A non-loud Thai after-market exhaust?

[Andrew Hastings]

I’m looking for a quiet aftermarket exhaust for a CBR250.

Leo Vince SBK Evo II is one that meets EU noise standards, but is not available anywhere anymore.

Leo Vince GP corsa is available for only 8,500b but owners complain about the loudness, so I definitely would.

Arrow also have one that meets EU standards, but cost 18k for a slip-on, which is a bit much on a bike worth 60k baht when I also want to add an EJK fuel controller for 8k baht.

Tsukigi had one about 3 years ago that had a TIS stamp, but is not available anywhere any more.

The only one that seems to be available is the Delkevic from the UK, pretty cheap there too, but then there’s shipping and likely custom’s 30% excise on top.

Anybody know a Thai made brand that are not loud?

DBS, PR2 all seem to be overly loud on the small single-cylinder bikes (the DBS sounds good on a Ninja250). Over here they seem to pride themselves on how loud their little single-cylinder can be.

One can presumably get a bigger, longer baffle made (extra hassle), but wouldn't this also effect the performance (bogging it up) and also risk burning it from excessive heat?

A non-obnoxious Thai made muffler or full system that also doesn't rob performance or fighten the neighbours would be good. Any info?

[ll2]

for cbr250r, never seen a quiet aftermarket pipe. even with the baffles.

i had dan moto pipe and with baffle it was relatively OK still not quiet.

Maybe delkevic is the best option but dont think so it is quiet as well.

[Andrew Hastings]

Delkevic passes the UK Noise Regulations, also the 18 inch, 450mm version gets good reviews from people wanting a relatively quiet muffler. Also comes with a decent dyno.

laokengseng look like they have a decent Akrapovic copy for 6k baht. It is 46cm, so longer than the 450mm Delkevic, which should presumably mean it's quieter than other local made shorter mufflers.

The exit is a strange shape so I have asked if it comes with a baffle/db killer, which they might not understand.

http://laokengseng.com/forum/index.php/topic,24.0.html

[ll2]

Delkevic passes the UK Noise Regulations, also the 18 inch, 450mm version gets good reviews from people wanting a relatively quiet muffler. Also comes with a decent dyno.

laokengseng look like they have a decent Akrapovic copy for 6k baht. It is 46cm, so longer than the 450mm Delkevic, which should presumably mean it's quieter than other local made shorter mufflers.

The exit is a strange shape so I have asked if it comes with a baffle/db killer, which they might not understand.

http://laokengseng.com/forum/index.php/topic,24.0.html

You can fit many fake pipes and length might not mean anything.

Bc it is also about the packing, which types of materials used etc.

Better get delkevic than a 6000 thb slip on. Also there are many shops selling pipes for cbr250 like u turn, k speed etc.

Good luck.

[mikebell]

I hate to inflict my noise on anyone by bike/TV/loud car music. So it is that I resent folk who own look-at-me bikes/cars who have the thumping bass vibrating your windscreen at traffic lights; or yapping dogs that need disciplining especially at night.

I am a grumpy old man but would not deliberately offend others by my selfishness.

[ll2]

I hate to inflict my noise on anyone by bike/TV/loud car music. So it is that I resent folk who own look-at-me bikes/cars who have the thumping bass vibrating your windscreen at traffic lights; or yapping dogs that need disciplining especially at night.

I am a grumpy old man but would not deliberately offend others by my selfishness.

if having a louder than stock pipe is selfishness, than asking quietness is also selfishness for me just bc you are an old grumpy man.

A louder pipe is for my safety and some extra grunt, not for showing people!

check the planes flying over you or lorries with open pipes or boats with open mufflers echoing from the sea.

[Andrew Hastings]

I hate to inflict my noise on anyone by bike/TV/loud car music. So it is that I resent folk who own look-at-me bikes/cars who have the thumping bass vibrating your windscreen at traffic lights; or yapping dogs that need disciplining especially at night.

I am a grumpy old man but would not deliberately offend others by my selfishness.

I agree completely.

But also for myself. Going for long rides is great, having a loud, constant drone gnawing at your eardrums the entire time isn't. I don't wear earplugs for safety reasons.

I am considering the full system DBS (only 7k baht).

http://www.grim-dbs.com/tdbs1.php

You buy the baffle seperately on page 3, for 300b.

I asked the copy akrapovic shop if they come with this baffle:

No reply.

