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This is something everyone should read when compareing dyno sheets from all around the world.http://en.wikipedia.org/wiki/Horsepower. I been seeing alot of dyno sheets that seam rather high for the state of mods some motors have,then i fugured out what was up some of us use dynos that read in sae hp and some use din hp.If i read that web page right the raw uncorrected hp numbers for din hp is metric hp and its higher then the rateing for sae hp.One other thing i did was convert some of the weather conditions to what we use in the USA then used sae c/f factors for those weather conditions.the sae c/f factors take away much more hp on good weather days then the Din c/f that i have seen so the din c/f must be was different then the sae to.Any of you math /engineer guys out there check it out ,its way to much for my mind lol.
 

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Dyno results certainly do open up a can of worms, and different standards of measuring the results don't help. My bike made about 2 DIN BHP and 2ft/lbs torque more in December 2008 than it did in January 2009 (with open stacks and stock CDI). Same dyno, same operator, but different weather conditions. Maybe the tension under which the bike is tied down even has an effect. The actual figures acheived are useful when comparing one mod to another on the same bike, on the same day, with the same operator. Even that is not 100%, as temperature and humidity changes from one hour to the next, although the c/f (correction factor) shown on my dyno read-outs is supposed to compensate for these differences.
 

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Discussion Starter #3
Truth be know ether c/f factors dont work .temp and air pressure changes dont change raw hp as much as factors show.motors do make alittle more hp in cold weather with good air then they do in warm weather and bad air,but these bikes dont change raw numbers anywhere near what the factors show us.the standards where based on FI motors in a lab carb motors dont ack the same.Itake all my dyno runs to uncorrected numbers and look at the weather the day it was run to comapare along with what the fuel mix was the day of the run.The fuel mix will change with weather to unlike efi motors that adj the mix them selfs.
 

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Discussion Starter #4
Rob your raw numbers where under 3 hp between the 2 best runs from the 2 days.The first run you had 88.39 with a c/f of .982 so that would be 88.39 din hp x 1.018 =89.98102(uncorrected did hp)X.986=88.72 (sae raw hp).
Your last run had a c/f of.989 and the sae raw hp on that would be 86.067 .
The weather was better for your tune the first run that makes since.

Now for the crazy crap about sae c/f factors they would be .95 or lower for both your runs if you give them both .95c/f factors you would have 88.72 x .95 =84.284
86.067 x .95=81.76
Now you can see why i say c/f are way wrong.
 

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Mike

You have my head spinning now LOL, but I see what you are saying.

As I said before, comparing before and after mods on the dyno is useful to see if a gain or loss has occured. The foam filters and short stacks certainly wrecked my engine's power and torque curves. The Procom CDI works better than the stock CDI on my bike.
 

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Discussion Starter #6
yea they droped hp for sure did it go rich with them? If they dont flow enough it should make it go richer(just like putting the choke on) if so you could jet it leaner and pick alot of that back up.You cant feel 1 or 2 hp at high rpm.You droped like 9hp you can feel that.Man I hate to see that good motor eat all that dirt,stacks are ok for the race track though.I think if i where you I would find the best filter out there and tune it with them.Use the stacks when you want to race it.Its your bike do what you want lol.
 

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You're right, it was running very rich.

I've run the motor on open stacks for getting on for 4,000 miles. When the head was off to install the big valves, there was no discernable wear to the valve seats, guides, piston rings or cylinder bores. In fact, the valves and seats had a mirror finish - amazing!!! Engine oil has been replaced every 2000 miles, which must help.
 

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Discussion Starter #8
oh it might run great for many miles till you get in some dirty road and a bunch of dirt gets in the stacks then it wont take but a few miles it will be torn up.You know why i am so hard on you about this ? Maybe I did that my self lol.
 

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I agree with mike, for a road going bike, filters are the way to go. You've had a lucky 4,000 miles, you'll know about it when a small bit of gravel gets flicked up, sucked in one of your carbs and just happens to fit nicely between a valve and the piston at 7,500rpm. Myself, I wouldn't risk it, especially with the time, effort and ££ you've put in to your pride and joy. A good set of pods will lose you some at the top end, but would you really notice it on the road. It's a great looking Thrux and obviously goes very well, but it's your engine and your choice.

On the dyno figures subject, in future I'll quote U/C figures and SAE figures. As U/C figures are real on the day, but SAE are good for comparison.
 

