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Discussion Starter · #1 ·
Okay, my tii broke and i got a vnt in its place, ive since learned of more opinions on this swap and know most people wouldnt go this route for a mod. But i have it and i need to know how to make it work with a boost controller with a 89 daytona 2.5. Thanks in advance for any help
 

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The VNT does not use a wastegate, it uses a nozzle ring that changes position depending on load to increase and decrease boost.
There are 3 separate solenoids that are all computer controlled that control the variable nozzles.
As far as I know you would need a VNT controller and the proper solenoids for the system to work.
You are also limited to mods, part of the VNT boost control system is exhaust backpressure so ANY mods/changes to the exhaust system will increase exhaust flow and will result in a Boost Creep/Overboost/Turbo Overspool Condition.

The VNT was only used on the 89 CSX and limited production (about 900 total) Daytona/Lebaron/Shadow in 1990.
 

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Discussion Starter · #4 ·
whats the difference in how they act? And i didnt really plan on doing much for mods. I just need it to work
 

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You can try to T into the wastegate fittings on the VNT turbo and see what that gets you, but as NAJ has said, the VNT turbo doesn't have a wastegate to dump excess boost, it uses a collection of small vanes in the turbine housing that can be adjusted based on boost in the manifold. The adjustment speeds up or slows down the turbine (just to be brief) to control the boost being delivered. You just dont have the controls needed to properly control the VNT turbo.
 

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The reason Chrysler used the VNT was to try to eliminate turbo lag.
From Chrysler...
The 89 T-2 hit full boost (12 lbs) from a standing start in 4.6 seconds.
The 90 T-4 VNT hit full boost (12 lbs) from a standing start in 2.3 seconds.

First gear in my car winds out in a hurry so I do not know if the gearing is different between the 89 A555 trans and the 90 A568 trans.

Most have said that because the VNT is smaller than the Garrett T-2 it chokes itself at higher RPM's, I never driven a T-2 so I have nothing to compare my VNT to.
When I was bracket racing my car with (and did not have overboost issues) I was hitting the stripe at 6100 RPM's in 3rd gear and she was still pulling.

As far as controlling the VNT with a boost controller, I do not know.
 

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The reason Chrysler used the VNT was to try to eliminate turbo lag.
From Chrysler...
The 89 T-2 hit full boost (12 lbs) from a standing start in 4.6 seconds.
The 90 T-4 VNT hit full boost (12 lbs) from a standing start in 2.3 seconds.

First gear in my car winds out in a hurry so I do not know if the gearing is different between the 89 A555 trans and the 90 A568 trans.

Most have said that because the VNT is smaller than the Garrett T-2 it chokes itself at higher RPM's, I never driven a T-2 so I have nothing to compare my VNT to.
When I was bracket racing my car with (and did not have overboost issues) I was hitting the stripe at 6100 RPM's in 3rd gear and she was still pulling.

As far as controlling the VNT with a boost controller, I do not know.
 

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Yes, it can be done. I had mine running like that years ago as an experiment, so that I could go to a megasquirt controller. I did it with a series of check valves and a grainger valve boost controller. It worked practically identical to stock in terms of lag. No I did not draw it out, and went back to the solenoids for control. There are plenty of other VNT cars and diesels out now and there are guys hanging these turbos on other cars, look up vnt15 on google. the dune buggy guys seem to like these turbos because the small vnt is sized right for a VW motor. Here is a link to a manual VNT controller from Austrailia.


Manual Boost Controllers : VNT Manual Boost Controller
 

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I attached a pic that I found. Ignore the solenoids, they don't exist under your hood. run the blue line direct to your intake. Somewhere in the blue line, insert a check valve. hopefully there is an arrow on the check valve. Make sure the arrow points to the intake. Take the purple line and attach to the intake also. Add a check valve with the arrow pointing to the turbo. After the check valve, add a boost controller. The orange line is not used. The green line is not used. The port the green line is run to is likely under pressure, so the purple line may be able to be plugged in there.

Remember, one port on the turbo actuator is vacuum(blue line)
The other is a pressure line(purple line)

Now your boostin. If anybody see anything wrong, please respond.
 

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There are two vacuum ports coming from the intake...
1)One is for the PCV Valve, do not use that port.
2)The second port comes out of the intake in the front and the factory vacuum harness was/is connected to that.

The "VACUUM/VAPOR HOSE CONNECTION in the pic is the one you want.
 

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Discussion Starter · #17 ·
okay, ive got instructions for two lines, but four ports on the turbo, do i just cap the other two off?
 

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The two on the compressor housing inlet pipe you would cap. The two on the 'waste gate actuator' are the ones you will need to connect. Though technically it is not a waste gate actuator, its a variable vane attenuator!
 

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Discussion Starter · #19 ·
Do i run the lines together to the same port on the intake or is there something im not seeing. And again thanks for the help and sorry for needing so much of it
 

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yes, you can use a tee fitting if needed. think of the purple line as the line going to the old turbo wastegate. you add a one way check valve to block vacuum from being at that port. The blue line is for vacuum to make the vnt smaller at idle. You use a check valve to allow vacuum at the port, but block pressure.

a good website to check out is thedodgegarage.com. it has a turbo database section with some vnt info. It has a working theory of what a vnt does and how it works.
 
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