Ramair filter arrived...

Speedy said:

Painting with a pretty broad brush there! Absolutely, if everylast hp at peak rpm is desired, this is not the way to go. If you want the most average hp across a wide range of rpm, a properly sized plenum is the only way to go. If you run the salt flats or drag race exclusively, run individual TB runners. But if you want a wide power band, use a plenum much like virtually every modern roadrace bike has under the tank. All performance choices on street bikes involve compromises. Let each rider choose what works for their riding style and useage. To say that this or that kills horsepower is useless unless you say how much is lost, at which rpms it is lost, and more importantly, acknowledge where power may be gained. Only then are potential users informed and able to make better choices.

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IMFASTTOO said:

WELL you would need to size and tune the plenum and thats going to be a lot of R&D and a Dyno

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Speedy said:

My response was not to "tell you" anything but to remind Art that his statement was so broad as to be near meaningless. I acknowledge that he is correct but also that having the most peak horsepower is not every rider's wish. Many of us prefer a broad power band with early torque delivery and accept that we won't win at the drag strip.

As to the stock plenum, it is a compromise as well. However, the problem with it is not the plenum itself but the dual small inlets into it and the ducting to them. The inlets are in the wrong place; they are too small, there are two of them; and the ducting leading to them is very constrictive.

The model I posted is a compromise as well. Several weeks of computer simulations of the intake, cams, and exhaust systems of the R3 led to the development of a header and intake modifications and then to two plenums, one of which you see here. Dyno testing evaluated the designs and indicated that the designs while not perfect where way better than stock. The design goals where to stay under a 6,500 rpm limit, work very well with stock cams and a good aftermarket header, such as the Predator by Sam, or the one I designed, built and use, which is not marketed, and then also work with cam upgrades that do not move the rpm limit to 8,000 plus rpm but stay in the stock range.

I have no issue with Carpenter Racing, their engine modifications, or exhaust header. They apparently work well and are reasonably reliable. My hat is off to them for accomplishing what they set out to do. Nonetheless, their package is not for everyone.

As to what one can expect with a sound plenum design: more average horsepower over the designed rpm range. This plenum will start making a difference at about 1,900 rpm, increase torque significantly at 2,400 rpm, levels off up to 3,000 rpm and then rapidly increases torque to 4,000rpm at which point ithe torque curve begins to taper back. There is a loss of horsepower above 5,500 rpm compared to individual filters but power there is still greater than an under tank K&N. And all of this is varied by the exhaust system used.

The combination I used on my bike, with stock head and cams, was tested on an eddy current dyno which allows controlled acceleration rates (and one I did not own or operate.) At 20% throttle, 75.79 ft/lbs were developed at 2,500 rpm. At 30% it pulled 103.59 ft/lbs and at 40% throttle it pulled 120.85 ft/lbs at 2,500 rpm. For those of you who have dynoed your bikes on eddy current dynos, these last numbers are probably close to what a stock bike with Jardines and three filters pulled at WOT. And at WOT it pulled 155.75 ft/lbs at 3,936 rpm. However, by 5,500 rpm torque was down to 114.10 ft/lbs where it leveled off and gradually dropped to 107 ft/lbs at 6,500 rpm. I have dyno charts to back these numbers up as does the shop that did the testing. And my bike is listed on their shop wall as producing more torque than any naturally asperated bike they have ever tested.

This suites my riding style and the fact that I ride two up with my spouse frequently. I don't care that it doesn't have more total horsepower than some other R3's. With this much torque across the normal operating range it is a blast to drive, is smooth as silk, has no intake chirpping, and pulls like a 16 year old with a new PlayBoy.

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Speedy said:

One of the reasons that I am reluctant to change the rpm range significantly is that you can't change the final gearing. The R3 is geared fairly tall. When I am cruising at 3,000 rpm I am right in the middle of my rpm and power band. If my powerband would run from 3,500 rpm to 9,000 rpm, to cruise in the same "sweet spot" the rpm would be 6,000 or more. A wee bit fast to cruise for my taste. Sure, I can drive around in 4th or maybe even 3rd gear but then I have effectively went from a 5-speed to a 3 or 4 speed tranny. It is analogous to having a '69 Z28 Camaro with 2:73 final gears. Runs great at 55mph (but I am in second gear to do so). I know, I know, that some will say but my R3 runs great at 2,500rpm, or even slower. I am sure that it does, but it probably has less power there than a stock bike. And to use that power all you need to do is drop 2 gears down.

Now, give me a shorter gear set for the R3 and my cylinder head will be off and on the CNC faster than a blazing rocket.

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Speedy said:

One of the reasons that I am reluctant to change the rpm range significantly is that you can't change the final gearing. The R3 is geared fairly tall. When I am cruising at 3,000 rpm I am right in the middle of my rpm and power band. If my powerband would run from 3,500 rpm to 9,000 rpm, to cruise in the same "sweet spot" the rpm would be 6,000 or more. A wee bit fast to cruise for my taste. Sure, I can drive around in 4th or maybe even 3rd gear but then I have effectively went from a 5-speed to a 3 or 4 speed tranny. It is analogous to having a '69 Z28 Camaro with 2:73 final gears. Runs great at 55mph (but I am in second gear to do so). I know, I know, that some will say but my R3 runs great at 2,500rpm, or even slower. I am sure that it does, but it probably has less power there than a stock bike. And to use that power all you need to do is drop 2 gears down.

Now, give me a shorter gear set for the R3 and my cylinder head will be off and on the CNC faster than a blazing rocket.

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