^ So then you don't agree, because I'm arguing the point you just made, and you just agreed with the guy arguing against that point.

No, I was arguing against the point where you said no exhaust producer would fake those gains. I gave a reason why they would do it. There's a big difference between why a manufacturer would do it and whether it should be believed.

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.

Motordyne mentioned some of those same things in the reasoning for the design of their upcoming exhaust :tup:

Are you kidding me? lol

Look a the dyno. It shows almost no or negligible gains throughout the majority of the revs. You act like I put up a dyno where the car gained 30 whp and then believed it to be credible.

I didn't say anything about that specific dyno, I barely even looked at that one. I was just talking about in general.

so, if gains are believable, the default is to believe the manufacturer completely?

Hell yeah! Buy up those 60+whp chips on eBay!

I'll order two just to be safe. No reason they can't be stacked as long as I run an extra battery, right?

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.

lots of companies do it. In fact, every car company I've ever seen has done it at one point...including IP.

But seriously, it is not relevant to the thread. We aren't talking K20s here...they have forums for that:rolleyes:

besides, mal-intent aside, runs weren't done on the same day, and they compared max runs. They're useless

I've been running a single 3" for ~2 years with good results... 297whp NA with uprev tune and stillen intakes, stillen shorties, straight pipe and single burn's stainless muffler... you can hear it on youtube on my 'travis370z' account... sounds great IMO

here

Sound evil!!!