Lack of top end speed?

R

rc390cr

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Hello guys,

I have a 2017 RC390.... I have the following mods:

- Akrapovic full system
- Powertronics
- Air filter open lid

Bike has tons of torque and bottom end response is great... but there's no way I can go beyond 174 km/h.... (without Powertronics I was not able to go beyond 167 km/h) no matter if it is long straight or even downhill, it won't pass 174 km/h....

A friend of mine has a 2015 RC390 completely stock and he makes 185 km/h...

So I'm wondering... is my bike having a problem? Are these new models (BS4) mechanically limited? Cause electronically limited should have been cancelled by the Powertronics...

Don't get me wrong, I love my bike and I know the bike was meant for track use, hence more focus on bottom end power... but I'm curious comparing to the 2015 one...

Let me know your thoughts...
 
ReidMcT

ReidMcT

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First, are you certain that you are measuring speed accurately and consistently?
 
R

rc390cr

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Well.. it is what the speedo reads hehe... but yes.. I have done the same measure on the same place several times.. result is always the same.. and my friend's RC390 as well... same places both...

And to further clarify... bike is not even reaching rpm limit (which I left as OEM with the Powertronic @10500)... it gets up to like 9500 rpms and just stays there...no further "power"....
 
ReidMcT

ReidMcT

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Using two different inaccurate devices (on-board speedometers) to measure two different vehicles' speeds pretty much limits what can be discerned about your bike's speed. Testing both bikes with a single consistent device (e.g., a GPS tool) would be far better.

Your RPM observation, though seems more telling.

If you are saying that the engine will never exceed approximately 9500 rpm regardless of what gear it's in (including neutral), that would suggest a rev limitation imposed by the ECU.

On the other hand, if you are saying that the engine will never exceed approximately 9500 rpm in top gear, then it could be the ECU (mapping) or it could be a fuel delivery limitation (injector?). If the engine runs smoothly (no sputtering at its rpm limit), I would be looking hard at the ECU mapping as the culprit.
 
R

rc390cr

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Thanks for the input!

In fact what I meant was the engine won't pass 9500rpms in top gear... it would get easily to the rev limiter in all other gears, but not in 6th...

I took the bike to a dyno to tune it... and we set the map to have a safe AFR of 12.3 accross all rpms at full throttle...

So the only other thing that can be done is spark advance... but it makes no difference at all, as with 0 spark advance o 4 degrees as per new map, result is the same....

Bike runs super smooth, and as I said, in any other aspect is a beast... except top speed... and that's why I'm so intrigued....
 
ReidMcT

ReidMcT

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Running that rich, I wonder if you need a bigger injector. But I'm just guessing here, at the boundary of my actual experience/knowledge. I'll bet that Chad (jwell) would know for sure. Maybe you can reach him?
 
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