The sole purpose of this guide is to go through in fair detail what it takes to get as much power out of a KO3/KO3S as possible in a reliable way. I’ve had experience with a 2001 GTI 1.8T of my own, and now with my girlfriend’s 2004.5 Jetta GLI 1.8T. We’ve recently dyno’d her car on a DynoJet and made 258whp and 322wtq, which to date, seems to be the highest dyno numbers anyone has ever achieved on the stock turbo. Therefore, I feel that going through the performance mod list would be very beneficial to anyone looking to crank some numbers instead of going straight to a bigger turbo.
When I first started modding my GTI, I learned just about everything from Dizzy, aka QuickKO3Crap. I owe a lot to him as he set me in the right direction on what types of mods to do and what works/doesn’t work. Then, as I went on and performed these mods myself, I gained my own experience and knowledge of how everything works together and what makes my girlfriend’s Jetta a powerful yet reliable car to drive everyday.
So let’s begin shall we? I’ll be dividing up this write-up mod by mod, assuming whoever reads this will be starting from any point in performance modifications, whether you are completely stock or you have a good number of mods already done.
1. CHIP: ($500 NEW)
This is by far the most important modification one can/should do to a 1.8T, right out of the get-go. You will find that some people have just done a diode mod, manual boost controller (MBC), and a higher bar fuel pressure regulator (FPR) to achieve chip-like boost levels. Personally, I’ve never gone this route and think that to get where I’ve gotten, a chipped program is an absolute must. If you want to get the most out of your stock turbo, you need some good programming. Custom is great, but you shouldn’t do it unless you have every other mod done, as your tuner will be able to make use of all your other parts and get more power. Therefore, you have to choose between the now 5 available: APR, GIAC, REVO, Unitronic, & Tapp(Eurodyne). I’ve never been a fan of APR’s programming. It makes decent power, but it just isn’t aggressive enough. REVO seems to be quicker than APR, and they have the Stage II that uses an SPS Controller so you can adjust boost and timing yourself. When I had my GTI, I ran an old GIAC file. The only person who was quicker than me was a friend with another GTI that still to this day runs GIAC X+, which is their latest file. Now, my g/f’s GLI is also running X+. I’ve yet to see an X+’d car lose to REVO or APR with similar mods. So my suggestion to you is to find the nearest GIAC dealer. You’ll get the most aggressive file for your car. If super aggressive isn't something you're after, I've been in quite a few Unitronic cars, ranging from their Stage 1 up to Stage 2, and all pull extremely well. I have zero experience with Tapp(Eurodyne), and thus can not comment on it. Keep in mind also when choosing a software provider that you use either a local shop or one you trust to help you with possible problems that may arise. Also, if planning on going with a bigger turbo setup in the future, realize that both Unitronic and Tapp(Eurodyne) offer credit toward a Big Turbo file if you currently have a stock turbo file. Therefore, you aren't paying full price twice.
As for the extra options provided, that’s soley up to you. If you have access to a lap top that HAS A 9 PIN SERIAL PORT, don’t bother with the Race file, as you can make timing adjustments using a free program called Lemmiwinks. Unitronic also has a similar program called UniSettings, available for download on their website. This program does all the same functions and controls as Lemmiwinks, however it is to be used with a USB cable, not a serial. This is beneficial to those of you with newer laptops that don't come equipped with a serial port. If you’re not one to mess with things, then get the Race file. This allows you to get the most out of putting in 100 octane gas. The valet mode will cut power to keep others from beating on your car. If you ever plan on using an MBC, you can do that yourself. Get what you think is worth it to you.