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Discussion Starter #10
what it all boils down to is who knows whos got what as far as hp goes .I guess what we all should do is use the dyno as what it is a tuneing tool.Dont compare numbers just improvements.So we can all learn what works and what does not work.If joe blow started with 50hp and now he has 70 we know what he did worked.It would mean the same on another guys bike that started at 55 hp and now makes 75 hp.The gain is the same.The one thing that stands out to me on these bikes when you get them built to the max ,little changes mean alot of hp.There very touchy as far as tune.1 jet size change will make mine run like crap.
 

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Well when I work with engines calculations I use newton meters per second. That is, power = force * linear velocity. Force is measured in newtons and linear velocity in m/s.

From there I use bmep which is power/ (swept volume * revs per second). Basically its the average power across a number of engine revolutions.

From bmep one can calculate BSFC (brake specific fuel consumption) which gives a value in kg/kWh.

One can also work with the force (known as driving force in kN) and the length of the crank to work out the brake power in kW. Driving force is the input for calculating torque.

I dont use HP.
 

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Ohh complex stuff, and some good links.

To throw something else into the mix, I would have thought there was a difference between 'horsepower' and 'usable horsepower'. In other words it's not just the maximum horsepower dyno reading that matters, it's where this hp is developed and ultimately how this translates to how the bike rides on the road. That is how 'usable' the bike is when riding - you probably wouldn't want to use a Moto GP bike as a daily driver for example.

Any thoughts?

Dave
 

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Ohh complex stuff, and some good links.

To throw something else into the mix, I would have thought there was a difference between 'horsepower' and 'usable horsepower'. In other words it's not just the maximum horsepower dyno reading that matters, it's where this hp is developed and ultimately how this translates to how the bike rides on the road. That is how 'usable' the bike is when riding - you probably wouldn't want to use a Moto GP bike as a daily driver for example.

Any thoughts?

Dave
Yes...

Your statement is one of ther best I've heard in months. USEABLE HORSEPOWER. Finally, someone gets it.

Torque is what you are referring to, and torque near the usable range, say 2000 to 6000 RPM. Torque is what gets you going from a standing start, and what gets you from zero to 60 and such. Horsepower is merely a mathematical calculation based on torque, and other factors (see other post attachments). Horsepower takes over when the torque curve drops, and high horsepower allows you to go fast, as in 120+ MPH, if you do that often enough to justify the effort.

Next time you go riding, place some masking tape next to your throttle. Mark it "0", 1/4, 1/2, 3/4 and "F". Now make a mark on the throttle next to zero.

Go on a normal run, and see at what throttle position you spend most of your time. It's not "F".

It would be great to see a real "Torque" contest, to see who has the highest, and flattest torque curve. This is what you use on the street. High Horsepower numbers on a piece of paper are great for bragging rights, and, if used correctly, for monitoring improvements. The best way to see if you are increasing the EFFICIENCY (VE) is to see an increase in torque, which the Dyno computer translates mathematically to HP. For your use, look at the torque graph first. Most people only relate to HP, as Marketing Folks have been using this number for many years. Usually, when you bring up "torque", people say "Huh", and refer back to HP. Many fab ntastic bikes have higher torque numbers than HP. These are refered to as "Stump Pullers", and are a blast to ride.

How about it? Who has the highest, and flattest torque curve, best for the street, and most usable?
 

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Gob-ny-geay +1 on the torque.
I think that the HP dyno info here is great stuff with some good tuners on this site adding their knowledge. For my money I love stump pullers. I ride for pleasure and commute and would love to have 60-70 lb/ft of flat torque. I think that may be a great asset to the new "Thunderbird". The last info from Triumph was "Over 80 HP and Over 100 lb/ft of torque. Now that would be fun, if only it looked like a Triumph. Just my personal preference, but I love to roll the throttle @ 2000 rpm and just feel the pull.
 

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Right you are Derby Boy. I agree, there are many, many great tuners on this sight, and there is definitely good info to be obtained from a Dyno run. As you rightly point out, just offering an alternate perspective.

As you know, tuning for torque, and tuning for horsepower can be two very different things. Bring in maximised tons of air, compress it, ignite it, and blow it out through big straight pipes gets lots of HP, but not necessarily torque. More and more RPM's will be needed, and maybe a tweek of the Rev Limiter, to attempt to bring in more and more air for higher HP readings. This is why many Japanese bikes have such high RPM capabilities, and multiple cylinders, etc. HP sells. Torque readings most folks shrug at.

