Forces Posted February 8, 2007 Share Posted February 8, 2007 *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? Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 8, 2007 Share Posted February 8, 2007 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 a second (H) behind an (X)goes a long way to destroy resonance Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 8, 2007 Share Posted February 8, 2007 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? Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 8, 2007 Share Posted February 8, 2007 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. Quote Link to comment Share on other sites More sharing options...
wheelman Posted February 8, 2007 Share Posted February 8, 2007 How much does the X or H pipe affect the volume of the sound produced by the dual exhaust? What impact will either have on reducing drone at middle RPMS? Wheelman Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 8, 2007 Share Posted February 8, 2007 this (above) requires this (below) from the header collectors Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 8, 2007 Share Posted February 8, 2007 "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 Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 8, 2007 Share Posted February 8, 2007 ^^^ Is this true even with properly designed/placed multiple X-pipes? ^^^ Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted February 8, 2007 Share Posted February 8, 2007 Im not sure what YOUR asking? most of those systems have two cylinders feed a (Y) then a single exhaust with no (H) or (X) just a single small muffler like a glass pack on each of the 4 individual runs Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 8, 2007 Share Posted February 8, 2007 ^^^ I'll post a graphic later tonight. A picture will explain my meaning better than words. Quote Link to comment Share on other sites More sharing options...
Forces Posted February 8, 2007 Author Share Posted February 8, 2007 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. Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted February 8, 2007 Share Posted February 8, 2007 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. Quote Link to comment Share on other sites More sharing options...
eec564 Posted February 8, 2007 Share Posted February 8, 2007 *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. Quote Link to comment Share on other sites More sharing options...
gvincent Posted February 9, 2007 Share Posted February 9, 2007 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 Quote Link to comment Share on other sites More sharing options...
Forces Posted February 9, 2007 Author Share Posted February 9, 2007 My buddy ran side pipes w/ glass packs on his mustang, and it had very similar symptoms. I hate my glass packs. I wouldn't recomend glass packs to anyone unless they are going on an old 70 something step side truck. Quote Link to comment Share on other sites More sharing options...
Savage42 Posted February 9, 2007 Share Posted February 9, 2007 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. Quote Link to comment Share on other sites More sharing options...
pparaska Posted February 9, 2007 Share Posted February 9, 2007 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. Quote Link to comment Share on other sites More sharing options...
Forces Posted February 9, 2007 Author Share Posted February 9, 2007 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? Quote Link to comment Share on other sites More sharing options...
pparaska Posted February 9, 2007 Share Posted February 9, 2007 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. Quote Link to comment Share on other sites More sharing options...
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