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Mazda 2.3


zerorace
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If it did fit I'd want to workout the flow speeds through the valve..putting to bigger a valve in slows the air speed down at lower revs..This in turn will cause the inevitable fuel drop out, meaning you will have to richer the mixture.

I will assume you have a zetec, a 2.0 head flows 100 HP per ltr. No need for bigger valve unless your spinning beyond red line. Zetec ST170 has larger valves but tests prove not needed.

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I don't know what tests you are referring to. Sure the inlets are larger on the ST but the exhausts and exhaust ports are the same. Useful work can thus be done on both heads, valves and ports especially on the exhaust side. That's not to say that work on the inlet side and the chambers is not useful. And I still don't have 100bhp per litre.

 

Nigel

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Nigel

 

Flow bench tests on a 2.0 zetec using standard valves, all be it modified, have proven very little work is required to achieve.airflow that allows 200 bhp plus..and it's been proven on a dyno. The 170 head was done in same manner and showed less.air flow.at lower lifts, BUT, more at higher rpms. This indicated that the larger valves stalled the air thus slowing it down.

I have seen independent tests by various well respected companies that all show same thing..Rick Wood..Northampton Motorsport..et al..

The debate is good as it proves how good the head is to start with and how little work and therefore cost is needed to improve it. Just by putting in bigger valves on a head will not improve it.un less the ports and shape is modified to suit and the engine Wi be able to use the airflow, general at higher rpms.

I have build a few of these zetec now including my own 1800cc and I can assure you, built right as a package and over 100bhp is very easy to achieve. More power means more revs I prefer to build for torque which sometimes sacrifices ultimate bhp, but can make for a quicker package. As with all modified engines, get the components working together and reap the rewards.

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