Audi DIY, Audi A3, Audi 100, Audi Convertible, AudiCoupe, Audi RS6, Audi S2, Audi A4, Audi S4, Audi A6, Audi S6, Audi A8, Audi TT, Audi Q7, Audi Allroad

Audi A4 GT28RS Answers

OK I have been getting all sorts of questions on my set-up from installation to parts to how it runs so I am making this thread to refer people too. I am not responsibale for anything bad that happens, so do at ur own risk and all that good stuff

gt28rs turbo
gt28rs -> v-band adapter
3" test pipe
3" downpipe
upgraded exhaust
exhaust manifold with t25 flange
exhaust manifold gasket
copper sheet (make your own gaskets, all atp's surfaces are not flat)
misc hardware

2 90 degree silicon bends
vr6/2.75" maf housing
misc clamps
3" filter
3" metal pipe
turbo to f hose adapter

440cc injectors
walbro 255lph fuel pump
adjustable fpr
fp gauge

These fittings

oil filter housing to 4an adapter
2 atp cnc banjo bolts and fittings
atp cnc machined oil pan adapter
gasket material (dont use atp's)
misc clamps

manual boost controller,
10' of silicone tubing
a couple tee connectors

clutch (capable of 400+ tq
wideband a/f (highly recommended but not necessary)
misc hardware/gaskets, etc

*Give yourself at least 4 days of downtime. My car took 4 days 18hrs a day to get installed and running, but i didnt buy the atp kit.
**This is not plug and play, and keep in mind you WILL be under the hood every weekend getting things right again.
-First remove old turbo and all related parts, oil/coolant lines, intake pipes, cat, etc
-install new oil lines, the feed is self explanatory 4an hose. The return (10an) needs to have no restriction otherwise your $1g turbo is done, and its not rebuildable! Make you own gasket for both cnc flanges, on the pan and turbo. The bolts for the pan are a major pita to tighten, I had to bend a wrench

-install the coolant lines. both are 6an and will attach to the turbo via banjo fittings. For the feed, uses the barb fitting and clamp it around a rubber hose which goes to the stock location.
For the coolant return there is a pipe sticking out of the block, clamp the ss hose around this pipe
-Install exhaust manifold. I had a custom one so i had to shave off some of the head, but that shouldnt be necessary with most manifolds. install gasket and wastegate blockoff flange.
-clock turbo, to that comp housing is turned properly, This is done by very carefully looseing the nuts on the comp housing and turning. You will need to extend and twist the wastegate arm. Some people need to make a new wastegate actuator bracket but that wasnt necessary for me. Also adjust the wastegate so that it has 7-8 lbs of preload.
-Bolt turbo to exhaust manifold. Make sure you use a gasket with a fire ring. Tighten all hardware.
-Trace v-band adapter and make gaskets for the both the v-band and the 5 bolt discharge out of copper. Then bolt this up, along with the downpipe.
-Take out the maf element from the stock housing. Dremel the vr6 hosuing so that the stock element fits in. Silicone it in. Extend maf wires about 1 ft.
-Cut a 1" hole in the silicone elbow for the bypass valve return.
-find a way to connect the turbo outlet to the f-hose. I initially used a second f hose cut in half, as well as a 2" pipe with flared ends. now i have custom intercooler pipes.
-Connect the silicone 90 degree bendwith hole clamped to the maf (make sure direction is correct, then 2nd 90 degree bend, then 3" pipe, then air filter which should sit behind the passenger foglight.
-Connect maf wires and bypass valve return
-connect wastegate vac line, and boost controller.
-disconnect the n75 valve vac lines, but leave it plugged in mechanically.
-cut pcv pipe

and find a rubber bend so that the oil doesnt drip onto the downpipe or manifold
-install programming
-install injectors, fuel pressure regulator, and fuel pressure gauge. Make sure to uses fuel injection clamps on the gauge install and also make sure its on the fuel feed hose not return.
-install fuel pump, in order to make the walbro mustang pump work in the audi, you will need a piece of rubber hose to keep it tight in the pump holding contraption. Look for john baas's install on audiworld.

-clean up tools, get blood off hands, drink beer,
-pull fuel pump fuse and crank over to get oil into the turbo
-install fuel pump fuse andstart up car. It will idle like ****, maybe no idle at all but it will eventually adjust. check for any leaks of anything, and fix where necessary.
*It will smoke for while
- Let it warm up and take it out for a test drive keeping a careful eye on the boost gauge (i pinned my gauge the first time due to improper wastegate preload.


