Basic Assumptions: (all of which are “facts” stated by the professionals I have worked with)
1.8T is capable of 350 foot pounds of torque on the stock rods, that is the first limitation of the hardware.
Drivetrain is good to 450HP (as said by some pros)
The GTRS is capable of 22PSI all the way to 7K RPM.
Methanol Injection at 50/50 water to alcohol is 100% equivalent to 116 octane fuel, allowing for significant HP gains due to more advance under boost.
Nitrous is a power adder that adds fixed HP and torque at any RPM, low or high. Nitrous is a full stroke power adder as the burn is not a quick flame wave, but is distributed across the entire power stroke (told this by my supplier). He used an analogy to “exploding foam”. Mikey likey exploding foam analogy…
Stand Alone ECU allows for precise control of fuel, timing, and boost pressures so you can dial in your RPM curves for all of these attributes.
So with those assumptions in mind, there is a lot to tweak here…
- Fuel (11:1 under boost, 14:1 cruising, XX:1 to make it idle)
- Timing (as much as possible without pinging at any RPM / boost)
- Boost (how much at any RPM – maybe even a spike at medium RPM and then taper off as you rev out)
- Methanol (what boost level to activate, what boost level to be at 100%)
- Nitrous (how much HP jetting, what PSI to switch off)
One known fact from my limited 4X experience with Dyno Tuning as well as many years of software engineering (which might only have this one similarity) is that it is very easy to get 90% there, and the last 10% cost and spans about 90% of the money, time, and effort.
Now for the tuning: Start with the basics: Boost, Fuel, Timing.
Boost – You want to run as much boost as your turbo and internals will safely allow. On the 1.8T, that means a lot of boost , so much so that if you do not want to see boost drop off as you pull into the higher RPMs the turbo gets so large that low end boost is just plain gone. I am talking like 22PSI on 91 octane CA gas. The GTRS, which can provide this boost, spools nothing like the K03, you have to WAAAAAIIIIIIITTTTTTT for the spool. It takes FOREVER, and almost anyone in any car can pull anything on you until you hit big boost. Let’s face it, you are not going to drive around at 5K all the time just so some JA in a neon can’t cut you off in traffic. FWIW – the GT2X does not spool much faster than the GTRS, but does run out of steam after about 5500. It is not until you buy one and install it that you find this out. Yes it can do 20PSI, but only to 5500, then you pull boost down to about 15PSI to 7K. That is a real bummer feeling. Skip the GT2X. I wish I would have. Any more boost than this and you probably need to change rods, so I did not consider larger turbos.
Verdict – GTRS (and slow spool) is your only choice
Fuel – There are many options here and I chose 034 standalone. Since then, 034 has began selling the Unichip line. I am pretty sure they can make a map that works very well with the rest of the hardware I have and I might have just been a bit early on my purchase there, but alas, I am not really complaining. Another development and a certain swap for me is the Genesis dual cone injectors. The folks at 034 swear by them and I figure I can sell my green top and trade up. They are supposed to have much better drivability. 034 standalone is a nice unit with a very granular control of fuel, spark, and boost maps. I am sure there are many others out there, both chips, piggybacks, and standalone ECUs. The point of this section is just to say that you should dial in your fuel so that you are around 11:1 under boost, this is a nice safety margin. Some folks might say go lower like 10:1, and they are probably right, but it seems a bit rich to me. Some dyno testing would be nice here to see what power is lost for the safety. You are going to need a wideband O2 sensor here, I like the PLX devices and the Innovate O2 controllers.
Timing - Once you have a safe 11:1 (under boost) fuel map, you can start to add timing. A good ECU will allow you to have correction factors for air temp, water temp, altitude, etc, so whatever your map is, it can be adjusted for these real life conditions. If you get on a nice load simulated dyno, like those 4 wheel dynapack jobbies, you can create conditions that allow you to dial timing under various load conditions as boost conditions. The general rule that running as much timing as possible under load without pinging is going to give you the most power, but I have been told by the dyno folks that this isn’t quite true. A nice knock sensor with an acoustic adapter, a voltage or graph readout will do the trick here. Learn how to read your sensors readings and you will see signs of knock before an actual event occurs. Any high boost knock is bad, even the ones on the dyno, so be careful. The dyno I mentioned above will actually show you your torque output and if you have a lot of time and money, you can fidget with timing and see where max power is made.
