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Performance Mods

Improved Airflow

Like most tuners, I began with my intake.  I tried popular foam and/or cotton gauze filters.  Both have one thing in common: THEY REQUIRE OIL TO TRAP DIRT.  I'll skip the debate regarding oil contaminating MAFs.  But I do know this: The drop-in versions of these filters allowed dirt into my intake.  Since dyno runs on MY CAR proved only a 1-hp difference between a paper filter in the stock box and no filter/box at all, I returned to paper for quite some time.  But something changed in 2005.  AMSOIL introduced their new EA AIR FILTER which uses synthetic nanofiber technology by Donaldson.  In a nutshell, these filters flow like cotton gauze but trap dirt like paper.  Best of all, they do this WITHOUT OIL.  Their problem is a lack of availability in my application.  Therefore, I adapted an airbox from a Ford Mustang to work in my car.  The result is an intake that'll flow more air than I'll ever need combined with a better air source (beneath the engine bay).  The elimination of the stock "accordian pipe" also reduces intake restrictions (a good idea for turbo upgrades).

New Engine Programming

Changing the engine programming provided the most dramatic increase in engine performance of all engine modifications.  Therefore, I highly recommend it as anyone's first move.  The cost is between $200-$550, depending on the model year and level of programming (newer TDIs are more expensive to tune than the older models).  You can count on a reliable 25-30% increase in power and torque from the modest programs without concerns of damaging your engine.  IMHO, anything more aggressive than 30-40% will increase the risk of engine or transmission troubles unless precautions are taken (upgraded clutch, for example).   But more aggressive tuning is available and supported with appropriate hardware.  For example, I'm about 70% over stock (keep reading for details).   Naturally, the driving experience is greatly enhanced.  Experimenting with various programs is a snap due to my A3's socketted ECU.  I've used Rocketchip, Alligator, and Upsolute programming.  I believe Rocketchip and Alligator provide the best flexibility of tuning for cars modified beyond a simple chip upgrade.  Plenty of folks like "tuning boxes," too.  They have their merit.  But I'm biased toward changing the program itself since a proper tune operates the car in truth instead of via sensor deception.  The choice of tuner is yours and should depend upon your location and timeframe.  Personally, my choice of tuner is Rocketchip since he's not far from me and he has a lot of experience with TDIs.  He also builds a variety of programs depending on the desired power gains.  I'm currently experimenting with "RC6," a program that provides power to 6000 RPM.  FWIW, I almost never rev that high, even when drag racing.  It just feels WRONG to drive beyond 4200 RPM.  But it's good to be able to hold onto a gear and still have good power beyond 5000 RPM on the autocross course.  Check out THIS FAQ SHEET for more tuning info.

More Fuel

Another popular upgrade is to replace the fuel injector nozzles with larger units for more fuel flow.  Check out a set of PowerPlus Performance Diesel Injection Nozzles by Fratelli Bosio of Italy.  These nozzles are available in North America exclusively from KERMATDI.  They provide a better spray pattern and flow more fuel than the stock nozzles.   The result is a 10-20% increase in power and torque, depending on your choice of nozzle and the tolerances of your specific fuel pump.  I haven't done dyno tests to prove anything.  But I CAN tell a difference between the stock nozzles and the PP520s (a troubleshooting venture required me to switch back and forth several times).   It is said that a change of 7-10 horsepower can be felt by the driver.  So that's my estimated difference: 7-10 hp and 14-20 lb/ft.  Later, I upgraded even further to PP502s and perceived a tad more power (and more smoke).  So I think upgrading straight to PP502s from stock units may yield a gain of up to 20 hp and 40 lb/ft with appropriate tuning!      In addition to the injector nozzles, I also use an in-tank lift-pump from a 2005-2006 PD-100 TDI to pressurize the fuel supply to about 4-6 psi.  The reason for doing this is to allow the injection pump (IP),  which is at the front of the car, to maintain proper timing at higher RPMs.  This is especially helpful to ailing IPs such as mine (I can hardly wait to replace it with an 11mm IP).   The lift pump is also great for priming the fuel filter and IP after maintenance actions.  Also, be advised that the fuel gauge may not work the same on an A3.  My fuel gauge was so boogered up I disconnected it (it worked backwards).   I'm going to research a low-pressure, external fuel pump that will allow me to return to my stock sender so my fuel gauge to work.  CAUTION: If you install one of these pumps, ensure it is powered via relay that is activated by the input to the N109 fuel cut-off solenoid.  This will enable the ECU to shut off the lift pump in the event of an accident (airbag deployment or engine failure)  instead of pumping fuel all over the accident scene.