Begin by hooking up the vag-com, and start up the car remember to let the fuel pump prime before turning over. The vag is just to make sure you can see whats going on if there is any issues. It will probably idle like crap or not idle at all, but should smooth out after 15 min of driving. In my case it didn't and I spent the next 2 months playing around with maf sizes, fuel pressures, and injectors and not idle at all. I had to keep my foot on the gas the whole time which meant left foot on the clutch and right hand on the ebrake when i had to stop.

Once you get your idle set, more than likely your fuel trims have adjusted. Get out the vag-com and monitor knock sensor voltages, timing correction, o2 sensor values and any codes you may come across. Make adjustments where necessary. Remember if you start pulling alot of timing like over 9 degrees or so, you need to do something about it otherwise the motor will not last long. Also listen for knock (marbles in a tin can) I have never heard it personally but i very rarely listen to my radio now, I'm always listening for knock just incase.

Check your codes and do logs very often to keep track of whats going on. fuel trims within 20% are in spec and will not throw a cel, but if possible try to keep them within -+10%. Also remeber -10% is rich, +10% is lean. A bad o2 sensor will cause the fuel trims to either not adapt, or adapt incorrectly causing clouds of black smoke, stained bumper, lots of backfires terrible gas mileage, and other problems...dont ask me how i know. Lets say once you start shooting out fire, ppl tailgaiting will no longer be a problem

Next build a pressure tester. You will be springing boost leaks like least i am. The consists of a 2" pvc cap with a bike tire valve epoxied to it. You clamp it around the turbo outlet tube, inflate to 15psi or so and spray all vac lines and charge pipes with soapy water and check for bubbling. You may be surprised what you will find.

Some other little tricks to help with the many strange issues that come up are moving the location of your maf housing. Idealy you want at least 6" of straight tubing on each side of the maf but that not gonna happen with this set-up. Also make sure the bypass valve plumback is not entering to close to the maf otherwise it will disrupt flow, and cause bad readings and crappy idle. Another important maf thing to keep in mind is when ppl say 3" maf they are refering to 3" od which is really closer to a 2.75" id which is what is important..again dont ask how i know.

Driving Impressions
You most likely will not get in the car the first time and drive it and be shocked like most other set-ups, it runs like complete **** for a while, you tune it and gradually get it better and better, until finally you either put up a good time at the track or whoop up on some sti or corvette. Then you realize what you have done, and the grin will not be wiped off your face until the next time you break down which honestly, probably wont take long. (always, always carry extra tools, duct tape, and the sleeping bag that comes in the audi survival package, na u shouldnt need the sleeping bag but the other stuff is very important)

The car is really alotta fun, at 15psi the thing begins to haul very very quickly and by 20psi its feel unstoppable. Power comes on very smooth from a roll and is much more drivable in the corners than a chipped ko3 or ko4 because there is not a sudden torque spike. Once spooled it feels like it will pull forever. Its pulls on the highway like nothing else and you really really hafta watch your speed. Maybe I should add a valentine 1 to the list of materials needed. If properly tuned it should run mid 12's with an experienced driver (not me), so thats faster in a straight line than many ferrrari's, porsches etc.

I know a guy who runs 34psi on this turbo on stock internals "when i need a thrill" He says" image driving down the highway at 30mph, punching it and getting sideways with awd from a 30mph roll." I have never done this in my car but you really do hafta be careful on wet or dusty roads because once boost begins it will occasionally break loose and get a little sideways in 1st or 2nd gear. I also have aproblem with overrevving when stuff like this happens. I have pinned my tach on several occasions. Aparently the atp rev limiter only works under load.

Overall this turbo kit will cause alot of blood sweat money (in my case credit cards, which are finally being paid off), rediculous amounts of time everyweekend, and many times stranded on the side of the road...i havent had to get towed yet but if you dont know your way around the car and how to diagnose stuff add money to the mod fund for tow trucks fees cause stuff will break! As long as you do all the work and everything you will learn alot of this as you go along, but DO YOUR RESEARCH first. What I have listed in this post is not everything you need to know, but just some of the important stuff that i remember off the top of my head.

Oh yea, if you get frustrated, put the keys down, drink a beer go to sleep and try again in the morning, you will be thinking much clearer

Here's a couple vids hopefully for inspiration.
Winter 05: ko4 -> gt28rs
Gt28rs at 16psi with many leaks

No comments: