Topic: 4-2-1-2 exhaust

[ratranger]

This might be pointless, i.e. no benefits, but has anyone ever done what is basically a 4 into 2 pipe with a crossover or x pipe after the 4 into 2 merge?  The bike I'm working on will look better with a pipe on each side, and I'm leaning away from 4-4 because it doubles the muffler costs, and 4-1 would either leave a hanger unused which I would prefer to not cut off.  It's a slimline featherbed frame from norton.

[jgger]

79 CB, and others, has a 2 into one on each side. But the 650 exhaust is not compatible with the 750 engines. The 650 is straighter up than the 750, it is closer to the 500/550.  Look up a stock 79 650 picture to get a visual.

[carnivorous chicken]

Not sure I get this -- why not just a regular 4-2?

[scottly]

Here's an example of an aftermarket 4-2 exhaust on a 550; there are similar systems for 750s.

[ratranger]

Not sure I get this -- why not just a regular 4-2?

 I'm going to have to make my own pipes due to not using the stock frame.  I know V6 and V8 engines benefit from an X or H style crossover between the banks, and with inline 4s a 4-2-1 style has benefits.  So I was curious if anyone had ever messed with doing a setup on these with cylinders 1-2 and 3-4 paired with a crossover between them.  I also know that it might not be done for packaging reasons, cost, or it doesn't provide any benefits.  So mainly asking to see if anyone else had tried it.

[scottly]

I think there was an expensive 4-2-1 system that was touted to increase horsepower, but there was no proof? A 4-2 system will be much simpler for your application.

[ratranger]

I think there was an expensive 4-2-1 system that was touted to increase horsepower, but there was no proof? A 4-2 system will be much simpler for your application.

 Yeah, a basic 4-2 wouldn't be hard to do.  I know there are a few 4-1 systems that vary how the collector is done and a very few 4-2-1 systems available.  Most custom systems wil never see dyno testing and have little to no proof to back up claims.  It's not easy to quantify tiny gains.  Going stock to a decent aftermarket can have noticeable gains, but the difference between a 4-1 and a 4-2-1 might only be noticeable on a dyno.  I've seen exhaust shootouts for newer bikes that the variation between systems basically falls within the margin of error for the dyno. 

[Rayzerman]

Just for interests sake.... I recently acquired a '92 Yamaha XJ600S/Seca2 (Diversion in EU).  It has a 4-2 exhaust where the headers from 1-3, and 2-4 cross over each other and go into two mufflers.  Different for sure, but more or less an X......  just an idea in case you're thinking of building custom headers.........

[jgger]

Ray, I think i read someplace that a system like your Seca develops a more even or consistant " back pressure "  over a 1&2-3&4 system. Which is the purpose of a cross over i think. But I'll let the pros sort that out.

[ratranger]

Just for interests sake.... I recently acquired a '92 Yamaha XJ600S/Seca2 (Diversion in EU).  It has a 4-2 exhaust where the headers from 1-3, and 2-4 cross over each other and go into two mufflers.  Different for sure, but more or less an X......  just an idea in case you're thinking of building custom headers.........

I know a few bikes have had 1-2 and 3-4 merge with a crossover between 2-3 about a foot from the ports.  Most newer aftermarket systems are a 4-2-1 style.  The XS1100 had the "spaghetti" pipes aftermarket that merged 1-4 and 2-3.  Merging 1-3 and 2-4 is uncommon enough for me to assume there is no advantage.  I'm looking at the fairly standard way of having 1-2 and 3-4 merge.  I posted this mainly because I was wondering if there had been any 4-2 systems with a crossover after the merges.

[PeWe]

X-pipe has been up before.
Same company/person that sold the ignition Maxi dwell.

https://www.xpipe.org/

Bigger bore, higher compression are otherwise proven to increase the fun.  Followed by a cam, ported head etc.

[ratranger]

X-pipe has been up before.
Same company/person that sold the ignition Maxi dwell.

https://www.xpipe.org/

Bigger bore, higher compression are otherwise proven to increase the fun.  Followed by a cam, ported head etc.

 Interesting,  I hadn't seen them before.   Their power gain claim is hard to believe, especially with the MS paint looking "dynograph".  Also their merges remind me of the stamped factory merges.  But nice to see my thought process isn't completely out in left field.

 I have 836 pistons for the bike I'm building,  I plan on sending the head to cycle x for guides and porting.  I'm undecided on a cam as I don't want to give up midrange since I'll daily it.

[Rookster]

Dunstall made a system where the 4 down pipes terminated into a single pipe with an outlet on either side.


Scott

[PeWe]

 I have 836 pistons for the bike I'm building,  I plan on sending the head to cycle x for guides and porting.  I'm undecided on a cam as I don't want to give up midrange since I'll daily it.

