Exhaust size ?????????

[Anonymous]

Hey Guys,, I got a 250 Crossflow with mild work done to it,,, I was just wondering what exhuast size I should run,,, Im currently Running a 2-1/4 inch with a sports muffler all the way through,,, If I go bigger will this give me more HP.


Thanks

 

[aussie7mains]

Heres goes, Ive derived a formula for pipe restriction. (rough)
(sorry for non metrics)
2 inch is good for about 150bhp
2.25 good for about 200
2.5 good for 250
3 inch is good for about 350
For a given flow:- 3inch is about half as restrictive as a 2.5.
2.5 is about half as restrictive as 2.25
and so on.
So if your 250 is about 200bhp, then 2.25 is fine. (Probably lower than this)
BTW 4litre OHCs have 2.5 stock to the cat, then 2.25 back from there.
A7m

 

[Anonymous]

my falcon has 201.3hp @wheels so whats that at the engine i,m running a 2 1/2 inch exhust you think i should go bigger

 

[aussie7mains]

If your running a manual tranny in direct drive, then around 230 NET installed BHP.
If its auto, then higher, say 240.
So my rule of thumb is somewhere near?
A7m

 

[Anonymous]

running tricked up auto

 

[xctasy]

Ew yukky. My 50 mm (2") pipe is way to small then. Funny thing is , the old hump still does flat 16's with passengers. The extractor set gets a free run to an EFI-spec pipe that becomes a smaller carby-spec pipe from the back muffler. Been the same way since we bought the old hump in 1995!The 130 kW or 175 flywheel hp I estimate I'm running happens in spite of this.

:idea: My LP gas XE sedan runs no plastic fuel tank, and I've been considering throwing two diagonal 2.25" Lukeys to exit out on the left side, with a couple of 2.25" pipes with no mufflers at all from the single 2.5" collector. Hope that liberates a few more "neddies".
Darn Watts linkage rains on the parade for a proper pre XD Falcon dual set up. Then the stupid spare tyre well on the right hangs down like a cow stomach or a munted haggis too. Not exactly as cool as a slammed V8 XR-XC with dual pipes hanging out like a wild wheelbarrow!

: Why couldn't we just have a Mustang Fox style Quadra shock a$$ end. Can't have wheel walked any worse than the Watts linkage, but at least you could shove a set of spunky pipes on it. That's why people like Falcon Utes and wagons. Room for proper GTHO-style pipes. The philosphy I have is Ricers can point there Howitzer fart tube at me, but I'd rather have two barrels pointing back at them.

.

:splat: