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Did a bit of a search, and it seems that 4-2-1 headers have better ground clearance, and better mid range, and that 4-1 is focused on top end.

It seems the MX-5 1.8 (no VVT) has great top end power already, but shocking mid/lows.

I'm basically looking at replacing my header, but I can't figure out which to choose. If I put my foot down flat on a mildly wet/slippery surface, the wheels just grab right away, but then they spin at 5000rpm+ Would good quality 4-1 headers compound this, making the car slow below 4000 and really nice above 5000rpm?

I feel like I want 4-1 for track and 4-2-1 for street.

With good 4-1's there should be no appreciable loss in power down low-mid maybe negligible gain with all your gains made up top where as, as you said 4-2-1's focus on low to mid range.

If your happy with power up top look into for 4-2-1's

Is this going on a stock exhaust? Whats your current setup like?

Jono.

I have a 2.5 inch system (I think? off an SE, mazdaspeed) which an exhaust place is going to chop up, and reweld to fit my NB8A.
I'm going to hold off on that for a bit until I figure out the headers I want, and whether to use the SE cat, the NB8A cat, or another cat.

I'd just use whatever car has the largest cells (ie: lowest Cells per inch)

When I had the high flow fitted to mine the car became noticably louder under load, or at revs, the note changed to be less refined, and the exhaust started to blacken heaps.
It also pops and crackles a bit.


I can't remember what cell count mine is, but each cell is about the size of a maccas straw, the stock ones are about the size of a toothpick.

How does one figure out the cell count?
Can't seem to see it written..

22Silver wrote:I feel like I want 4-1 for track and 4-2-1 for street.

You got it. Racing Beat is probably one of the best 4-1s (as I have) and Maruha is it? best 4-2-1.

mazmad wrote:

22Silver wrote:I feel like I want 4-1 for track and 4-2-1 for street.

You got it. Racing Beat is probably one of the best 4-1s (as I have) and Maruha is it? best 4-2-1.

The Jackson Racing design (which has been ripped off by OBX and some other clone manufacturers) is also a great design for 4-2-1 header - nice collectors and great flow, especially when you can get a set for under $300 in mild steel.

4-2-1 is the choice for street driving, generally speaking.

22Silver wrote:How does one figure out the cell count?
Can't seem to see it written..

Either google in the case of OEM ones, you might find something.

But if you're buying new it should say so on the specs.