1990 Toyota Corolla Headers and mileage

1990 TOYOTA COROLLA
90,000 MILES • 4 CYL • FWD • MANUAL
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JACKOLSON
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I'm working on a stock 4AF carb toyota engine, 1.6L 16valve

The first upgrade we did is we installed a 4-2-1 header and straight thru exhaust

4-2-1 design
primary pipes - 32" long 1.5" diameter (sequential pairing, 1-2 and 3-4)
secondary pipes - 22" long 1 5/8" diameter
short 2" collector
no cat, no resonator, no muffler - just straight thru exhaust pipe 2.5" diameter about 6' long
all are mild steel

after install, i had to dial a richer air fuel mix almost 1
1/2 turns more than the stock
now i know that lowers the mileage but is it normal?

the car runs great with peak torque coming in at about 3500 rpm then stays high until about 6000 rpm
i realize it has more top end power now but sometimes it bogs down when WOT @ 2nd gear only

any idea on this one please? thanks and more power
Oct 16, 2010 at 7:42 AM
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MMPRINCE4000
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Most likely it is too rich.

Headers alone will give you some power, but I would say MAYBE 2-3 hp.

Only way to get more power is to increase air into engine.

Camshafts, heads, or forced induction are traditional ways of doing this.
Oct 16, 2010 at 7:53 AM
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JACKOLSON
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thanks,

but one last thing, why does the engine bog down when at WOT particularly when using 2nd gear?

thanks again
Oct 16, 2010 at 8:39 AM
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MMPRINCE4000
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Other than timing, it would be a rich fuel mixture.
Oct 17, 2010 at 8:40 AM
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JACKOLSON
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[quote:90cc4ed7fd="mmprince4000"]Other than timing, it would be a rich fuel mixture.[/quote:90cc4ed7fd]

thanks, i heard that a gas analyzer can be used to determine the correct A/F ratio. what readings on the analyzer should i aim to get for a good A/F mix?

thanks and more power again
Oct 17, 2010 at 9:17 AM
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MMPRINCE4000
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You can use a wide band O2 sensor on a chassis dyno, that would give you AF ratio under load.

Generally under WOT you would want an AF ratio of 12.5-13.0.
Oct 18, 2010 at 8:29 AM
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JACKOLSON
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[quote:cfa1ca9dfe="mmprince4000"]You can use a wide band O2 sensor on a chassis dyno, that would give you AF ratio under load.

Generally under WOT you would want an AF ratio of 12.5-13.0.[/quote:cfa1ca9dfe]

Thanks...what should be the AF ratio when idle?
Oct 18, 2010 at 9:22 PM
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MMPRINCE4000
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ECM will try for a 14.6 AF ratio at idle.
Oct 19, 2010 at 8:50 AM
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