I noticed the WGDC went up a little bit with the Wagner on stock turbos. Makes sense the Helix and others may behave similarly. I also don't think staggering the fins within the turbo air path is a good idea. If staggering fins only do it for a few inches worth. With cores of these size its wasted added back pressure. Staggered fins on the ambient air path is probably a good idea. Helix would look to be superior to Wagner from the extra rounding of edges and the larger air passage in the end tank that feeds the upper portion of the stepped core. Is it worth the extra money? No, I don't think so in the least.
Conclusion for me for E85 + stock turbos upgraded intercooler has minimal benefit mainly coming from ability to run lower E85 ratios and hit same target, better throttle response, and quicker spool (i haven't confirmed spool in logs, going off feel). The intercooler will allow you to flow more and make a little more power, but you are going to drive your turbos harder when they are already way way out of their efficiency range. The higher pressure drop from cooling the air more efficiently causes the turbos to need to generate more boost at the outlet to reach the same target. This causes the compressor outlet temp to rise which causes more pressure to be demanded. And on and on and on.
I didn't do any testing for 91 only but would imagine these intercoolers would have more value there since lower IATs will get you significantly more knock protection.
Original post... http://www.n54tech.com/forums/showthread.php?t=16893