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Yesterday, I started installing some of the accessories that I've been accumulating over the last coupla' months. As part of the process of installing the Fuel Controller, I removed the airbox and backing plate. Examining the airbox, it suddenly hit me; our stock airboxes are sucking intake air from between the two cylinders: HOT, low-density air, that is. The manufacturers of virtually all normally-aspirated vehicles (especially performance vehicles) go to great pains to assure that their intake systems are sucking relatively COOL/relatively DENSE ambient air, not hot lower-density air from around the engine, or from the middle of the engine compartment. Hot, low-density, air costs power and performance; this has been understood for at least a century. Damn, that means that, in my quest for more mid-range oomph, I'm going to be compelled to source, buy, and install an air intake system that will suck cooler "outside air".
While in there, I also noticed that, like Harleys, our 1300's use a splay-port intake manifold with true 90º un-radiused sections! It's long been understood, in fluid-flow and dynamics circles, that this is the worst possible, least efficient, energy-and-power-robbing configuration you can possibly use to feed two end-points from a common source. A splayed port with radii is far superior. However, given the inter-cylinder space constraints of a V-twin, maybe there are no options. I know that Harley and Jerry Branch have been fighting this problem for years, with Harley finally resorting to reversing the heads on their XR-750 racers, in an attempt to make them breathe more efficiently. I don't think I'll be reversing the heads on my Fury any time soon! External intake comin' up!
To further add insult to injury, our exhaust ports appear to have cast-in, integral-to-the-head, sharp, energy-robbing, 90º bends, effectively precluding any of the traditional porting manipulations one might otherwise indulge in to improve the breathing efficiency of the exhaust system. Jerry Branch, where are you? I guess we're reduced to the option of adding a marginally more efficient after-market exhaust system (pipes) in our quest for better performance.
Well, lets see, what's left that would increase mid-range torque? Ah yes, the time-honored re-sleeve and over-bore. Voila', instant torque increase. But wait, according to the American Sleeves catalog (the penultimate source for all re-sleeving issues), the 1300 cylinder blocks have "cast-in" sleeves, meaning that the steel sleeve is in-situ when the aluminum block is cast around it, which means that the sleeve probably has radially elevated annular flange located somewhere (probably about the mid-point) along its length. This flange very effectively locks the sleeve in place, but precludes the simple pressing-out procedure for removal; it must be machined out, and then radius-bored to get rid of the remaining flange. Looking at the shop manual and gauging with my un-calibrated eyeball, I don't see a lot of meat between the O.D. of the sleeve and the cylinder studs that could be bored to accommodate a larger diameter sleeve (maybe there's enough, without measuring, I can't tell); a few thou increase in bore wouldn't justify all the effort and expense.
So, what's left? Stroking? Very expensive, and, by itself, not very effective in the small increments we have access to (close-fitting cases and rod bolt extensions become an issue; a lot of expensive machining. Cams, maybe, though increasing cam timing/s and lift/s tend to favor the high end of the power band at the expense of the mid-range and you simply can't wind these shared-journal V-twins up very much further; those that have tried end up with rods sticking through the cases. Larger throttle body? Only if you can increase the displacement of the engine (bore it) enough to increase the potential mass flow, and then establish, via flow bench testing, that the stock throttle body can't handle the increased flow. Increased compression ratio? Our engines' compression ratio is rated at 9.2:1, so shaving the heads to gain a relatively small increase in break mean effective pressure isn't, I'll contend, worth the cost of being restricted to the use of the higher (read more expensive) octane fuels or having to add octane booster each and every time you fill up.
What else then? Turbo-charging is doable, but you better be exceedingly clever and have a REALLY thick wallet. Plus, the associated and necessary plumbing is an antithesis to the whole concept of a "chopper"; the idea is to get rid of shit, not add shit! NitrousOxide? Cheaper, by far, than turboing, but , again, stowage and plumbing would tend to detract from the otherwise clean look of our Furys. Plus, it's hard to find N/O on the road.
I guess we're just stuck with optimizing the induction system with a decent filter and a forward-facing, cold-air pick-up tube, a well-designed, optimized-flow exhaust system, and a fuel controller to adjust for whatever small increases in mass-flow that derive from these two changes.
