I have a question about the differences I see here on the forum regarding hp/tq ratings and the differences in dynos used. Is there really that big of difference from one dyno tune to another? Some folks here produce BIG numbers and others only state "normal" numbers using the same basic build!

The reason I ask is that I had my bike dyno tuned at Daytona Bike Week by Speed's Performance Plus and I had approximately 100hp and 106tq (see my sig for motor build). I understand that my exhaust choice may be leaving a little to be desired when it comes to maximum numbers, however it runs like a preverbial "swiss watch" and really scoots. In fact I would be willing to wager that it will run with any HD running a similar build, and yet my numbers seem lower than some seem to have obtained.

So what gives? Are some dynos highly optomistic when giving out their numbers?

Tim

 

Don't know what Custom Pipes are but they are probabaly holding you back.

There are differences in dynos and there are different parameters that can vary the numbers up to 5%; calibration, correction factors (STD,SAE, DIN) 4th gear pulls vs 5th gear pulls, tire compound/pressure, clutch condition, oil type and temperature, fresh air exchange in the dyno room, tuned for numbers or tuned for mileage, etc. You could have a less than optiimum tune. Then there are "happy" dynos; dynos that produce numbers that will not be replicated on another dyno. Dyno your bike in the AM, again in the early PM and again in the late PM and you will get three different readings.

If you are happy with the way the bike runs, forget about the numbers and ride. If you are not happy with the way the bike runs or just want a second set of numbers, take it to another tuner.

 

On my last two bikes I have seen over 10 hp and tq difference between dynos with the same motors. A good shop will do a baseline run before any work is done, and then one after the work. It's a tool to see the gain or loss of the work done, if it run's good don't worry about the numbers.

 

Tim,
Your level of "headwork" and exhaust, may be a strong contributing factor as to why the question.
We have 107"ers all over the country, tuned all over the country, that show between 115-125 hp,(a client in Kentucky just had his Wood 6/Our Stage III Head/107" tune off at 115/120 @ H-D of Bowling Green, for example, and BTW that is the SMALLEST cam that Bob Wood manufactures.) and constantly hover in/around the 125 ft/lbs mark.
And more can be had as well, if more is wanted.
Happy, sad, glad, mad, dynos.
Must be the dyno's that our builds get tuned on are all happy ones.
At least I know our clients are.
Scott

 

What djl said.

 

What little I know about these Harleys I have learned somewhat by accident.
When I was younger I remember just the length of, Drag Pipes, (open exhause) made a big difference. I didn't know volicity and scavenging from hamburger then.
Late models now respone the same to exhaust. Enormous differences between exhaust systems.
I got a V&H Big Radius 2-1 when I bought the bike new. 2008 FLSTF. Just cause I did.
Lots of engine modifications later I realized this works pretty well. One reason was the 1 7/8 in. short pipes. Aquried by accident, but I learned what I had next.
But loud as hell.
I got a good set of pipes, the D&D Fatcat and found the 1 3/4 in long pipes hurt the engine, as I had it.
So I got a Borizilla Quite. 1/78 in long pipes and the engine is happy again.
Just that pipe size change.

And somewhat quiter.

 

Just leave it alone and ride the damn thing, I don't believe half of the dyno #'s quoted on here and the other half are lies.

 

Yeah man just ride and don't worry about #'s. I've seen budget se builds put out some pretty good power and also seen some "highly recommended" shop builds using all top shelf parts put out some less than "advertised" hp/tq. You can't ride a dyno sheet.

 

Oh, I see.

 

Easy there Scott, it's more a general comment on how I perceive Dyno numbers, with skepticism on my part. No offense meant.