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If you lose 5 kg. you can catch the same kg/HP ratio
negative sir you math is wrong assuming a 200 lb person to start with

stock the bike is listed as 417 lbs with the 200 lb rider that makes 617 lbs with 112 hp for a 5.5 lbs/hp

the akrapovic exhaust dropped 6 lbs to 611 lbs and added 7 hp for 119 for a 5.13 lbs/hp

your hypothetical loosing 5 kg is 11 lbs or 606 lbs total with the same 112 hp for 5.41 lbs/hp, no where near the 5.13 lbs/hp

you would need to get to 575 lbs total weight to match the 5.13 lbs/hp which is a 42 lb weight loose or 19kg almost 4 times what you said

and if you lost the 42 lbs and added the akrapovic you would get to 4.79 lbs/hp, now that would be braaaaaaaap!!!

:)
 

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Would you say, that a flash would be worth the money on a totally stock bike or only worth it when installing pipe, filter etc?

We have some pretty strict laws where i live, and the chance to take when doing aftermarket exhaust is not worth it for me. But if the gains on the stock bike makes it run even better i would consider doing just the flash.
The bike in stock form with stock ecu is deffently better then my 18model was, and it pulls lovely. But again, if it makes it even better and it is something you can tell i would consider it :)
 

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Would you say, that a flash would be worth the money on a totally stock bike or only worth it when installing pipe, filter etc?

We have some pretty strict laws where i live, and the chance to take when doing aftermarket exhaust is not worth it for me. But if the gains on the stock bike makes it run even better i would consider doing just the flash.
The bike in stock form with stock ecu is deffently better then my 18model was, and it pulls lovely. But again, if it makes it even better and it is something you can tell i would consider it :)
Even if your bike is completely stock, a good ECU flash can still make the bike feel smoother, run cooler, and in some cases run more efficient/get better distance/gallon.
 

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Even if your bike is completely stock, a good ECU flash can still make the bike feel smoother, run cooler, and in some cases run more efficient/get better distance/gallon.
I know all the basic benefits by flashing as you describe, but i want to know if it will make more power that you feel and not just dyno figures on a stock bike. By flashing it i will void my 5 year warranty on the engine, so for me at has to do something “major” to the engine feel to be worth voiding the warranty.

I traded in my 16’ gsxs1000f for the 21’ mt09sp, and compared to that, the ride by wire combined with the cp3 is a blast and alot, and i mean ALOT, more smooth then the suki. Despite the differents in CC and HP the 09 is a faster bike where i ride - thats why i ended up trading it.
It also feels better then my previous 18’ mt09sp, so the flash on my 21’ would need to do something for me to make it worth it. And the best way was to wait for someone who has done the flash on a stock bike and then ask so i get the real picture and not just numbers :)
 

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I know all the basic benefits by flashing as you describe, but i want to know if it will make more power that you feel and not just dyno figures on a stock bike. By flashing it i will void my 5 year warranty on the engine, so for me at has to do something “major” to the engine feel to be worth voiding the warranty.

I traded in my 16’ gsxs1000f for the 21’ mt09sp, and compared to that, the ride by wire combined with the cp3 is a blast and alot, and i mean ALOT, more smooth then the suki. Despite the differents in CC and HP the 09 is a faster bike where i ride - thats why i ended up trading it.
It also feels better then my previous 18’ mt09sp, so the flash on my 21’ would need to do something for me to make it worth it. And the best way was to wait for someone who has done the flash on a stock bike and then ask so i get the real picture and not just numbers :)
It's a hard call this one.... Mine is smoother and gained torque and power all over the rev range but it's not stock. Just by unlocking the top end power on this bike without any mods would be worth it. Maybe @vycyclenut can answer this as he has been mapping his bike from stock !🤩
Aleks
 

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Hey guys, I had my bike up at 2wheeldynoworks in Kirkland, WA specifically to get the ECU flashed.

They also installed my Akrapovic Carbon exhaust as well as the DNA Stage 2 Air filter.