Other than reducing, and by a quite significant amount, the body mass of the guy sitting in the saddle, did I miss anything in my considerations of options for increasing mid-range performance and acceleration?
There ain't no magic bullet! Our engines are basically hundred-year-old technology (just like all Harleys) that they slapped an EFI system onto.
Cheers
While in there, I also noticed that, like Harleys, our 1300's use a splay-port intake manifold with true 90º un-radiused sections! It's long been understood, in fluid-flow and dynamics circles, that this is the worst possible, least efficient, energy-and-power-robbing configuration you can possibly use to feed two end-points from a common source. A splayed port with radii is far superior. However, given the inter-cylinder space constraints of a V-twin, maybe there are no options. I know that Harley and Jerry Branch have been fighting this problem for years, with Harley finally resorting to reversing the heads on their XR-750 racers, in an attempt to make them breathe more efficiently. I don't think I'll be reversing the heads on my Fury any time soon! External intake comin' up!
To further add insult to injury, our exhaust ports appear to have cast-in, integral-to-the-head, sharp, energy-robbing, 90º bends, effectively precluding any of the traditional porting manipulations one might otherwise indulge in to improve the breathing efficiency of the exhaust system. Jerry Branch, where are you? I guess we're reduced to the option of adding a marginally more efficient after-market exhaust system (pipes) in our quest for better performance.
Well, lets see, what's left that would increase mid-range torque? Ah yes, the time-honored re-sleeve and over-bore. Voila', instant torque increase. But wait, according to the American Sleeves catalog (the penultimate source for all re-sleeving issues), the 1300 cylinder blocks have "cast-in" sleeves, meaning that the steel sleeve is in-situ when the aluminum block is cast around it, which means that the sleeve probably has radially elevated annular flange located somewhere (probably about the mid-point) along its length. This flange very effectively locks the sleeve in place, but precludes the simple pressing-out procedure for removal; it must be machined out, and then radius-bored to get rid of the remaining flange. Looking at the shop manual and gauging with my un-calibrated eyeball, I don't see a lot of meat between the O.D. of the sleeve and the cylinder studs that could be bored to accommodate a larger diameter sleeve (maybe there's enough, without measuring, I can't tell); a few thou increase in bore wouldn't justify all the effort and expense.
So, what's left? Stroking? Very expensive, and, by itself, not very effective in the small increments we have access to (close-fitting cases and rod bolt extensions become an issue; a lot of expensive machining. Cams, maybe, though increasing cam timing/s and lift/s tend to favor the high end of the power band at the expense of the mid-range and you simply can't wind these shared-journal V-twins up very much further; those that have tried end up with rods sticking through the cases. Larger throttle body? Only if you can increase the displacement of the engine (bore it) enough to increase the potential mass flow, and then establish, via flow bench testing, that the stock throttle body can't handle the increased flow. Increased compression ratio? Our engines' compression ratio is rated at 9.2:1, so shaving the heads to gain a relatively small increase in break mean effective pressure isn't, I'll contend, worth the cost of being restricted to the use of the higher (read more expensive) octane fuels or having to add octane booster each and every time you fill up.
What else then? Turbo-charging is doable, but you better be exceedingly clever and have a REALLY thick wallet. Plus, the associated and necessary plumbing is an antithesis to the whole concept of a "chopper"; the idea is to get rid of shit, not add shit! NitrousOxide? Cheaper, by far, than turboing, but , again, stowage and plumbing would tend to detract from the otherwise clean look of our Furys. Plus, it's hard to find N/O on the road.
I guess we're just stuck with optimizing the induction system with a decent filter and a forward-facing, cold-air pick-up tube, a well-designed, optimized-flow exhaust system, and a fuel controller to adjust for whatever small increases in mass-flow that derive from these two changes.
Other than reducing, and by a quite significant amount, the body mass of the guy sitting in the saddle, did I miss anything in my considerations of options for increasing mid-range performance and acceleration?
There ain't no magic bullet! Our engines are basically hundred-year-old technology (just like all Harleys) that they slapped an EFI system onto.
Cheers