Thais like loud, so the market here is for loud obnoxious pipes, half of which are robbing the torque and rideability.

[Rhys]

I hate to inflict my noise on anyone by bike/TV/loud car music. So it is that I resent folk who own look-at-me bikes/cars who have the thumping bass vibrating your windscreen at traffic lights; or yapping dogs that need disciplining especially at night.

I am a grumpy old man but would not deliberately offend others by my selfishness.

I agree completely.

But also for myself. Going for long rides is great, having a loud, constant drone gnawing at your eardrums the entire time isn't. I don't wear earplugs for safety reasons.

I am considering the full system DBS (only 7k baht).

http://www.grim-dbs.com/tdbs1.php

You buy the baffle seperately on page 3, for 300b.

I asked the copy akrapovic shop if they come with this baffle:

No reply.

Thais like loud, so the market here is for loud obnoxious pipes, half of which are robbing the torque and rideability.

Thanks for the photo of the slip on and baffle....I'm not a tech person, could you explain how the torque is affected, please.. I understand the rideablity....too much vibration, too loud..

Thank you.

[ktm jeff]

Rhys , if the exhaust offers too little reistriction to the outgoing gasses , they , at lower revs , may not have enougth negative pressure pulse ( almost like a "suck" ) at the right time , to help pull the new fuel mixture through the engine .Reducing both power and torque slightly. This is a simple explanation and maybe some one else can offer a better , but understandable , one .

[dave_boo]

I agree completely.

But also for myself. Going for long rides is great, having a loud, constant drone gnawing at your eardrums the entire time isn't. I don't wear earplugs for safety reasons.

I am considering the full system DBS (only 7k baht).

http://www.grim-dbs.com/tdbs1.php

You buy the baffle seperately on page 3, for 300b.

I asked the copy akrapovic shop if they come with this baffle:

No reply.

Thais like loud, so the market here is for loud obnoxious pipes, half of which are robbing the torque and rideability.

I have the DBS triangle carbon fibre on my '08 Ninja 250. Nice sound with the dB killer in.

[dave_boo]

Rhys , if the exhaust offers too little reistriction to the outgoing gasses , they , at lower revs , may not have enougth negative pressure pulse ( almost like a "suck" ) at the right time , to help pull the new fuel mixture through the engine .Reducing both power and torque slightly. This is a simple explanation and maybe some one else can offer a better , but understandable , one .

Good enough for a lay person to understand.

You can go into the resonance and bernoulli effect, but that's getting really deep.

I'll take a stab at it though.

Let's imagine your bike idles at 1200 RPM. Now, as you have a 4 stroke, only 1/2 of those rpms (each stroke is an up and down motion, and two strokes equals 1 rotation; the strokes are 1. intake, 2. compression, 3. power, 4. exhaust) are on the power/exhaust cycle. Let's assume you have a cam that has exhaust lobes with a 216 degree duration. That means that for for 216 out of the 360 degrees of rotation they'll keep the exhaust valve(s) open. That is greater than the 180 degrees that the 'exhaust stroke' is equal to. Why? Because if the exhaust valves start opening before the end power stroke, when the piston reaches the end of that stroke and begins its upwards travel it is not fighting as much against those gasses. Fighting against those gasses loses power.

BUT, you are not going to have the exhaust valves opening 39 degrees of rotation during the power stroke and close when the piston reaches the top. Why not? Because you have created a vacuum. Means that the engine needs to fight against that vacuum to bring in the new air fuel mixture. If on the other hand you keep the exhaust valves open for some time when the intake valves open (this is what is called overlap), the fresh mixture can help push the exhaust gasses out. Also the exiting exhaust gasses can help create a vacuum after the piston reaches the top that helps draw the fresh mixture in.

Let's go back to that 1200 RPM number. That's 20 revolutions per second. Each revolution lasts for 0.05 seconds. Now, as the exhaust cam has a duration of 216 degrees, it will be open ²¹⁶/₃₆₀=0.60 (60% of 0.05 seconds or 0.03 seconds) of 1/2 those rotations. Obviously as it will be 0.07 seconds until the exhaust cycle starts again, the gasses have plenty of time to clear the area.

