Contour Enthusiasts Group Archives Forums Modifications Zetec Maintenance Terry:Zetec Header????

Ok, are they for two completely different directions when it comes to performance? I am not too sure, just curious.

Headers,if designed correctly,should assist the 'extractor' effect by using the the firing cylinder 'pluses' to give a depression in the primary pipe just before the next cylinder exhausts,improving the 'scavange' improves the cylinder filling.A tubo does not want 'pulses',it needs a smooth flow of gas into and past the turbine blades to maintain speed.

Thanks for the insight Terry. I guess I will wait until the headers are developed to make a decision if I want to go all motor, or forced induction

Prediction: the hybrid electric car of the future will use an exhaust turbine to run a second electric generator.

If you think that's funky... check out this . That could be the alternative.

i heard something about 4-1 headers are better for top end and that 4-2-1 headers being better for low end torque, which our cars need badly. wouldn't it make more sense to go that route? any truth to this?

Depending on state of tune there are two types of header design.Either for 'independance' or 'interference' of engine pulses to aid extractor effect.Rembember headers are like camshafts,they are a compromise and only operate within certian rev ranges to give optimum power etc...as a cam.

in layman's terms?

4 to 1 is best for all round performance.As you increase the size/dia of the primary pipe you move the max torque further up the rpm range,it does not increase it just moves it to higher rpm.Example a 16V 2.0 dohc 'motor' in comp trim may make the 7000-9200 rpm range with primarys of say 2"OD and 28-30" long,for road use that same engine will only need 1 3/4" OD @ 38" long.Always rembember that with headers,whats gained at the top is lost at the bottom and vice-versa......

so you're saying a 4 into 1 won't improve low end anything, it will make it worse and only increase top end?

No,I said to move the torque peak up the rev range you need bigger dia primarys that are shorter.To have the torque at the lower end of the rev range you need smaller dia primaries that are longer...check the 'example' dimensions I've given.