much more to tie in some extra boost control, vane actuator control, and maybe even a boost bleed for some extra fun along the way.
Obvious roadblocks and drawbacks:
Custom Calibration will be necessary
Boost Control will be more difficult than with a single turbo
The fuel system will need to be upgraded
Engine internals will also need to be upgraded to handle these boost levels.
A great amount of custom work is involved, as this is no longer bolt-on work.
This is obviously a job for someone who loves custom work and wants to try something a bit different. I thought about this idea for a while, and being a VNT guy, I think it's the ideal turbo for this setup on our engines, as it's one of the only turbos that will spool quick enough to be effective in a Twin Turbo application, and it's small enough that it won't be as difficult to find room for it.
I'll try to add replies with some drawings if I can get any done before things get really busy around here. Very curious to hear some input on what will and won't work with this idea.
Whorse