HP vs. TQ
Seasoned HDF Member
Joined: Nov 2004
Posts: 8,129
Likes: 1,981
From: Ottawa, CANADA
RE: HP vs. TQ
ORIGINAL: faber
I get the bore & stroke issue. Thanks for spelling it out, Clammy. Cheers to ya.
Before I got my Harley this year, I messed around with 70s-vintage 650s/750s (Triumphs and Yamahas, mostly--still have a few). But I know what made the Hondas stand out back then was going to the 4 cyl 750 with smaller cylinders/pistons--essentially the first modern sportbike. But they just don't have the low-end pull of my old Bonnie or XS650s. That's my simple-minded way of understanding the difference between HP & TQ.
But.....the L-twin in the Ducati 1098 puts out 180hp stock! With 99 ft-lbs TQ (at a slightly lower RPM then peak HP, I'm guessing.) Calling that bike stock is like calling a Lamborghini stock, I know. The bore is bigger than HD but the stroke is shorter, as I recall (someone can look it up). So...more piston mass through a shorter range of motion and thus able to rev higher, I guess? And maybe the 90° angle gives engineers a little more breathing room to design for higher output (RPMs), as opposed to our iconic 45° twin. But the Ducati also is liquid-cooled and street-legal AND track ready--no Stage I/II, etc.
So, it's not the air-cooled issue that has us HD owners tuning for TQ, but the long-stroke V-twin. I guess I've been misled by those who hope that HD releases a liquid-cooled V-twin for the whole line. That would be good for other reasons, I guess, but not necessarily affect HP/TQ, right?
Winter storage.....
I get the bore & stroke issue. Thanks for spelling it out, Clammy. Cheers to ya.
Before I got my Harley this year, I messed around with 70s-vintage 650s/750s (Triumphs and Yamahas, mostly--still have a few). But I know what made the Hondas stand out back then was going to the 4 cyl 750 with smaller cylinders/pistons--essentially the first modern sportbike. But they just don't have the low-end pull of my old Bonnie or XS650s. That's my simple-minded way of understanding the difference between HP & TQ.
But.....the L-twin in the Ducati 1098 puts out 180hp stock! With 99 ft-lbs TQ (at a slightly lower RPM then peak HP, I'm guessing.) Calling that bike stock is like calling a Lamborghini stock, I know. The bore is bigger than HD but the stroke is shorter, as I recall (someone can look it up). So...more piston mass through a shorter range of motion and thus able to rev higher, I guess? And maybe the 90° angle gives engineers a little more breathing room to design for higher output (RPMs), as opposed to our iconic 45° twin. But the Ducati also is liquid-cooled and street-legal AND track ready--no Stage I/II, etc.
So, it's not the air-cooled issue that has us HD owners tuning for TQ, but the long-stroke V-twin. I guess I've been misled by those who hope that HD releases a liquid-cooled V-twin for the whole line. That would be good for other reasons, I guess, but not necessarily affect HP/TQ, right?
Winter storage.....
All else being equal, a liquid-cooled engine might come from the factory with more hp/tq because the reason HD motors are choked right now is due to emissions, which are easier to address in a liquid-cooled engine. This would allow Harley to open the heads up, resulting in more power.
Another limiting factor that I forgot to mention is that the HD engines use pushrod actived valves too. Overhead cam engines are able to be revved up higher than pushrod engines.
Having said all that, I wouldn't change anything about the 45 degree, air-cooled , pushrod engines for Harley Davidson bikes. You can still make GOBS of power with them, and even dead stock HD motors are stump pullers! Also, they look and sound better and are still easier to deal with maintenance-wise, upgrade-wise, and repair-wise than liquid cooled engines.
Cheers!
[sm=icon_rock.gif][sm=icon_rock.gif][sm=icon_rock.gif]
Ultimate HDF Member
Joined: Sep 2007
Posts: 8,831
Likes: 15
From: Nomad
RE: HP vs. TQ
ORIGINAL: Clammy
Happy to help.
All else being equal, a liquid-cooled engine might come from the factory with more hp/tq because the reason HD motors are choked right now is due to emissions, which are easier to address in a liquid-cooled engine. This would allow Harley to open the heads up, resulting in more power.
Another limiting factor that I forgot to mention is that the HD engines use pushrod actived valves too. Overhead cam engines are able to be revved up higher than pushrod engines.
Having said all that, I wouldn't change anything about the 45 degree, air-cooled , pushrod engines for Harley Davidson bikes. You can still make GOBS of power with them, and even dead stock HD motors are stump pullers! Also, they look and sound better and are still easier to deal with maintenance-wise, upgrade-wise, and repair-wise than liquid cooled engines.
Cheers!
[sm=icon_rock.gif][sm=icon_rock.gif][sm=icon_rock.gif]
Happy to help.
