Looking for a thread which I thought was in advanced tech?

Tried the search, and even listed history in this forum - still no luck.

I'm pretty sure I read about this comparison here? If not shoot me, and
let's start a discussion.

When and why to use an H configuration over an X configuration.

Quick thought: H-pipe does it's job at low RPM. X pipe has a smoother
flow ( due to the junction angle) to equalize pressure between banks more
effectively at higher RPM (higher velocity exhaust gas) to
improve cylinder filling.

Educate, or point me to the post please and thanks.

 

I know that an H-pipe will give you a deeper sound than the X-pipe will. The X-pipe will give you better gains than the H-pipe though.

 

Is there data to support these statements? I'd be really interested in seeing it. Just interested where this comes from.

 

ive seen a couple dyno tests that showed the x-pipe was worth a small amount of extra power in the upper rpms.

i went with an h-pipe because i prefer the sound, and i dont really miss the 5-10hp.

 

data? well a few buddies have X pipes and one has an H pipe. dyno tests have proven the X pipe over the H pipe but as far as sound goes the H pipe is deeper.

 

In addition to my original question, is there a simplified formula to calculate
flow of a tube based on:

Engine RPM, displacement, VE%, pressure, etc?

Just wondering how to effectively calculate the minimum tube diameters for
intake and exhaust flow.

P.S. I don' t mean volume of a cylinder.

 

the less 'turns' the exhaust has to make = the more power will be made. thats pretty simplified.

 

I disagree, that is EXTREMELY OVERSIMPLIFIED.


Information Available: Engine displacement (cubic inches)................638
. Rate BPH............................................... ..............250
Full load RPM............................................... ....2200
Asperation type.............................................. ......T
Cycle............................................. ...........................4
Exhaust flow rate (CFM)*...............................1650
@ (F)............................................... ....................1000
Silencer inlet size (inch).........................................6
Level of silencing.....................................200 Level

Exhaust Gas Velocity = 1650 = 8,405 ft/min
.1963

The Pressure Drop = 9 inches of Water (using Pressure Drop Graph).

*If the exhaust flow rate is not available, it can be approximated by the following equation:

CFM = Engine Displ (cu in) x Full Load RPM x Eff x (Exh Temp F + 460)
C x 941760

CFM = exhaust flow rate in cubic feet per minute
Efficiency = .85 for naturally aspirated engines
Efficiency = 1.4 for turbo-charged engines
Efficiency = 1.2 for engines with scavenging blower
C = 1 for two-cycle engine C = 2 for four-cycle engine

If exhaust temperature is not available, use:
T = 1200F for gasoline engine
T = 900F for diesel engine


Does anyone know a formula to find the proper diameter exhaust pipe to handle
exhaust flow when given at a minimum:

Displacement
RPM
VE%

 

go ahead and throw your numbers together. the dyno doesn't lie about numbers.

 

Is there a rule of thumb for how far back to place the X or Y from the collector?

Some old timer sayed to spray paint the area and to look for the hot spot.

 

HotRod just had an article saying that the paint burning thing is completely wrong. They also found that 18" of pipe provided them with optimum power levels. However that was as far as an "exhaust system" went. Its probably completly different for a real system.

 

The painting method is not accurate. There are formulas to calculate length
of the pipes according to RPM, valve timing, etc.

I have a book which explains this formula. I'll skim through and try to find it
for you tomorrow night.

As for the placement, I CLEARLY remember discussing this subject in Advanced
Tech., yet I can't find the thread!

My last response was, placing the H/X closer to the collectors would probably
have more effect because the pressure pulses are stronger near the collector,
rather than downstream.

I don't recall any replies to confirm my theory.

In any case, TTT. Still looking for some answers to my Q

 

I havent been on the board for a couple of years but Im putting my ride together again.

Its a LT4 396 with hookers and I am fabricating true dual 3in to the rear.
I have the BMR tube crossbrace with a bend for clearance, I thought of placeing the X pipe there. I wonder if It will be to far away or not?

I have 300 cfm heads and RPM around 6500

 

2.5" duals = 3.5" catback
3" duals = 4" catback.

as far as all those numbers, its just exhaust! try something and if it doesn't work, change it.

 

from what ive seen, it seems most pros keep the X or H as close to the header as possible. for example, take a look at http://www.drgas.com/ nascar and hooters procup exhaust systems, whether they use the X or H, its right after the headers. im guessing the scavenging effect is probably stonger when its closer.