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Discussion Starter #1 (Edited)
so a buddy of mine has a '07 street glide. he recently pulled a 110" motor out and put in a 120r with rush pipes and thundermax. i told him his dyno sheet looks screwed up. can anyone tell me what this means. looks like they didnt know what they were doing.
 

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Look at the scaling, a bit hard to see, but it looks like Torque is on the right side, HP on the left, but the scales are different, looks like the left side starts at 70, right side starts at 100??

The formula, HP = torque/5252, means that the lines will always cross at 5252 rpm IF the scaling for the 2 values is the same.

Also, the HP will always be going up as long as the rpm is rising faster than the torque is falling.


A fine example of how you can make a dyno sheet look alot of different ways, none of which have any affect whatsoever on how the engine actually runs.
 

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Discussion Starter #6
Again, just the way the print preferences were set up.

Possible that the tune is so far out of whack at the bottom end that the tuner didn't want to show the curve??
thanks for the reply tdkkart
i guess ultimately would like to know if this tune looks good or if it needs retuned by someone else that knows how to tune it right.


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thanks for the reply tdkkart
i guess ultimately would like to know if this tune looks good or if it needs retuned by someone else that knows how to tune it right.


The shape of the torque curve looks OK, and the AFR chart at the bottom looks pretty flat, which ,means the tune is probably pretty decent.
I do know that most people dump the stock 120R cams for something else.

No, the paper chart doesn't show anything below 3000 rpm, but that's more than likely just a dyno operator and graphing technique issue more than anything. If the operator doesn't hit the "record" button and crank the throttle till 3000rpm it won't show anything, has no real bearing on how it runs on the bottom.

I designed and built an inertia dyno for kart racing engines close to 10 years before all the bike shops had dynos. I am the reason Performance Trends http://performancetrends.com/index.html adapted their data acquisition systems to work with dynos. I worked directly with them for several years developing their software to collect and graph the data.
I can tell you that operator technique/methods have a HUGE bearing on what you see on the printed graph.

My inertia dyno website, written more than 10 years ago to show kart racers how to build an inertia dyno. http://tdkmotorsports.com/
It's a bit dated now, but it still gets tons of traffic. Performance Trends has sold literally hundreds of the dyno data acquisition systems from this info.
 

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I can't see the sheet really well, but the hp looks ok, the tq curve looks like it could use some improvement, maybe a different cam.
 

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I went blind trying to read that chart.

The devil is in the details and we can't make out the details.:confused:
 

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Like I said, the person that set up the graph made it look really funky, it's got a scale spread of 50HP on the left side, while the right side is only a 25ft/lb spread.

Try this, make a copy, redraw the torque curve using the scale on the left and show us that. We'll all realize that the torque curve is actually quite flat, starting at 125ft/lb at 3500 rpm and only dropping 10ft/lbs by 57-5800 rpm.

Alot of this game is more presentation/perception than anything.
The dyno/engine guy is doing himself a dis-service by presenting the info that way he does, simply because it doesn't follow "convention".

Regardless of what the paper says, I'll bet the bike runs damn good. Not the best I've seen, but pretty decent for a bolt in crate motor that we really don't know much about.
 

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If you re-draw the torque curve with the right scaling it'll look just like the green line(bottom one in the top group) of this graph from 3500 to 5800.
The only thing changed on these runs was the exhaust.

 

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Isn't the 120R supposed to do something like 135 rear wheel horse out of the box? Numbers seem weak. They tried to tune my uncles last friday and the dyno broke, but untuned it had numbers right around that.
 

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Isn't the 120R supposed to do something like 135 rear wheel horse out of the box? Numbers seem weak. They tried to tune my uncles last friday and the dyno broke, but untuned it had numbers right around that.
Is the graph i posted above showing up for you?? It worked for me at home(no its not from my computer), but it doesnt show up at work??
Anyway, that graph shows that the 120r does indeed make 135hp with the right exhaust, or 125 with what is apparently the wrong exhaust. Alot of causes for a motor to not make power, and 10% or less is REALLY easy to misplace.
 

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Discussion Starter #17
Is the graph i posted above showing up for you?? It worked for me at home(no its not from my computer), but it doesnt show up at work??
Anyway, that graph shows that the 120r does indeed make 135hp with the right exhaust, or 125 with what is apparently the wrong exhaust. Alot of causes for a motor to not make power, and 10% or less is REALLY easy to misplace.
no your graph didnt show.


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I'd run that! (talking about whats in tdk's link)

That dyno sheet is junk. The pull starts at 3200RPM, and there's plenty of power available, but the overall sheet is screwed up by scaling and makes you wonder why the operator presented like that. As tdk said, it's a diservice as it looks like shit and implies he doesn't know what he's doing.

What's really important is how the engine runs, if the guy is starting the pull at 3200rpm because it won't take WFO at 2500 who fuking cares what happens above 3200 unless it's only run at WFO in drag racing and is geared to run and launch above 3200. In which case it better turn more RPM ...
 
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