But remember back when we were talking about using the engine characteristics to help move gasses? You can do that outside the cylinder also. Having a low pressure area (a "vacuum") accelerates the gasses entering the area. An easy way to do that is to slow down the gasses as they exit the exhaust port or actually have them 'bounce' back so that when the hit the closed exhaust port and start back towards the muffler tip they are creating the vacuum just as the exhaust valve opens.

Now, it doesn't have to be the preceding exhaust pulse that actually causes the current to be pulled out. It can be one from a cycle that happened 4 or 6 or however any many cycles ago as it will be far enough down the pipe to hit a restriction that causes it to 'bounce' back. Upon bouncing back it will hit another pulse which will hit another and so on just like in billiards. Obviously the closer you can start this chain of events to the exhaust valve the better.

Now exhausts are tuned. And if you insert a part in that was not tuned for that engine, and specific engine speed, it can obviously change the rate at which those pulses come back. And going back to the billiards example, if you just poke away all willy-nilly, you sure aren't going to pocket the balls very well are you?

[ktm jeff]

dave_boo , Rhys just fell off his chair !! . You explained in far greater detail than i , and spot on . Some extra points , you say , in your first line , each stroke is an up and down motion - its an up OR down motion , not trying to be a smart ass , i know , you know , what you mean . Line 1 , paragraph 2 , you mean 36 degrees , yes . The valve overlap and gas "exchage" greatly helps volumetric efficiency , fuel consumption , power . This is helped even further if you can "suck" the waste gasses out ( exhaust tunning ) . If the incoming gasses are traveling quickly , they help scavange the waste gasses out , but if the inlet ports / valves / carb / injection body is too large , for the engine revs , VE will suffer . This was the idea of Yamaha V-MAX linking up carbs above certain revs .Now just imagine you could vary the time and / or amount those valves could open , as in variable valve timing / lift . Or activating an extra set of valves at higher revs . Now ive just fell off my chair. . As a engine revs between 1,200 RPM and up to 15,000 RPM , no matter what we do we cant have it spot on at all revs. The higer the revs , the less time you have to fill / empty the cylinders , so you then need bigger valves / carbs etc , which are poor at low revs. Im still staggerd at how an engine works for so long on just some fuel , oil and cooling medium.

[Andrew Hastings]

dave_boo, on 05 Feb 2015 - 23:26, said:

Andrew Hastings, on 04 Feb 2015 - 11:40, said:

I agree completely.

But also for myself. Going for long rides is great, having a loud, constant drone gnawing at your eardrums the entire time isn't. I don't wear earplugs for safety reasons.

I am considering the full system DBS (only 7k baht).

http://www.grim-dbs.com/tdbs1.php

You buy the baffle seperately on page 3, for 300b.

I asked the copy akrapovic shop if they come with this baffle:

No reply.

Thais like loud, so the market here is for loud obnoxious pipes, half of which are robbing the torque and rideability.

I have the DBS triangle carbon fibre on my '08 Ninja 250. Nice sound with the dB killer in.

I agree.

You see them a lot on the Ninja 250's. They sound great, even if a little loud, the lovely sound and note make the slight loudness okay.

This is due to the firing sequence they have on their twin cylinder.

On the single cylinder jack hammer engine, not so nice at all.

Having seen this well produced amateur video, I have opted not to go with a DBS.

https://www.youtube.com/watch?v=8BEx_r1FF_g

I am in contact with Delkevic about getting one shipped to Thailand. 6k baht for the exhaust, I am waiting for a quote on their shipping - I would guess about 3k baht. 9k baht is fine, but then there may well be 30% custom and excise on top (I believe they charge 30% on what they say the value is, and not what any receipts show, though sometimes you can be lucky.) Any way, as I will also get the EJK fuel controller for 7.5-8k baht, I'm not sure I want to spend 20k on the air and fueling system on a bike that cost 60k baht.

The info and dyno is good:

http://www.delkevic.co.uk/?section=shop&product_category=exhaust_s7rhj&sub_category=silencers_hl3s5&product=450mm_stainless_steel_oval_silencers&variant=cbr250r__mc41__11_14-3242&start=0&search_term=&order_by=

[Andrew Hastings]

Rhys, on 05 Feb 2015 - 21:05, said:

Andrew Hastings, on 04 Feb 2015 - 11:40, said:

Thais like loud, so the market here is for loud obnoxious pipes, half of which are robbing the torque and rideability.

Thanks for the photo of the slip on and baffle....I'm not a tech person, could you explain how the torque is affected, please.. I understand the rideablity....too much vibration, too loud..

