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It aint no good locking the doors, when the madnes
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Discussion Starter #1
Now this throws me a little...

The XR according to the handbook is putting out 74.1 ft/lb at 3500 rpm and the XL is putting out 79.1 ft/lb at 4000 rpm ?????
Now why in hell would they print figures like that, one at 4000 rpm and the other at 3500 rpm!!!!
All i can think of is its down to the cams, it cant be anything to do with the gearing as these figures are at the crank.

Then if you look at the HD web site and the specs of the bikes it gives both at 4000 rpm, the XR is 74 ft/lb and the XL's are 79 ft/lb........Work that out!!.........Due to different cams i suspect, but still, i am baffled!

Also the XR (10.0/1) has a slight rise in compression as compared to the XL (9.7/1)

Anyone care to try and throw some light on this, feel free. Because its bugging the hell outa me! :eek:
 

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WTF???
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I don't know all of the answers, but the reading should be the max torque at the rpm that the engine makes max torque. So if one engine makes max torque at 500 rpm less or more than another engine, that would explain the 3500 and 4000 readings.
 

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It aint no good locking the doors, when the madnes
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7,305 Posts
Discussion Starter #3
I don't know all of the answers, but the reading should be the max torque at the rpm that the engine makes max torque. So if one engine makes max torque at 500 rpm less or more than another engine, that would explain the 3500 and 4000 readings.
Either way it shows the XR as putting out less than the XL's

The XR handbook gives the same figure for the XR at 3500 rpm as the HD website gives for the XR at 4000 rpm :rolleyes:
 
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If you look at the torque curves, the XR peaks at around 3500 rpms, hence the lower number. However, the XL doesn't rev as high as the XR motor. HD gave a little bit of low-end torque to get a higher-revving engine and and ultimate higher HP rating (90 vs. ~ 72 at the crank).
 

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It aint no good locking the doors, when the madnes
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Discussion Starter #5
That makes sense as far as the figures the handbook gives but no the HD website, the website gives them both at 4000 rpm.

So from this i am now assuming the difference is gonna be the cams so the XR gets slightly more HP at the top end. And as you say looses a bit of torque to compensate.

It just seems to show that the downdraft intake manifold doesn't really do much for the XR, so now i am thinking that an XL manifold with a better choice of airfilter could help the XR breath better, providing it could be squeezed in there between the oil lines.
 

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WTF???
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I don't have my dyno sheet with me right now, but my XR has a relatively flat torque curve from about 2000 to about 6000 rpm.
 
G

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Did my first service today, so while I was at it, went ahead and threw it up on the dyno when I was finished. The results were what I expected so I was not disappointed in any way.
When I finished my runs, we threw Dan's Sportster on just to have a little shoot-out fun. I would say that in this shoot-out that I got spanked. With a little work I could best his numbers, but then with a little more work he could top mine again also.
Altho his numbers are bigger, I did notice that mine revved up alot faster than his.
I heard some pinging on excelleration with his bike, if he retarded his timing just a little bit and went down one size on his main jet his bike would rev up a little faster and gain a couple more horse power.

Dan's Sportster is an 02 883 with the 10 to 1 comp 1200 kit, bolt in SE cams, but the heads are regular 883s as is the carb.

My XR is stock.

Dan's run is in blue and my XR is the red one:







It does show on this graph that the old Sport has a peak torque at about 4 grand and the XRs is around 3500.

Notice how rich my fuel line is for the power run, it seem to run real lean on part throttle runs (steady throttle/ cruising speeds) at about 15 to 1 and more. I can see how Xieds would help here, but what would they do for the power runs/ wide open throttle/ haulin ass? Is the computer smart enough to re-adjust for ther extra fuel that the Xieds tell it to send?
 

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It aint no good locking the doors, when the madnes
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Discussion Starter #8
So Dan's bike is running the same compression as the XR but has stock sidedraft/carb intake apart from a free flowing filter, i presume, and is putting out more power than the XR with its downdraft EFI induction. (sorry about the sidedraft/downdraft thing, i just couldnt resist...I is only joking):D
It would be interesting to see how much change you get with some mods...


I just altered this post as i didnt read your post properly
:eek:
 
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....
Notice how rich my fuel line is for the power run, it seem to run real lean on part throttle runs (steady throttle/ cruising speeds) at about 15 to 1 and more. I can see how Xieds would help here, but what would they do for the power runs/ wide open throttle/ haulin ass? Is the computer smart enough to re-adjust for ther extra fuel that the Xieds tell it to send?
Is your AFR line the one in Red that matches the Red TQ/HP lines? If so, it looks awful lean for a power run at 14:1, going up to 13:1 at higher RPM.
 