Torque comes from increased and tweeked to the max Volumetric Efficiency, which requires very high velocity air, through very carefully designed intake ports and valve shapes, compressed inside very specially designed combustion chambers, and exhausted through very specially designed exhaust valves, ports, and narrow to large very specialized diameter and length exhausts. The brains of this outfit is the Camshaft set, and valve to valve seat shapes, all carefully and specifically engineered. All this within an timed pulse wave to efficiently fill each cylinder void, and raise the VE to it's highest achievable level. Old School methods used to call for increasing the stroke to increase Cubic Centimeters, hence Torque as well, but this only works if you also increase the VE accordingly, and in a linear fashion.

As you so rightly state, the results are great, and an absolute blast to ride. Some divide this a into type 1, 2 and 3 bikes. #1 being stock, #2 being "street" modified for higher torque and pragmatic / usable power, and #3 being a very high HP, low torque model, best suited for the track, but not the street. On a #2 Bike, MPG should also remain close to stock through the increased efficiencies, and no high RPM revs are required to launch from a stoplight, or to feel real power under the seat.

Also, the heavier the bike, and YOU, the more the torque is needed to bring the bike from a standing start, or low end speed, up to highway speeds. Torque makes a bike QUICK, horsepower makes it continue on at high speed. Both have a definite place, but I suggest they must be extremely carefully balanced for the individual riders needs, and end goal.

Am I "Torqueing the Torque" now?

I recall a bike from "??"USA that had a very nice, flatline torque curve from 1000 RPM right across the board. As I recall, in the "70ish" Ft./lb. range. Anyone remember that post? The guy spent a ton of cash on the bike, but you cpould pare down the list to only items associated with the torque output, and the cost was then reasonable for the average Joe.
 

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Discussion Starter #17
You need both and there one in the same some what.If you got more torque at what ever rpm you allso have more hp at that rpm.What max hp is on these bikes is how much of the torque that you have on bottom and mid range that you can hold on to at high rpm.Most of these bikes with big hp numbers allso make big torque numbers.You want a motor that pulls all the way through.Most of the guys that do mods on these motors have way more torque then a stock bike.Another thing you need to look at on dyno readings as far as torque goes,what you are seeing is at the rear wheel its alot more at the crank like a stock bike is figured.
As far as going 0 to 60 on these bikes you have to shift to 2nd to do that,what hp does is hold higher rpm when you shift (motor dont drop off as much )thats what hp does and it is faster.
 

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Gob-ny-geay
Fairly flat torque curve here with at least 85% of the maximum torque available between the measured 4000 and 8500rpm. 91.5% of maximum torque is available between 5100 and 7700rpm.


mikeinva

With 19/41 sprockets & Procom CDI, my Thruxton hits 60 in 1st, and that is with the grey/black faced T100 speedometer, which reads lower than the original white faced speedometer.
 

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Yes...

Your statement is one of ther best I've heard in months. USEABLE HORSEPOWER. Finally, someone gets it.

Torque is what you are referring to, and torque near the usable range, say 2000 to 6000 RPM. Torque is what gets you going from a standing start, and what gets you from zero to 60 and such. Horsepower is merely a mathematical calculation based on torque, and other factors (see other post attachments). Horsepower takes over when the torque curve drops, and high horsepower allows you to go fast, as in 120+ MPH, if you do that often enough to justify the effort.
As I have always known it, usable power is simply the width of the powerband, that is the point either side of that which the engine is tuned.

Power is related to linear velocity. In other words force * (distance / time). Torque is a turning moment and therefore non-linear, so it will be something like F x (length / time)

One can see that power and torque have a relationship in that force is applied for a period of time.
 

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Here's a nice article that explains all this, and is much better written and condensed than I could quickly achieve.

http://www.totalmotorcycle.com/school-SectionSixB.htm

Whole point of my post was: Don't forget to consider the benefits of a low end, flat curve torque when building your bike. I do not believe everyone is looking for the exact same results for their individual bikes.

There are also some good "click-ons" near the bottom of the page, to take you back to previous articles on engine theory as well.

Horsepower is wonderful, and useful, but low end torque should also be considered carefully for the street, as it is sometimes lost in the efforts for more top end HP. Having tons of HP is fine, if:

a.) You are actually utilizing or requiring it. Or...
b.) You are an endless tinkerer, and just want to see how much you can squeeze out of a given motor.

Both are obviously fantastic reasons, and both are admirable. After all, most (some ?) of the posters in this thread are obviously interested in the subject matter, therefore there must be an interest in either defining what HP is, or understanding and debating the pro/con impacts.

Otherwise, what is the main point of this thread. Maybe I'm missing something?
 
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