2. EXHAUST: ($500-1000 NEW)
A quality turboback exhaust system is another great mod to do right away. The stock system is extremely restrictive, especially the downpipe. If you’re modding one part at a time, do a bigger downpipe FIRST, as you’ll see the bigger gain from this. There are arguments up and down about which is better: 2.5” or 3”. Some think 3” is overkill, and they’re wrong. I had a 3” on my GTI, my friend has a 3” on his GTI, my g/f’s GLI has a 3”…never a problem. The 3” systems are a little bit louder, but sound has a lot to do with whether or not your exhaust comes with a catalytic converter, resonator, and/or muffler. There are some cheap systems and some expensive. GHL is QUALITY, and they have a lifetime warranty. You can buy a downpipe from someone and fab the rest yourself too. I've also had experience with 42 Draft Designs, and their systems are well put together as well, but are not stainless. Try picking an exhaust tailored to your sound requirements, and what type of weather it'll be subjected to. If you are going to use a non-stainless system in harsh conditions, such as winters with salty roads, invest in some sort of protection like high temp ceramic paint or exhaust wrap.
Two things that you’ll probably experience after installing your exhaust is a Check Engine Light (CEL) for an O2 sensor, saying catalyst below threshold. That O2 sensor is just seeing more flow than it’s supposed to. You can let it go and your car will run just like it always has…well better since you now have a freer flowing system. A way to remedy this is adding a spacer to back the sensor out of the exhaust stream. Here is a thread that shows exactly what you’ll need to do. The other solution is to look into software that can delete the code for you. Revo Stage 2 and Unitronic Stage 2 both were written to delete the code for the O2 sensor when using an upgraded exhaust. The other problem some see is if the car is lowered and you get a 3” system, you may hear it rattle over your rear axle. This is just common sense because a bigger diameter pipe in a smaller gap will start hitting stuff. To remedy this, grab 2 zip ties, and get under the car from the rear. Look at the muffler hanger between the muffler and rear axle. Wrap the zip ties vertically around the rubber piece and tighten them up to pull the rear part of the exhaust system up higher. By doing this, you’re moving it away from the axle, so it will no longer rattle.
3. INTAKE: ($100-300 NEW)
Definitely one of the most questionable mods you could ever do to your stock turbo’d 1.8T. I’ve actually done testing on this, and found that there are very little differences between setups. The most reliable and cheap thing to do is to buy a K&N flat panel filter, smooth out the insides of your stock airbox, and you’re done. I’ve run open inlet, a cold air, short ram, stock airbox, and nothing feels noticeably different than the other. One thing to remember about cold airs is you can’t COMPLETELY SUBMERGE the filter or you’ll risk hydrolocking your engine. I’ve driven through heavy downpours, all of winter, and never had problems. You just need to be smart about not getting curious when you see a puddle. By upgrading to anything but stock airbox, it will get you the PSSSSH sound from your diverter valve (DV). I’m running an ESE Colormatched cold air on the GLI…and mainly because Jen thinks it looks good. It gives some room in the engine bay also. If you’re willing to spend the money, the absolute BEST OF THE BEST intake to buy is the EVOMS V-Flow. It’s a short ram design that utilizes a venturi and velocity stack to suck in air faster than a hoover vacuum. I ran tests on chipped boost levels, and I’ve seen data on big turbo setups. It’s definitely a worthy intake, and it’ll get you the cool sound too.
4. TURBO INLET: ($200 NEW)
If you’ve ever seen pictures of the stock turbo inlet pipe, it is a squished piece of metal and a restriction on the intake side of your turbo. If you’ve opened up the exhaust side, do the same to the intake. You’ll see quicker spool and hold more boost in the upper rpm range. ABD and Neuspeed both sell just the lower half, which is a metal pipe replacement. The problem is you’re still stuck with the accordion-like rubber piece up top. Back in the day when Samco was still around, it was the part to buy. Now, you can either go Forge or APR. They make an entire silicone hose that runs from your Mass Air Flow (MAF) sensor down to the turbo. It’s definitely the better option. Some have trouble installing it and sliding it past one of the coolant lines along the block. You can either unbolt the line, or, lube up the hose like a porn star and push from the top and pull from the bottom. It’ll come right on down.
