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[snowrider13]

What would be the differences in tuning a bike in 4th 5th or 6th gear? Different numbers? Just curious.

[CVODON]

What???

[grc]

What would be the differances in tunig a bike in 4th 5th or 6th gear? Different numbers? Just curious.

Are you talking about making WOT runs on the dyno in either 4th, 5th, or 6th gear, and why, or are you asking if there should be a different tune for each gear?   

Jerry

[snowrider13]

Talking about WOT runs in different gears. I see some tuners use different gears in thier tuning. Is there any differences in the end result with the final numbers? Talked to a fella that uses 4th gear, says there is no reason to spin the drum crazy fast. Claims that this way shows SLIGHTLY lower numbers.

[Tractor Bubba]

Hmmm.  I can't say as I've ever pondered the question.
My first I impression - from a physics standpoint - is that it shouldn't really matter.
HP = (TQ x RPM) / 5252.
So mathematically, wouldn't the values be similar in whichever gear your in...
...as the relationships between HP and TQ will be the same regardless of how fast
your turning the treadmill. The variances in observed performance would
be due to the ability and accuracy of the instruments and individual...wouldn't they?
Again, never considered the question, and perhaps my early morning logic is flawed.

[grc]

Hmmm.  I can't say as I've ever pondered the question.
My first I impression - from a physics standpoint - is that it shouldn't really matter.
HP = (TQ x RPM) / 5252.
So mathematically, wouldn't the values be similar in whichever gear your in...
...as the relationships between HP and TQ will be the same regardless of how fast
your turning the treadmill. The variances in observed performance would
be due to the ability and accuracy of the instruments and individual...wouldn't they?
Again, never considered the question, and perhaps my early morning logic is flawed.

The type of dynamometer used is a big part of the equation, not just the simple formula.  The type of chassis dynamometer used by most places is an inertia unit.  It basically just measures the rate of acceleration of a drum of known mass, and then uses mathematical algorithms to approximate HP and Torque values.  One of the guys who actually uses one of these things all the time would be the best person to explain it in detail, but basically an inertia dynamometer is just a tool for the tuner.  The good ones these days add a brake of one sort or another that allows for tuning at part throttle and variable load, which is how these bikes are really ridden 98% of the time and are thus the most important areas IMHO. 

If the software is set up to compensate for the actual gear ratio being used, one might think the results would be the same no matter which gear the operator makes the run in.  However, I've seen comparisons before and there always seems to be a small difference when using say fourth gear and then fifth gear.  I chalk that up to the fact those numbers are a result of many mathematical calculations and as we all know, rounding of numbers in a long chain of calculations can result in noticeable differences in final results.  As long as we go back to the true purpose of this kind of dynamometer, any small differences don't mean a thing.  If the only thing people care about is the WOT chart and maximum numbers for bragging rights, they can have a smart operator tweak things to produce whatever numbers they want. 

JMHO - Jerry

[snowrider13]

Just had bike done and instructed the tuner to make it rideable and consistant. Numbers were only secondary. He claims that is the way he tunes. Am VERY happy with the results, much more rideable, smoother, cooler, good mileage. I swear it even sounds different, wifey said so also. I just wanted to see if the group knew of any differences in the gear used. Thanks for the input.

[CVO Couple]

From what I've learned about dynos on bikes and vehicles it should be done in whatever gear is 1 to 1.

[grc]

From what I've learned about dynos on bikes and vehicles it should be done in whatever gear is 1 to 1.

The reason for using the gear that is 1:1 is that theoretically you would have less parasitic power loss though the transmission in direct drive, so the maximum output at the rear wheel would be higher.  Unfortunately, the way Harley designed the Cruise Drive trans leaves more than just one gear set turning in 6th gear, so that theoretical advantage tends to go out the window. 

Jerry

[Dan_Lockwood]

Just my observation, but in any of the three gears, the "tune" would be the same.

If you had your bike tuned and then put it on a dyno to run it in all three gears, the numbers would probably be slightly different.  But you didn't change the "tune" of the bike, only the read-out.

So if the guy tuned your bike and you like it and it's all you hoped for in the riding experience, the numbers as you say are secondary.

[CVO Couple]

The reason for using the gear that is 1:1 is that theoretically you would have less parasitic power loss though the transmission in direct drive, so the maximum output at the rear wheel would be higher.  Unfortunately, the way Harley designed the Cruise Drive trans leaves more than just one gear set turning in 6th gear, so that theoretical advantage tends to go out the window. 

Jerry

1 to 1 ratio is for one revolution of the crankshaft their is one revolution of the trans output shaft?

[grc]

1 to 1 ratio is for one revolution of the crankshaft their is one revolution of the trans output shaft?

Nope.  It's one revolution of the trans input shaft equals one revolution of the trans output shaft.  The crankshaft and trans input shafts turn at different speeds due to the primary gear ratio (crank sprocket to clutch basket sprocket).  The 1:1 ratio I mentioned is just the transmission input to output ratio.

Jerry

[CVO Couple]

Nope.  It's one revolution of the trans input shaft equals one revolution of the trans output shaft.  The crankshaft and trans input shafts turn at different speeds due to the primary gear ratio (crank sprocket to clutch basket sprocket).  The 1:1 ratio I mentioned is just the transmission input to output ratio.

Jerry

I was thinking of vehicles again and forgot about the primary.