EXHAUST BALANCE PIPE

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cobbadiggabuddyblooo
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Re: EXHAUST BALANCE PIPE

Post by cobbadiggabuddyblooo » Wed Dec 11, 2013 8:43 am

Welcome to Engineering school from Proffessor Rod..
So true about the system you choose and what you want from it. Internal diameter, position of the balance point and even the length to the collection box on a 2 into 1 all tune the system for a certain purpose.
Look at most aftermarket systems and they will joint before splitting again close to the same position as the std balance pipe. Some may different slightly to allow for tuning on the actual diameter of the header and link pipes. Then when you look at the design of an Akrapovic 2 into 1 and the variations of diameters and collection point.
Even with the collection of the two headers right down by the rear shock pivot to aid in boosting midrange performance , they still have a small balance pipe half way between the merge and exhaust port to aid in smoothening the pulse at lower rpm’s.

With headers from the head 2mm larger than std exiting the head opening up via the conical shaped header after the first bend to 2mm larger than say a Over system for example . These all aid in finding that 5.2HP gain at 4000rpm with the longer collection point than other 2 into 1 systems that just collect at the std link point.
The shorter collection point on other systems will aid in giving you a boost higher up in the rev range. Here is why the engineering of the Akrapovic reins supreme because of the choice of pipe diameter still allows for a 2.9hp gain at 7500rpm which will still match most larger aftermarket systems without that sacrifice of midrange due to their choice of length and diameter just to gain 3 or 4 hp at 7500rpm. (which is fine on a fast track where your running between 6000 -8000rpm
Even the thickness and type of material used all have a tiny input to that resonance.
This principal is used you will find on any quality products and the same reason you will find top quality speaker cabinets made from birch..
Last edited by cobbadiggabuddyblooo on Tue Oct 02, 2018 9:25 am, edited 2 times in total.
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Trx envy
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Re: EXHAUST BALANCE PIPE

Post by Trx envy » Mon Oct 01, 2018 1:49 pm

Interesting read. As to the scavenge point at the merge collector on aftermarket pipes, it works by the pulse of one cylinder creating a venturi effeect on the other, no? In which case on the trx engine being an uneven firing 2 cyl, using this principle it would only be possible to tune for a scavenging effect on one cylinder but not the other....? Unless the merger was at a point that coincided on a resonant point for both cylinders, perhaps at different points in the rev range on each?? Its above my head lol.
Please correct me if im wrong.
Anyway, has anyone any info or feedback on the Yoshimura pipes? 2-1-2. Any good? Known power increase?

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Re: EXHAUST BALANCE PIPE

Post by cobbadiggabuddyblooo » Tue Oct 02, 2018 9:42 am

You picked the Yoshi titan and you’ll be happy mate.
It’s been noted by a number of trx owners and spirited riders on how cylinder no.1 runs a little richer than No2. General consensus was put down to heat dissipation due to the cam chain galley next to no2.
I tend to believe it’s more an exhaust pulse issue.
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Re: EXHAUST BALANCE PIPE

Post by Trx envy » Wed Oct 03, 2018 4:01 am

Cheers mate. Im going nuts waiting for the bike. Hopefully today or tomorrow. I think ive watched and listened to every soundbite of throaty trx's on youtube now. The zorst is on its way. Any day now.
Harebrain idea for gutting the yoshi cans; tapered perforated tube. If i taper the perf tube from the 2" or whatever it is at the inlet down to say, 1.75" at the outlet, do you think that would be to the detriment of a deep, crisp not and performance? Or would it sound shit and hurt power?
Planning on chucking some FCRs at some stage too.

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Re: EXHAUST BALANCE PIPE

Post by cobbadiggabuddyblooo » Wed Oct 03, 2018 7:54 am

Just run with 50mm
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Rod.s
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Re: EXHAUST BALANCE PIPE

Post by Rod.s » Wed Oct 03, 2018 3:02 pm

You could always just fit the exhaust and ride it
If it's not made in China, it's a fake!