Thank you.

In a word (or two). Back-pressure.

No back-pressure - poor running engine, likely to lack torque and rev poorly while riding, you will likely experience dead spots in the low and mid range.

It is why I have a phobia of *cheap Thai-made exhausts that offer no dyno.

I say cheap, but that is relative, they often cost similar to some decent branded exhausts from World reknowned companies in the West.

For example, the R+D'd Delkevic costs the equivalent of 6k baht in the West. In Thailand, the backyard cheap fake Akrapovic looking exhausts cost that much and don't even come with a baffle, let alone a dyno. Likely to both rob performance and deafen you.

The Leo Vince SBK costs the equivalent of 8,500 baht in the West. For that here you can get a PR2 exhaust that looks good, but offers no dyno, hasn't passed any government regulations and you have no idea how it will affect the performance or how much it will deafen you, or how long it will last before it changes color and implodes.

So really, when it comes to it like this, the cheap Thai exhausts aren't actually cheap at all, they are the same price as proper brand name exhausts in the West, but with shipping and customs extortion you have little choice if you ride a cheap bike and don't wish to spend 1/3 of its value on modding the breathing and fueling systems.

[Rhys]

Thanks the the MA and Ph.D. level of discussion... ... I basically wanted to change the stock exhaust system because it sounds... sick... I went to the Thai AKP system because the guys at the shop suggested it... I did not know it was the Thai version.. Did a little research, I was pricing at 18k to 6k.. At this point, alll seems fine.. certain the AKP Thai version is lighter. The noise and vibration have seem to settled and work. It does what I want, other bike and cars look out more.

I look for the open roar for the need of LOUD.... but pretty tame when cruising in the residential areas.

Funny, I have had the bike for 3 weeks now.. CBR 300R and have only ridden it 6 times.. it has less than 200k on the clock.. Making more modifications.. hand lever are too far for my small hand.. thus looking with a more easy pull.

OH..Mr. Tech guys..

On the B.S. level of explaination.... I seem to recall the concept of speed shifting.. Could you explain that again to me.. thanks..

From what I recall and have tried long ago on a Honda SL100 is you keep the throttle open and shift and the same time?

The engine makes a funny sound...

Another question.. perhaps information overload.. and too much youtube videos on riding..

Shifting.. give it a little gas, rev it up, then shift.. keep the RPM high..

Braking.. when using the the engine only .. and making sure not to blow the engine.. shift down with appropriate RPM.. don't let it over whine..

Thank you Gentlemen..

Cheers.

[Rhys]

Rhys , if the exhaust offers too little reistriction to the outgoing gasses , they , at lower revs , may not have enougth negative pressure pulse ( almost like a "suck" ) at the right time , to help pull the new fuel mixture through the engine .Reducing both power and torque slightly. This is a simple explanation and maybe some one else can offer a better , but understandable , one .

Good enough for a lay person to understand.

You can go into the resonance and bernoulli effect, but that's getting really deep.

I'll take a stab at it though.

Let's imagine your bike idles at 1200 RPM. Now, as you have a 4 stroke, only 1/2 of those rpms (each stroke is an up and down motion, and two strokes equals 1 rotation; the strokes are 1. intake, 2. compression, 3. power, 4. exhaust) are on the power/exhaust cycle. Let's assume you have a cam that has exhaust lobes with a 216 degree duration. That means that for for 216 out of the 360 degrees of rotation they'll keep the exhaust valve(s) open. That is greater than the 180 degrees that the 'exhaust stroke' is equal to. Why? Because if the exhaust valves start opening before the end power stroke, when the piston reaches the end of that stroke and begins its upwards travel it is not fighting as much against those gasses. Fighting against those gasses loses power.

BUT, you are not going to have the exhaust valves opening 39 degrees of rotation during the power stroke and close when the piston reaches the top. Why not? Because you have created a vacuum. Means that the engine needs to fight against that vacuum to bring in the new air fuel mixture. If on the other hand you keep the exhaust valves open for some time when the intake valves open (this is what is called overlap), the fresh mixture can help push the exhaust gasses out. Also the exiting exhaust gasses can help create a vacuum after the piston reaches the top that helps draw the fresh mixture in.