5. DIVERTER VALVE: ($125-200 NEW)
With the higher boost levels you’re seeing, you may consider getting a new bypass valve, which is what’s making that PSSSH sound when you let off the gas. A cheap option is to buy the factory Audi TT valve through a dealer for $35 or so. There are TONS of companies that make aftermarket ones in different shapes, colors, and configurations. Some have a metal piston and others have diaphragms. The diaphragms are lighter, and therefore react quicker, but they also tend to rip. Forge has a special polymer reinforced diaphragm that supposedly will hold up. We’re running a Forge 007 piston type valve with no issues. Some piston type valves may require you to oil them once in a grand while. As for the Blowoff Valve (BOV) vs. DV issue, it’s hit or miss. What’s going on is your MAF meters air coming in, and stock, it knows that air your turbo already compressed is gonna come right back into the intake and down into the turbo again. By using a BOV, that air is gone, but the MAF doesn’t know that. What you may run into is running rich, because you now have the same amount of fuel for less air. Richness may make the car run unsteady or stall when coming to a stop. My g/f’s GLI HATES BOV’s, and a great way to test to see if your car doesn’t mind is to go to Home Depot and find a 3/4” plastic PVC plug. Pull your DV out of your intake hose, and plug the hole. Turn the car on and start driving around. You’ll feel a difference if it’s bad. At idle the rpms will bounce around randomly. The only difference between a BOV and DV really is the sound, and that’s what most people care about. BOV’s are usually always louder, but DV’s aren’t necessarily quiet. Stick with what works for YOUR car, and not what someone tells you over the internet because it works on theirs.
Another option on rigging up your DV is relocating it to a “cold side” position. Stock, it’s connected to the pipe RIGHT AFTER the turbo. Most front mount intercooler kits also run the DV like this too. Relocating the DV means putting it right before the throttle body, after your intercooler. There isn’t going to be a HUGE gain from doing this, but what it does is this: When you let off the throttle, the throttle body slams shut, and all the boosted air in your piping has to get out. At the stock location, all the air has to go backwards to your DV to be let out. If you relocate, you keep the air moving in the same direction, which theoretically, would help with spool up since the turbo isn’t working against itself. To make a return line, either go custom and use some sort of pipe or find hose that is big enough to fit over the DV outlet.
6. SPARK PLUGS: ($15 NEW)
When you start running higher boost levels than stock, your plugs are going to need a change. With higher boost means higher temperatures inside the combustion chambers, and therefore you’ll want a colder plug. The most commonly talked about/used plugs are NGK BKR7E’s. You can get them just about ANYWHERE and they’re cheap. I’ve paid around $12 for 4 of them. Make sure they are gapped at .028 for optimum performance. Gapping them to high will result in the spark just blowing out as boost enters the combustion chamber, and gapping them to low will keep an actual spark from occurring. The electricity will jump right to the electrode so fast and it’ll be so small that it won’t ignite the air/fuel mixture.
Another mod to do around this same time would be to invest in some coil pack hold downs. Sometimes, the remedy for a coilpack coming up off the valve cover is retorqing your spark plugs. But I’ve had times where even with them properly torqued, the coilpacks would still pop up. A user on VWVortex by the name of enginerd custom makes and sells a set of hold down brackets to go over the coilpacks. If you don’t have the style coilpacks that have the holes in them to bolt them to the valve cover, get these, as they are more of a reliability mod and you’ll drive assured they will never come out on ya.
7. UPGRADED INTERCOOLER: ($400-1000 NEW)
The stock side mount intercooler is a big heat soak and is basically like a condom…it’s only good for one hard use. Most people upgrade to a front mount intercooler (FMIC) because it not only keeps your intake temperatures down, it looks appealing as well. BoostFactory and Tyrolsport make quality upgraded sidemount intercoolers (SMIC), but they are more stealth because you can’t see them as easily. The nice thing is they bolt up in the stock location. There are many FMIC kits out there, and you’ll pay around $700 or so for a quality one. Another option is to just buy a core and custom make your piping yourself. If you do, run 2.25” piping from your turbo to the intercooler, and 2.5” piping from the intercooler to the throttle body. Going custom would be a great time to relocate your DV as well. I chose to look on eBay and buy just a bar/plate core and make custom piping. If you do this, look for SSAutochrome, as they have quality cores for cheap. Do some searching for clamps and couplers yourself as you’ll find many places and perhaps cheaper places than I found. Finally by going custom, you’ll need a Manifold Absolute Pressure (MAP) sensor flange from 42 Draft Designs. Most kits have one welded on, but by going custom, you’ll need to buy one in either aluminum or steel (depending on your piping material).
