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Discussion Starter · #1 ·
View attachment 29856 Attatched Dyno Run, Any thoughts? Is this a good TQ curve, Any potential problems here? Any areas that need improvement?

2004 FLSTFI
SE Air Cleaner
Stock Heads
95"
SE-211 Cams
22868-00 HC Forged Pistons
SERT
SE Slip Ons
 

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XLIII
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Looks pretty nice, but you'd think the folks in the big red barn could be honest enough to use SAE like everybody else instead of inflating the numbers w/ STD.
At least they put on the chart that they ran it in 5th. Unfortunately, that's another way to inflate numbers.
 

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Another Old Fart
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241 Posts
Same dealer did my dyno run but it looks like my numbers are much lower with the exact same build.
Mega what did you mean by SAE vs STD and numbers inflating........Thanks......... Mike..........
 

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Hellbound Train
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5,595 Posts
STD is not "inflating" numbers. STD is a real time picture of your performance. Using SAE smoothing is just that, you are smoothing out the peaks and valleys of the curve, making it easier to read. Neither method is inflating or deflating, they are apples and oranges and as long as the graphs are labled STD or SAE no one is trying to bullshit you. You just interpret them for what they are. The same goes for 5th gear runs. Dynos are not meant for comparing different bikes or tuners. They are a tool for tuning "your" build.
 

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Infidel
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I think we're confusing terms here...STD Smoothing is just a program setting to eliminate the jagged lines that a dyno can produce, it smooths by averaging. STD and SAE has to do with the HP and Torque settings...STD is actual for that day, temp, humidity, etc. SAE is manipulated for a theoretical standard day so that you can compare an engine dynoed at sea level and 90 degrees to one in say Alaska at 6000' at 20 degrees. It supposedly will eliminate temp, elevation, humidity etc from the equation. At least that's the way I understand it...a dyno guru can chime in if I'm wrong.
 

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XLIII
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No guru, but STD numbers are about 4% higher than SAE which is the common standard that is used in these here Yew Nited States.
5th gear runs are about the same 3-4% higher than 4th gear runs, which are the norm.
Sorry, Chuck, but guys don't post their sheets on here so they can see how their build stacks up against their own bike stock. It's to compare, and comparing with an 8% smoke and mirrors advantage only tells you that the dyno operator is inflating.
Smoothing smooths, but if it says STD instead of SAE, its a 4% inflation.

Borrowed from BryanL:

SAE (Society of Automotive Engineers), USA. Power is corrected to reference conditions of 29.23 InHg (99 kPa) of dry air and 77 F (25°C). This SAE standard requires a correction for friction torque. Friction torque can be determined by measurements on special motoring dynamometers (which is only practical in research environments) or can be estimated. When estimates must be used, the SAE standard uses a default Mechanical Efficiency (ME) value of 85%. This is approximately correct at peak torque but not at other engine operating speeds. Some dynamometer systems use the SAE correction factor for atmospheric conditions but do not take mechanical efficiency into consideration at all (i.e. they assume a ME of 100%).

STD or STP Another power correction standard determined by the SAE. This standard has been stable for a long time and is widely used in the performance industry. Power is corrected to reference conditions of 29.92 InHg (103.3 kPa) of dry air and 60 F (15.5°C). Because the reference conditions include higher pressure and cooler air than the SAE standard, these corrected power numbers will always be about 4 % higher than the SAE power numbers. Friction torque is handled in the same way as in the SAE standard.
 

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Hellbound Train
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csoday said:
. Neither method is inflating or deflating, they are apples and oranges and as long as the graphs are labled STD or SAE no one is trying to bullshit you. You just interpret them for what they are.
Was his dyno sheet not labeled STD and 5th gear run.
 

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XLIII
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Yep, but everybody isn't as smart and experienced as you, Chuck.
They might (no, they do, based on what we read on here) think they got 8 HP more than they did, comparing apples to apples.
 

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As long as you compare apples to apples, there's no issue. In order to be a fair comparison between two dynos, both would have to be done on the same dyno, the same day and by the same operator.

Despite the common perception here, there's nothing "wrong" with STD/5th gear - it's just another measure - like using American standard or metric.
It doesn't matter if it's STD, SAE or something entirely different. A dyno only provides a measure of rear wheel power.

"When estimates must be used, the SAE standard uses a default Mechanical Efficiency (ME) value of 85%. This is approximately correct at peak torque but not at other engine operating speeds. Some dynamometer systems use the SAE correction factor for atmospheric conditions but do not take mechanical efficiency into consideration at all (i.e. they assume a ME of 100%)." -- from the description of SAE.

So - seems to me that we should be using STD in order to see a more accurate representation of what the engine is doing at normal operating speeds instead of just at its peak.

Also - we could as easily consider SAE to be 4% low instead of STD 4% high.

It's all in how you want to use the tool and to Chuck's point, there's no deception - it's clearly marked.
 

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Discussion Starter · #10 ·
Chi-Town

I just did my build in Feb. Too cold to ride much, but liked what I've seen so far. When did you do yours, how do you like it?
 

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I had my graph printed out in both STD and SAE and I showed about 1hp and 1ft/lb more in STD than in SAE so it really depends on the enviroment at the time it is being run. It is actually under the right conditions to get lower STD than sae. If you go back to the dyno and they saved your info in the computer they can print you out a copy in std, sae or din. I wish HDMD88 was back he could explain dyno stuff better than anyone.
 

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Hellbound Train
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I had posted this in a PM but repeating it here. It's my theory and it is along the lines of the above post by MTclassic.
With todays technological advances in dynos and climate controlled booths, built in correction factors are becoming outdated. SAE assumes the dynos are less than 85% effecient over the band and that atmospheric conditions are less than nominal. Many tuners today are more particular of their machines calibrations and in the gulf coast area are installing booths that are damn near medical quality. Due to that, I don't put any creedence in a 4% assumption. Many of these tuners consider STD to be a more accurate measurement. They do mark their charts accordingly. There is no missleading or dishonesty as long as that is noted.
 

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Another Old Fart
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JuggsItis said:
Chi-Town

I just did my build in Feb. Too cold to ride much, but liked what I've seen so far. When did you do yours, how do you like it?
JuggsItis my build was done last July, I am happy with it but If i had to it over again I would of used different cams. I wish I would of found this site before the build because of the knowledge I got from reading about other members builds. This was my first twin cam and first 95. I basically relied on the dealer's suggestions. The bike runs very well but the powerband comes in above 2500, I would of like it to start above idle. I will probably change them out again when the warranty is out. Hope this helped ...... Mike........
 

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csoday said:
I had posted this in a PM but repeating it here. It's my theory and it is along the lines of the above post by MTclassic.
With todays technological advances in dynos and climate controlled booths, built in correction factors are becoming outdated. SAE assumes the dynos are less than 85% effecient over the band and that atmospheric conditions are less than nominal. Many tuners today are more particular of their machines calibrations and in the gulf coast area are installing booths that are damn near medical quality. Due to that, I don't put any creedence in a 4% assumption. Many of these tuners consider STD to be a more accurate measurement. They do mark their charts accordingly. There is no missleading or dishonesty as long as that is noted.
Interesting theory and around here, I have noted some newer, very nice dyno rooms. Modern, very well ventilated. Haven't asked about temperature control, but I'd assume they are. Could very well be that STD in a lot of cases is closer to the actual power produced.
 
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