Exhaust crossover question

[jbgroby]

I saw this on ebay as a selling point to a 60-66 truck What is the purpose of having a crossover like this is you ran duals?

[Captainfab]

The 'H' pipe like that helps tone down the exhaust noise slightly and is also supposed to help in the scavenging of exhaust gases from the cylinders.

[markeb01]

A couple of years ago I had a new exhaust system installed that duplicated the worn out version, except this time I had them add the H pipe, specifically for noise reduction. The difference was substantial. Without the H pipe the mufflers really barked when the throttle was cracked, now they sound more like a 60's Corvette. The pipe is also credited with building more low end torque, but on a street engine like mine I really couldn't detect any perceivable difference.

[Nix62]

Originally Posted by markeb01

The pipe is also credited with building more low end torque, but on a street engine like mine I really couldn't detect any perceivable difference.

That's what I understand happens with twin cylinder motorcycles.......I added an H pipe to a Chinese boxer twin bike I have, did make a bit of a difference in the mid range.

[jbgroby]

Ok Thanks I'll look into that also when I "mufflerize". I wonder just how much lowend torque we could possible want with the 305 already, its not like we don't have enough.

[vin63]

Originally Posted by jbgroby

I saw this on ebay as a selling point to a 60-66 truck What is the purpose of having a crossover like this is you ran duals?

The H-pipe or crossover pipe was/is mainly used to reduce exhaust noise or drone since it causes turbulence/reduces velocity in the exhaust flow. There are a lot of different theories about its benefits, but like a lot of advertised performance increases, often they are realized at upper RPMs or WOT (which a street driven vehicle does not see that much time). From my experience from countless dyno sessions and flowbench testing, the scavenging affects of an H-pipe or crossover really only happens at WOT for extended periods, such as in oval track racing, etc.

[LostMy65]

I could of just asked my question by starting a new thread.
But instead I typed 'exhaust crossover' and found this thread.
Love these forums.

[terbronco7]

I recently had new exhaust put on mine, at first it was 3 inch true duals with flowmater 50 series, sounded great but I was getting a baffle effect (kinda like going back and forth between pipes, added the h pipe and now more even flow and better sound, as far as performance gains really have not noticed but the sound is better. and no baffle.

['65 chevy lover]

Originally Posted by Captainfab

The 'H' pipe like that helps tone down the exhaust noise slightly and is also supposed to help in the scavenging of exhaust gases from the cylinders.

This is the main advantage I have heard about along with, increased torque.

[LostMy65]

Here is one BadProStreet Post:
.

Originally Posted by 1Bad62Pro/Street

The h-pipe is used to help equal the back pressure on both sides of the exhaust

The x-pipe is the same but is much better at equalizing the pressure.

There's a big misconception about the intended function of the X-Pipe versus the H-Pipe.

The H-Pipe does balance out the pressures and slightly helps start the scavange effect on the next exhaust pulse. But it's most effective use when properly placed and sized is for it's tuning function. Sound waves enter the tube changing to a specific frequency that was found to be a problem. Prehaps a droaning noise at highway speeds. With the correct placement in the system and correct inside diameter, sound waves entering the tub shift to the problem frequency. When like frequencies collide, they cancel.

The power comes from opening up the exhaust. A slight add comes from the scavenge effect but ultimately the H-pipe is to counter the noise from opening up the exhaust.

The X-Pipe on the other hand is more effective in sound cancellation. By forcing the exhaust streams to collide, some sound frequencies are cancelled. (In a much larger range than the H-Pipe.) You would think the two exhaust paths colliding would cause more backpressure. In reality, the exhaust flow mass follows the path down the same side. (Bending around the inside of the X.)

The sound frequencies cross paths of the exhaust. Cancellation of like frequencies occur even though the mass of the exhaust flow hits and deflects into the same side pipe.

This is all assuming WOT condition or near full mass flow rate. At lower flow rate, the X-pipe does make the low frequency idle sound a little irratic. Something desireable in a Mustang or Corvette. But a Cadillac wouldn't care for it.

This is used as a band aid in tuning high performance vehicles to meet the legal pass-by requirements. Something that is difficult to do on a car like the Viper Roadster or Corvette.

The X-pipe idea was tried on the Viper roadster but ultimately they used the H-pipe design. If you've ever seen the OE system on a Viper Roadster, the exhaust exits the headers, enters an un-Godly hot converter that I have seen damage body panels and melt basalt packing back into a crystal solid. It runs down the side of the car into the main muffler and then to the rear axle. Then it turns to the opposite side and hits the H-pipe which is over the axle and exits out before the axle on the opposite side of the car. If it were not for the Pass-By requirements, this would be an easy design.

Designs like this and the birth of the X-pipe all stem from the need to meet the requirement. Again, the X-pipe just allows the exhaust to be opened up more while tuning out undesireable frequencies. It's ability to "add" power is a debate most drawn up by aftermarket marketing managers. Everyone loves a gadget.

[1Bad62Pro/Street]

Yea Buddy.. LostMy65

X-pipe and H-pipes synchronize the balance of the exhaust pulses from each bank of cylinders based on firing order which increases velocity and scavenging from each cylinder. Most people agree that X-pipes are better at improving performance than H-pipes, especially at the top end. However, H-pipes tend to have a deeper sound than x-pipe equipped vehicles and generally build power down low. These are general claims and your engine and exhaust combination could have different results.

X Pipe vs H Pipe - Summit Racing Quick Flicks
https://www.youtube.com/watch?v=Y0Va3sDhqwI




SVTPerformance.com 2012 Mustang GT - X-Pipe and H-Pipe Test
https://www.youtube.com/watch?v=bU6nZnAgNsI

X-Pipe vs H-Pipe vs Factory Pipe - Ford Mustang V6 - Exhaust Flow Simulation
https://www.youtube.com/watch?v=2crCWF5cmLk