I have seen various headers, most have 2 inch inside diameters although there is at least one that is 1.5 inches. Does anybody know the inner diameter of the stock headers pipes (not the collector but the 4 tubes)

The reason I ask is that too big of an opening hurts torque and the XB does not have extra to lose.

I have also heard that the 4-2-1 is better than the 4-1 but how much because the 4-2-1 seems to be more expensive most of the time.

I know the header flows more air and at high rpm's it's definitely going to breath better but does it hurt the low end at all?

Any change in gas mileage with a header?

 

with a header you'll improve your fuel economy along with a heavier foot the header goes great with your choice of axle back muffler

from what i heard the 4-2-1 is great for the low to mid and the 4-1 is great at the mid to high end of the rpm range

free'er flower exhuast= improved fuel economy just as long as you keep your foot out of it + you should get either the K&N drop in air filter(33-2211) or a short ram intake of your choice

 

I have the exhaust and the K&N with the snorkel removed so it's feeling pretty peppy already.

I figure the header will be happenin' about christmas time along with some 15mm rear hub spacers.

I have tried shifting when it just crests 3100rpm so it drops back to 2000 to see what happens with gas mileage-but it just sounds and accelerates so good up there closer to 3800-I can live with 30mpg

 

I got 4 hp with the MMW 4-2-1 Stainless header. The dyno shows that it improved the mid & upper range HP & TQ. It suffered at the low end. I'll try to find my dyno sheet.

 

Blue line is before header. You can see the lower end didnt do so well, but overall i got about 4 hp outta it. The header looks nice too :D

BTW I've got an auto. Manual tranny will probably see better numbers.

 

Going by butt dyno how does it feel?

 

I feel it kick in around 4k rpms

Pretty much when the dynograph says so.

If you're asking if I can feel a difference from stock... I'd say a little bit. About 4hp worth :D

I can tell a difference tho'.

I got my header for pretty cheap.

When i'm rolling up to a red light that I know is about to turn green i'll put it in 1st and keep my rpms high, and when it turns green, if I punch it I can really feel the improvement then.
Am I making any sense

 

Hahaha, I thought that I was the only one that put it down to 1 when coming up to a red light that I know is about to turn green... lol... I do that all the time... I makes me feel a little bit faster... haha

 

So basically the header isn't needed unless you go turbo or supercharger? Good to know. I'm just glad the stock header is so well designed.

 

Yea I guess. 4hp is 4 up though. Add an intake & exhaust you probably get a couple more. After I did the dyno I got the ram air scoop for my volant and i think i got a little bit more hp. My mpg went up too. I want to get an exhaust next and see what it does.
The hp adds up here and there.