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VW TDI high performance and stock economy

5920 Views 11 Replies 7 Participants Last post by  BigDaddyTDI
I posted this on another TDI specific site, but I figured I would post it over here too so I could catch some other TDIers opinions :)

I have been thinking about modifying my newly acquired TDI. Diesel is a new thing to me, but I am very capable with conventional gasoline engines. I got rid of my "street" jeep to get this TDI for the sake of fuel economy but the hot-rodder inside of me has a hard time not modifying anything.

So in an attempt to heighten the performance of my Jetta while retaining the economy of it I want to ask if anyone has any experience with a dual stage set up on their car.

I am thinking the use of a dual-stage boost controller with one setting at the factory level and the other setting at a higher lever (dependent upon supporting modifications).

Accompanying the dual-stage boost controller would be a system for supplying the correct amounts of fuel for both boost setting. i.e. a factory fuel map for the factory boost and a tailored fuel map for the higher boost.

I have been doing a bit or reading but so far I have not seen anything specifically for the VW Jetta TDI that would support that? Or is there something and have I missed it? For the sake of my project I would not be against running two ECUs (one with the factory settings, or tailored to run as close to factory as possible with larger injectors, and one ECU with the custom settings) with the supporting wiring to be able to switch back and forth.

Supporting modifications would be ones that I hope (though I may be wrong) would not adversely effect the economy of the car when in factory mode and are as follows:

Better downpipe and exhaust throughout the rest of the car
Larger or more efficient intercooler
Larger injectors (which may have a negative effect on economy I hope proper ECU tuning can work out for the factory mode)

And for the sake of peace of mind, gauges to monitor boost, EGT and other functions that I may need to keep a eye on.

Thoughts? Please correct me if I am wrong in my thinking. I am actually taking this idea from a turbocharged gasoline (capri xr2) car I used to enjoy modifying.
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All good ideas. Personally I would put the money into: 11mm injection pump, lift pump in fuel tank, larger injectors/turbo+chip tuning in addition to the supporting mods you mentioned.

You could probably do a dual ECU but I have not personally seen it on TDI. The boost setup on TDI is not exactly the same as on older cars. For one thing, my boost controller on another car is set up to let pressure pass the dual stage solenoid in response to its boost sensor (Blitz id-3). Your car moves the N75 solenoid to let vacuum pass in response to boost. I don't know if a conventional boost controller will work on mk4 and newer TDI due to the setup and vacuum can instead of wastegate other than sending it into limp mode. Not saying it won't work but I don't know how.

ECU tuners can set up the ECU to switch the line between vac and pressure for VNT-nonVNT swaps, they would know the details.

Take a look at this article: http://www.myturbodiesel.com/1000q/a4/VNT-wastegate-adjust.htm for some details on how the VNT can works.

Feel free to talk to kermatdi.com, one of the site sponsors, they have a lot of supporting parts in addition to engine tuning. There are many other places to buy parts and get tuned as well.
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