Dyno questions?
 

does the weight of the rider and the gearing affect dyno numbers? seems in my uneducated mind that it would have to?

Not really, it effects performance, but not engine output. Now gearing matters with how accurate the dyno's measurement is, but the tach led is suppose to allow the dyno software to account for any gear ratio.

that is a debated topic of dynojet vs flowjet numbers.

It won't but that is ONE of the many points that makes the above differences.

Gearing yes (possibly, depending on if you can get a tach signal)
Rider weight, no. There should be no rider weight on the bike when running on the dyno. Rider should stand straddling the bike.

never seen it done like that honestly

here ya go.

he's straddling it, but not really putting any weight on the seat.

http://i203.photobucket.com/albums/a...h_buell007.jpg

u know-i was lying, cuz thats your bike, and i watched most of the 1st one i think. oops lol


in person, always feets on the pegs tho-could just be the one side im standing on tho

:idk: all I've seen have been fully standing.

though one foot on the peg shouldn't affect that much, but it could throw it off.
just like if you put the tire back on the drum it will give a low reading, and forward on the drum will give a high reading. It's gotta be centered to be accurate.

And yup, that's mine. Bitch ran good that night :dthumb:

Should not matter as long as its the same each time. In other words don't let the fat guy do one pull and the thin guy do the next pull. Always go out of your way to make each run the same. Check and adjust things like tire pressure and engine temperature.

The numbers don't really matter much its the difference from the stock pull to the modified pull. You should not compare dyno umbers with a different dyno.

P.S. I disagree with the standing over the bike as you can not properly work the controls and if needed for some emergency the rear brake would be hard to apply quickly. Not to mention a all gear run would be tough and they can help find a float level or starvation problem.

same here... they're always sitting cause they have to shift... and it takes too much coordination apparently to do with out sitting :lol:

Most dyno runs (that I've seen) are a single gear pull. usually one gear down from top (ie 5th for sportbikes, 4th for most HD's) as that is the closest to a 1:1 ratio.

Me either. Dood was sitting on mine when it was done.

I have always used 4th on sport bikes. When not doing a all gear pull.

From what I've seen doing that will probably give you a slightly higher torque number, and a lower hp number.
At least that's what I saw on the dyno down in IA.

5th is the closest to a 1:1 gear ratio

That can't happen....... (Torque x Engine speed) / 5,252 = horsepower ...... Its mathematically impossible.

Riddle me this then. Why are the peaks from 4th 5th and 6th not all identical? (run started in 2nd)
All gears were run to redline :idk:

http://i203.photobucket.com/albums/a...R/scan0001.jpg

I did not say that it would not increase. I said they must remain proportional.

Horse power is just another way to measure torque that also considers RPM. You can take a given torque and RPM and use math to get horse power. This is the reason that torque and Horse power are always equal at 5252 RPM if they are not then the correction factor is really messing up your measurement.

I would suspect that your HP increases in higher gears are either from the correction factor. Or because the weighted drum has higher energy(harder to stop) at higher speeds. It might even be a flaw in the machines sensors.

Thats reason all gear runs are only used to look for lean or rich float or main jet conditions and the actual numbers should not be considered for actual measurement.

Here I'll show you say you have 40 Ft/pounds of torque at 4000 rpms

40 X 4000 / 5252 = 30.4645849200304645849200304...... HP

Every time, the math never changes its always that HP for that torque at that RPM. If the torque goes up for a given RPM the horse power has to follow they cannot go in different directions. They are always proportional they can not be inversely proportional.

Gotcha. I misunderstood your first post. Now it makes sense.

I kinda key in on this point

that's why I ride a vtwin. HP ain't shit w/o torque.

lol-i think u missed his point

no. a v twin will make a higher torque number at any given HP number.
A I4 will make a higher HP number at any given torque number (compared to said vtwin)

That was my point. I do know that they increase together.

What?

A v-twin makes more torque than the same displacement I-4 because it's port velocity is higher because in general they have less valve area/displacement.

You might want to read my post here

Inertial Dyno's are not that accurate.

so I forgot to put in the "same displacement" part... :idk:

You also left out that it's the rpm that determines how much hp x amount of torque makes, and if a twin and a four make the same torque at the same rpm, they're making the same hp.

It depends on if someone is getting some tuning actually done, or if they just want a piece of paper to wipe their ass with. For tuning, you want the rider sitting on the bike. The bigger key is that no matter which way you do it, standing or sitting, you need to be consistent. Some guys always sit. Some guys always stand. But whichever, you need to stick with one to keep your consistency.

One of the good reasons to ride a v-twin is the decreasing torque curve. Its kind 0f a built in traction control. As the revs increase the torque eitherstays flat or decreases, post peak torque anyway.

If you look at just the torque curve on a inline 4 they tend to increase through most of the rev range. Where as a v-twin tends to decrease so as they rev (like during tire spin) they tend to have less torque than a few rpms lower.

On reaseon for that early lowend torque is the flywheel weight and big monster pistons.

Not to mention they have what I call a longer coast than most inline 4s. This is what the new R1s try to emulate with the big bang engines.