Let's go back to that 1200 RPM number. That's 20 revolutions per second. Each revolution lasts for 0.05 seconds. Now, as the exhaust cam has a duration of 216 degrees, it will be open ²¹⁶/₃₆₀=0.60 (60% of 0.05 seconds or 0.03 seconds) of 1/2 those rotations. Obviously as it will be 0.07 seconds until the exhaust cycle starts again, the gasses have plenty of time to clear the area.

But remember back when we were talking about using the engine characteristics to help move gasses? You can do that outside the cylinder also. Having a low pressure area (a "vacuum") accelerates the gasses entering the area. An easy way to do that is to slow down the gasses as they exit the exhaust port or actually have them 'bounce' back so that when the hit the closed exhaust port and start back towards the muffler tip they are creating the vacuum just as the exhaust valve opens.

Now, it doesn't have to be the preceding exhaust pulse that actually causes the current to be pulled out. It can be one from a cycle that happened 4 or 6 or however any many cycles ago as it will be far enough down the pipe to hit a restriction that causes it to 'bounce' back. Upon bouncing back it will hit another pulse which will hit another and so on just like in billiards. Obviously the closer you can start this chain of events to the exhaust valve the better.

Now exhausts are tuned. And if you insert a part in that was not tuned for that engine, and specific engine speed, it can obviously change the rate at which those pulses come back. And going back to the billiards example, if you just poke away all willy-nilly, you sure aren't going to pocket the balls very well are you?

Thanks Dave...now for Speed Shifting... please.. cheers

[dave_boo]

Thanks the the MA and Ph.D. level of discussion... ... I basically wanted to change the stock exhaust system because it sounds... sick... I went to the Thai AKP system because the guys at the shop suggested it... I did not know it was the Thai version.. Did a little research, I was pricing at 18k to 6k.. At this point, alll seems fine.. certain the AKP Thai version is lighter. The noise and vibration have seem to settled and work. It does what I want, other bike and cars look out more.

I look for the open roar for the need of LOUD.... but pretty tame when cruising in the residential areas.

Funny, I have had the bike for 3 weeks now.. CBR 300R and have only ridden it 6 times.. it has less than 200k on the clock.. Making more modifications.. hand lever are too far for my small hand.. thus looking with a more easy pull.

OH..Mr. Tech guys..

On the B.S. level of explaination.... I seem to recall the concept of speed shifting.. Could you explain that again to me.. thanks..

From what I recall and have tried long ago on a Honda SL100 is you keep the throttle open and shift and the same time?

The engine makes a funny sound...

Another question.. perhaps information overload.. and too much youtube videos on riding..

Shifting.. give it a little gas, rev it up, then shift.. keep the RPM high..

Braking.. when using the the engine only .. and making sure not to blow the engine.. shift down with appropriate RPM.. don't let it over whine..

Thank you Gentlemen..

Cheers.

The term you are looking for is "power shifting". It's a bit stupid and hard on your driveline.

Basically you keep the throttle pinned (or near enough) and keep your toe under the shifter. When you have passed max HP, you stab the clutch while simultaneously applying upwards pressure to the shifter. And it really is just a stab. The engine will redline (or near enough) due to the lack of a load and then as the transmission hopefully enters the next gear without damage you hope that your rear end doesn't break free due to the sudden increase in rear wheel rotational speed.

Speed shifting is what I do all the time; you roll of the throttle and keep pressure on the shifter. When the revs match (meaning that in a higher gear for the same speed you will obviously have a lower engine RPM and the driveline naturally wants to be there) the transmission pretty much pops into the next gear by itself. Nice and easy and no damage...unless you try to force it. Note that aftermarket speed shifters do this, but instead of relying on you to roll off the throttle they cut fuel/spark momentarily.

[dave_boo]

dave_boo , Rhys just fell off his chair !! . You explained in far greater detail than i , and spot on . Some extra points , you say , in your first line , each stroke is an up and down motion - its an up OR down motion , not trying to be a smart ass , i know , you know , what you mean . Line 1 , paragraph 2 , you mean 36 degrees , yes . The valve overlap and gas "exchage" greatly helps volumetric efficiency , fuel consumption , power . This is helped even further if you can "suck" the waste gasses out ( exhaust tunning ) . If the incoming gasses are traveling quickly , they help scavange the waste gasses out , but if the inlet ports / valves / carb / injection body is too large , for the engine revs , VE will suffer . This was the idea of Yamaha V-MAX linking up carbs above certain revs .Now just imagine you could vary the time and / or amount those valves could open , as in variable valve timing / lift . Or activating an extra set of valves at higher revs . Now ive just fell off my chair. . As a engine revs between 1,200 RPM and up to 15,000 RPM , no matter what we do we cant have it spot on at all revs. The higer the revs , the less time you have to fill / empty the cylinders , so you then need bigger valves / carbs etc , which are poor at low revs. Im still staggerd at how an engine works for so long on just some fuel , oil and cooling medium.

