ok Raux, I get the anti reversion thing... but that wont do any scavenging. I would have thought scavenging was pretty important?

HPD, Australian links, but donuts can be got here...   http://www.mantapro.com.au/index.html
                                                                            http://www.bestmufflers.com/

Quote from: monsta on February 22, 2012, 02:47:21 PM
ok Raux, I get the anti reversion thing... but that wont do any scavenging. I would have thought scavenging was pretty important?

HPD, Australian links, but donuts can be got here...   http://www.mantapro.com.au/index.html
                                                                            http://www.bestmufflers.com/

This is all theory... the antireversion would eliminate the reverse pulse that stops the flow out of the cylinder. by allowing the cylinder to continue to flow the exhaust the need for scavenging can be reduced. In addition valve overlap may help push the exhaust a bit through the cylinder as well...

so antireversion with 1100 cams (more overlap) and variable ergal cam gears. yeah i'm crazy.

Quote from: Raux on February 22, 2012, 03:06:45 PM
This is all theory... the antireversion would eliminate the reverse pulse that stops the flow out of the cylinder. by allowing the cylinder to continue to flow the exhaust the need for scavenging can be reduced. In addition valve overlap may help push the exhaust a bit through the cylinder as well...

so antireversion with 1100 cams (more overlap) and variable ergal cam gears. yeah i'm crazy.

Thanks for the links on the donuts, I´ve never seen those before. I will have to look around if someone is doing them a bit closer to here (Sweden).

I would also like to see the whole document about the anti-reversion thing, looks like it is out of a patent application?

However, if I had just seen the picture, I would have assumed rather the opposite: By supplying this area increase, the sonic overpressure wave sent down the header pipe on exhaust valve opening would reach the area increase and reflect an opposite-sign, i.e. underpressure wave towards the exhaust valve.
Correctly timed thru header length this would arrive at the still-open exhaust valve, helping suck residual gasses out of the cylinder during valve overlap.
This was my reasoning behind the design of the 2-1 system shown in another thread on more or less the same subject, the aim beeing to have the presumed correct header length and still having a convenient (if not very pretty) installation  .

Since this reasoning is more pro-reversion than anti-reversion, the full document would be very interesting to read. Where can it be found?           

 

Quote from: koko64 on February 24, 2012, 02:03:30 AM

Beeing a not very experienced forum user, I´m not sure what this smiley exactly means, but I´d be hard pressed to assume something positive.
I figured these tech&mod forums were for discussing tech and mods for the mutual benefit of everyone, myself included, with an open mind and an interest in technical matters.
Well, maybe I was wrong....?

Anyway, for anyone interested in learning exhaust system basics, this is a better place to start than most:

http://www.burnsstainless.com/techarticles.aspx

 This is an excellent topic, no negative is implied.
often means someone is interested or entertained, watching closely and waiting for more. If someone is building a bike project it is often a vote of interest in the project and a compliment.
means in this context, an interesting technical topic. So I am watching with interest and waiting for the next contribution.
I have a particular interest in performance oriented topics.

Quote from: koko64 on February 25, 2012, 01:25:01 AM
This is an excellent topic, no negative is implied.
often means someone is interested or entertained, watching closely and waiting for more. If someone is building a bike project it is often a vote of interest in the project and a compliment.
means in this context, an interesting technical topic. So I am watching with interest and waiting for the next contribution.
I have a particular interest in performance oriented topics.

OK, sorry, my misinterpretation  . I´ve also found this topic very interesting so I hope more is to come

No worries.

 

 

in reality, what kind of %'s of loss are we talking about here?
i.e. if i continue to use the DP slip-on system i have compared to running two formula derived header pipes with a small expansion chamber of sorts at the length determined to be most suited into two stylised mufflers. are we talking in the region of 3-5 or 10+ hp or torque loss? would u need an expansion chamber or would a fat muffler be enough to have a similar effect?

for the use, looks, and fitment to my bike id ideally like an independent twin system but I'm a Little scared of the implications. i don't wanna throw away power unnecessarily, after all it is just an 800, but a few hp isn't an issue as its a city commuter with the occasional country/hill run a few hp isn't going to worry me.


I'm looking into gettin access to a dyno at a fair price. id be happy to use my bike and make a twin exhaust out of mild steel (completely impractical mainly straight with minimal bends just to get the pipe away from the engine) and test and cut and test to see what happens...
i imagine it being a case of making two header pipes the max length thought to be practical, make a slip on clamp style expansion chamber and muffler setup. run it, then remove the slip on section, cut the header and try again. with 2 inch increments id hazard 5-10 tests would give a good curve of power and torque changes vs length. my guess would be near a full day on the dyno. I'm thinking i could set the base fuel mixture setting for the initial length and then do all tests at that setting. if i found one length to be ideal i suppose you could set it again to see the potential at that length...

anyone see any major flaws or reasoning not to do this?

I'm happy to see this done.  i have the two into two. with no back pressure i was having issues i think the expansion chamber at the stock crossover point will fix it

Quote from: Roaduser on February 27, 2012, 08:31:17 PM
anyone see any major flaws or reasoning not to do this?

None whatsoever ..... partly because I´ve done more or less the same thing myself even if it did not turn out as thorough as I might have liked (I suppose you´ve seen the parallel thread about torque cones in he Tech section?).
I for one will be very interested in the results you´ll get.     

had a reply from burns stainless about their recommendations for a 2 into 1 using their "x-design" program. the results confirm my theory practiced earlier about length and diameter too a t!!
only thing is they don't take into account the port length (admittedly i didn't give them that information) nor do they account for what appears to be another inch or so of pipe in their collectors. combined, this would could add 3inches to the headers. not that i think the change in results would be dramatic at all but just out of interest itd be nice to check such things



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the collector they sell and recommend uses a expanding transition after the collection of headers out to a 2.5inch tail pipe! that's a big tailpipe for a 800cc engine....

Very interesting, it´s the first time I see the result from the Burns X-design.

It pretty well matches what I´ve been doing. This does not indicate any particularily high level of knowledge on my part, rather it implies that they also use the same basic and generally well-known theories. But the header section is big for an 800 cc motor....   

The 2-1 for the Monster uses the stock 37 mm id headers for the first bit, then 38 mm pipes for the rest, and a 54 mm id collector. Header length is about 680 mm from valve face to where the header ends into the id 54 mm bit.

The Rain Bike 2-1 uses pretty much the same setup, but header length 800 mm ending in the Y connection tapering up to the 54 mm id collector.

I´ve been trying to find some thin-wall tubing with 40 mm id, but so far no luck. I think if you stick to the Burns basic design, and do not go any bigger on the header id, I think it will work just fine.

I have not checked yet, but if it is possible to fit the megaphones I have to the headers on the Monster without cutting them up, I might do a dyno check on what will happen with 400 mm (open) megaphones on 700 mm headers.  if nothing else, the noice will be interesting ...