Ok just to clear something up, I was always under the impression that a twin turbo system had two different sized turbos, a small one and a large one. the small one would spool up first to eliminate turbo lag and the the second one would come in as the first one was nearing its peak output and give you another boost of power. is this true or not? it seems like in the greddy kit the turbos are both the same size. do they both come on at the same time, if so what is the bennifit of having two smaller turbos instead on one large one. If anybody could solve this problem for me it would be great. thanks in advance

 

you're talking about sequential twin turbos whereby the smaller turbo spools quicker for lowend power while the larger secondary turbo is for highend power. this is great for the auto manufacturers for power gains over naturally aspirated while maintaining a certain level of reliability.

the greddy system utilizes a turbo for each bank of cylinders versus a sequential system where the exhaust manifolds meet into one pipe where the sequential turbos would be. they are each the same size and spool up according to the exhaust output for each respective cylinder bank.

with advances in turbo technology there are no real advantages to smaller turbos except for fitment but a larger single turbo will allow for greater topend power merely by the volume of compressed air that can be moved at any time. of course this is not to say that 2 good sized turbos wouldn't be able to push out as much if not more air than a single T78 big turbo.