Verdict – Pick the best you can afford… My advice, keep it simple, if you can flash your ECU and run 21PSI, that sounds nice… There is a lot to take for granted that your remapped stock ECU will provide.
Once I had 21 PSI, 11:1 fuel, and decent timing, I was sad and disappointed in my serious turbo lag. I needed to do something about the spool. I started with adding Methanol injection with the thought that if I could add more timing from low boost to high boost, my spool wouldn’t crawl from 2 PSI to 15 PSI as it does before it really “kicks in” and shoots to 21 PSI. That is a lot of wait time… 6PSI, 7 PSI, 8PSI, 10PSI, 12PSI… come on!!!
Methanol - Truthfully, with a tuning session on a dyno and spark handled by the 034 ECU, the 034 folks themselves could not tune much more than I already had in the timing maps. There was no sign that my 50/50 methanol water mixture was providing me 116 octane fuel. I would love to explore this more on a better dyno with a better knock sensor than we had at the time. We were reading the VAG logs of the factory knock sensor voltages, good enough for Bosch and Audi though . This was a real let down. On the other hand, I do feel as though I have a safety margin and a potentially tunable system that is lying dormant here. It was just that the first tuning session after installing it correctly, jetting it correctly, and having some of the best dyno operators in the area (034) do their thang, I did not leave with 40 more horses, more like 5, and this might have been from adjusting the timing outside of the methanol kit.
I beg anyone good at dyno tuning with methanol to join me for a session, and I challenge any of these companies to increase my HP by just 20 or pay for my dyno time…
The saga held tight with that setup as I had a long commute many miles of which were freeway, therefore I had longer stretches to smoke fools and I was closer to the 4K+ RPMs needed to get into the power band. Then my job changed, and I was driving mostly short distance surface roads.
This is when it all started to bug me, I had like $10K in this setup (parts / labor / tuning) and it sort of sucked for my situation. I seriously considered going back to a K03, you cant beat that low end torque on that little 1.8T with a chipped K03… Well, nut unless you have something like nitrous…
So I thought quick, salvaged a rarely used nitrous kit off of my 1970 Camaro (braggart!) and purchased the pieces needed to adapt the kit to the A4.
Nitrous – The idea of nitrous on a turbo will sound crazy to you until you do it, just as methanol might sound to a young tuner, and even chipping could be to the newbies… Many N2O companies sell “quick spool” kits with advanced controls for sensing boost, fuel pressure, and other vitals, but as I see it, with my experience with basic nitrous kits, and no blown motors to date, I could get by with a simple Hobbs switch setup. A Hobbs switch is a pressure switch that can be adjusted over a range of PSI to either open or close a circuit at a given PSI. Quick spool kits would have NC (normally closed) switch that operates in the 8-12PSI range. In my case, with my calculations, and my experience doing this on one other turbo car in the recent past, I figured I would add 50HP up to 8PSI, that should get the turbo spooled and then boost will quickly soar to max! Sort of… This solution does solve the lag problem, no question there, it is basically instant boost. It is nice…. This configuration was decent in low gears at lower RPM ranges, but not enough in higher gears at lower RPM (less than 4K). In other words, it was pretty good in many cases, but not the best configuration for my driving habits. So I have recently adjusted to to 40HP and 12PSI cutout. I did this after a long conversation with one of the nitrous professionals at my supplier. The folks at 034 want me to pull timing under N2O, but the folks at the nitrous supplier say 50HP is really small and pulling timing at lower boost levels is not necessarily required with small amounts of giggle gas.. So I went 40HP just in case 
. This setup is very nice. You get strong acceleration and a real quick spool up to 12PSI where there is enough boost to help carry you right on up to max. It is almost seamless with a very small drop in pull at the transition point in 3rd gear and higher. Maybe someday I will try 30HP to 15PSI, but I would need to buy another Hobb switch that is adjustable in that range, so it will probably never happen.
Verdict – Squeeze is a nice way to get instant spool on a small displacement big turbo motor.
Should have bought an S4… I am sure I would have dropped the $10K still, but I would have at least another 100 ponies. Live, burn, learn…
References:
http://www.034motorsport.com
http://www.atpturbo.com
http://www.coldfusionnitrous.com/
http://www.nitrousdirect.com/
http://www.plxdevices.com/
http://www.innovatemotorsports.com/
http://www.snowperformance.net/
http://www.alliedelec.com
