According to the HD website the "side draft throttle body and ham can cleaner" cant be that bad, as the Nightster is chucking out 79 ft/lb at 4000 rpm and the XR is only 73.9 ft/lb at 4000 rpm, and its lighter by 23 lbs !!!
Even the 2007 was putting out 79.1 ft/lb at 4000 rpm so the side draft throttle body seems to perform as well if not better than the downdraft, and you would get better airflow from the filter surface on the side draught throttle body with it being a larger filter surface area so you get a better CFM rate. The filter surface is a very small area on the XR and no matter how much bigger the airbox was made (not that you can get it much bigger) the surface area of the filter is very limited, and restricts air flow.
This, in my mind is why the XR is down on power from the XL's. Not the airbox but the filter surface size.
Matt was talking about the ram effect on these things, to my mind that has no effect on the XR as it has a ram style airbox and is down on power.
And the 2006 carburated XL1200's were putting out 79 ft/lb at 3500 rpm, which again is higher than the XR. Which also gave the same MPG figures as the XR 45/52 MPG, so much for EFI
Now, why is it EFI runs much hotter with the same MPG as a carb...!!
And that is why i am not a great lover of the EFI on these bikes, just a lot of electronic witchcraft with no benefits as far as i can see.
It costs you an arm and a leg to buy something that gives you access to play with it.
You have around 10 electronic parts you could throw in the trash if you had a carb on the bike, which is then easily tunned.
Maybe if the airbox was bigger it might perform a little better but i dont think a bigger airbox is gonna give you much more than 6 or 7 ft/lb's anyhow, and even then you would have to raise the filter surface area, which would put it right in the same figures as the XL1200.
Maybe the top end HP would be ever so slightly better, but torque is where its at with these things, anyone that was buying an XR or any Harley for that matter, for the HP is playing with the wrong bike.
As much as i love the XR, it is a bit of a pig in a bag if you look into it properly, its the heaviest and has less torque than the rest of the 1200 range...Go figure.
I can see when folks start tunning the XR for performance that air box and downdraft manifold is gonna go completely, to restrictive and impractical to do anything with.
Most people in my opinion loose sight of the fact that this is a pushrod motor and i honestly dont think the downdraft intake makes the slightest difference, Harley's own figures pretty much tell you that.
The only thing that makes the XR feel quick is the 883 gearing, without that it would feel exactly the same as an XL in the motor department
My recipe for more power out of the XR is...
11/1 Compression
Stage two or three headwork (which is a bit of a grey area as yet)
A good performance two into one exhaust system comprising of Remus headers and Supertrapp tunable muffler.
Free flowing larger surface air cleaner, which in my eyes will mean stretching the filter surface area around the side of the airbox.
And cams (again a grey area as yet)
Nearly forgot...A 40/42mm Mikuni carb to make tunning much easier (another plus side to a carb is you could dump the oil cooler)
Whatcha think??__________________
Even the 2007 was putting out 79.1 ft/lb at 4000 rpm so the side draft throttle body seems to perform as well if not better than the downdraft, and you would get better airflow from the filter surface on the side draught throttle body with it being a larger filter surface area so you get a better CFM rate. The filter surface is a very small area on the XR and no matter how much bigger the airbox was made (not that you can get it much bigger) the surface area of the filter is very limited, and restricts air flow.
This, in my mind is why the XR is down on power from the XL's. Not the airbox but the filter surface size.
Matt was talking about the ram effect on these things, to my mind that has no effect on the XR as it has a ram style airbox and is down on power.
And the 2006 carburated XL1200's were putting out 79 ft/lb at 3500 rpm, which again is higher than the XR. Which also gave the same MPG figures as the XR 45/52 MPG, so much for EFI
Now, why is it EFI runs much hotter with the same MPG as a carb...!!
And that is why i am not a great lover of the EFI on these bikes, just a lot of electronic witchcraft with no benefits as far as i can see.
It costs you an arm and a leg to buy something that gives you access to play with it.
You have around 10 electronic parts you could throw in the trash if you had a carb on the bike, which is then easily tunned.
Maybe if the airbox was bigger it might perform a little better but i dont think a bigger airbox is gonna give you much more than 6 or 7 ft/lb's anyhow, and even then you would have to raise the filter surface area, which would put it right in the same figures as the XL1200.
Maybe the top end HP would be ever so slightly better, but torque is where its at with these things, anyone that was buying an XR or any Harley for that matter, for the HP is playing with the wrong bike.
As much as i love the XR, it is a bit of a pig in a bag if you look into it properly, its the heaviest and has less torque than the rest of the 1200 range...Go figure.
I can see when folks start tunning the XR for performance that air box and downdraft manifold is gonna go completely, to restrictive and impractical to do anything with.
Most people in my opinion loose sight of the fact that this is a pushrod motor and i honestly dont think the downdraft intake makes the slightest difference, Harley's own figures pretty much tell you that.
The only thing that makes the XR feel quick is the 883 gearing, without that it would feel exactly the same as an XL in the motor department
My recipe for more power out of the XR is...
11/1 Compression
Stage two or three headwork (which is a bit of a grey area as yet)
A good performance two into one exhaust system comprising of Remus headers and Supertrapp tunable muffler.
Free flowing larger surface air cleaner, which in my eyes will mean stretching the filter surface area around the side of the airbox.
And cams (again a grey area as yet)
Nearly forgot...A 40/42mm Mikuni carb to make tunning much easier (another plus side to a carb is you could dump the oil cooler)
Whatcha think??__________________