Trx envy
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Re: EXHAUST BALANCE PIPE

Post by Trx envy » Wed Oct 03, 2018 10:17 pm

Rod.s wrote:You could always just fit the exhaust and ride it
Yes that is definitely step 1

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Re: EXHAUST BALANCE PIPE

Post by Trx envy » Tue Oct 09, 2018 12:08 am

Ok, so here is the Yoshi Titan merge pipe. Its stainless steel. The headers and the other two pipes are Ti though. The headers are roughly 1 1/2" and the fat pipes about 2".
The thing with this is where the two fat pipes are slash cut, welded together and then inserted into the merge piece prior to welding, they are not trimmed flat, so you have two say 3/4" segments of 2" pipe protruding into the air stream and creating about a 40mm aperture in a 60mm hole.
Not sure if this is a design feature that capitalises on pulse timing or some other black magic, or just another way to shut the decibels down a bit to meet the JMCA requirements or simply a cost cutting excercise.
I picture tells a thousand words. Unfortunately i couldnt get a coherant pic of the inside of it, but i included a scale(ish) drawing of whats going on. The pic is deceptive - the two fat pipes are merged at about 60* prior to being inserted into the merge collector. I'd love any opinions on whether i should just gut that bit on not.

Anyways, the cans are indeed chambered and the openings are about 32mm (from a 52mm pipe lol) So one can assume this system was made for show more than go, My plans are to simply fit it and ride it for a bit, and then gut the whole lot.

Image

cobbadiggabuddyblooo
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Re: EXHAUST BALANCE PIPE

Post by cobbadiggabuddyblooo » Tue Oct 09, 2018 9:47 am

Leave the merge collector alone.
Yoshi doesn’t act in half measures and even the Over system has a similar piece in the 2-1-2 merge.
Go to town on the cans tho but don’t go over 50mmID ( you’ll pick up a couple of HP.) Going to 55-60mm you’ll loose too much down low and midrange for the sake of 1-2 Hp at peak HP.
If you want to get funky you can make tea strainers to fit into the 50mm ends . This will give you gains again down low with minimal loss at peak HP.
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Trx envy
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Re: EXHAUST BALANCE PIPE

Post by Trx envy » Tue Oct 09, 2018 10:22 am

Cheers cobba. The plan is to use 2.25" as it will cover the imperfect way the 2" Ti link pipes line up with the flange, but actually taper the tube down to 44mm by cutting out a fillet and then closing it up esentially making a slight cone shape if that makes sense.
Shit idea or no?

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Re: EXHAUST BALANCE PIPE

Post by Trx envy » Wed Oct 10, 2018 1:43 am

Ok so I've been googling the shit out of this and not really finding any answers or even precedent for tapering an absorption muffler smaller at the end, except theoretically, an exhaust that tapers gradually from the header to the tip makes some sense in some schools of thought in that it will maintain velocity as the exhaust gasses cool and contract.
Also apparently back pressure is a bit of a myth that has been busted on dynos a bunch of times and has never helped anything but pressure wave tuning is very important.. its all above my head,, im guessing even if you had a doctorate in fluid dynamics and computer modelled the shit out of it it would still come down to real world trial and error in the end.
My half arsed theory is with a tapered perforated tube it might be a bit more efficient at absorbing high frequency noise at the expense of the packing life span...? fuk't if i know. Will defo leave the merge pipe as is as you recommend Cobba.
Ill post results eventually. Been going mad waiting for this bike. Finally got on to the dealer. They're waiting on the cam-chain. No ETA as yet :/

Trx envy
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Re: EXHAUST BALANCE PIPE

Post by Trx envy » Wed Oct 10, 2018 3:43 am

The Over merger looks very similar to the Yoshi one in design, except appears to be a two piece pressed or hydro-formed sheet metal construction,,, one would have to assume its completely smooth inside unless they added something extra in there..
https://img1.croooober.com/api/v1/photo ... 3091s0.jpg

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Re: EXHAUST BALANCE PIPE

Post by cobbadiggabuddyblooo » Wed Oct 10, 2018 11:00 am

That’s correct , but there is a length inside between the headers that runs down inside the merge till about mid way.
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Trx envy
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Re: EXHAUST BALANCE PIPE

Post by Trx envy » Wed Oct 10, 2018 10:23 pm

^ That's interesting. Like a divider? If so, and assuming Yoshi intentionally incorporated that reversion-inducing looking feature in theirs then Yoshi and Over have taken two completely different schools of thought even though from the exterior both merge pieces look very similar.

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Re: EXHAUST BALANCE PIPE

Post by cobbadiggabuddyblooo » Thu Oct 11, 2018 3:37 am

Yes , all depends what the system is tuned to do. I know the Over system is more so tuned for higher RPM work.
A number of comments I’ve seen over the years have given feedback on good midrange gains from the Yoshi...
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