H Pipe vs X Pipe vs Y Pipe

[Rapid Red]

I get what you're saying, and for that, the details will matter. Fortunately, exhaust flow is a series of pulses, so the left and right banks aren't going to be at peak flow at the same time. Even if they did, you'd only effectively need about 40% more pipe diameter in the merged section.

FWIW, the catalytic converter in my other post was rated to flow 600 cfm at about 1 psi pressure drop. Or only about a 2.5% or so loss of peak power and smaller sacrifices in torque everywhere below that.



You would still get the benefit from essentially putting the mufflers in parallel for less pressure drop. But . . .



On a 90° V8 with a flat-plane crankshaft and proper header design, maybe not (though the mufflers in parallel matter would still be present). Think 3.0 liter Cosworth DFV here, not the recent GT350 here.

With a crossplane crank, the firing orders for 90° V8 engines put two cylinders in the same bank firing in sequence, first on one side, and later on the other. This dumps a combined flow from two cylinders down each pipe, in side to side alternating fashion. This is where your classic V8 rumble is coming from. But this also means you get periods of somewhat higher backpressure some of the time. An X-pipe merges the flows and splits them more equally going rearward to the mufflers, whose resistance is also dependent on exhaust gas flow.

I got pretty deep into this. Here's a rough approximation of how it plots up. The big widely spaced peaks are your low-frequency V8 rumble, and the red trace is what a fully merging X-pipe (or pair of Y's, your choice) would end up giving you. The smoother, higher frequency appearance of the X-trace is obvious.

I'm not discounting that at all. I was more than pleasantly surprised at how my effort above turned out.


Norm

Good post Norm !!

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[GregO]

Norm

I respect your post and insight.
I understand the timeless X-pipe H-pipe exhaust pulse arguments.
Everyone can get deep in the weeds here but for me personally I’ve moved away from the idea of X-pipe pulse scavenging (IMO the header collector creates pulse scavenging if designed properly) and moved more towards the effects of exhaust gas boundary layer creating flow resistance.

 

[Rapid Red]

As in stepped tubes, pirmary being the largest?

 

[WildHorse]

As in stepped tubes, pirmary being the largest?

I think step tubes are gimmicky, and only needed where real estate is a issue. I think the coyotes firing order and exhaust cam timing does more for scavenging than an x-pipe. X-pipe on the single non vct cam with the classic 1-8-4-3-6-5-7-2 firing order works a lot better.

 

[Jaymar]

If you put a y-pipe on a GT, something has gone wrong

Somewhere in America, I'd like to believe that an Ecoboost owner read a thread about increasing the rasp and gaining top end power and ordered an X-pipe only to realize the errors of his ways while under the car.

 

[Mike Pfeifer]

What brand of H Pipe was this that was not fully open between the crossover?

 

[GregO]

Y-Pipe done up proper with merger collectors in and out.
I don’t make this stuff up.
Looks a bit like the Magnaflow Y-Pipe muffler that yielded a faster 1/4 mile.

 

[Super-Genius]

 

[DrumReaper]

Is there an option for no pipe?

 

[Rapid Red]

Good detective work

That is pathetic, the perfect example of the good deal.

A reason I look at a supplier like Roush for these kind of parts. One has a much better chance of getting what they pay for.

The X pipe for me, design wise has better flow characteristics . Think path of least resistance .

 

[Norm Peterson]

I think step tubes are gimmicky, and only needed where real estate is a issue.

Like many aspects of automotive tuning, "it depends".

The Header Test (hotrod.com)

I think the coyotes firing order and exhaust cam timing does more for scavenging than an x-pipe. X-pipe on the single non vct cam with the classic 1-8-4-3-6-5-7-2 firing order works a lot better.

X vs H is about instantaneous flow and pressure conditions, not just scavenging.


If you're paying close enough attention standing behind an H-piped crossplane V8 at idle, you can hear the rumble alternate from bank to bank. You can see that in the plot I posted earlier. Maybe think stereo (H) vs two speakers tied to the output of a mono amplifier (X) here . . .


Norm

 

[DrumReaper]

Don’t forget side pipes, as in the 2012-13 Boss 302 side pipes. Best sounding stock exhaust ever.

 

[Norm Peterson]

Real side pipes . . .

Norm

 

[Blithe16]

Can be yours too!

https://www.steeda.com/ford-racing-mustang-side-exit-exhaust-system-2015-gt-161-m-5220-m8.html

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