Good comment on the dyno differences iclick.

Harleytuner, I was told by my tuner that the SuperFlow WinDyn results were appoximately 10% lower than would be measured on the DynoJet system. They provided a chart with my HP readout that shows the WinDyn number (81.6), STTP (77.1) and the SuperFlow SAE numbers (74.1). Also, my numbers for TQ and HP are consistent with others and Jamie's data WHEN "corrected" from the SuperFlow number to the DynoJet using 10%.

I also researched this on Google and pretty much across the board they confirm the differences between the two to be 10-15% based on the technique used to measure HP and TQ.


So what do I really have?

 

I got a couple questions for someone who might know. 1st, how much difference does tire air pressure make during a dyno?. Would the end numbers be higher or lower?. 2nd, I have seen this guy Dr. Dyno who uses a trailor mounted dyno unit. How accurate do you think a unit that is trailered and bounced around the country can be? I've seen him tune a few bikes so he know his stuff, just wonder how sensitive the inards are.,,

 

Ok so here is something I have wondered for a long time. You go to these rallies and see the guy with the Dyno setup in the parking lot. He does a Dyno pull on a bike comes out with a printed sheet showing what he bike is doing and says I can make it better. 15 minutes later he does another Dyno pull and comes out with a better sheet and better numbers. Now my question is, can he by throttle play change the numbers on a Dyno pull to make it better or worse? Can he trick the owner in thinking he helped the bike by how he uses the throttle during the Dyno pull I guess is what I am asking?

 

I personally wouldn't want a tune done on a mobile trailer. Dyno drags and dyno shoot outs on one is one thing, but a full on tune i'm not sure about. Like you said, all that bouncing around can't be real good on the euipment. Tire pressure can have defiantely have an impact on the results of a dyno run.

 

There are some things a dyno operator can do to manipulate the results. Thorrlte position being one of them. Fans on off being another. On a FI bike he could let the bike finish it's warm-up enrichment for one run and start the bike and immediately make a pull for another, he certainly couldn't do much tuning in 15 minutes, besides, if the bike had a SERT, SEST or TTS, he would have to have the MAP to make any adjustments, since the MAP isn't retrievable he would couldn't tune just the 100% TP. He would have to be using some other trick, like the ones mentioned above.

 

Got a question then harlytuner. I called fuelmoto cause i was running a little rich at idle and my throttle position was at 0 but i was idling a little low. They said my whole map would be off if i didn't get the low idle taken care of. I can kind of understand if all of the measurements are based off of the throttle position. esp. if idle is supposed to be around 1k and im idling around 750. I have a 01 electraglide with the magget mirreli fuel injection. What do you think?

 

It's really hard saying, dynos vary. I have only tuned on DynoJet 250's. It's all in how the software interperates the data being collected. Dyno's are a tuning tool, you really can't compare bikes that have been run on seperate dyno's.

 

The idle speed will not affect your tune, however if the throttle position setting is not correct with PC III this will shift your map slightly. Idle issues are a very common problem among the 96-01 EFI bikes, most commonly the stepper.

 

A mobile dyno would be generally unaffected in a trailer as the dyno itself it is basically a drum on large roller bearings, and the pickup is a solid state circuit board which measures force x speed. The dyno electronics are also all solid state components. The bigger question is if the dyno operator is taking the proper amount of time to develop your tune as a bike rally is less than ideal conditions. It generally takes at least several hours for a Power Commander tune, including but not limited to tuning the fuel table for each cylinder, logging and tuning ignition timing, maintaining the proper operating temp during the tune, letting the bike cool down and checking the cold startup, and also verifying your test results. TTS/SERT/SEST will take longer as you cannot tune them in real time and there are also additional tables/utilites which may require tuning.

 

Harleytuner,

Excellent info here!

Thanks!