I only picked up the bike up a few hours ago but, oh my gosh it's an entirely different bike now.

View attachment 168042

It's so smooth, and it just wants to pull even harder than it did before! The engine braking was smoothed out as well so when I'm off throttle it doesn't throw me forward. I'll keep you all updated when I get some more time on the bike. But, so far so good!

2wheel has more information on their site for the '21 ECU flashing service

And Links:
DNA stage 2 Air Filter
Akrapovic Racing Line (Carbon)

Also, if you are curious about the "Airbox" Mod for the 2021's feel free to message me. It was tried and... yeah

Edit : Here are the other comparison charts


View attachment 168055
View attachment 168056
View attachment 168054
Your bike picked up 4+ hp and 5+ Ft lb torque, along with a smoothed throttle and some delicious sound. Both are negligible gains unless your on the track and a crack rider. If your riding the streets, commuting as a intermediate rider you may never push that bike hard enough to get to use that power.
I’m not throwing shade on ya, that’s awesome that you got the upgrades and the extra power you were looking for. Ride safe out there!
 

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Hi guys,
Can anyone direct me to a discussion of different mods to the airbox for the Gen3 2021 Yamaha MT-09? I can't find any - only this thread and Vcyclenut's shortening of the ports and removal of the top bellmouths. It seems it didn't make a significant difference - thanks to David for sharing this info - much appreciated. Intake testing - FLASHED BY VCYCLENUT . David didn't increase intake area though - has anyone tried adding an extra intake port to their airbox?

The reason I'm asking is that I have a background in engineering and a lifelong hobby in speaker design, plus I've modified airboxes and discovered some half-baked principles that I hope to try out on my MT-09.

1. Bellmouths are a must to maximise flow down a pipe - simply cutting holes is bad if there is no attention to inlet area increase / diameter of inlets / location of inlets / pressure changes / resonance.
2. Increases in inlet area should be in proportion to expected gains in torque/power to maintain airbox vacuum pressure - for example, I found a 6% increase in fuelling needed for a 35% increase in inlet area + DNA (who claim a 6.4% increase) on a Ninja 650R (Poiseuille's Law applies? The quad root of 1.35 is 1.078)
3. Adding long narrow inlet pipes can boost low down torque with appropriate fuelling changes and I think this works when it matches the slower flow rate at lower rpm and the resonance of the pipe is boosting flow.
4. Shortening an existing pipe offers more induction noise but only a small change in performance and requires changes to fuelling (it should increase flow but it doesn't seem to in practice perhaps because of the airbox volume/shape and changes in pressure and resonances - depends a lot on the airbox design).
5. Modifying the air temp sensor resistance to add more fuel is unreliable because the sensor is a non-linear themistor - using a thermistor works but getting matching specs is a pain to achieve. Rule of thumb is a 20 deg C drop is 4% more fuel.
6. Using a precision op amp circuit to gain the voltage on the throttle body inlet air pressure (IMAP) sensor allows extra fuel in a precisely controllable and predictable manner and can be finely adjusted on-the-go to dial-in the right feel (on low power engines that I know very well - I'm not a racer so I'd need data on high power bikes) - checking the spark plugs is essential too.

The idea for the MT-09 is to keep the intake tops, maybe change port length, and add an extra port to increase maximum flow. This is where I'd like:
Product Automotive design Automotive air manifold Automotive exterior Font

Basically, my theorising/experimentation on other bikes and from what I've read, the engine works like the speaker driver, and this pressurises the airbox/speaker cabinet with a vacuum in pulses. While a speaker experiences positive and negative swings in pressure as the cone moves forwards and backwards from a central position, a normally aspirated airbox only experiences negative from the induction pulses. The inlet pipes work as ports that tune the box - each port will have a resonant frequency determined by its dimensions and the volume of air in the box (there's software to calculate this - WinISD), and the specs of the "driver" (engine) interact with this. Engine capacity and valve duration would be equivalent to speaker cone dimensions and excursion. Above the resonant frequency, the induction noise is suppressed, and below, it flows freely - longer tubes have lower frequencies so they suppress noise more. At resonance, the flow is boosted. So, cutting the tubes down will affect resonance not only because of the change in length but also because airbox volume increases slightly - this changes the frequency, volume (amplitude), tone (frequency), and airflow at different rpm. Overall, this tends to result in more noise and changes in airflow/pressure occur but that these don't seem to offer a big performance gain for the MT-09. David's dyno runs seem to support this.

