3 weeks ago a couple guys came over, one with an arrogant flair asked me to draw him a modification map to make his new subaru WrX as bad *** as the sti version...boy this is an ugly car lol... but alas, I asked the gurus of turbocharging to come up with the answers and we made the plan, which he liked, turns out the guy is rich, son of some movie producer... so he left the car and I set out to parts ordering and stuff, we pulled the engine, fitted better components on the boxer four, re mapped the fuel system and fitted it with one rather large bore ball bearing turbo kit, I knew this would not be ok since the lag would be unbearable, so we went one step further and added an assist via a bit of laugh juice, not too much, only around a 20 shot to be armed manually when driver needed the low end pick up (like at a drag for example) in order to spool the turbo faster without damaging the engine... as luck would have it there was no way I could dyno tune all 4 wheels here, so we temporarily disengaged the front wheels... this gave me only a slight problem with having to use an outside sump for the oil to go in and out of while the back end sat on the dyno spinning, alas I meassured a successful 434bhp and 376 foot pounds of torque... so began tunning and playing with the air fuel ratios, ended up at 349bhp and 310 torque... thing is I know that once all 4 wheels get to work the figure will be lower slightly, so in fact this car may be now just as fast as a factory STI... however having much more torque and less lag should be able to destroy a factory version

let me explain, you do understand the car's powerband right?

you see in order to generate enough exhaust pressure to "spool" the rather large bore turbo, the car now needs to make more rpm, thus this creates a slight lag at the bottom end between pedal push and reaction = boost, ok, you are correct about the nitrous cooling the intake charge making it dense, however this is where careful tuning takes place, inject too much at the wrong rpm and you end up with catastrophic results, inject too little and you can stall your turbine due to a high volume of exhaust without enough pressure to push the hot side, which can result in a turbo burn out and parts flying out of exhaust pipe, not good

so basicaly you run it on dyno, use tools to look at what engine is doing, find the weak spot, which in this particular car happens to be around 2k - 3.1k rpm, so you schedule the system to open certain things at certain points, allowing more air at a milisecond between 2k push, (provided the nitrous is armed at this point) the voulume of extra air is very small, the volume of N2o is also small enough not to cause too much cooldown, but just enough extra oxygen is added here, remember that this intake air is going thru intercooler before going to engine anyway, math comes into play here, (flock this up and bye bye car) the nitrous only shoots between 2k and 3.1k rpm, the fuel injectors go into overdrive, at this time my magic is telling them that the throttle is wide open, thus they dump extra fuel, the MSD module receives signal to send big spark at this time, sounds dangerous, it is, usualy all this part of tuning is done without the exhaust on, the calculation is different for every car but fairly close between same models, you cannot do this with a stock ECM, this is why the addition of a piggyback or a stand alone "fuel computer" (which is nothing but a module with the settings I have programmed) comes in, it is all high tech it seems but it is all logic, the additon of a boost controller allows even more play, as you can control just how much air gets compressed into your engine this way by adjusting both the wastegate and in some turbos even the blade or spool angle of attack, however you need to balance it all in a custom setup, more air needs more fuel, more fuel need hotter spark, hotter spark needs stronger components, stronger components need to be light enough not to rob you of power, too light of a rod or crank and you can break those, so no, not anybody can tune a car, nowadays many cars come factory with nearly indestructible internals, so this makes the job even easier, subarus are not this kind however and it takes hours upon hours to get it right, lots of close calls, a few burns, etc, yes much bigger injectors were added, yes a small turbo would suffice for a nice turbo set up with less lag, however you are limited in the amount of power you can produce, you can spin a TD05 size turbo up to 27,000rpm and still only get max out put of 9psi compression... however you spin godzilla size R01 or T60 at 14,000 and you are making an easy 18-21psi... for this application we also wanted linear power and not a boost that would come in full blast at 5k rpm, we wanted to come in at a much lower end, where the car needs it, remember this is not gonna be a daily driver car, if it was I would have opted for the smaller maybe even a twin turbo set up for low and high power, and perhaps you don't understand how the nitrous system works, you see this is how it goes, you start car, drive normally, nothing happens with it, but lets say now you are in a track, you go ahead and at any time you hit button, guess what nothing happens here, the system is simply armed, now, the next time you come to a corner and slow down, the system is ready to operate, there is no need to push anything again, you drive normally, however the moment you down shift, and depress pedal to get out of that corner, get ready because the firey demons from hell are coming loose, and you did not press anything, your turbo spools so quick that your response is nearly like a naturally aspirated engine, your engine revs so fast that your eyes go cross eyed... and this will continue to happen for the next 5 hours, due to the actual shot being so small this was the estimate we made from the size of bottle, in fact maybe more due to the fact that the nitrous does not stay pumping past the 3.2k rpm, this is self sustaining boost at this time, get to next corner with porsche dude behind you all pissed off lol ( when he told me the story I pictured Richard hammond getting upset behind me, hahaha) until you hit button again, then your "N2 assist" gets disarmed and you are back to normal turbo driving, you are still fast but it takes you a bit longer to get out of the hole, another advantage of the bigger bore is that the power is exponentially increasing so when you think you ahave reached the top, it keeps going and going and going until your head starts spinning like the exorcist chic