Dual inlet stacks
- Thread starter MVma
- Start date
Laverdalothar
Hero member
- Location
- Germany
Hi JLO,
from what I read about them (and that is also true for the v-stack from factory pro), the measurable effect is quite low. something like 2-3 % difference to stock or other stacks. And that was on very high revving GSX-R's or Yamaha R1's. On our bikes that rarely see 8.500 revs (so basically half of what is redline with a R1 or so...) I would consider them to be a lot of money thrown at almost no effect.
It is maybe similar to the "Power Blade" system used in intakes of KTM's with Keihin Carbs. It is basically a horizontal blade that is splitting the velocity stack into a low-end and a high-end segment with a 8mm hole at the front to equal out the transition between the two areas. I have them in the Jota and the 1000 SFC. To be honest though, besides a bit more "punch" in very low revs, it doesn't do anything that I would notice when riding. Loved the challenge though to built them and install them in the stacks...
So - if you have the money laying around to also do the setup of the carbs afterwards properly, go for it if you like. At least they will lead to a lot of attention on the next meeting, I am pretty sure...
from what I read about them (and that is also true for the v-stack from factory pro), the measurable effect is quite low. something like 2-3 % difference to stock or other stacks. And that was on very high revving GSX-R's or Yamaha R1's. On our bikes that rarely see 8.500 revs (so basically half of what is redline with a R1 or so...) I would consider them to be a lot of money thrown at almost no effect.
It is maybe similar to the "Power Blade" system used in intakes of KTM's with Keihin Carbs. It is basically a horizontal blade that is splitting the velocity stack into a low-end and a high-end segment with a 8mm hole at the front to equal out the transition between the two areas. I have them in the Jota and the 1000 SFC. To be honest though, besides a bit more "punch" in very low revs, it doesn't do anything that I would notice when riding. Loved the challenge though to built them and install them in the stacks...
So - if you have the money laying around to also do the setup of the carbs afterwards properly, go for it if you like. At least they will lead to a lot of attention on the next meeting, I am pretty sure...
MVma
Hero member
Thanks Lothar.
The goal is not to gain more hp only at top end. In my experience, the 180 engine is quite hard to tune up on all the power band, compared to the 120. Basically all that can be done in favour of top end power (including short stacks) dramatically affect torque at mid rev. And reciprocally. Much more than on a 120 engine. Thus the interest about these dual inlet stacks that are supposed to work as variable lenght inlets. I've not found much on this subject on the web.
The goal is not to gain more hp only at top end. In my experience, the 180 engine is quite hard to tune up on all the power band, compared to the 120. Basically all that can be done in favour of top end power (including short stacks) dramatically affect torque at mid rev. And reciprocally. Much more than on a 120 engine. Thus the interest about these dual inlet stacks that are supposed to work as variable lenght inlets. I've not found much on this subject on the web.
Those horizontal blades Loathar was on about do have a seat of the pants effect,maybe measureable with a stop watch but not for max acceleration.I fitted one either side,inlet and outlet to my dirtbike with a Keihan 37mm flat slide fitted to a 250 single 4 stroke.Very big carb on a small engine that tends to overwhelm it,especially with a poorly timed and strong accelerator pump squirt.These blades allow a clean pull below 1/2 throttle.Helpfull in poor traction situations.Over a tight course it would be intesting to see how it would time,with and without these double trumpets.The blade didn't need a jet change,worked well in my case.
Laverdalothar
Hero member
- Location
- Germany
MVma said:
not much, but some articles are out there. However, i am pretty sure you found the below already, but especially the PDF is very interesting. Looking at the graphs, I can not find a dramatic improvement, and that is on a highly tuned engine already. But maybe, you can overcome some issues our engines have with this system. Definitely not sure that the results in the PDF are comparable with our bikes...
http://www.gixxer.com/forums/showthread.php?t=197814
http://www.macmadigan.com/BusaECU/Sekalaista/Yoshimura%203%20EU%20SEMINAR%202006%20R1000-Engine%200601161.pdf