Yeah it was late when I posted and you are correct on all your points ensuring my post is good information.

And you are a smart ass...but just right in your critique.

[ktm jeff]

dave ,hope you took the very small corrections in good humour Your a technical guy , with a sense of humour , yes , and im sure you will have many chances ( in the best possible taste ) to correct me. Heres the first. When the + pressure wave goes down the pipe , hits the open end , then returns as a - pressure wave , what happens when this meets another + wave coming from the exhaust port ?. I dont believe they cancel each other out. Speed shifting , without stabing the clutch , gives me smoother changes. Rhys , it takes some gentle practice !. When down shifting you want the revs to increase to about 5,000 RPM during normal riding. This gives good "engine braking" and puts you in a good rev range to accelerate or brake more as needed. Despite what the manual says , take it for an oil / filter change about 500 to 600 KM.

[Rhys]

dave ,hope you took the very small corrections in good humour Your a technical guy , with a sense of humour , yes , and im sure you will have many chances ( in the best possible taste ) to correct me. Heres the first. When the + pressure wave goes down the pipe , hits the open end , then returns as a - pressure wave , what happens when this meets another + wave coming from the exhaust port ?. I dont believe they cancel each other out. Speed shifting , without stabing the clutch , gives me smoother changes. Rhys , it takes some gentle practice !. When down shifting you want the revs to increase to about 5,000 RPM during normal riding. This gives good "engine braking" and puts you in a good rev range to accelerate or brake more as needed. Despite what the manual says , take it for an oil / filter change about 500 to 600 KM.

Thanks Jeff

Understand better now... But with the new bike will not do this.. Even with the CBR 150.. I will not try. I just recall back in my wheelie dirt days.. power shifting was something " On Any Sunday Riders" tried. It did not feel right the first few times, then I never tried again.. did not want harm the transmission.

By the way, I am enjoying the discussion between you (Jeff) and Dave (Prof)

On the pegs.

[Andrew Hastings]

I decided to forget all the Thai pipes and instead bought a Delkevic from the UK.

Price: 119 Sterling + 40 for shipping.

20 pounds was deducted for VAT as it was being shipped outside of the UK, so total: 139.99 pounds. 6,960thb.

Possibly with up to 2,600b to pay in import tax and VAT etc upon arrival.

So really in all, the same as people would pay for a Thai pipe from someplace like DBS or PR2.

No brainer really, imo.

[dave_boo]

dave ,hope you took the very small corrections in good humour Your a technical guy , with a sense of humour , yes , and im sure you will have many chances ( in the best possible taste ) to correct me. Heres the first. When the + pressure wave goes down the pipe , hits the open end , then returns as a - pressure wave , what happens when this meets another + wave coming from the exhaust port ?. I dont believe they cancel each other out. Speed shifting , without stabing the clutch , gives me smoother changes. Rhys , it takes some gentle practice !. When down shifting you want the revs to increase to about 5,000 RPM during normal riding. This gives good "engine braking" and puts you in a good rev range to accelerate or brake more as needed. Despite what the manual says , take it for an oil / filter change about 500 to 600 KM.

There's a whole bunch of math that accounts for the propagation of waves. If you want to see a visual representation, throw a stone into a pond and then shortly thereafter throw another one near by (you're doing it for science, but it probably harkens back to doing it as a kid...so just do it). Look how the waves interact. There's a bit of 'cancellation'(practical example below shows why it's minimal), but Sir Isaac Newton's law still holds (and as an aside, the mass of the water molecules plus the interaction with the surrounding medium which should have more friction than an exhaust pipe causes the waves in the practical example to dissipate more quickly than the exhaust pulses should).

There are problems with both the 'throw a couple of rocks into a pond' and the billiards example I gave earlier. The biggest one is that the exhaust gas is compressible. Technically both water and billiard balls are also, but to much less of a degree. So...to get a more complete idea, imagine using tennis balls on a billiard table. As the one you've designated the cue ball strikes another one, both compress slightly and then expand back to their original shape as the go the different ways. This re-expansion adds a bit of velocity. The exhaust pulses do the same.