Adding more inlet area lowers pressure (in speakers, this is the damping back pressure, which is key to getting maximum sound pressure levels, spl, from the speaker driver). But if it is lowered excessively, this will reduce the pressure needed at various rpms for max power (max spl). While I get speakers, engines and airboxes are a complicated balance that I don't fully grasp. For example, I don't yet know the relationship between resonant damping, pressure and volumetric flow. However, I am sure that getting the most power from the engine means increasing gas flow over standard. To get more gas flow almost certainly means more intake area over standard, along with more air flow through the air filter and exhaust, and then getting the fuelling right for this extra flow. This is basically what DNA did with their stage 2 filter. The question is, how best to do it.

A bellmouth on the port end effectively lengthens the port and improves/increases flow because it is more laminar/less turbulent. Bellmouths have dimensional requirements to follow. Always use a bellmouth at the end of a tube. The other option is to use an orifice - this has no tube length so it needs a sharp edge - that means using a chamfer/bevel at the hole edge across the thickness of the material. No tube means no resonance.

So, has anyone tried adding an extra port to their airbox and done dyno runs/fuelling changes?

PS sorry for all the edits...I will keep changing this to make sure it is correct. Here's my Ninja modified airbox - I added the centre port as the increase in intake area.
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We could also see some gains from a change of stack lengths, also need some back to back runs with the snorkels trimmed & removed.
View attachment 168063
 

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Hi guys,
Can anyone direct me to a discussion of different mods to the airbox for the Gen3 2021 Yamaha MT-09? I can't find any - only this thread and Vcyclenut's shortening of the ports and removal of the top bellmouths. It seems it didn't make a significant difference - thanks to David for sharing this info - much appreciated. Intake testing - FLASHED BY VCYCLENUT . David didn't increase intake area though - has anyone tried adding an extra intake port to their airbox?

The reason I'm asking is that I have a background in engineering and a lifelong hobby in speaker design, plus I've modified airboxes and discovered some half-baked principles that I hope to try out on my MT-09.

1. Bellmouths are a must to maximise flow - simply cutting holes is bad, especially with no attention to inlet area increase.
2. Increases in inlet area should be in proportion to expected gains in torque/power - for example, I found a 6% increase in fuelling needed for a 35% increase in inlet area + DNA (who claim a 6.4% increase) on a Ninja 650R.
3. Adding long narrow inlet pipes can boost low down torque with appropriate fuelling changes
4. Shortening an existing pipe offers more induction noise but no significant change in performance
5. Modifying the air temp sensor resistance to add more fuel is unreliable because it's a non-linear themistor - using a thermistor works but getting matching specs is a pain to achieve.
6. Using a precision op amp circuit to gain the voltage on the throttle body inlet air pressure sensor allows extra fuel in a precisely controllable and predictable manner and can be finely adjusted on-the-go to dial-in the right feel.

