Well, things certainly do change every now and then, sometime for the better and sometimes for the worse.
I guess the most earth shattering change that I have experienced lately in TDI World is when I was working on my 99 Jetta installing my new Techtonics Tuning 2.5" cat back stainless steel exhaust system and I thought I'd fiddle around with the turbocharger some. This "fiddling" has let me on to some very BIG TIME HORSEPOWER and TORQUE increases this past weekend. With the stocker OEM TDI putting out 90HP and 155 lbs of torque, and my Wetterauer software upgrade raising that to 115HP and 185 lbs of torque, I figured that my Techtonics exhaust upgrade added another 8-10HP and another 15-20 lbs of torque for a current grand total of 125HP and 200 lbs or torque give or take a few.
Well, yesterday when I was fiddling around with the turbocharger I saw the name "GARRETT" stamped in larger letters on the compressor housing (it appears to be stainless steel as it has not rusted at all while the cast iron exhaust manifold containing the turbine is all rusted). Looking closer on the side of the turbokompressor on the side facing the right front passenger wheel, there is a ground down flat section on the kompressor that states:
"VW-AUDI VNT15" along with the serial number and some more words, "MADE IN FRANCE."
Since that verification of my hypothetical beliefs that indeed the USA TDI's had the EuroSpec Garrett VNT15 turbo is now completely true beyond ANY shadow of ANY doubt. It changed my way of thinking about my tubo hop up plans on my 99 TDI JETTA and my 98 TDI NB. Mostly because now I know there is NO WASTEGATE on either of my TDI's and the turbo boost pressure is not regulated via a wastegate like the Garrett GT15 turbos on the previous A3 TDI's (that is probably why the differnent HP and Torque designations between the A3 and A4 TDI's, A3's are 90HP at 4,000rpm and 149 lbs torque at 1,900rpm, while the A4's are 90HP at 3,750rpm and 155 lbs of torque at 1,900rpms).
After realizing these facts it dawned on me to scope out the Variable Nozzle controller on the VNT15. Sure enough it was located between the compressor and the turbine and there was NO WASTEGATE outlet on the turbine side since the Variable Nozzle actuator is smack dead in the center of the two assemblies. Knowing from watching my AutoMeter Turbo Boost guage for the past month, that the boost is increased in repsone to throttle increases and torque increases, I knew then that the ECU wastegate controller solenoid was not pulsing a wastegate open like on the A3's, instead it is opening the vanes on the turbine wheel and constricting the nozzle to speed up the turbo. Indeed, that was exactly what is happening, step on the gas and from the get-go the Variable Nozzle actuator is pulling down on the vane controller with pulses of vacuum from the ECU. Closely inspecting the vane controller on the VNT15, I could easily see that there is an adjuster on the actuator with a screw up or screw down adjustement to change the parameters on the VNT turbine vanes and nozzle. So, adjusting it three turns to the right produced same maximum compressor pressure (about 16-17 PSI) with much slower ramp up speed giving an anemic feel to the engine, however adjusting it four turns to the left produced ungodly increase in turbo compressor max (28-30+ PSI) with instant resonse (scary!
). I liked the peak boost alot but felt it was too dangerous an overload for the engine so I turned it back one full turn to give me a max of 26 PSI peak boost, which is about 10 PSI above the Wetteraurer programmed peak boost. It immediately reaches peak boost in an instant and then is pulled down by the ECU to about normal sustained max of 18PSI, which is real strong too.
So now with my peak boost mods to the turbo, I figure my 99 Jetta TDI is putting out about 140HP and about 235 (250?) lbs of torque, it is ungodly how fast it goes through the gears now. The rpm limiter comes on so fast I hardly have time to shift as the engine roars through the rev range. The tires are gripping the pavement trying hard not to break loose as the sound of the turbine and compressor screaming up to max boost are heard over the roar of the engine. Who says the USA can not have EuroSpec power, I've got it right NOW??? In addition, I also installed my other VDO boost guage in the 98 NB TDI and boosted its kompressor max to 26 PSI too, it is an absolutely unreal screamer now. This is what I always wanted from these cars and now I have it. ABSOLUTELY TOTALLY SATISIFIED with the VW TDI powerband - no further performance mods needed, except an electric fan installed on the rear of the intercooler for even more serious power.
For those of you who can never believe anything and are always questioning reality, I have sent Fred photos of the mod, as well as the install of the Techtonic Tuning exhaust system for him to post on the board.
BTW, I refuse ALL responsibility for anyone attempting this mod. You do it on your own and you are responsible for what you do, NOT ME. There are too many variables involved with this for some backyard mechanic to take it on without instantly destroying his engine.
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99 JETTA TDI HERR WETTERAUER TORQUEMEISTER
98 KAFER WETT SPEKTAKULARE TURBOKOMPRESSOR
97 KTM 620 ADVENTURE RALLY PARIS-DAKAR SUPER THUMPER
ICH LEBE MEIN TECHORAD VW TDI'S MIT DIREKTEINSPRITZER TURBOKOMPRESSOR
[This message has been edited by SkyPup (edited October 13, 1999).]