True HP
Results 1 to 13 of 13

This is a discussion on True HP within the Comparison: WRX vs World forums, part of the Community - Meet other Enthusiasts category; For a long time, I have wondered why cars with "inferior" whp have been able to keep up with motorcycles ...

  1. #1
    Registered User britishbikes's Avatar
    Join Date
    Oct 2003
    Location
    Cantonment, FL
    Posts
    96

    True HP

    For a long time, I have wondered why cars with "inferior" whp have been able to keep up with motorcycles with "better" power to weight ratios, and I'm not talking about at warp speed where wind drag is a major factor.

    Most of the mag hp and shop hp is Dynojet HP or "DJHP" as listed here.

    If car dynos are more accurate (ie true brake dynos) this could be why:


    http://factorypro.com/dyno/true1.html
    Last edited by britishbikes; 06-26-2005 at 07:14 PM.

  2. Remove Advertisements
    ClubWRX.net
    Advertisements
     

  3. #2
    Registered User IntercoolerOnTo's Avatar
    Join Date
    Jan 2004
    Location
    Arizona
    Posts
    64
    Well from coming from a motorcyle myself a triumph daytona 955. i noticed the same thing, cars with less power to wieght would keep up with me. The reason that cars can do this is becasue of torque that is produced from a bigger engine. For instance, my motorcycle has 147hp but only 86ftlbs of torque. I am a firm believer in the saying "hp sells cars, but torque wins races."
    It has a REDLINE for a reason!!!

  4. #3
    Registered User cyrilgrey's Avatar
    Join Date
    Nov 2002
    Location
    Queens, NY
    Posts
    2,190
    Screw this HP/TQ, 1/4, 60ft ****.
    What we need is a simple device that can time all sorts of acceleration stats. From 0 - whatever, each 10mph segment along the way, rolls ons from various speeds in different gears. I believe some motor magazines compile this data.

    That is the only true way to get an idea of how a vehicle as a total package is going to perform across a spectrum.

  5. #4
    Registered User astricii's Avatar
    Join Date
    May 2004
    Location
    Denver
    Posts
    746
    Quote Originally Posted by cyrilgrey
    Screw this HP/TQ, 1/4, 60ft ****.
    What we need is a simple device that can time all sorts of acceleration stats. From 0 - whatever, each 10mph segment along the way, rolls ons from various speeds in different gears. I believe some motor magazines compile this data.

    That is the only true way to get an idea of how a vehicle as a total package is going to perform across a spectrum.

    ...


    Anyway. I used to have a 03 Speed Four in Retro Tangerine. I miss that bike. Wasn't too fast but alot more fun than my suby in the summer. Winter, it shifted back to the rex.
    Adam

    Quote Originally Posted by svc
    Fvk the elves, it's bling season

    Sponsored by: BoostBuddy.com

  6. #5
    Registered User cyrilgrey's Avatar
    Join Date
    Nov 2002
    Location
    Queens, NY
    Posts
    2,190
    Quote Originally Posted by astricii
    ...


    Anyway. I used to have a 03 Speed Four in Retro Tangerine. I miss that bike. Wasn't too fast but alot more fun than my suby in the summer. Winter, it shifted back to the rex.

    Anyhow,

    Cultural practices such as late planting, careful selection of seedbed location, and elimination of weedy hosts can help prevent severe infestations. If planting is delayed until the last week of May or first week of June, few flies will be present to deposit eggs. Seedbeds located as far as possible from growing areas and protected from egg-laying flies with a gauze cloth will less likely be infested. The use of transplants grown in North Carolina at elevations below 3,000 feet will eliminate the danger of introducing the maggots on infested transplants. The fall destruction of turnip and cabbage stumps and weeds such as wild mustards will eliminate many larvae or pupae associated with these plants. Proper fertilization, irrigation and good soil practices also lessen maggot damage by improving plant tolerance

  7. #6
    Registered User
    Join Date
    Sep 2004
    Posts
    4
    What the heck is this about???


    "Anyhow,

    Cultural practices such as late planting, careful selection of seedbed location, and elimination of weedy hosts can help prevent severe infestations. If planting is delayed until the last week of May or first week of June, few flies will be present to deposit eggs. Seedbeds located as far as possible from growing areas and protected from egg-laying flies with a gauze cloth will less likely be infested. The use of transplants grown in North Carolina at elevations below 3,000 feet will eliminate the danger of introducing the maggots on infested transplants. The fall destruction of turnip and cabbage stumps and weeds such as wild mustards will eliminate many larvae or pupae associated with these plants. Proper fertilization, irrigation and good soil practices also lessen maggot damage by improving plant tolerance"

  8. #7
    Registered User IntercoolerOnTo's Avatar
    Join Date
    Jan 2004
    Location
    Arizona
    Posts
    64
    Quote Originally Posted by astricii
    ...


    Anyway. I used to have a 03 Speed Four in Retro Tangerine. I miss that bike. Wasn't too fast but alot more fun than my suby in the summer. Winter, it shifted back to the rex.
    Sweet bike, mine is a 02 silver with a remaped ecu and a carbon fiber pipe.
    It has a REDLINE for a reason!!!

  9. #8
    Registered User DinoGuan's Avatar
    Join Date
    Aug 2003
    Posts
    427
    Yea i think its about power curve also, cars have to be civil and need a wider higher torque band to be driveable, where tiny little bikes dont need that, and just make triple digit hp numbers at 10krpm for like half a second. BHP is a stupid term, I want cars to come with power curve pics instead of bhp@xx rpm ft/lb@xx rpm.

