Stage 1 upgrade results from "free" dyno - Harley Davidson Street Forum - Street 500 and 750
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post #1 of 5 Old 03-28-2017, 04:29 PM Thread Starter
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Stage 1 upgrade results from "free" dyno

Okay, a disclaimer before anyone gets all bent out of shape: the following is NOT from a genuine dynamometer run! It is strictly and entirely "for the **** of it."

I did some upgrades on my bike, and it definitely feels a lot stronger -- although, I fully admit, I could be being lured into thinking so simply because it's a lot louder. I wish I had so much money and time that I could have done a "before" and "after" run on a dyno to see what the true results are, but I didn't, and knew I wasn't going to. However... there's a "free" alternative that might give some insight, or perhaps at least be interesting as a data point...

The computer in the Street bikes is capable of calculating the horsepower and torque being generated at any given moment, under any given load. And, the Fuelpak FP3 and the RPMitUp app both have the ability to report those numbers. They don't graph 'em like a dyno would, but they report them. So I thought... eh, why not just install a screen capture program on my phone and do my own "dyno runs" and graph it myself?

So that's what I did. Before installing any of the new hardware, I set the FP3 to display RPM, HP, Torque, and the Speedometer. I turned on the screen capture program, and then set about doing a number of full-load wide-open-throttle runs in various gears, running from about 2,000 RPM all the way up to the rev limiter. I then laboriously went through the video and entered each value into a spreadsheet.

I then installed all my "Stage 1" go-fast gear: a Screamin' Eagle muffler, the V&H VO2 Naked intake, and remapped the computer with the FuelPak FP3 using the closest appropriate map. I then ran another series of "dyno runs" with the new gear installed, and transcribed those numbers.

Now, first things first -- I don't believe the numbers are "accurate", and neither does Vance & Hines; they say right on their website:
Quote:
these values are not as precise as a dyno session, but are pretty close and fun to view.
I find that the numbers in general are only generally "close"; for example, the Fuelpak's cumulative fuel mileage readout always displays about 10% better gas mileage than my bike actually gets. But, it's consistently about 10% off, so -- even though it's not accurate, it's consistent, so it's still of some value. And I found that with the dyno numbers -- even though they don't come close to matching verified dyno charts that we've seen posted of the Street 750, I will say that the numbers were very consistent between each run, at each RPM level.

So these numbers aren't the same numbers that you could get off a dyno. Sorry, can't help that, didn't feel like torching $200 on multiple dyno runs, so -- it is what it is. But, what it is is pretty interesting, and it does match up with the "butt dyno".

First interesting thing is that the FuelPak FP3 map has raised the redline on the bike. The stock bike maxxes out at about 8000 RPM, it looks like the FP3 map has raised that to about 8500 RPM.

Second, there's not much of a performance difference until about 4000 RPM. After 4000 RPM, things take a big turn, but prior to 4000 RPM they're about the same.

Third, the Screamin' Eagle Nightstick muffler claims that it's optimized for torque. That certainly seems to be borne out by this "dyno" chart, as there's a huge thick fat torque increase right where you'd want it, at about 4000 to 6000 RPM.

Fourth, K&N posted a before & after dyno chart of their high-flow intake kit, which showed a peak power difference at 4900 RPM and a peak torque difference at 3700 RPM. Interestingly enough, the FP3's "dyno" shows a peak power difference at 5125 RPM, which is extremely close to their chart. The torque difference happens at a different point, but to be fair, K&N didn't install a pipe on their test run, so it makes sense to me that the FP3 chart on my bike shows a bigger torque difference. But in general, both the K&N chart and the FP3 chart show generally similar envelopes of where the power is close, where the window opens up, etc.

Which is all to say: don't take any of this too seriously. It's not a dyno run. These numbers are not accurate, the actual numbers don't match real dynos and they don't match the specifications that Harley has published. But -- as an intellectual exercise, I think it's still interesting, and it does seem to sort of match up to other dyno runs in the overall curve characteristics, even if the numbers themselves aren't accurate. And, it does generally explain how much better the bike seems to perform by feel (the aforementioned "butt dyno").

Here's the horsepower chart:


And here's the torque chart:
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post #2 of 5 Old 07-17-2017, 12:20 PM
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I appreciate all the work you did. Interesting exercise-- any newer observations? I'm interested in a remap of my 500 just to fatten it up a bit to insure a healthy engine. I really don't want to spend the money for an FP3 since I'm not looking for increased performance-- just better running. SE Nightstick and K&N filter is all I've done and I have no further plans.
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post #3 of 5 Old 10-29-2018, 01:22 PM
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Hi Gaijin,

Could you repost your charts please? The links seem to be broken.

I just installed the V&H VO2 intake and already had the Screaming Eagle exhaust. I'm stunned by how much more power I'm getting and I haven't remapped the engine at all yet. All the normal fueling issues have disappeared and theres now a meaty "bwaarp" to the exhaust note at about 3/4 throttle - where the **** did that come from?

Hoping you can help,
Piers
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post #4 of 5 Old 10-29-2018, 05:55 PM Thread Starter
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Let's see if attaching them as files will work...
Attached Images
File Type: jpg Harley Street 750 FP3 Dyno Torque Chart.jpg (141.5 KB, 38 views)
File Type: jpg Harley Street 750 FP3 Dyno Horsepower.jpg (149.1 KB, 39 views)
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post #5 of 5 Old 10-29-2018, 09:32 PM
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Brilliant! That worked a treat. Thanks.

Those numbers pretty much match what I'm feeling on the bike - its a huge increase from the VO2. I don't remember there being any discernible increase in power from just the Screaming Eagle exhaust, just a way better (and louder) sound, complete with the pops and bangs on overrun. Its pretty impressive really.
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