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pglaves
#13338
Ask Akrapovic. Unlike some other brands BMW does not make it easy to "remap" the ECU. You can't just hook something up and fiddle with the map. A new chip might be available - again ask Akrapovic.
My hunch is that the O2 sensor and ECU adaptation will take care of any issue but ask Akropovic. If they don't know or otherwise give waffling answers don't buy their product. It is one thing to bend pipes and weld mufflers. It is another thing to know exactly and precisely what that does to engine tuning.
alancoles
Dress for fall & avoid it
From the Revzilla Website info for R1200RTW Slip-on:
Not sure that helps as you'd really be best to find someone who has tried the RTW both ways on the dyno to know for sure. Asking Akrapovic directly might help. For instance, it would be interesting to know if those dyno figures and chart they post are for a completely unmodified bike with no fuel enrichment/mapping or for one that has been optimized. It would also be interesting to know:
a) if the figures are 100% stock with slip-on than what gains can be expected with tuning? Might be within the parameters of the stock ECU adapability. (I'd want a minimum of 2%-4% to consider tuning)
b) if the figures are post-tuning then what were the figures without any tuning?
Not sure that helps as you'd really be best to find someone who has tried the RTW both ways on the dyno to know for sure. Asking Akrapovic directly might help. For instance, it would be interesting to know if those dyno figures and chart they post are for a completely unmodified bike with no fuel enrichment/mapping or for one that has been optimized. It would also be interesting to know:
a) if the figures are 100% stock with slip-on than what gains can be expected with tuning? Might be within the parameters of the stock ECU adapability. (I'd want a minimum of 2%-4% to consider tuning)
b) if the figures are post-tuning then what were the figures without any tuning?
36654
New member
Excluding a few wiggles in the torque curves, it looks like you may gain a nominal 1-ft-lb gain from 2500 to 6000 rpm Is that going to be significant?
alancoles
Dress for fall & avoid it
Rudy, if those are your goals, than the Akrapovic will achieve them without anything required other than the 30~ minute install. Go for it and report your impressions back here. I'm still trying to justify spending the $$$ in my mind, as there is no shortage of places to spend my limited resources. ;-)
Only reason I suggested contacting them was if you were looking for a power increase. They show a 3~ HP and TQ gain through the middle of the rev band which would be noticeable as a small but nice improvement. Anything much less than that you couldn't notice.
My question was if that was achieved w/o any tuning. I've sent off an email to Akrapovic asking them exactly that and also if the figures are w/o tuning, what might be expected with tuning. Sometimes there is nothing to be gained and sometimes there is more. I'll report back here with their response if I receive one.
Wouldn't bother asking BMW. It isn't their product so even if they did know most everything about it they might or might not be inclined to tell you. It is surprising sometimes how tight-lipped they can be for legal liability reasons, etc.
Only reason I suggested contacting them was if you were looking for a power increase. They show a 3~ HP and TQ gain through the middle of the rev band which would be noticeable as a small but nice improvement. Anything much less than that you couldn't notice.
My question was if that was achieved w/o any tuning. I've sent off an email to Akrapovic asking them exactly that and also if the figures are w/o tuning, what might be expected with tuning. Sometimes there is nothing to be gained and sometimes there is more. I'll report back here with their response if I receive one.
Wouldn't bother asking BMW. It isn't their product so even if they did know most everything about it they might or might not be inclined to tell you. It is surprising sometimes how tight-lipped they can be for legal liability reasons, etc.
lkchris
Active member
A pretty trusting guy to believe fitting this exhaust will make any difference at all as regards how your engine runs. Trusting of aftermarket hype, that is.
Geez, you've got O2 sensors in your exhaust system (ahead of the muffler) constantly telling your fuel system how much to inject and you'd better believe there is going to be zero/zip/nada change in the quantity/quality of air injested to mix with this fuel ... but if there were, the O2 sensors would register that.
Geez, you've got O2 sensors in your exhaust system (ahead of the muffler) constantly telling your fuel system how much to inject and you'd better believe there is going to be zero/zip/nada change in the quantity/quality of air injested to mix with this fuel ... but if there were, the O2 sensors would register that.
alancoles
Dress for fall & avoid it
Kent, the O[SUB]2[/SUB] sensors don't tell the your fuel system anything. They send a voltage signal to the ECU or some other computer within a system. That value associated with that signal is used by the computer, along with all the other signals/data it utilizes by the computer to identify what commands to send to the fuel injectors.
The computer is trying to accomplish some pre-programed value within the fuel mapping to reach it's goal - an Air/Fuel ratio that is somewhere between Lambda (14.7:1 the Stoichiometric Ratio) the ideal for emissions/economy and the best "power ratio" (typically between 12.5-13.2). While the O[SUB]2[/SUB] sensor is a "narrow band" sensor, there is room within the entire system to adjust and adapt for many variables including putting a freer-flowing muffler. How much room? I don't know, and that is why I sent a message to Akrapovic.
I'm not one who casually dismisses any and everything said by a company as false or only self-serving. That is an over-simplified view of the world. I own my own company and when I make a public statement it is supportable and, I stand behind it.
There is real data collection available via a dyno and Akrapovic provide a dyno sheet showing a 3.5 HPm (R1200RTW rated at 125 HPm at the crank) gain.
https://d1sfhav1wboke3.cloudfront.net/ImageServer/Apim2media/Documents/14625/f2886515281f41c5bdc70bdb7be536b7.pdf
Given that they have published this, they do have a responsibility to a provide product that actually generates those results or be sued for false advertising. Keep in mind that many of the top International motorcycle racers in the world use their products and while there are some areas where a race team will use a product that doesn't do much simply for advertising revenue, this does not occur in the areas of power production as each team is trying to find every single 0.1 HP and spending significant money doing so. Championship MotoGP Teams like Yamaha (Lorenzo and Rossi) have used Akrapovic exhaust and would only do so if they knew there was an advantage.
My question to Akrapovic was simply did they get the 3.5 HP gain with or without tuning. I am not suggesting that they did, simply trying to determine what was required to get those figures on their dyno sheet.
The computer is trying to accomplish some pre-programed value within the fuel mapping to reach it's goal - an Air/Fuel ratio that is somewhere between Lambda (14.7:1 the Stoichiometric Ratio) the ideal for emissions/economy and the best "power ratio" (typically between 12.5-13.2). While the O[SUB]2[/SUB] sensor is a "narrow band" sensor, there is room within the entire system to adjust and adapt for many variables including putting a freer-flowing muffler. How much room? I don't know, and that is why I sent a message to Akrapovic.
I'm not one who casually dismisses any and everything said by a company as false or only self-serving. That is an over-simplified view of the world. I own my own company and when I make a public statement it is supportable and, I stand behind it.
There is real data collection available via a dyno and Akrapovic provide a dyno sheet showing a 3.5 HPm (R1200RTW rated at 125 HPm at the crank) gain.
https://d1sfhav1wboke3.cloudfront.net/ImageServer/Apim2media/Documents/14625/f2886515281f41c5bdc70bdb7be536b7.pdf
Given that they have published this, they do have a responsibility to a provide product that actually generates those results or be sued for false advertising. Keep in mind that many of the top International motorcycle racers in the world use their products and while there are some areas where a race team will use a product that doesn't do much simply for advertising revenue, this does not occur in the areas of power production as each team is trying to find every single 0.1 HP and spending significant money doing so. Championship MotoGP Teams like Yamaha (Lorenzo and Rossi) have used Akrapovic exhaust and would only do so if they knew there was an advantage.
My question to Akrapovic was simply did they get the 3.5 HP gain with or without tuning. I am not suggesting that they did, simply trying to determine what was required to get those figures on their dyno sheet.
36654
New member
Why would the typical RT rider care about a HP gain that occurs beyond peak torque at 6600RPM?
Exactly.
More open exhausts typically can give only modest results at high rpm, sometimes at equal expense of mid range. The only reasons to fiddle with mufflers is sound and weight- the potential minor high rpm power gains don't justify the cost. And on a touring bike its questionable whether the weight reduction matters much- unlike a topcase, a muffler is pretty low
My idea of an ideal machine
1) Turns thought into velocity
2) Makes no sound
3) Is invisible on command
More open exhausts typically can give only modest results at high rpm, sometimes at equal expense of mid range. The only reasons to fiddle with mufflers is sound and weight- the potential minor high rpm power gains don't justify the cost. And on a touring bike its questionable whether the weight reduction matters much- unlike a topcase, a muffler is pretty low
My idea of an ideal machine
1) Turns thought into velocity
2) Makes no sound
3) Is invisible on command
36654
New member
alancoles
Dress for fall & avoid it
Most shouldn't.
But that isn't what one should look for anyway. What the typical RT rider likely cares most about is torque in the low-mid range where the bike spends most of it's cruising time, 2,500-4,500 rpm.
That is precisely where the chart shows the Akrapovic providing it's biggest TQ gains, approximately 5.6% gain at 2,800 rpm and maintaining a healthy advantage up to about 4,200 rpm.
No one is saying that there is an economic case to be made for these things, simply that they are of interest to some of us and that there are a few benefits to them. Those few benefits do come at a fairly hefty premium (primary reason I don't have one), but actually provide as much or more "real world" value than perhaps 50% of the frackels most BMW riders adorn their bikes with, but, to each their own.
pauls1150
MOA #24991, south of Los Angeles
Maybe I'm misinterpreting the plot provided here
, and I have not looked directly at the Akro site, but to my eye, the "smoother" of the plots is the torque, and the bumpier/sharper one is the horsepower.
What that shows is almost NO torque increase until about 6200 rpm, but the HP increase from about 2600 to 4800 rpm is significant.
If this interpretation is wrong, say so and I can accept that...
, and I have not looked directly at the Akro site, but to my eye, the "smoother" of the plots is the torque, and the bumpier/sharper one is the horsepower.What that shows is almost NO torque increase until about 6200 rpm, but the HP increase from about 2600 to 4800 rpm is significant.
If this interpretation is wrong, say so and I can accept that...
36654
New member
Maybe I'm misinterpreting the plot provided here
What that shows is almost NO torque increase until about 6200 rpm, but the HP increase from about 2600 to 4800 rpm is significant.
If this interpretation is wrong, say so and I can accept that...
Smoother curve is the HP. It still climbs, at a slower rate, after 6600-rpm, while the torque drops.
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pauls1150
MOA #24991, south of Los Angeles
How can you tell which is which? I just went to the Akro site, found that plot, and did not see where they define this.
I've seen a few plots "live", as they were being generated, and the "bumpy" plot is typical of HP, including the dip just before 5K rpm (often attributed to intake restriction).
And as previously inferred, low- and mid-range torque is more beneficial to a touring bike, while high-end HP is desirable for a racer.
I've seen a few plots "live", as they were being generated, and the "bumpy" plot is typical of HP, including the dip just before 5K rpm (often attributed to intake restriction).
And as previously inferred, low- and mid-range torque is more beneficial to a touring bike, while high-end HP is desirable for a racer.
36654
New member
I would suggest a high order polynomial curve-fit of the results (both HP and Torque), then making a comparison. Those humps and wiggles in the torque curve appear to be the selected transition points between the individual runs in each gear.
36654
New member
HP = Torque * RPM / 5252