  10. #9
    Registered User britishbikes's Avatar
    Join Date
    Oct 2003
    Location
    Cantonment, FL
    Posts
    96
    Quote Originally Posted by IntercoolerOnTo
    Well from coming from a motorcyle myself a triumph daytona 955. i noticed the same thing, cars with less power to wieght would keep up with me. The reason that cars can do this is becasue of torque that is produced from a bigger engine. For instance, my motorcycle has 147hp but only 86ftlbs of torque. I am a firm believer in the saying "hp sells cars, but torque wins races."

    Part of what I was trying to illustrate is that hp is a mathematically defined quantity of power, the same as 746 watts. It doesn't really matter where in the powerband the peak occurs as long as there is a transmission capable of keeping the engine close to the peak power during a race. Hp wins races, torque is just torque. I have demonstrated this to people on several occasions where a torqey bike can somtimes keep up at first, but as soon as the high powered one comes on the cam, the race is over. Yeah I guess if I never reved past 5,000 rpms I might lose, but that is not where the engine breathes. F1 cars rev to 18,000 rpm and they move right along. If reving to a peak of 5,000 rpm, where the torque number would be higher than the hp number would win the race, don't you think that is how they would be tuned? The cars that keep up with a 955i are make a lot of hp!

    Anyways, the dynojet dynomometer is an inertia dyno that measures how quickly a bike can accelerate a rotating drum. It does not actually measure hp. There is a "correction factor", but it is the same for all bikes, big and small. A motorcycle with a large flywheel load like a Harley or old Triumph twin would show relatively lower numbers than a quick reving two stroke mx bike.

    Bhp is brake horsepower and is often expressed in watts and then converted to hp. A brake dyno measures the ability of an engine to maintain a given speed when presented with a load. This is the real mathematical hp that matters, especially at higher speeds. It doesn't penalize an engine that has a large flywheel and heavy tires. Or one with turbo lag.

    I saw the real hp numbers for a 600 Ninja. They were more like 90, not 105, etc. Djhp numbers are inflated. Obviously a 600 Ninja is still very fast, but I started to notice hp numbers that were impossible without a sigificant amount of boost. The air rams on a bike are not pressurized on a dyno... (1lb at like 140 mph or something. Worth like 7-9 hp). All the numbers were showing a bike making less hp than the et vs hp formulas. They were also showing over 100% volumetric effeciency even at the wheel. A little over 100% at the crank is one thing, but at the wheel: impossible, especially at high revs. Djhp is a sham. It is feelgood hp, not hp.

  11. #10
    Registered User britishbikes's Avatar
    Join Date
    Oct 2003
    Location
    Cantonment, FL
    Posts
    96
    "What we need is a simple device that can time all sorts of acceleration stats. From 0 - whatever, each 10mph segment along the way, rolls ons from various speeds in different gears. I believe some motor magazines compile this data."


    I think a G- tech can do this for cars, including a lap of cornering force measurements.

    It does not work on bikes. I called the company. They said that vibration from a bike interferes with the accelerometer measurements. It is also incapable of measuring cornering forces on a motorcycle, even with its 3 axis accelerometer and a smooth engine. There is a device for bikes that works off a magnetc pickup on the rear sprocket. It is not accurate according to Cycle World: as much as 10% off.

  12. #11
    Registered User
    Join Date
    Nov 2003
    Location
    WV
    Posts
    259
    you guys are looking too far into it. Most bike guys can't ride...

  13. #12
    Registered User britishbikes's Avatar
    Join Date
    Oct 2003
    Location
    Cantonment, FL
    Posts
    96
    How hard is it to shift gears a little past the power peak? Does it take some sort of special talent to "roll on" a motorcycle? It is so easy. At least as easy as in a car. I can see cornering being difficult for the faint of heart, but just winding the engine out? I don't get it.

    I hate to think riders are that bad, unless they aren't really racing. Then again you are right. I can remember outdoing geeks with my Kia in the twisites, while I couldn't keep fast guys in sight for 1 curve. They were just gone.
    Last edited by britishbikes; 07-01-2005 at 08:18 PM.

  14. #13
    Registered User
    Join Date
    Nov 2003
    Location
    WV
    Posts
    259
    Quote Originally Posted by britishbikes
    How hard is it to shift gears a little past the power peak? Does it take some sort of special talent to "roll on" a motorcycle? It is so easy. At least as easy as in a car. I can see cornering being difficult for the faint of heart, but just winding the engine out? I don't get it.

    for example, a fair weather sunday rider on a gxsr1000 that's trying to race and sti from a roll on the highway:

    Is he actually accelerating at the bikes full potential? Probably not. Those things can pull the wheel up at 100mph in 3rd gear, so the guy might be kind of scared of that. Also, if they are anticipating that, they might only have the throttle cracked open at 1/2 way instead of on the edge of having the front wheel float off the ground.

    Along with that, what if they're shifting early so as to avoid having too much power put down, or what it they're running it past redline and letting sit in the dead zone.

    I know my 03 r6 redlines at 15.5k rpm, but stops putting out power at 12.5k. providing an over rev for turns when ever you're really tearing them up.

    What if it's some one just cruising and staying ahead of the person, but not letting the bike open 100% of the way because they don't feel like doing 150mph?

    What if the bike is in serious need of a tuneup?

    What if the person loves the acceleration, but doesn't like to do triple digit speeds?

    There's a million things that could cause a car to be close, but 80% of those, I would think would have to be a rider.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •