I’ve looked at the headers/manifolds available on the aftermarket for the 2ZZe-ge motor and it’s pretty obvious some people haven’t got a clue!

This motor is lacking in torque. It needs a 4-2-1 design to have any chance of addressing this trait. Even Toyota acknowledges this! Look at the std layout (v.2bular) here.

You can see they’ve brought cyl no.4 over to join cyl no.1, (std connections with a 1-3-4-2 firing order, then split the Cat pipe into two, to make a 4-2-1 design header/manifold. I remember being told the splitter in the Cat pipe was to heat up the gases before they reached the Cat, to help “light-off” and thus keep emissions down.

If that was the case, why didn’t they do this with the 1ZZ-fe motor?

Here, there is no attempt at creating a 4-2-1 layout, no splitter in the Cat pipe. Why? Because the 1ZZ-fe motor does not lack torque - at least not compared to the 2ZZ-ge. The use of these designs means there’s plenty of scope for real gains to be had with a header/manifold using the correct bores and merge collectors plus a good re-map to put the increased fuelling demand exactly where it’s needed.

My 4-2-1 design for the 2ZZ-ge uses a stepped primary. This keeps the gas-speed up at lower revs (and gas-speed is everything when it comes to torque).

Moving further up the rev-range, you need a larger diameter primary to cope with the increased gas-flow. If you used this one size, you would definitely damage mid-range torque.

I use race-style merge collectors on all of my header/manifold designs for maximum efficiency/flow. A wide-band Lambda boss is fitted for mapping purposes.

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