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Old 11-19-2015, 02:23 PM   #3 (permalink)
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I'm looking forward to what you come up with, Tim. The best I can recall from what I know about small block Chevy engines:

-Decreasing tube diameter increases low-rpm exhaust speed, which in turn helps low-end torque through more efficient cylinder scavenging. This *may* lower upper rpm power, but how bad could it be on a 1.0?

-Longtubes are better than shorty or block hugger headers for low-rpm situations (towing, economy).

-Thicker material and/or header wrap will keep heat inside the collector tubes, keeping exhaust speed up for better scavenging. This is for all rpms.

-Port match!

All dyno test I have seen are at WOT. Since we rarely go past 1/2 - 2/3 throttle for short periods and spend a lot of time at part-throttle, this seems to indicate smaller tubes than usual? I think you could go down to ~1" on the collector tubes, since each cylinder is only 0.33 liters of displacement, versus 0.713 liters/cylinder on a 350 SBC.

Remember, thank a fellow EM'er for a helpful post!!!
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Past threads:
ZX2 modding thread
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ZX2 Aerodynamics: Shooting for 0.15 Cd
ZX2 coast-down testing for Cd & Crr
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