Jump to content
HybridZ

H-Pipe vs. X pipe.


Recommended Posts

*posted in V8 forum due to true dual exhaust being inapplicable in L6 forum*

 

As I understand it, the purpose of a cross over pipe is to equalize the exhaust flow between 2 pipes in a dual exhaust system, attinuate residual exhaust decibles, and create a vacuum to help draw the exsaust from each header. Without a cross over, be-it X or H pipe, you will notice 'chugging' or surging in your exhaust, correct?

 

Which is more effective in treating this flaw?

Link to comment
Share on other sites

THE (X) BY FAR is more effective, the (H) may equalize the pressure to a great extent but the (X) blends and exqualizes the flow,

http://www.uucmotorwerks.com/html_product/sue462/backpressuretorquemyth.htm

 

whats the differance?

lets say for the example the exhaust pulse is a quart to water moving at several hundred feet per second, but unlike water it can be compressed,since the exhaust pipe inside dia. is set the length of the pulse or slug of exhaust exiting the engine every 90 degrees of rotation (v8) has inertia/energy/mass, if it passes a right angle low pressure exit point, at first it flows into both routes but as the mass passes the opening a slight negetive pressure forms and it reverses and the flow changes, put a vacuume gauge on the (h) and it vibrates, wildly.

install an (X) and the flow from both sources is FORCED to BLEND, line up, equalize and BOTH sections of the up stream flow benefit from the

as each inertia/energy/mass, and slight negetive pressure that forms, but its far more equalized.

put another way if one side was pumping out dark green water and one side was pumping clear, an (H) would have dark green exiting one side and light green exiting the other, an (X) would have both sides an equal, slightly lighter green flow .now at low rpms , or with a smaller than ideal pipe dia. thats no big deal, but at high rpms, BOTH the SCAVAGING of the cylinders your trying to inhances and the reduction of the restriction to flow tends to be better with the (X) put a vacuume gauge on the (X) and it vibrates. but not to nearly the same extent, and the changes in pressure reading remain more consistant

 

DON,T be thinking that either is a mandatory huge improvement, it may or may not help the power, the degree of restriction, displacement, compression ratio, cam timing and the efficiency of the headers has a good deal to do with your results, and sticking restrictive mufflers on past the (X) or (H) can effectively kill most of the potential benefits

 

wlk-40313.jpga second (H) behind an (X)goes a long way to destroy resonance

Link to comment
Share on other sites

Great read, GRUMPY. Can you explain how the cross-pipe in this picture helps equalize pressure? Maybe the collector connected to directly to siamese exhaust ports?

 

wlk-40313.jpg

Link to comment
Share on other sites

GRUMPY... How much do you know about "dual/dual" exhaust systems? By this I mean runing four separate pipes all the way to the back... only two cylinders per pipe. Any good designs available for "big cube" SBC's and/or BBC's?

 

FORCES... I'm sorry if this is hijacking. I just figured you'd be interested too.

Link to comment
Share on other sites

"How much do you know about "dual/dual" exhaust systems? By this I mean runing four separate pipes all the way to the back... only two cylinders per pipe. Any good designs available for "big cube" SBC's and/or BBC's?"

 

Ive only messed with that a few times, mostly on T-buckets, but in most cases it sounded good but didn,t produce the same potential power and it tended to make the tq curve very peaky

Link to comment
Share on other sites

DON,T be thinking that either is a mandatory huge improvement, it may or may not help the power, the degree of restriction, displacement, compression ratio, cam timing and the efficiency of the headers has a good deal to do with your results, and sticking restrictive mufflers on past the (X) or (H) can effectively kill most of the potential benefits

 

 

My main concern is the ambiguos sound of my exhaust. The pulse/ slug of exhaust sounds very similar to a small back-fire through the tail pipes...which kinda cought me off gaurd until I realized that the problem was un-equal exhaust pulses. As for as restrictive mufflers go, how could you lose the benefits if the X is before the muffler? I don't think that my mufflers are particularly resptrictive, but I am probably going to change my existing glass packs to perforated magnaflow mufflers.

Link to comment
Share on other sites

FORCES... My SBC 350 probably has an exhaust similar to yours. Mine has the shorty block huggers into glasspacks (I think) into 3" pipes straight back. It's loud and rumbling and it pops really loudly when I left of the gas after a good run... RRRRRR... POP POP POP POP POP POP POP POP!!! It's actually sort of fun sometimes:mrgreen: But I really want the most performance I can get and the noise does get to me every once-in-a-while. I'm sure there are timing and AFR issues adding to the situation too.

Link to comment
Share on other sites

*posted in V8 forum due to true dual exhaust being inapplicable in L6 forum*

 

My 64 Jaguar XKE is a straight 6 and runs true dual exaust. Two exaust manifolds, three cyl per manifold. Sounds great with dual glass packs, no crossover pipe.

 

The true dual exaust (also glass packs w/o crossover) on my 74 Nova does chug a lot at idle but gets quieter while cruising. Never sounds like it's backfiring, and just purrs when I decel.

Link to comment
Share on other sites

What about side pipes, there is no way you can "X" or "H" them so they are considered a true dual correct? so performance wise they are similar to the T-bucket exhaust Grumpy mentions above and not producing all the potential power a dual with an "X" pipe would, but I love the sound and look of them though.

Thanks,

Greg

Link to comment
Share on other sites

Funny you should mention old pickups......as I had a built 350 in my '67 Chevy short-wide pickup with Doug Thorley headers, glass packs and exited right infront of the rear tires. I ran true dual with no connector and had the raspy, pop-pop-pop deceleration noise. Once I added in an "H pipe" (not an X), it improved driveablity, made the exhaust sound much smoother and quieter and got ride of interior noise. I was so glad I did it. I recommend some sort of crossover, just for the benefits. Just my experience.

Link to comment
Share on other sites

You can see my complete system here, with description and photos:

http://alteredz.com/exhaust.htm

 

With the X-pipe, and the mufflers in the back sounds very even - not like a typical uneven sounding V8 at all, past 2000 rpm or so. It actually sounds very European if you ask me. It is a bit loud for my tastes at idle, but only really old snotty people think it's too loud.

Link to comment
Share on other sites

Nice work. With the amount of fab it took to route both tail pipes in the stock location, why didnt you replace the fuel tank with a cell, or get a tank that would be centered so you could run a single tail pipe on each side?

 

Realize that this was a long time ago that this was done, relative to HybridZ's birth, etc. I didn't want to have a "race car", and wanted to keep the stock tank to not have to deal with the issues of filling the fuel cell, etc. I thought about using another tank that would allow a muffler on each side, but just got lazy about finding one that would work and have enough capacity. This way, the tank is no smaller than stock, and I have two HUGE mufflers to handle flow and noise. But all the bends to get to the mufflers may well have hurt the flow too... Always a compromise.

 

Since doing this, the fuel cell has been done many times in these cars, and I'd probably go that way if I did it over. I'd probably do a 2.5 into 3" single too, or mufflers in the tunnel, etc. etc.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...