Turbo Upgrades

Turbo swaps are a serious investment in time, money, patience, and managing expectations.  I tried a T3 PROJECT in 2004.  The most painful and expensive part of the experience was the continuous need for altering the exhaust tract.  After seven months of trial and error, I canned the project since it was a money-pit and the large turbo would not spool fast enough to give me the low end torque I had previously enjoyed.  Therefore, I returned to the stock turbo and considered alternatives.  I eventually had a K03/K04 hybrid built.  As evidenced by the 5mm larger compressor wheel in the photo (hybrid on the right),  the hybrid flows slightly more air and provides a MODEST GAIN of ~9 whp and 12 lb/ft in the middle of the band.  Using the relatively-small K03 exhaust housing, this turbo still limits top-end horsepower.  However, using the stock exhaust housing ensures this hybrid is a DIRECT REPLACEMENT for the stock turbo.  I wouldn't buy a K03/K04 hybrid for the power alone.  However, it IS a wise purchase for one who is replacing an aging K03 or GT15 and wants a turbo upgrade that bolts directly to the stock location.  I'd love to get a large variable-vane (VNT)  hybrid turbo such as a VNT 17/22 to work for a lot more power.  But the VNT path is VERY lightly-treaded on the A3/B4 platforms due to the mechanical and electrical modifications required to make them work on the older TDIs.  I'm not inclined to pioneer another turbo project (big VNTs are awesome on the newer TDIs!).  So I think I'm going to see if someone else figures out how well they work on an A3 or B4.  In the meantime, I will enjoy the low-end torque that pulls me through tight low-to-mid-speed autocross courses.

"Mufflerectomy"

The main goal with exhaust systems is to reduce exhaust back pressure.  This allows the engine to flow more air and improve turbo response.  Many owners go with some sort of commercial 2.5" exhaust system.  This usually costs over $800!  Instead, one can get the same benefit by replacing the muffler and resonator with a straight pipe.  The turbo and catalytic converter do a pretty good job of muffling engine noise.  FWIW, I would not perform this mod on a perfectly good stock exhaust system IF your car still has the stock turbo.  It's just not worth the time or money since the stock system already flows quite well.  But if your muffler develops a leak or something, cut it off and replace it with a straight pipe.  The change in noise will be minimal.  If you install a larger turbo, THEN go ahead and upgrade the exhaust since the larger turbo MAY flow enough air to benefit from the straight pipe.  I went a couple of steps further by installing KERMATDI's A3 downpipe with a divorced wastegate isolation flange (WGIF)  as well as a 2.5 inch diesel cat by Magnaflow (#93006D).   The improved accelation and response was more than I expected.  The new cat and WGIF flange reduced back pressure and gave me some unexpected low-end power and torque.  Dyno testing showed a MILD POWER INCREASE of ~9 whp and 10 lb/ft; but the horsepower extends higher in the rpm band.  Oh, since I know you're wondering, the new exhaust note is pretty appealing.  A friend who frequents Europe says my car sounds like the V6 TDI.  HERE'S A SMALL AUDIO FILE (remember that I have a large, open exhaust).   :-)

NOTE: THIS PARAGRAPH and DYNO GRAPH DOES NOT REFLECT MY LATEST RC6 TUNE and IP MODIFICATION...          Once I was finished messing around with turbo setups (as if I'm EVER done),  I decided it was time to finally get some dyno measurements.  I wanted to use a dyno that could provide consistent, repeatable results in case I decide to visit again.  I chose to visit a shop with a DYNAPACK chassis dynomometer.  Measurements are taken directly from the hub.  It's VERY consistent and repeatable.  My best dyno pull to date is 136 whp and 263 lb/ft.   Using a popular A3 transmission loss of 17%, that calculates to ~163 hp and 316 lb/ft at the crank.  That will certainly move me out of the turns on the autocross course!  Check out my MY DYNO VIDEO (6 MB).  Click here to see my recommended path to TDI performance upgrades.  Oh, for the record, I do NOT recommend the use of lightweight flywheels in TDIs.  They simply do not rev high enough to make them practical.  In fact, my experience with one was rather painful.  Feel free to read MY REQUEST FOR HELP at TDIClub.com.  In short, my lightweight flywheel took me on an adventure that saw the replacement of programming, injectors, the injection pump, and even the ECU before tracing my issues to the flywheel.  The good news is I now have a lot of spare parts for my aging TDI.   ;-)

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