The idea for the MT-09 is to keep the longer narrower port on the left unchanged because I think this aids low down torque and creates a low note for the induction noise. The other ports can be shortened to allow more induction noise, especially the largest/shortest/straightest one in the middle since that is designed mostly to suppress intake noise at high rpm - but I love this induction noise! Who doesn't? The longish large pipe on the right might benefit from a slash cut since the pipe is curved. Perhaps adding another short port with a bellmouth will increase flow without screwing up airbox pressure - where the mid pipe used to be.
View attachment 172114
Basically, my theorising/experimentation on other bikes suggests that the engine works like the speaker driver, and this pressurises the airbox/speaker cabinet. The inlet pipes work as ports that tune the box - each port will have a resonant frequency determined by its dimensions and the volume of air in the box (there's software to calculate this - WinISD), and the specs of the "driver" (engine) interact with this. Engine capacity and valve duration would be equivalent to speaker cone dimensions and excursion. Above the resonant frequency, the induction noise is suppressed, and below, it flows freely - longer tubes have lower frequencies so they suppress noise more. I haven't done the maths, but I think engine "frequencies" are far above these resonant frequencies. So, cutting the tubes down will affect resonance - airbox volume increases slightly lowering the frequency, and volume (amplitude), tone (frequency), and to a limited extent, airflow, but not airbox pressure, are changed. So, more noise and only small changes in airflow/pressure occur. David's dyno runs seem to support this.

Adding more inlet area lowers pressure (in speakers, this is the damping back pressure, which is key to getting maximum sound pressure levels, spl, from the speaker driver). Lower pressure creates lower resonant frequencies but if it is lowered excessively, this will reduce the pressure needed at various rpms for max power (max spl). While I get speakers, engines and airboxes are a complicated balance that I don't fully grasp. However, I am sure that getting the most power from the engine means increasing gas flow over standard. To get more gas flow almost certainly means more intake area over standard, along with more air flow through the air filter and exhaust, and then getting the fuelling right for this extra flow.

A bellmouth on the port end effectively lengthens the port and improves/increases flow because it is more laminar/less turbulent. Bellmouths have dimensional requirements to follow. Always use a bellmouth.

So, anyone know of any threads where the airbox has been redesigned either by trial and error or whatever? Has anyone tried adding an extra port to their airbox and done dyno runs/fuelling changes?

PS sorry for all the edits... here's my Ninja modified airbox - I added the centre port as the increase in intake area.
View attachment 172115
Your insight is appreciated it’s however the explanation of the intake process over my head. Keep up the good work.
 

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Thanks for the kind words. I am trying to understand this very cool airbox - hoping someone will step in and correct me... or even share their experience of changing the airbox.

I did some maths on the frequencies - maybe someone can check it for me as my brain is rather old...

The lowest idle speed is 1200rpm, so divide by 60 for seconds (so we can get Hz) and that's 20 revolutions of the crank per second. For a 4-stroke there's an induction every second revolution so that's 10 inductions per second, and for a triple, that's 30 per second. The firing order is, I think, every 240 degrees, so induction will be the same, and that's a regularly spaced pulse for a normal sounding 30Hz. So,1200rpm = 30Hz = a factor of 40. 10,600rpm is 265Hz, so the box is experiencing a frequency range similar to a woofer, with three resonant frequencies. The nearest equivalent speaker enclosure design is a bass reflex but 3 ports in that would sum to 1 not work as 3 different ones as I think they do in an airbox - this video gives an explanation - skip to about 5mins in to see visuals of resonance.

I also checked out DNA's website cos they do two air filters for this bike. The Stage 2 air filter replaces the top and inlet pipes. The P-Y9N21-S2 page says Stock Airbox and OEM Air Filter Air Flow: 94.20 CFM and DNA Air Filter Air Flow: 145.80 CFM. But, P-Y9N21-01 – the drop in replacement - page says OEM Air Filter Air Flow: 167.70 CFM and DNA Air Filter Air Flow: 210.80 CFM.

How much flow does the engine need? Each cylinder is going to draw in 296.67 cubic centimetres at each induction, which is 0.0104766842253 cubic feet. A four stroke triple at 10,600 rpm is drawing in 265 of each cylinder volume per second, and 15,900 per minute. That's 166.5 cubic feet per minute - about the same as the OEM filter (not airbox?) and a little more than DNA's stage 2 filter. Did I get that right? I'm sure DNA did so maybe I'm a little off, and/or they calcuated for a lower max rpm.

