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Discussion Starter #1 (Edited)
2011 CBR250R - Changed My Exhaust Pipe To A Two Brothers Carbon Fiber Slip On

I am a new forum member to just wanted to say greetings to everyone. Some good stuff being discussed around here.

I bought a CBR250R recently and then I just changed the standard exhaust pipe on the bike to a Two Brothers Black Series Carbon Fiber slip on a few days ago.

I had read mixed stuff about what to expect and whether or not I would need to change the ECU and/or at least remap it after the pipe change.

Lots of what I read before changing the pipe was confusing so I thought I would try and share my own observations so that other people can get an idea of what they might expect from just a pipe change if they are considering it too.

I also want to say I rode the bike for a few weeks before changing the pipe so I at least had a good idea of how the bike performed previously with the standard pipe before I changed it. This way any changes in performance would be more easily recognizable.

First of all, without a doubt, the bike now sounds like a proper beast. It also doesn't pause and feel like it is being suffocated when you lay on the throttle. According to the Two Brothers pipe's specs I gained about 10% HP and some extra torque as well. I didn't remap anything and my mechanic who changed the pipe for me told me I might even feel a bit of drop in speed since I was increasing the amount of oxygen getting back into the engine without having any increase to the amount of gas going into the engine as well. But I don't believe what he told me is actually so true. I sense the bike probably adjusted the mapping a bit itself to match the new pipe and possibly something the mechanic didn't anticipate happening since the standard ECU mapping on CBR250R bikes is known to be constrained and he normally works on bigger bikes where the ECU is already mapped to more of a racing spec right out of the factory door.

What I can say from riding the bike after the pipe change is that bike has a lot more torque in all the gears now and a lot more get up and go in the upper gears in particular. The RPMS get up there pretty quick in the lower gears now and I have to change much quicker out of the first 2 gears or I red line pretty fast. Before I could get up to 70km/h in second gear before it started red lining, but which is something I really can't do anymore. I would say 40-50km/h max in second gear now before it starts approaching red line. So the first 2 gears are pretty useless now getting off the line since I need to change gears almost immediately if I want to get the bike moving, but once I get into 3rd gear the thing starts taking off. So as long as I change the gears quick then the power and performance is delivered much quicker. And in the upper gears, say when I am riding up around 80km/h and I lay on the throttle hard, it doesn't pause like it did before. I hated how it was so slow in the upper gears before. The jump from 80km/h to 100km/h for example is much faster now. The bike revs higher in all gears now as I said, but I realized that is a good thing because it gets me into where the power band is at the higher RPMS more quickly and where I need to be to get the bike to accelerate faster. Before it took longer to get the RPMS up there and thus that made the acceleration slower. The first day riding it after I changed the pipe I was a bit concerned because I felt like I lost most use of the 2 lower gears, but I realize changing gears into the higher gears more quickly is what you want to be able to do and something I wasn't able to do before because the RPMS were too low to change gears as fast as I can now. Also, the upper gears would cruise at lower RPMS before the pipe change, which means they had less get up and go before. So now I am able get into the gears where there is more power to begin with (and now with added torque in those gears as well), it gives the bike a lot better acceleration overall. So I have had to change the way I ride it a bit and change gears more quickly, but its really nice now with that extra power at hand.

And it sounds great. I love the throaty sound of the Two Brothers pipe. When you drop from first into second gear and gun the throttle the sound is so deep and loud. It doesn't sound anything like a 4 cylinder big bike would say, but for me it is just right and a nice sound. Before the pipe change you could hardly hear the bike approaching. The loudness is a good thing for me as it makes riding more safe in a way since the city where I live there are lots of stray dogs that often run out in the street.

I am still debating whether or not I should even try to remap the ECU an/or add a Power Commander or a Juice Box. My initial thoughts are no because unless it is going to drastically increase acceleration I don't see the point. At the end of the day it is a 1 cylinder, 4 stroke bike. So it is what it is and I doubt by adding any mapping components to control fuel intake that it is going to make that bike significantly faster off the line. I would be interested to hear other people's views on that and if it is worth the added investment of changing and/or adding other electronic modules to the ECU to control fuel intake.

I think the pipe alone was a very worthwhile investment though for sure. It makes the bike sound much better, it added torque, the ability to have faster acceleration resulting from quicker gear changes, and a quicker jump up in general to where the power band is up at the higher RPMS.
 

