Custom Y-Pipe/hfcs

[LineItUp]

Hey guys,

Once the wallet recovers from Christmas/Uprev etc I'm looking at getting my awful compliance cats (which are different! and also different lengths... great) and cheap ebay y-pipe replaced with a custom setup.

I was looking at 2x 2.5 inch metal cats (remember I have Uprev, so check engine lights aren't an issue), would I be better going for a single 3 inch cat after the two pipes merge?

Has anyone gone down this route?

[SMOKEYV35]

i think the 2 hi flow cats will flow better than a single larger diameter cat.

If you think about it, 2x2.5 is 5" of area - where as a single 3" is.....3" of area.

Also - the exhausts hang very low to begin with. A center mounted cat after the Y-pipe would punish your ground clearance significantly.

[sonicii]

If you think about it, 2x2.5 is 5" of area - where as a single 3" is.....3" of area.

Umm. No. 2x2.5in diameter pipes do not have the flow of one 5in diameter pipe.

Remember pi x R squared. So you will need 4x 2.5in pipes to equal 1 x 5in pipe.

[SMOKEYV35]

groan.

righto - so 2 x 2.5 inch pipes will be 8.86 square inches vs one 3 inch pipe which has a pipe area of 6.49 square inches - so even though i'm not a maths geek - the theory is sound.

http://www.exhaustvi...-pipe-diameter/

(the above calculations have taken into account the gauge of steel used in the piping so use I/D measurements)

Edited January 8, 2013 by SMOKEYC34