Mine's 1.5".
Wait.....wrong thread!
What's all this fussin and fightin? What does it matter the TB diameter? I thought this thread was about a best intake for the Zetec.
Well, my $3 on the topic would be a completely uninhibited flow of the coldest air possibleis ideal. Little/no resistance + coldest possible air = more performance. I think I remember reading Terry Haines sayin something about every 13degrees F you reduce the air intake temp is ~1hp??? So, you want to minimize resistance in the intake, all while insulating it and moving the actual inlet port as far away from a heat source (like say....the motor?) as possible. So ideal/best? No filter, just a tube straight up and away from the motor.
No, don't really do that.
Heck, I've got an intake tube for a ZX3 in my garage. You'll need a filter and a 3" silicone coupling to attach the MAF. It has an accordian tube right after the elbow at the TB. PM if you want it.
Now, I may have a Duratec now, but back in the day, I knew my way around that peppy 4 banger.
I had the CTA on my car and it gave some obvious gains. It's an easy kit to install, except my breather tube was melted to the valve cover and I had to whittle it off.
It took my dumb ass a little more than an hour to install it. Also, you have the 'Bling Bling Factor'. Chrome = secksi, and the CTA is all platted out with the finest in underhood blingage. It got many props while in my fly hooptie. If you're looking for mad performance-you might have to make something yourself; along the lines of that ZX2 posted above. I'd definitly relocate the battery and maybe the fusebox; although I don't know how much work it is to move the fuse box.
Thus putting the filter right behind the driver's side headlight; which can easily be removed for racing.
Anything else?