The main benefit of running an upgraded IC is the temperature drop at the intake manifold. If you use Lemmiwinks, you can raise your ignition timing to gain more performance. When you get toward the end of the stock turbo mod stick, you’ll be glad you have one as this is what will keep you running efficiently.
8. PULLEYS: ($200 NEW)
Another mod that has been argued over many a time, lightweight pulleys are used to replace your stock crank, power steering, and alternator pulleys. These stock pieces, especially the crank, are heavy, and thus require more energy to rotate them. By swapping for lighter ones, you free up some of that energy and it’s of course, easier to spin a 1lb pulley than a 10lb one. The alternator pulley may be too difficult for some to replace as newer 1.8Ts use a specialty bit needed to remove the nut. ECS has them and you can rent it out but pay for it. I haven’t replaced the alternator pulley in Jen’s GLI…just the crank and power steering ones. Those two are far heavier than their lightweight counterparts, and thus I believe to be the important ones to replace. Unorthodox Racing also makes lightweight pulleys, but I’ve never installed them. Go with ECS and forget about it.
9. INTAKE MANIFOLD SPACER: ($70 NEW)
There are a few out there, but the most known brand is made by New South Performance, called the Powergasket. It’s a replacement gasket for your stock intake manifold to head. What it does is keep engine heat from radiating up into the intake manifold because of the polymer it’s made out of. The stock gasket is a very thin metal and easily transfers heat. There is a new version called the Powergasket Plus which has a coating on it so there is no need to apply any sealant. I’ve seen two melted Powergaskets before, and both were on big turbo, high HP setups, so there is no need to worry about yours going bad. Get the latest version and you shouldn’t have any problems. Taking off the intake manifold is no easy task for some, but the gasket comes with directions to help ya along the way. This mod coupled with a FMIC will show some very low intake temps.
10. MANUAL BOOST CONTROLLER: ($40-200 NEW)
Your car comes with an electronic boost controller from the factory, called the N75 valve. It’s plugged into the inlet hose and has two vac lines running to it. What happens is as boost is made, it travels through the one line, goes through the N75, and out the other. The other line leads to the wastegate (WG) which is the actual boost controller. When enough pressure pushes on the WG actuator, it opens the gate inside the exhaust side of the turbo and bypasses exhaust gas around the turbine, and thus, keeps the turbo from spooling up any more. There are “race” N75 valves offered, but I’ve never cared to use them. I hear mixed feelings and getting the wrong one can make your car run like poo. Investing in a MBC may be the best option for ya. I’d recommend going with a Boostvalve setup, as they are reliable and easy to install. There are a few ways to hook them up, but what I believe to be the best way is to not use the N75 at all, and just run the boost and WG lines to the MBC alone. DO NOT UNPLUG THE N75. This will put you into limp mode, which limits boost to 5psi. You’ll have to plug the port for the N75 in the intake hose. Currently Jen’s GLI is using a DualStage MBC from Boostvalve, which lets us run 2 different boost levels. This is where some reliability comes into play because we can run low boost daily and not put as much stress on the turbo and engine components. With the simple flick of a switch, we’re back to high boost.
MBC’s seem to give quicker spool than the N75. The N75 is more like a bleeder valve because it slowly lets boost by to the WG actuator. MBCs completely block boost until it’s high enough to overcome spring tension, and therefore, the WG isn’t touched until this point. One issue you’ll run into is what’s called “part-throttle surging.” What happens is you apply the gas half way, and boost spikes up to what you’re set at, and then falls back down. You aren’t requesting that it make that much boost, but it flies up that high anyways, and may feel jerky. By learning how to deal with it, you’ll forget about it. Most people just give up and go back to a N75 or run the lines using the N75 also. What I do is just hold the gas steady, and the boost falls back down without jerking the car. Being in low boost also keeps it from surging as much because it only initially spikes to 8psi, instead of much higher.
Modified by SAVwKO at 5:33 PM 7-31-2008