So it seems the airbox is a restriction - 94.20 CFM from a filter that can do 167.70 CFM. That's if the info is correct... hmm... so I've emailed them and asked about increasing intake area and/or shortening pipes. Let y'all know what they say...
 

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BTW, if anyone wants the easiest way to derestrict the airbox AND trusts DNA's numbers, then don't change the intake tubes - instead, cut 2 or 3 perfectly circular holes in suitable locations. Add a bevelled sharp edge from the inside of the box around the hole - the bevel inside, flat outside, with a sharp edge to the hole. No need for a bellmouth on such a sharp edged hole. DNA's numbers suggest the box needs an extra 70 CFM and that is roughly one 40mm diameter hole, or two x 28mm, or three x 23mm. This is based on normal max air temperatures from 25 to 40 deg C, and the ability of the engine to create -0.1 psi inside the airbox at max rpm (a rough but reasonable estimate - it would be good to measure this to be absolutely sure of the size). This will need refuelling changes of course.

EDIT - after much reading, I decided to buy a differential manometer to measure pressures inside the box and see if I can find a suitable area to test this as a possible way forward.
 

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How much flow does the engine need? Each cylinder is going to draw in 296.67 cubic centimetres at each induction, which is 0.0104766842253 cubic feet. A four stroke triple at 10,600 rpm is drawing in 265 of each cylinder volume per second, and 15,900 per minute. That's 166.5 cubic feet per minute - about the same as the OEM filter (not airbox?) and a little more than DNA's stage 2 filter. Did I get that right? I'm sure DNA did so maybe I'm a little off, and/or they calcuated for a lower max rpm.
It's been a while since I last did this and I already forgot all the details... I made 2 mistakes. I did not include volumetric efficiency (how well the engine can fill the cylinder - guessed at 0.9) or pulsation factor (how the filter affects the induction pulses in the airbox - 1.2 for a 4-stroke triple). The theoretical demand of this engine is 180 CFM.

So, the drop-in DNA or another filter than can flow over 180 CFM is needed to get the most from the engine, plus a modified airbox and new fuel map.

Here is a calculator that can work out what size circular hole(s) are needed to get the airbox to flow more. Calculator: Air Flow Rate through an Orifice | TLV - A Steam Specialist Company (Worldwide) If you click on advanced, you will see it allows you to change the discharge coefficient - this is the factor caused by the shape and sharpness of the hole. A bad hole can be as low as 0.4, but make the effort to make a hole as I described earlier and 0.7 is reasonable. Perfect could be 1.0 but nature doesn't do perfect. That only leaves the need to measure the pressure in the airbox.
 

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Cutting additional holes in an airbox defeats the whole idea of a resonant airbox. If it was all just about airflow we'd be back in 1980 with individual air filters or velocity stacks on each carb/throttle body.

If you give the airbox an easy way for the air to get in, you also make it easy for the air to GET OUT. There goes your positive pressure buildup. The oversimplified idea with these airboxes is you want it to be easy for the air to get in but not so easy for it to go back out.

This is what I did...

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Thanks for the reply and sharing the pic of a bellmouth on a short pipe. I bet that sounds glorious. :) Can I ask - how did you calculate the radius and length of the new pipe? Do you know the new resonant frequency? What was the length and surface area of the original? Obviously the new port changed the resonance of the single pipe and box (Gen 1 airbox?), so where in the rev range did it change the fuelling? I'm guessing you probably needed more fuel at the top third of the rev range, and at one point further down - maybe aroud 5,000rpm? where the original torque curve is not rising normally as it does elsewhere. I guess Yamaha designed this as a low noise rpm for the fixed speed test and the valve overlap. All the fours I owned in the 90s had this dull spot. Anyway, more details would be really helpful - thanks.

Regarding your comments, pipes in a box subjected to a pulsed wave of pressure will resonate at a given frequency with an amplitude peak at the resonant frequency and a moderate roll off on ether side - the Gen 3 box has 3 such resonances, which is why it is so interesting.

