We got to play on the dyno and test various intake lengths. It seems there is plenty to gain for the bikes that run at high RPM!
https://ibb.co/e211O7
https://ibb.co/e211O7
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Intake testing 2-12-18
Fixed with an actually readable dyno chart
Fangfactor
Member
Interesting. Thanks for posting 
I notice the RC390R has a shorter Intake ram tube. Are these the results of a 90mm tube length? Any idea what length the 390R intake tube is?
I notice the RC390R has a shorter Intake ram tube. Are these the results of a 90mm tube length? Any idea what length the 390R intake tube is?
Interesting. Thanks for posting
This was our version of the 390R tube, I got the dimensions from secret sources inside KTM.
Fangfactor
Member
Thanks for that. Im playing around with different lengths myself and its interesting to see dyno graphs to back up what Im feeling.
I will be doing some track testing next weekend.
They really respond well to the extended rev limiter, it pulled easily to about 10800
Fangfactor
Member
streetfighter
New Member
What does your intake ram tube looks like? Any photos?
Sent from my iPhone using Tapatalk
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Deleted member 452
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The dyno sheet provided shows power decreases after 9.8K RPMs with torque falling after 8K RPMs (Just like most properly tuned 390s with stock cams). Our bikes are known to suffer from valve float with stock cam springs above 10K RPMs so why would anyone want to keep reving past that?
Rev2
I revised the air horn and then overlayed a supersport bike as well, both bikes share the exact same parts list. I don't have any pictures of the air tube at this point because it is far too ugly for pictures, this is all just preliminary testing prior to receiving the RC390R official part. We run titanium valve spring retainers and that reduction in weight means no valve float. This setup will provide a massive advantage on track, but for street use is almost entirely useless as you can see the torque and hp drop in the midrange are significant. I didn't tune on the pcv etc yet as you can tell with the huge dip at 9800 but this is all just a theory test.
https://ibb.co/cHnQSc (clicky)
I revised the air horn and then overlayed a supersport bike as well, both bikes share the exact same parts list. I don't have any pictures of the air tube at this point because it is far too ugly for pictures, this is all just preliminary testing prior to receiving the RC390R official part. We run titanium valve spring retainers and that reduction in weight means no valve float. This setup will provide a massive advantage on track, but for street use is almost entirely useless as you can see the torque and hp drop in the midrange are significant. I didn't tune on the pcv etc yet as you can tell with the huge dip at 9800 but this is all just a theory test.
https://ibb.co/cHnQSc (clicky)
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It should show massive drops after 9500 or lower. What dyno was this run on?
D
Deleted member 452
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That makes sense- Thanks for providing the additional info.
Fangfactor
Member
Does anyone know if the 390R will have a different cam profile to suit the shorter ram tube
It has a new fork, shock, air tube, top triple and clip ons. Thats it.
Fangfactor
Member
Cool, sounds like mine is 'R' spec already then hehehe.
So by rights the 390R airbox including short air tube should be available as a spare part?
Sounds like the additional race kit has all the other goodies.
Hopefully! I am working with KTM to make that part available to the public. The race kit is ridiculous but thats why I don't race WSS.
You gained .9 hp over previous run. Did you compare run times of acceleration on that dyno data? I suspect the short stack run took much longer. The losses on the front side are HUGE from the 90 mm stack. It lost peak torque too (looks like) 3 ft/lbs. That will be extremely noticeable even on track IMO. You will feel it layover too in that 9800 rpm dip in hp pulling thru there. I tried shortening the stack in my kit builds long last year to see if I could get it to respond. I cut the stock one down to 100 mm and attached a FCR plastic velocity stack to it. It had a much nicer bell/throat then oem rubber. It did not respond well to it even at 48 hp. It lost front side and made no more peak power or power anywhere. I don't want to high jack your thread, just thought I would give you my findings on when I tried it. It is interesting that the "R" comes with that new stack. I'll be curious to see it on my dyno when we get one.
It certainly took longer to get the run done, however it also added 1000 RPM to the run so it isn't a completely back to back test. I think the theory behind the runner is sound but it certainly going to be dependent on what track and the ability of the rider to keep it spinning. My current runner is such a POS that I believe that plays a large part in the dip. It is certainly an interesting part and it will have its uses, but not everyone will need it. I am always open to friendly discussion, thats why this thread is called testing!
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Also remember that Pacman is running in OMRRA where airbox mods are not allowed so there will be some variances with club rules which may determine who can benefit from changes in the airbox. I would expect there would be differences based on if the lid was on vs off... Of course, the real answers are on the Dyno and factual back to back runs to see which changes net gain and which ones don't.
I love seeing the discussions on changes and what does what. Even better when we get Dyno results published so there isn't vague hand waving around impacts.
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