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Before I could get up to 70km/h in second gear before it started red lining, but which is something I really can't do anymore. I would say 40-50km/h max in second gear now before it starts approaching red line. So the first 2 gears are pretty useless now getting off the line since I need to change gears almost immediately if I want to get the bike moving, but once I get into 3rd gear the thing starts taking off.
Glad you like your pipe. But i'm calling BS on this passage. Unless the pipe added so much power that it's causing your clutch to slip, or, you making so much 'powah' that your back tire is spinning. Speed is a constant based on gearing, not horsepower (assuming you've got the horsepower to push it). Theirs no way short of severe clutch slippage or a boiling back tire to explain your difference in speed at redline.

Obviously, this isn't the case as clutch problem tend to show themselves in top gear under load. So I'm calling this passage seat of the pants editorial license :D
 

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Discussion Starter #3 (Edited)
Steve - I am not a mechanic nor do I totally understand all the science of how the exhaust pipe change will affect the performance of the bike. I am strictly providing my own personal experience of what I physically observed and felt after changing the pipe versus riding the bike for a few weeks with the factory pipe before changing it. I thought it might be useful for others who bought a stock model of this bike like I did and are also considering changing the exhaust pipe and wondering if it would be worth the cost of an after market pipe versus any sort of physical performance improvements they might benefit from after replacing the pipe. Full stop.

According to the manufacturer the pipe should add 10% HP as I said and I forget how much torque. But the torque is already noticeable by the higher RPMS in the lower gears at lower speeds. Also the new slip on pipe is probably about 1/3 of the weight of the old one. So some net weight has probably been taken off the bike as well, which may help a bit too.
 

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Interesting writeup marcbkk, I'm considering getting a 2Bros slip-on for mine as well in maybe another month after the winter break money crunch is over. Two questions that I'm hoping you'll be willing to answer:

1.) What was your total mileage when you switched to the new pipe, and how much mileage have you put on since? I'm curious only because I'm trying to get an image of how long the stock ECU (no Power Commander or hard reset, etc.) takes to 'adjust' itself to changes in the engine airflow configuration.

2.) Did you leave the Powertip that comes with the Two Brothers exhaust in?
 

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Discussion Starter #6 (Edited)
Thanks.

1 - When I switched to the new pipe I had about 600-700 total kilometers ridden on the bike already. I would say it took about 2 days of riding around in short distances for the ECU to adjust itself after that. It didn't take long, but I didn't feel the increase in power in the upper gears right away either. I don't think an ECU reset is necessary at all at this point unless you are going to change the full exhaust system. A slip on is really a nominal change for the ECU to handle and it can adjust to it on its own. In fact, I just took the bike to the Honda service center at the dealer to have the first oil change done and the guy there was admiring the pipe. So I asked him if I need to reset the ECU and he said no to it as well. I am also debating adding a Power Commander or Juice Box, but I doubt with a bike like this it would make much difference to justify the cost.

Also, the first couple of days the bike sometimes stalled either during start up or when driving at low speeds a few times. That stopped after the first 2-3 days completely, which would suggest it has adjusted as well.

2 - I left the Powertip in the pipe. Basically I put it on as stock the way I bought it from FlyinCycle. If you watched the above video I posted then I can say that the sound in real life is much deeper and bassier than it sounds on the video. I think the audio range of the camera I shot the video with is not really capable of capturing the sound as it really is. I must say the sound of the pipe is really sweeeet.
 

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Thanks for the thoughtful replies marc! This is the first time I've heard about an aftermarket exhaust putting the engine into a low-rev stall but it makes sense upon consideration due to the change in the fuel-air mix ratio. So long as the ECU adjusted quickly it still sounds good though. I agree that an aftermarket fuel mapper seems mostly wasted on the little CBR outside of major configuration changes.

Your video was just fine. My imagination filled in all the necessary blanks... I'll have to have one soon, that's for sure. Probably in Black Edition/Stainless Steel to go with my red/silver!
 

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Discussion Starter #8
Your welcome. Before I bought the pipe I also was wrestling over which finish to get. I was leaning towards titanium, but felt it might discolor after a while and same for the stainless which was actually my last choice. The carbon fiber is amazing though. Even after a long ride the pipe is cool to the touch. So it displaces heat really well. It's also an advantage if you want to park the bike and throw a cover over it right away as you don't have to wait for the pipe to cool down first. If you have the extra scratch I would go for the carbon fiber. It will look great on a red bike too.
 

