A properly sized turbo that is larger will improve the volumetric efficiency of the engine by removing the resistance the smaller wheel turbo causes :-) I started thinking about some of the turbos available and decided it might be good to clarify that not all turbos are created equal by deeming them larger. A good case for this would be the GT2871r turbo vs the GT2860RS...... The GT2871R is a larger turbo, but it is mis-matched and has a really large compressor wheel, but the same smaller turbine wheel as the GT2860RS..... The GT2871R turbo is larger and can produce more boost and because it can make more boost can make more power, but this would be one of the cases where at the same boost level as the GT2860RS would not be able to make more power because the exhaust wheel is the same and it is not allowing the engines efficiency to increase. For me this turbo would be a poor choice because for the same boost level you do not increase power and when you do turn the wick up you drastically increase the heat and backpressure. As the backpressure goes up you have a harder time keeping gaskets from blowing. The real upgrade from the GT2860RS where the compressor ind exhaust wheels both increase together is the GT3071R and this will again improve the effciency of the engine, create more power at the same boost level and reduce backpressure allowing for higher boost levels to make safe higher boost for serious safe power. Another example would be when some companies install just larger compressor wheels in the stock turbos......again this allowed the turbo to make more boost pressure , but did not offer any more power at the same boost level. They also created more heat and more backpressure and hurt a lot of motors. So when choosing larger turbos I would always suggest close to matching sizes on both sides of the turbo. For the guys really pushing the envelope with N20 remember the N20 creates even more exhaust that needs to get out, so if your running N20 all the way down the track you have to run less than full boost on small and medium size turbos. Only so much exhaust can get out of a certain size wheel before the pressure starts building and something else is going to relieve the pressure rather than make more power. If you need more power you need a bigger turbo ;-)