As long as there is pressure in the box, this will happen. The way to stop the resonance/damping is to cut the box open so much that there's no effective pressure which means there isn't a plenum so, yes, in such a case, we might as well employ cone shaped air filters directly onto velocity stacks and remap for that. I really hope no-one wants to do that.

The need to maintain pressure is why the openings always have to be calculated and designed - that's one of the golden rules. I'm working on that design but I'd really appreciate help as it's no small task and I've got a ton of paid work that's even taking over my spare time.

Airboxes act as plenum chambers but under cyclical negative pressure because of the induction from the engine. With no induction, the airbox is at atmospheric pressure, the same as the outside air (14.7 psi iirc). Flow happens when there is a pressure differential.
 

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BTW if you want examples of positive pressure, you should look at forced induction - compressors, turbos and even ram air. What people do with their Hayabusa is fascinating. One guy "NosGSX1300" says he measured up to +0.92 psi from ram air at some crazy speed - 192 mph - but then switched to a turbo. Clearly it needed more power. There's also some interesting stuff on car sites - guy with a Porsche 928 ( a 5.4 litre V8 6,000rpm engine) went from positive ram air pressure when off throttle at speed to -0.4psi WOT - about 0.5 psi change from putting his foot down iirc.

It might also help to look at DNA's stage 2 filter - it has no intake pipes - it replaces all that and looks like it creates an airbox open to the air at the air filter. Conceptually, this is somewhat the same as cutting the front half off the standard OEM box before the air filter. The stage 2 might still resonate - it is a large rectangular and very short pipe with porous cotton filler. I don't think the engine performance would be affected by it if it did though, except perhaps for vibration - energy not producing noise might get turned into heat or vibration...

DNA's stage 2 filter might flow more and this appears to be benefit the mid range but it has lost the resonant pipes and that is perhaps why it is not so good anywhere else in the rev range. So, although I've yet to test this, I think keeping the original resonant pipes untouched is essential, and then with that, is it possible to also increase flow into the box?

The air filter itself is a barrier - I'm not fully clear on the theory of this but I think the filter is, in practical terms, smoothing the induction pulses so it creates a more steady uniform pressure across its surface. This apparently causes a change in flow. What I do know for sure is that the filter needs a pulse correction factor when calculating CFM, and for a triple cylinder four stoke, the factor is 1.2.
 

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I got a reply from DNA -

"Thank you for your purchase and contact.

Concerning your request, unfortunately we can not share more RnD data to customers.

As you clearly saw we tested the complete airbox assembly with OEM air filter on our computerized flow bench because we developed a Stage 2 application for this model which offers more air flow than the stock assembly and has far better air flow dynamics for your bike.

The number you are looking for is completely theoretical and can not be achieved on the stock half airbox (bottom part) in place. The best possible results are achieved with our Stage 2 application.

As you want to have the best possible results from your bike we will suggest you to purchase our Stage 2 application and proceed to ECU tune your bike and you will see some great numbers and results.

Thank you for contacting DNA Filters LTD."

Sounds like it has confused bottom and top and if that's the case, then the "top" must be changed. They suggest a "top" that is designed with no intake pipes at all. It's literally a top with a filter cut into it. One could DIY that. :)

The other reading of this is the bottom half of the box is the limiting problem, not the top. If that's the case, a whole new box is needed. Who's got a 3-D printer, CAD software, a dyno, highly accurate pressure and flow sensors, and a month with nothing else to do? Don't all volunteer at once.
 

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Vcyclenut already tested the bike extensively and his results are impressive. Worth reading all his pages on this bike. When my bike is out of warranty, it is likely I'll be sending him my ecu...

I'm not sure there's much to be gained from the airbox either but the only way to know is to measure, calculate and test.

Shorter intake pipes have been tried by two people I've found so far, and didn't yield much at all for either, but that's not the only theoretical option.

First step to knowing is to measure pressures with a differential manometer, but I don't have time...
 

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