Had my bike on a dyno today, here's the print outs. Tech said AFR was "all over the place". I'm running a V&H FuelPak. I've asked in another forum too but has anyone had any luck sending a copy of the print out to V&H for tuning? What are your thoughts out there?
You have a low RPM engine. Look at your peak torque number. HP means nothing. Torque sends you down the road quicker is the torque curve.
So, she is looking good and that emissions down low in the rpm range is probably the most fun area you might be hitting about 3,100 rpm and now she starts to get some legs on her.
Now you look at what is factory stock HP/Tq numbers and compare; if that was worth all that mod and tuneup away from stock. Bottom line... Did you like the difference and was out of pocket the way to go, yes or no?
To go fast you have to upgrade from production slow. A chart means nothing. WOT does your azzfactor say is leave the wallet out of it.
I had two different FP settings dyno'ed and sent the chart to V&H hoping to get some feedback about lowering the AFR a bit, so far the have ignored me.
Fuelpak is a great inexpensive tool, but V&H tech support sux!
07 FXD with Stock engine and ECM, Big Radius with standard baffles, Big sucker AC.
Blue Line is FP-0597
Red Line is FP-1352
__________________ "It seems to take no time at all, A momentary lapse of reason that binds a life for life"
You have a low RPM engine. Look at your peak torque number. HP means nothing. Torque sends you down the road quicker is the torque curve.
So, she is looking good and that emissions down low in the rpm range is probably the most fun area you might be hitting about 3,100 rpm and now she starts to get some legs on her.Now you look at what is factory stock HP/Tq numbers and compare; if that was worth all that mod and tuneup away from stock. Bottom line... Did you like the difference and was out of pocket the way to go, yes or no?To go fast you have to upgrade from production slow. A chart means nothing. WOT does your azzfactor say is leave the wallet out of it.
Interesting HP comment, but I beg to differ. Sure, torque gets your a$$ movin' but without big HP numbers to back it up your done once off the line!
Take note of the chart, max torque is done and nosediving at just before 4K, however, the HP keeps climbing and "pulling" to around 5.5K.
That's because torque and horsepower always cross at 5252 Rpm's..
It's better to have the max torque early to get you going..
If there were More HP they would still intersect at 5252 but just at a higher HP value..
It looks to me,, at WOT,, his max torque came as soon as A/F fattened up a wee bit from 14.4 to 14..
There is no way of knowing without doing it to see if a wee more fuel coulda increased the HP/TQ at the lower R's and thus provided higher 5252 power..
There are other factors such as timing..
I've always been a big fan of gearing to achieve cheap Seat-of-Pants power..
Arm-chair chart interpretation,,, ain't it wonderful..
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Rooster Cogburn
Hi Twinpeaks,
I think I disagree slightly. Torque is what moves a vehicle in the form of tractive force at the tire contact patch. When calculating gearing to attain a desired performance we always worked with expected road load (tire rolling resistance, grade resistance and aerodynamic drag) and the pure force necessary to overcome them. The difference between the available torque at a specific RPM and the required torque at that vehicle speed yielded the grade climbing ability or available acceleration. The relationship between HP and torque is mathmatical; torque is where it's at
That's because torque and horsepower always cross at 5252 Rpm's..
It's better to have the max torque early to get you going..
If there were More HP they would still intersect at 5252 but just at a higher HP value..
It looks to me,, at WOT,, his max torque came as soon as A/F fattened up a wee bit from 14.4 to 14.. There is no way of knowing without doing it to see if a wee more fuel coulda increased the HP/TQ at the lower R's and thus provided higher 5252 power..
There are other factors such as timing.. I've always been a big fan of gearing to achieve cheap Seat-of-Pants power..
Arm-chair chart interpretation,,, ain't it wonderful..
I've always run the lower end on the fat side, if not for more "real" gains it always gives it a felling of more torque.
I had an Ironhead Sportster that I geared down so bad she would barely do 90mph, but damn, light to light was a trip.
Quote:
Originally Posted by Whopper
Hi Twinpeaks,
I think I disagree slightly. Torque is what moves a vehicle in the form of tractive force at the tire contact patch. When calculating gearing to attain a desired performance we always worked with expected road load (tire rolling resistance, grade resistance and aerodynamic drag) and the pure force necessary to overcome them. The difference between the available torque at a specific RPM and the required torque at that vehicle speed yielded the grade climbing ability or available acceleration. The relationship between HP and torque is mathmatical; torque is where it's at
I did not discount the value of torque but torque alone = a tractor. We do our builds for HP correct? Torque is generally a by-product unless you building a Dodge dually or a Johnny Deere.
There is no better practical example than the difference between my Dyna and V-Rod. The Dyna has about 15% more lbs of torque and 65-70 rear wheel HP. The V-rod with less torque and 110 rear wheel HP will simply castrate the Dyna. Bury it. Even out of the hole with much less torque and coming much later (max) in the rpm range the V-Rod will smoke the Evo. Whereas the Evo gets near all it's torque almost immediately. There is probably a 3 second differential in 1/4 miles times between the 2. Their is simply no substitute for that kind of HP.
Give me a lever long enough, and a prop strong enough, I can single-handed move the world.” Archimedes
Gearing is what gives the V-Rod the jump out of the hole if it has lower bottom end torque. Not having access to a V-Rod torque curve, I suspect that the 110 HP peak is out there around 7,500 RPM. The Big Twin is done 2,000 RPM shy of that. If you could spin a Big Twin that fast without it failing in a spectacular manner, it too could make impressive HP.
Give me a lever long enough, and a prop strong enough, I can single-handed move the world.” Archimedes
Gearing is what gives the V-Rod the jump out of the hole if it has lower bottom end torque. Not having access to a V-Rod torque curve, I suspect that the 110 HP peak is out there around 7,500 RPM. The Big Twin is done 2,000 RPM shy of that. If you could spin a Big Twin that fast without it failing in a spectacular manner, it too could make impressive HP.
Stock is in the 7200 neighborhood, the intake mod and 2-1 exhaust on mine lowered the curve into the mid 6000's.
Actually bottom end torque is lacking relative to an Evo, that's the price you pay for a quick, short stroke and smaller pistons, gearing (5 speed) is very well done but I would not solely attribute it to the V's launching capabilities. It's just mean all the way around.
Location: Winston Salem, Greensboro area of North Carolina
Posts: 130
Re: Dyno run, now what?
Here is my two cents. It may not be worth two cents but I'll give it anyway.
A dynamometer calculates HP by the amount of TQ that an engine has.
The SAE formula used by dynamometers is TQ multiplied by RPM divided by 5252. Without TQ, there is no HP.
The way to make more HP is:
(1) increase the TQ
(2) move the TQ band up the RPM band and increase the max RPM.
The HD engine wasn't designed for high RPMs. The HD engine can be modified to handle higher RPMs but there is a lot of cost and stress put on the engine.
Why not build the engine around the RPM that it was designed for?
The crotch rocket engines are built with a very short stroke and are designed to handle very high RPMs. Look at a dyno graph of a crotch rocket and you will see that the TQ band is located way up the RPM band. Also notice that the TQ band is very flat. Again, "TQ x RPM / 5252." Take your peak TQ and move it up just 2000 RPM (using this formula) and you will be amazed of the amount of HP you would have.
Keeping your gear changes in the sweet zone wins races. When you change gears, the drop in RPM should fall as close as possible to the peak TQ RPM.
This is proven in this video of my bike racing crotch rockets at a 1/8 mile track. By the way...my bike stops making HP at 5500 RPM.
Dyno run, now what? 
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