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Discussion in 'Parallel World (790/890)' started by doctorblanco, Aug 20, 2019.
Going to void the warranty. Lol
I'll just leave this here :)
I'll be waiting till someone like Bren tuning either cracks the PCM completely or someone offers a replacement like the Vortex. Coober seems to already make an ecm but seems to be shying away from offering decat tunes for whatever reason and doesn't seem to give the end user the ability to get in there and make changes, your stuck with their canned tunes. But I could be wrong on that.
Rottweiler offers a tuner and both stock and race tunes for decat and or AM mufflers.
I have to rewatch his earlier vid, assuaging any dangerously lean condition anxiety Coober had instilled in guys. But my next question will always be what functional difference will there be between a regular mid pipe, and something like Arrow makes with the megabomb like core, as the 2 designs relate to tuning. Did Rottweiler create his decat tunes with an Arrow mid pipe with that core or with just a straight pipe as many guys are buying? If it doesn't make a damned bit of difference then it's moot but if it does I'd like to know in advance of choosing my decat mid pipe...
Those are really good questions. I personally got the arrow part with the “powebomb”. I chose this for two reasons, one of them being that it should be quieter than a straight pipe and the second is back pressure. I am sure all engines need it to perform better on low rpm. High rpm is a different thing but 790 performs really well there.
I have little to no idea on the technicalities of the oem mapping / ecu cleverness, however I am informed by my dealer that doing a decat with a simple straight link pipe will just result in more fuel being squirted in (ecu saying 'make richer' - that's good given the imposed lean Euro5 restrictions) and it'll make more noise.
That's entirely subjective as i've not done a dyno run before and after... My bum dyno says the bottom end has not fallen into a hole! The acceleration from off 3K revs all the way to WOT still feels the same. The soundtrack has simply improved 100%.
I don't mind a little less fuel economy (fcuk the dolphins and I am recording mileage following the VEREX change) + I love a little more noise! Totally unscientific I know...
If it goes BOOM, it's on me :)
A piggyback controller is not what I'm holding out for. With a true ECM reflash the root tune and setting for other things like throttle maps, traction control, QS tweeks, speedo corrections, engine braking, etc can be fixed/tweeked. A piggyback controller like the PC5 is just fooling the ECM into doing what it wants as far as spark and fuel and isn't able to "fix" it in all the areas needed. Open loop they work pretty well but in closed loop it can get a little messy.
With all of the interest in these bikes for rallies, it's only a matter of time before someone does exactly that.
Back pressure is a myth.
Velocity is what changes low end performance, so as long as you aren't changing your primary exhaust diameter there should be no real change.
That's what my bum is telling me... and making my ears smile!
.....no one ever described either of my bikes as "subtle" we'll put it that way
I agree and disagree at the same time:
The proof of the pudding... etc, etc...
I know what my bike was and it’s performance was from day 1 and so until after the first 1K service. Am now at 7.5K kms...
Decat to simple link pipe has not resulted in a softcock performance off the bottom end.
Think that Coober are scaremongering cause they couldn’t crack the code, dunno.
But I am not saying your bike isn’t performing better than before! We are just trying to understand the theory behind arrow’s Decat design.
Two different things.
That is the open/closed tube thing in physics and its largely length based......if the diameter changes exactly on a "half" wave there is no effect on exhuast flow, issue is that the length only happens at X RPM
Well yea, when you get into the physics of it, back pressure is bad. Primary tube length and size is something that needs to be tuned for the engine, the "collector" is also important, the pipes behind it not so much as long as they flow enough to not restrict flow. While back pressure can help bottom end torque but it can hurt top end performance a lot more. Exhaust tuning is all about scavenging and using the pulses to pull air out of and sometimes through the engine. Inertia. It's possible the converter is acting as a tuned collector. Like anything else in an engine it needs to work as a package to give optimal performance.
And Orfeas, not directing this at you or disagreeing, just throwing it out there to help folks understand it's not as simple as back pressure like you said.
The back pressure myth is a zombie myth that won't die because people don't actually want to listen to engineers. Engines wants high velocity exhaust gas flow at low rpm and high rpm. Too big a pipe slows gas flow at low rpm because of expansion/cooling and may do the same thing at high rpm if the stock size wasn't a restriction
Back pressure may be a poor choice of words, but it is not a myth. It is just a term intended to describe the resistance the exhaust gases encounter as they rapidly expand in the exhaust system. The way this type of resistance is measured in a gas is called pressure. When the diameter of the downstream pipe is constant, it does not necessarily mean that the pressure is constant along the entire path, because the expansion rate of the hot compressed gasses and the pulse rate of those gases must also be taken into account. Engines don't "want" high velocity, or low velocity. Engines perform better when the pulses of gas flow do not "stack up" in the exhaust system. So what an engine needs from its exhaust system to perform at its optimal thermodynamic efficiency is a proper match of pipe diameter, gas expansion coefficient, and pulse frequency.
Oh to have a KTM engineer chime in - 'Hey, if I didn't have to worry about the EURO 5 crap this is how I would have sorted the 790 ADV exhaust system...'.
I don't think I've heard a explicit answer for how the Arrow mid pipe may differ in function from a regular $80 straight mid pipe. So I go back to a previous query - did Rottweiler use an Arrow mid pipe to derive his tunes? And if so, will a guy running a regular straight mid pipe be kidding themselves? Or will he (without the auto tuner) be granted the same performance across the RPM's as an Arrow mid pipe owner?
*I too would prefer replacing the entire ECM like I did on my HOG. Pulled the stock one and replaced it with a ThunderMax auto tuner ECM, and never looked back. I always viewed something like a PCV as a bit of a bandaid ... or patchwork solution.