All else being equal, a liquid-cooled engine might come from the factory with more hp/tq because the reason HD motors are choked right now is due to emissions, which are easier to address in a liquid-cooled engine. This would allow Harley to open the heads up, resulting in more power.
Another limiting factor that I forgot to mention is that the HD engines use pushrod actived valves too. Overhead cam engines are able to be revved up higher than pushrod engines.
Having said all that, I wouldn't change anything about the 45 degree, air-cooled , pushrod engines for Harley Davidson bikes. You can still make GOBS of power with them, and even dead stock HD motors are stump pullers! Also, they look and sound better and are still easier to deal with maintenance-wise, upgrade-wise, and repair-wise than liquid cooled engines.
Cheers!
[sm=icon_rock.gif][sm=icon_rock.gif][sm=icon_rock.gif]
Yeah, I know about the pushrod v. OHC thing and the EPA emissions issue. Do you know where I could find out more about *why* an air-cooled engine would have more problematic emissions (problematic by today's "standards," that is)?
I wouldn't give up my Harley either. I just love mine. Plenty of power for me. Given their decision to stick with the air-cooled V-twin, they certainly make the most out of it. Much nicer to cruise around at 2K rather than 6K, too. And there is something about a Harley that is just not present in other bikes, that elusive combination of build quality, fit-n-finish, "traditional innovation," and that classic American look.
Cheers [sm=icon_cheers.gif]
Cruiser
Joined: Nov 2007
Posts: 129
Likes: 0
From:
RE: HP v
I can't tell you when to shift...but this is the best "simple" explaination of torque vs/ HP I've ever read...
http://www.nrhsperformance.com/tech_power.shtml
I can put a wrench on the axle of my bike and put 200 pounds of force at 1 foot out on the wrench - thus putting 200 ft/lbs of torque on it - but the bike isn't going to go very fast. Being able to make lots of torque at a SIGNIFICANT RPM will result in accellerating the bike quickly - the ability to produce this torque at high rpm is expressed as horsepower. Being about to make 80 ft/lbs of torque at 10,000 is more advantageous than one that makes 80 ft/lbs at 3000 rpm.
The article explains it better than I ever could.
He also makes the point thatmaking torque at a very low rpm"feels" better when riding the bike- that lurch when the clutch is released,and for many, is more enjoyable - although it isn't the most effective way to wina drag race.
http://www.nrhsperformance.com/tech_power.shtml
I can put a wrench on the axle of my bike and put 200 pounds of force at 1 foot out on the wrench - thus putting 200 ft/lbs of torque on it - but the bike isn't going to go very fast. Being able to make lots of torque at a SIGNIFICANT RPM will result in accellerating the bike quickly - the ability to produce this torque at high rpm is expressed as horsepower. Being about to make 80 ft/lbs of torque at 10,000 is more advantageous than one that makes 80 ft/lbs at 3000 rpm.
The article explains it better than I ever could.
He also makes the point thatmaking torque at a very low rpm"feels" better when riding the bike- that lurch when the clutch is released,and for many, is more enjoyable - although it isn't the most effective way to wina drag race.
Cruiser
Joined: Jul 2007
Posts: 229
Likes: 0
From: Prescott, AZ
RE: HP vs. TQ
ORIGINAL: ebeattie
Only time you'd honestly EVER need to worry about when and where your engine is making power is when your racing... be it for money, slips, braket racing ect.
as others have stated, use yer butt and yer head and the situation involved to figure when to shift.
Only time you'd honestly EVER need to worry about when and where your engine is making power is when your racing... be it for money, slips, braket racing ect.
as others have stated, use yer butt and yer head and the situation involved to figure when to shift.
My fingers do not fall asleep due to vibration and my rings don't vibrate off my fingers with a Harley like they do with a high rev sports bike. That's one reason I like it. =) Lowryder
Road Captain
Joined: Apr 2007
Posts: 706
Likes: 1
RE: HP vs. TQ
Anyone wanting to understand why Harley motors are RPM limited and why they should be built with a torque biasneeds togoogle "piston speed"
In the July 1980 issue of Cycle World Peter Egan did a article on the "Aluminum Steamroller",the dual carbed 1190 cc creation of Vance Breeseusing Sputhecylinders and heads on stock 72 Sportster cases. It wasn't very exotic by todays standards, but up till that time was the fastest bike in the quarter ever tested by Cycle World 10.554@130.24The bike was geared for top speed and would run well over 150, but still had to leave the line in 2nd gear for the best 1/4 mile times
In the July 1980 issue of Cycle World Peter Egan did a article on the "Aluminum Steamroller",the dual carbed 1190 cc creation of Vance Breeseusing Sputhecylinders and heads on stock 72 Sportster cases. It wasn't very exotic by todays standards, but up till that time was the fastest bike in the quarter ever tested by Cycle World 10.554@130.24The bike was geared for top speed and would run well over 150, but still had to leave the line in 2nd gear for the best 1/4 mile times
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