| Here is a write up from Aus300zx.com that I did a while ago supporting our Group buy of GT28R's for people with stock engines. [ http://i4.photobucket.com/albums/y111/grahamrjohnson/GT28Rcompressorcurve.jpg ] If you look at it see how it reaches its maximum efficiency at between 5000 and 6000 revs. You can draw the conclusion that you can see it comes on boost at about 3500 revs and builds untill by 8000 revs its runs out of puff. Those lines I have drawn on there represent the amount of exhaust gas generated by the engine at those revs. So you can see that the more exhaust gas generated by the engine spins the Turbo up faster and so it moves the lines to the right across the graph. The SR20DET generates as was pointed out. 33% more exhaust gas as those revs. So the turbo spools up faster. So for the SR20 the lines move toward the right and the peak effeciency part of the curve moves to a lower rev range. Therefore the SR20 would spin this turbo faster earlier and come on boost earlier just cause it has more exhaust gas. Your peak efficency would be at probably 4000 revs but it would run out of boost a bit earlier at say 7000 which isnt a bad thing. Does that make sense? Keep in mind without a worked engine. The upper Rev limit is probably 7500 revs and the upper boost is about 20PSI. Beyond that we cant really use any extra turbo capabilities. To use high boost levels beyond 20 PSI you need forged pistons rods etc, essentially a racing engine. Now look at the AR 0.6 Disco Potato GT28RS [ http://i4.photobucket.com/albums/y111/grahamrjohnson/GT28RS.jpg ] The amount of exhaust gas we are generating hasnt changed. See how the 2000 and 3000 rev lines are in the area thats called the surge point. Cause we are off boost that doesnt matter too much. But the point is that the turbos come on boost later. To get to the point where the turbo is getting to it maximum efficency, we are looking at a point a good 1000 revs higher than than the GT28R. The big big advantage of the GT28RS is above 23PSI (where we are not going to use it). The damn thing just keeps pumping like a bitch way up to and above 30 PSI. Thats why it is so good on Johns slot car. His engine is built like a tank to take high boost levels and deliver very high power outputs. You can see how at 2 bar (14.5 PSI) The Turbo to be efficient has to be reved to almost 7000 revs. We have run out of our rev range at this point. So that high output isnt really realized. I think Johns Slot car revs to 8500 or so. The upshot of this is that the RS is a great turbo for high boost levels at high revs. Typically to release its best You have to run 30PSI. OMG at 30 PSI it would be AWESOME, No wonder John gets over 400 RWKW. The GT28R comes on boost earlier and is most efficient at 5000 to 6500 revs right where we need it. (A bit lower would be nice but what can you do). This why the SR20 DET would be good for this turbo cause it exhausts more gas and so comes on boost even earlier. Its not much worse for us it just comes on boost a slight bit later cause we only have 1500cc to drive it with. So the bottom line is. GT28R for stock engines running 24 PSI or under boost, and the Potato for High stressed racing engines built for high boost levels.
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