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It aint no good locking the doors, when the madnes
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Discussion Starter #10
BUMP.................I altered my post above!
 
G

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Is your AFR line the one in Red that matches the Red TQ/HP lines? If so, it looks awful lean for a power run at 14:1, going up to 13:1 at higher RPM.
stock form...lot's of horses still asleep...this would be very interesting with Xieds fitted for a second run

anyway that XL would not frighten me...who cares about dyno session when you got the suspension, brakes and ground clearance no other harley has ;)
 

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WTF???
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In another thread it was determined that while torque is fun to talk about, it is the horsepower that makes the bike go fast. And your XR has more HP than his XL. Interesting, my bike dyno'd at 83 rwhp right after the 500 mile service. I know things are never consistent, but we are talking 8 more HP. Like Benny said, I think with equal riders, my XR would beat your friends XL where it counts. Yours should too.
 
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After dyno'ing mine today, without putting any work into peaking the numbers on mine, it looks like if yours were tuned you would be matching his TQ numbers and beating him by at least 10 HP. Is that the downdraft EFI that I hear talking?? :D
 

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It aint no good locking the doors, when the madnes
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Discussion Starter #14
In another thread it was determined that while torque is fun to talk about, it is the horsepower that makes the bike go fast. And your XR has more HP than his XL. Interesting, my bike dyno'd at 83 rwhp right after the 500 mile service. I know things are never consistent, but we are talking 8 more HP. Like Benny said, I think with equal riders, my XR would beat your friends XL where it counts. Yours should too.
Ah but :D you will probably never use your top speed (125 mph) but what you will spend the lifetime of the bike actually using is the torque :)
So my point about torque still stands, its the torque that pulls you out of the corners and should you want to then go flat out (125mph) then you may need the hp, but mostly its gonna be torque ;)

Is that the downdraft EFI that I hear talking?? :D
No, its the cams :D :)
 

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Warning! Fat people are harder to kidnap.
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Must need to get away from the downdraft cams, I bet Scotty will not supply the part number for the sidedraft cams because he is that way. :D Later,
 

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WTF???
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Ah but :D you will probably never use your top speed (125 mph) but what you will spend the lifetime of the bike actually using is the torque :)
So my point about torque still stands, its the torque that pulls you out of the corners and should you want to then go flat out (125mph) then you may need the hp, but mostly its gonna be torque
Scotty, actually, what I was referring to was that it is the HP that actually accellerates your bike too. You can get 150 ftlbs of TQ out of a 1/4 horse drill motor is you gear it down enough, but it doesn't go very fast or very quick. You have to have the HP to actually get your RPM's moving up. Basiscally what it comes down to is that while an XR and a 4 cyl. 600 might make the same HP and go the same speeds if you keep them in the proper powerband, the XR will be much easier to keep in that power band. If an XR and XL had equal TQ numbers, but the XR has more HP, the XR is going to be faster (quicker) in all situations. An old Ford tractor has tons of torque, but it isn't very quick corner to corner even on the tightest roads, you gotta have HP to go with the torque.
 

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It aint no good locking the doors, when the madnes
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Discussion Starter #19
You have two guys with barrels of water at Point A that they need to get to Point B. One guy is really big, think Hungarian World's Strongest Man competitor, very strong but not all that fast. The other guy is a sprinter, maybe not that strong overall, but very quick. The big torque monster is going to carry all the water at once from A to B, just very slowly. The sprinter, who is like a small high revving engine, is going to run back and forth with smaller buckets of water, making several trips in the same amount of time but ultimately accomplishing the same thing.

Harley being a big slow revving engine produces high torque, Jap fours being small higher revving engine produces high horse power.
Which one of these do we have?
It is virtually impossible to get a Harley slow revving engine to produce high horsepower, so we utilise the torque to our needs.
This is why a Harley engine in general is nowhere near as fast top end than an equivalent high revving multicylinder engine. It canot produce the high end horse power.
You can then via different cams and compression move the torque up or down the rev range to suit your purpose.

Big strong man gets so far in front at first with his torque, then small agile man overtakes with his horsepower.

Ducati's for instance because of their mechanical valve gear can rev higher and so also produce more top end horse power.
 

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My giant goes with me wherever I go.
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14,911 Posts
aaarrrrgggghhhh.............

You guys are killing me with these HP-vs-Torque metaphors.......

It's like Mr. Miaugi said in Karate Kid.....Balance Daniel-san...Wax On, Wax Off!!

Neither of them means anything without the other.....Ying and Yang.....Good Needs Evil in order to exist.....What good would one Everly Brother be?

Torque and HP ..... and more of both is better.....more of either without the appropriate amount of the other is a waste of timmmmmeeeeee.....Wax on Wax off.....
 
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