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I also have the 2Bros carbon, and love it, but you not getting 10%. According to their dyno graphs(not the stupid chart that contradicts itself) best you can get is with the db killer removed, +1.44hp over 23hp at stock(their figures not mine) which is closer to 5% than 10.
But like I said I love the pipe, without the db killer you can feel the extra little bump in the torque curve down low, and the ringing in your ears that lasts long after the ride, but to like the 2Bros you have to like a thumpa if you don't you'll probably hate it.

2 links to "dyno chart" :)
http://www.twobros.com/Cust_Service/Dyno_Charts/dyno_2011_hon_cbr250_SO.pdf

http://www.twobros.com/Cust_Service/Dyno_Charts/dyno_2011_hon_cbr250_SO_No-Tip.pdf

as for the RPM's I do 6K in 6th doing 100kph(speedo indicated) same as most everyone else, might just get there a little quiker than it did stock, but not much.
 

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Discussion Starter #14 (Edited)
Do you happen to have a snap of what that looks like when you take the Powertip off? I am curious what that involves.

How much did the sound increase after you took the tip off? Or did you take it off before even installing it on the bike?

P.S. - I just looked at your profile and noticed you put on the other series pipe, not the black series one. That one was a bit less expensive, but not sure there is any performance difference between the two.
 

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Discussion Starter #16
As a clarification, contrary to some of the Two Brother's pipes which don't come with the Powertips installed, the pipes for the CBR250r do come with them preinstalled from the factory. So if you don't want it on the pipe then you would need to take it out as mentioned here on the 2B site here:

Two Brothers Racing :: Honda CBR250R High Performance Motorcycle Race Exhaust Systems

Personally, for the little bit of extra torque you might get out of it, I wouldn't bother. Already with the Powertip in my neighbors are not that thrilled about the bike. Its pretty loud now, so I am not sure any louder would be good unless you want it to sound like a real beast and feel even more vibration in the handle bars in the lower gears.
 

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^There is extra torque available down low without the "power tip" no "might" about it. And yes it is much louder, but the neighbors who's gas guzzling 4wd's take up almost all the parking (only street parking were I live), can f**k off.
I don't notice any extra vibration anywhere in the rev range. Did 2000k's with tip in, done 1000k's with it out. It will stay out until a cop defects me for noise, which I don't think is very likely(knock on wood).
 

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Discussion Starter #18
Thanks. In that case, maybe it is worth a try with it out. It is only a 5 minute removal process. Surely its going to draw even more attention to an already loud pipe, but if the performance increase is noticeable then it may be worth a go. If I don't feel the trade off is worth it after taking it out then I can always put it back in. Stay tuned.

I am also curious if the performance increases that Two Brothers claim you get from this pipe are based on with the Powertip in or out?
 

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I am also curious if the performance increases that Two Brothers claim you get from this pipe are based on with the Powertip in or out?
Two Brothers has 2 charts available on their website, both already linked by killstrelok in a previous post. There is a third configuration which they choose NOT to publish an official chart for, and that is WITH the power tip/dB kill installed and WITHOUT a Juice Box fuel mapper.

I'd really like to see that data to know exactly what's happening by comparison. The two possibilities that I see are both based on the assumption that 2 Bros, being a company that likes to sell their product just like any such business, doesn't show this chart because either....

A.) it would show that the Juice Box has only a nominal effect on horsepower/torque curves of the little CBR250, making people less likely to buy a Box,

or

B.) it would show that in the 'easiest' configuration of no Juice Box and the pre-installed dB killer in, there are actually points on the powerband where the CBR250 either has no real improvement or even suffers by comparison to stock (one would predict this at the lower RPMs), thus possibly making more casual buyers want to shy away from the brand and go to another that might give performance with a less-involved system.

I'm not negatively critiquing here, if anything it seems like 2 Brothers is one of the best (or at least better) exhaust manufacturers about documenting their product lines and giving the buyer maximum information, but just trying to extrapolate a reason for this omission of data.
 

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Thanks for the link Marc.

Its pretty loud now, so I am not sure any louder would be good unless you want it to sound like a real beast and feel even more vibration in the handle bars in the lower gears.
Just a final question. Did it add noticeable vibrations to the bike?
 
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