I would bet that this would perform similarly to a regular 70mm TP, but would have different drone characteristics.

 

Gernby,
thanks for taking the time to write all of this. I truly appreciate it. One thing I wonder, will it hurt any performance to run 70mm HFC with 63mm exhaust?

 

what sort of characteristics?

 

I didn't know it at the time of this thread, but I later found that every change in pipe diameter does change the shape of the torque curve. The increase in diameter at the header flange will cause an increase in torque at some RPM, and the decrease in diameter at the TP / exhaust flange would cause a decrease in torque at some RPM. The same occurs from the resonator and mufflers. That's half the reason why torque curves have dips and valeys. Intakes are to blame for the other half.

BTW, I'm looking for a manufacturer now for the exhaust system that took me over a year to design (officially patent pending). It totally eliminates every issue discussed in this thread.

 

what sort of characteristics?
[/quote]

Drone is caused by the resonant characteristics of the whole exhaust system. If you try an exhaust system that is typically known for large amounts of drone with all different combinations of header, HFC, and TP sizes, you'll find that some drone much more than others. Basically, every thread that discusses which exhaust drones or not really needs to be specific about which header and TP / HFC the exhaust is mated to.

 

BTW, my exhaust literally / technically eliminates drone AND has a nearly perfectly flat torque curve from 3600 RPMs with everything else stock while also encorporating an HFC. It also provides equal peak power and torque than a 3" straight single with even better mid-range. In my 10 years on this forum, I've not seen any information or marketing that even tries to claim what I've achieved, so I firmly believe I have the best exhaust system ever bolted to an S2000 at any cost.

 

definitely looking forward to seeing your exhaust on the market!

 

Me too, but there's a good chance that it won't ever go into production for the S2000. My patent is not S2000 specific, so the S2000 might not be the right platform to start with.

 

Gernby-
I hope this doesn't open the drone can of worms too big but... I have a stock headr,, berk 63 tp and evs ssp 70mm single exhaust. I'm picking up a berk 70mm tp very soon for performance gains. Do you think the drone wil increase or decrease?

Thanks for posting your findings

 

I don't know enough about the exhaust you have to give an opinion about what will happen to drone. It might get worse or better.