[dave_boo]

I decided to forget all the Thai pipes and instead bought a Delkevic from the UK.

Price: 119 Sterling + 40 for shipping.

20 pounds was deducted for VAT as it was being shipped outside of the UK, so total: 139.99 pounds. 6,960thb.

Possibly with up to 2,600b to pay in import tax and VAT etc upon arrival.

So really in all, the same as people would pay for a Thai pipe from someplace like DBS or PR2.

No brainer really, imo.

Yeah, except I had my DBS 24 hours after order. And the money stays in the local economy.

[Andrew Hastings]

dave_boo, on 07 Feb 2015 - 12:53, said:

Andrew Hastings, on 07 Feb 2015 - 12:35, said:

I decided to forget all the Thai pipes and instead bought a Delkevic from the UK.

Price: 119 Sterling + 40 for shipping.

20 pounds was deducted for VAT as it was being shipped outside of the UK, so total: 139.99 pounds. 6,960thb.

Possibly with up to 2,600b to pay in import tax and VAT etc upon arrival.

So really in all, the same as people would pay for a Thai pipe from someplace like DBS or PR2.

No brainer really, imo.

Yeah, except I had my DBS 24 hours after order. And the money stays in the local economy.

I guess that we all have different desires when buying an after market exhaust for our motorcycles.

The number of hours it takes to arrive and which market the money goes to isn't anywhere on my list, but that's just me of course.

Speaking of markets though. As they cost the same (actually the Thai DBS is more expensive) I'd rather give my money to a manufacturer that has used the money their customers pay to include dyno sheets and at least a semblence of R&D, and road legality.

This is no attack on you at Dave, your info is great and appreciated. But for example, the cheapest DBS pipe is 7,000. The Delkevic sells for less than 6,000b in the UK. Have DBS put any of the money that their customers pay into R&D and dyno's to provide for their customers, or have them stamped and certified as road legal in their main market (Thailand for DBS)? When I visit their site and have had contact with them I have seen no information of R+D, no information of performance (a dyno) and no information of if it is even legal to use on Thai roads (I think we can both resonably presume that they aren't legal to use on Thai roads as they have not been stamped by the TIS).

[ktm jeff]

Thanks Dave , i presume i will be arrested soon for throwing stones at the ducks !. I understand that bit , but - sorry to be a pain - when a + wave fron the engine , hits a - wave returning , what type is the "bounced" wave going back to the engine , + or - , or are they always - , as i sussect . I will shortly be on the phone to Honda F1 with some advice for them .

[dave_boo]

Thanks Dave , i presume i will be arrested soon for throwing stones at the ducks !. I understand that bit , but - sorry to be a pain - when a + wave fron the engine , hits a - wave returning , what type is the "bounced" wave going back to the engine , + or - , or are they always - , as i sussect . I will shortly be on the phone to Honda F1 with some advice for them .

Ever seen a Newton's cradle? I've included a picture.

I assume you have; as you remember from watching it, the pulses/waves don't change, they are merely redirected. On the cradle, when they reach the end of the arc (analogous to hitting the cylinder) they head back.

And contacting Honda's F1 team would be pointless. They have a deeper understanding than I and use CFD amongst other tools to do study it in real time whilst adjusting various parameters rather than theorise and do out the math long hand.

[Rhys]

Thus in the end.. buying a Thai made exhaust system..."replica" is........

[eeeya]

Thanks Dave , i presume i will be arrested soon for throwing stones at the ducks !. I understand that bit , but - sorry to be a pain - when a + wave fron the engine , hits a - wave returning , what type is the "bounced" wave going back to the engine , + or - , or are they always - , as i sussect . I will shortly be on the phone to Honda F1 with some advice for them .

Ever seen a Newton's cradle? I've included a picture.

I assume you have; as you remember from watching it, the pulses/waves don't change, they are merely redirected. On the cradle, when they reach the end of the arc (analogous to hitting the cylinder) they head back.

And contacting Honda's F1 team would be pointless. They have a deeper understanding than I and use CFD amongst other tools to do study it in real time whilst adjusting various parameters rather than theorise and do out the math long hand.

I think this video is a good example of newtons cradle applied to motorcycling