Check with forum member MRieck about head work as porting.
Add bigger in valves as 33.5mm together with new springs.

With higher compression, a hotter cam will not reduce low or midrange.

Unless you have low priced Cruzinimage 65 mm pistons with no deep valve pockets cams with higher lift and duration needs.

Ported head will give better result with a hotter cam.
New guides, cut seats and new valves are probably needed anyway.

[MauiK3]

I wonder if there is a measurable difference in which cylinders are paired. The original Triumph Trident Siamesed the center cylinder to 1 and 3 right near the head, probably just for design convenience.

[seanbarney41]

Kawasaki and Suzuki mostly had 4 into 2 systems with a crossover under the bike late 70s early 80s.  No idea what the actual effect would be.  A couple hypothesis?  smoothes out the sound or maybe it tricks the pipe into thinking it is longer than it would be if the mufflers were sticking a foot and a half out the back of the bike.  If your exhaust manages to drop 5 or 10 pounds in weight, that is a performance gain and all most of them manage to do.

[Don R]

 My GL1000 has a 4-2 with a crossover pipe from the factory. I assume it was expensive to manufacture so there must be some benefit. Hooker headers took their pipes pretty seriously, I think they paired 1-4 to the right and 2-3 to the left on their 4-2 sets.

[carnivorous chicken]

Kawasaki and Suzuki mostly had 4 into 2 systems with a crossover under the bike late 70s early 80s.  No idea what the actual effect would be.  A couple hypothesis?  smoothes out the sound or maybe it tricks the pipe into thinking it is longer than it would be if the mufflers were sticking a foot and a half out the back of the bike.  If your exhaust manages to drop 5 or 10 pounds in weight, that is a performance gain and all most of them manage to do.

This is what I'm curious about, but seems like the 4-2-1-2 -- turning the one back into two -- would add unnecessary weight if there is no gain.

I see bikes down here, I think mostly the Mexican Italicas -- that are singles but that, at the muffler, turn the one pipe into two. I always thought it was cosmetic, not to my taste but maybe people think it makes their bike look like a twin? But is anyone gaining anything despite a little more weight?

[ratranger]

Those dunstall pipes look like they were more about clearing body work than performance.   

 My old honda rebel 250 had a crossover under the bike on its 2-2 exhaust.  They seem fairly common on oem stuff. 

 As for which pipes are paired it might make a small difference, but doesn't seem big.  I've seen tests between headers on K series hondas and none showed much difference.  They all gained over stock, but nothing big over each other.

[ratranger]

Kawasaki and Suzuki mostly had 4 into 2 systems with a crossover under the bike late 70s early 80s.  No idea what the actual effect would be.  A couple hypothesis?  smoothes out the sound or maybe it tricks the pipe into thinking it is longer than it would be if the mufflers were sticking a foot and a half out the back of the bike.  If your exhaust manages to drop 5 or 10 pounds in weight, that is a performance gain and all most of them manage to do.

This is what I'm curious about, but seems like the 4-2-1-2 -- turning the one back into two -- would add unnecessary weight if there is no gain.

I see bikes down here, I think mostly the Mexican Italicas -- that are singles but that, at the muffler, turn the one pipe into two. I always thought it was cosmetic, not to my taste but maybe people think it makes their bike look like a twin? But is anyone gaining anything despite a little more weight?

Having a crossover on a 4-2 might not do anything that can't be proven without dyno testing.  OEMs might do it to get bikes quieter since the gasses can travel through both mufflers instead of 1.  I know 4-2-1 style pipes make the most power when built properly, and would be simpler and lighter than a 4-2 with crossover. I'm looking at a 4-2 to keep the look balanced, and really asked the question to see if anyone had done similar to try to get most of the 4-2-1 style advantages but with the symmetrical styling of the 4-2.

[MRieck]

Schule made a genuine 4/2/1 exhaust....I have one NIB. In general improved midrange without killing much top end. Most modern systems are 4/2/1...Akra, Arrow etc.
 As was mentioned....that Dunstall set up looks like it was more for convenience rather than performance.
Monty Campbell....quite a character from what I've read. Is he even walking the earth?

[WhyNot2]

Here's an example of an aftermarket 4-2 exhaust on a 550; there are similar systems for 750s.

Is the pictured bike shown yours?

If so where did you source the seat?

Thanks

[scottly]

Here's an example of an aftermarket 4-2 exhaust on a 550; there are similar systems for 750s.

Is the pictured bike shown yours?

If so where did you source the seat?

Thanks

No, it's member Mooshie's bike "Dash".

[WhyNot2]

Here's an example of an aftermarket 4-2 exhaust on a 550; there are similar systems for 750s.

Is the pictured bike shown yours?

If so where did you source the seat?

Thanks

No, it's member Mooshie's bike "Dash".

oh sorry