Originally Posted by Red__Zed

same principle applies to posting numbers that don't show losses.


FWIW, the IP dyno showed losses with that exhaust on both FG2s I saw run it, but that is not really relevant here.


For the curious, the 370z substantially benefits from running a crossover of some sort. Almost every aftermarket exhaust that shows gains has one, and that is honestly where they get most of their gains.

cylinder banks on the VHR look like:
135
246

with a 123456 firing order. The alternating pulses are ideal for a crossover exhaust, and can get funky flow characteristics if routed to a single pipe. These of course can be minimized by bring the join point farther back.






The backpressure issue is a little misunderstood by most. The engine doesn't so much need backpressure, at the risk of low end torque, as it experiences bad flow characteristics generated by the exhaust gases cooling en route.

You basically want zero backpressure from the collector back, coupled with maximum flow(not actually implementable, but not hard to get close). The header design does need to generate backpressure, as well as provide sufficient velocity that the system does not back up under overlap (won't ever happen at high rpms, will happen at low)


dual 3" is either going to create an eddy at the header output/cat/tp output, or require running a non-optimal header design (at best, a staged header diameter)


Vizard's numbers say the Z with full boltons needs about 720CFM of exhaust flow to prevent restriction. A single 3" pipe flows over 1000CFM, which means that it is in no way contributing to increased restriction, and any issues are in your muffler. 2x2.5 offers over 2000CFM of flow....

Any gains that come from different exhaust designs are mostly due to removing restrictions (cats, muffler), or tuning of exhaust pulses, not from increasing pipe diameter. Increasing pipe diameter is mostly likely to create funky flow characteristics due to either messing with the header piping, or creating eddies...as well as allowing exhaust gas to cool and back up.

Originally Posted by awkwardturtle

It's called using common sense... something that is clearly in short supply these days. If you think Go-Power, a reputable company, is falsifying a 4 whp gain, suit yourself bud.